Micro Mini 4

Streptococcus suis

In August 2005, it was reported that Streptococcus suis caused the death of 37 farmers in China. The illness is characterized by the sudden onset of hemorrhagic shock. This species is known to cause disease in pigs but only rarely in people prior to this outbreak. Peptostreptococci are one of the most common bacteria found in brain, lung, abdominal, and pelvic abscesses.

Salmonella Laboratory Diagnosis

In enterocolitis, the organism is most easily isolated from a stool sample. However, in the enteric fevers, a blood culture is the procedure most likely to reveal the organism during the first 2 weeks of illness. Salmonellae form non-lactose-fermenting (colorless) colonies on MacConkey's or EMB agar. On TSI agar, an alkaline slant and an acid butt, frequently with both gas and H2S (black color ***********), are produced. S. typhi is the major exception; it does not form gas and produces only a small amount of H2S,the organism is urease-negative . (Proteus organisms, which can produce a similar reaction on TSI agar, are urease-positive), the Salmonella isolate can be identified and grouped by the slide agglutination test into serogroup A, B, C, D, or E based on its O antigen. Definitive serotyping of the O, H, and Vi antigens is performed by special public health laboratories for epidemiologic purposes. serologically diagnosis by detecting a rise in antibody titer in the patient's serum (Widal test).

LISTERIA MONOCYTOGENES Clinical Findings

Infection during pregnancy can cause abortion, premature delivery, or sepsis during the peripartum period. Newborns infected at the time of delivery can have acute meningitis 1-4 weeks later. The bacteria reach the meninges via the bloodstream (bacteremia). The infected mother either is asymptomatic or has an influenza like illness. L. monocytogenes infections in immunocompromised adults can be either sepsis or meningitis. L. monocytogenes gastroenteritis:-Outbreaks are usually caused by contaminated dairy products, but undercooked meats such as chicken and hot dogs have also been involved. Laboratory Diagnosis:- Gram stain and culture in sheep or horse blood agar gram-positive rods resembling diphtheroids. Enzyme profiles &genomic analysis are also available. Treatment &Prevention :-Ampicillin with or without gentamicin. Trimethoprim-sulfamethoxazole is also effective.

PULMONARY ANTHRAX (woolsorter's disease)

Inhalation anthrax is not communicable from person-to-person, despite the severity of the infection. After being inhaled into the lung, the organism moves rapidly to the mediastinal lymph nodes, where it causes hemorrhagic mediastinitis. Because it leaves the lung so rapidly, it is not transmitted by the respiratory route to others. Pulmonary (inhalation) anthrax, also known as "woolsorter's disease," begins with nonspecific respiratory tract symptoms resembling influenza, especially a dry cough and substernal pressure. This rapidly progresses to hemorrhagic mediastinitis, bloody pleural effusions, septic shock, and death. Although the lungs are infected, the classic features and x-ray picture of pneumonia are not present. Mediastinal widening seen on chest x-ray is an important diagnostic criterion. Hemorrhagic mediastinitis and hemorrhagic meningitis are severe life-threatening complications GASTROINTESTINAL FORM Ingesting raw or undercooked meat containing spores.

Bacillus anthracis

Is a Gram-positive, aerobic, spore-forming large bacillus. Capsules composed of D-glutamate Spores are formed in culture, in the soil, and in the tissues and exudates of dead animals, but not in the blood or tissues of living animals. Spores remain viable in soil for decades

Cellulitis:

Is an inflammation of skin and underlying connective tissue.

Group A streptococci 4 toxins and hemolysins.

(1) Erythrogenic toxin causes the rash of scarlet fever. Acts as a superantigen. It is produced only by certain strains of S. pyogenes lysogenized by a bacteriophage carrying the gene for the toxin. (2) Streptolysin O is a hemolysin that is inactivated by oxidation (oxygen-labile). It causes beta-hemolysis only when colonies grow under the surface of a blood agar plate. It is antigenic, and antibody to it (ASO) develops after group A streptococcal infections. The titer of ASO antibody can be important in the diagnosis of rheumatic fever. (3) Pyrogenic exotoxin A is the toxin responsible for most cases of streptococcal toxic shock syndrome. it is a superantigen that causes the release of large amounts of cytokines from helper T cells and macrophages. (4) Exotoxin B is a protease that rapidly destroys tissue and is produced in large amounts by the strains of S. pyogenes that cause necrotizing fasciitis.(FLESH EATING BACTERIA) Note :-the other flesh eating bacteria are vibro vulnificus, clostridum perfringens, bacteroides fraglis, Aeromonas hydrophila.

Factors that lower resistance and predispose persons to pneumococcal infection include:

(1) alcohol or drug intoxication or other cerebral impairment that can depress the cough reflex and increase aspiration of secretions; (2) abnormality of the respiratory tract (eg, viral infections), pooling of mucus, bronchial obstruction, and respiratory tract injury caused by irritants (which disturb the integrity and movement of the mucociliary blanket); (3) abnormal circulatory dynamics (eg, pulmonary congestion and heart failure); (4) splenectomy; and (5) certain chronic diseases such as sickle cell anemia and nephrosis. 5.Trauma to the head that causes leakage of spinal fluid through the nose predisposes to pneumococcal meningitis. (CSF leaks can also occur in the ear through weaknesses in the roof of the middle ear, as well as from the nose after trauma or surgery.)

Strain S. agalactiae can be characterized on the basis of three serologic markers:

(1) the B antigen or group-specific thick cell wall polysaccharide antigen (Composed of rhamnose, N-acetylglucosamine, and galactose), (2) type-specific capsular polysaccharides (Ia, Ia/c, Ib/c, II, IIc, III to VIII), inhibit complement-mediated phagocytosis (3) the surface protein, C protein.

STAPHYLOCOCCUS AUREUS: PYOGENIC DISEASES

1) Skin infections are very common. These include impetigo, furuncles,carbuncles, paronychia, cellulitis, (2) Septicemia (sepsis) can originate from any localized lesion, especially wound infection, or as a result of intravenous drug abuse. Sepsis caused by S. aureus has clinical features similar to those of sepsis caused by certain gram-negative bacteria such as Neisseria meningi- tidis (3) Endocarditis may occur on normal or prosthetic heart valves, especially right-sided endocarditis (tricuspid valve) in intravenous drug users. (Prosthetic valve endocarditis is often caused by S. epidermidis.) (4) Osteomyelitis and arthritis may arise either by hematogenous spread from a distant infected focus or be introduced locally at a wound site. S. aureus is a very common cause of these diseases, especially in children. ø 5) Pneumonia can occur in postoperative patients or following viral respiratory infection, especially influenza. Staphylococcal pneumonia often leads to empyema or lung abscess; 6. Conjunctivitis typically presents with unilateral burning eye pain,hyperemia of the conjunctiva,and a purulent discharge. (contaminated fingers)

Identification of streptococci based on hemolysis

1. Alpha (α) hemolytic streptococci produce a greenish discoloration with partial hemolysis around the colonies. 2. Beta (β) hemolytic streptococci produce a sharply defined, clear, colourless zone of hemolysis, within which red cells are completely lysed. 3. Gamma (γ) or nonhemolytic streptococci produce no change in the medium. Lance field grouping Partial or alpha Viridans S. penumonia Beta Group A (S. pyogenes) Group B (S. agalactiae) Gamma (non hemolytic) Enterococci (group D) The traditional Lancefield classification system, which is based on serotyping, has been replaced by emm typing, which has been used to characterize and measure the genetic diversity among isolates of S pyogenes. This system is based on a sequence at the 5' end of a locus (emm) that is present in all isolates.

Enteric tract

1. Both within and outside - Escherichia, Salmonella 2. Primarily within - Shigella, Vibrio, Campylobacter, Helicobacter 3. Outside only - Klebsiella-Enterobacter-Serratia group, Proteus-Providencia-Morganella group, Pseudomonas, Bacteroides

Classification

1. N. meningitidis (meningococcus) has a prominent polysaccharide capsule that enhances virulence by its antiphagocytic action and induces protective antibodies . (2) N. gonorrhoeae (gonococcus) has no polysaccharide capsule but has multiple serotypes based on the antigenicity of its pilus protein. There is marked antigenic variation in the gonococcal pili as a result of chromosomal rearrangement; more than 100 serotypes are known. Gonococci have three outer membrane proteins (proteins I,Pro II, and III(Rmp). Protein II (Opa )plays a role in attachment of the organism to cells and varies antigenically as well.

Spore forming gram positive bacilli

1.Bacillus :-Bacillus anthracis - anthrax Bacillus cereus - food poisoning 2.Clostridium. These bacilli are ubiquitous, and because they form spores they can survive in the environment for many years. In 2001, an outbreak of both inhalation and cutaneous anthrax occurred in the United States. The outbreak was caused by sending spores of the bacteria through the mail. As of this writing, there were 18 cases, of whom 5 died.

N. gonorrhoeae Diagnosis:

1.Gram staining of urethral or cervical exudates Result :- Intracellular gram- negative diplococci). 2.Culture :- Chocolate agar is used to isolate Neisseria. when Neisseria is predominant bacteria in the specimen. Thayer-martin or modified Thayer-martin medium is used if the sample is contaminated with normal flora (contains vancomycin, colistin, nystatin.) Serological tests to detect serum antigonococcal antibodies, Tests for specific endotoxins, enzymes or fatty acids, demonstration of gonococcal antigens using enzyme immunoassays or DNA hybridization techniques. 1. Direct immunofluorescence 2. Hybridization techniques:-Assays based on DNA hybridization techniques are limited to laboratories with molecular diagnostic capabilities. Sensitivity and specificity of this method were found to be greater than 97% and 99%, respectively

S. pyogenes

A Beta Bacitracin-sensitive

Serogroups:

A, B, C, X, Y, Z, 29e, L, and W-135 A, B, C, and Y are widespread and are most frequently involved as human pathogens. Serogroups B -1&2 and C-1 Serotype Serotype B 2 is the most common isolate from human meningococcal disease. Type 2 antigens from both group are chemically and serologically identical, and they induce antibodies that are bactericidal in the presence of complement.

Acute post Streptococcal glomerulonephritis (AGN)

AGN typically occurs 2-3 weeks after skin infection by certain group A strepto-coccal types in children (eg, M protein type 49 causes AGN most frequently). Caused due to formation of antigen-antibody complexes in situ (Ag in the basement membrane of the glomerulus of the kidney and cross-reactive antistreptococcal antibodies) may be responsible Clinical picture → facial edema, dark urine(smoky) and hypertension. Diagnosis: Increase antibody titers to streptococcal enzymes, low levels of serum C3. Anti-DNase B test

Shigella Clinical Findings

After an incubation period of 1-4 days, symptoms begin with fever and abdominal cramps, followed by diarrhea, which may be watery at first but later contains blood and mucus. The disease varies from mild to severe . Shigella dysenteriae, which causes the most severe disease, is usually seen in the United States only in travelers returning from abroad. Shigella sonnei, which causes mild disease, is isolated from approximately 75% of all individuals with shigellosis in the United States. The diarrhea frequently resolves in 2 or 3 days; in severe cases, antibiotics can shorten the course.

Salmonella Clinical Findings

After an incubation period of 12-48 hours, enterocolitis begins with nausea and vomiting and then progresses to abdominal pain and diarrhea, which can vary from mild to severe, with or without blood. Usually the disease lasts a few days, is self-limited, causes non- bloody diarrhea, and does not require medical care except in the very young and very old. (HIV-infected individuals,) Salmonella typhimurium is the most common species causing enterocolitis in the United States, In typhoid fever, caused by S. typhi, and In enteric fever, caused by organisms such as S. paratyphi A, B, and C . the onset of illness is slow, with fever and constipation rather than vomiting and diarrhea predominating. Diarrhea may occur early but usually disappears by the time the fever and bacteremia occur. After the first week, as the bacteremia becomes sustained, high fever, delirium, tender abdomen, and enlarged spleen occur. Rose spots, ie, rose-colored macules on the abdomen, are associated with typhoid fever but occur only rarely. Leukopenia and anemia are often seen. Liver function tests are often abnormal, indicating hepatic involvement. The disease begins to resolve by the third week, but severe complications such as intestinal hemorrhage or perforation can occur. About 3% of typhoid fever patients become chronic carriers. The carrier rate is higher among women, especially those with previous gall bladder disease and gallstones. Diagnosis- blood, bone marrow,urine, tissue biopsy from rose spots. Septicemia is most often caused by S. choleraesuis. The symptoms begin with fever but little or no enterocolitis and then proceed to focal symptoms associated with the affected organ, frequently bone, lung, or meninges.

Anthrax

Anthrax is a major disease threat to herbivorous animals (cattle, sheep, and goats). People get infected :-- A) By the cutaneous route. (spores on animal products, such as hides, bristles, and wool. B) By inhalation (Woolsorter's disease), C) By ingestion (meat from diseased animals)

S.epidermidis and S.saprophyticus

Are coagulase negative staphylococcus S.epidermidis—responsible for hospital acquired infection. S.saprophyticus---responsible for community acquired infection S.epidermidis------normal flora of skin &mucous membrane. Can cause infection of I. V.catheters &prosthetic implants e.g heart valve. -major cause of sepis in neonates, peritonitis ---In patient undergoing peritoneal dialysis.& also causes cerebrospinal fluid shunt infection. The glycocalyx (= to capsule ) is responsible for the adherence of bacteria to prosthetic implant. S.saprophytis :- Normal flora of skin and periurethral area can cause urinary trat infection especially in sexually active women. The infecting strains are usually sensitive to most common antibiotic except nalidixic acid, & novobiocin .

LEGIONELLA Treatment &Prevention

Azithromycin or erythromycin (with or without rifampin) is the treatment of choice. Certain fluoroquinolones, such as levofloxacin and trovafloxacin, are also drugs of choice. These drugs are effective not only against L. pneumophila but also against Mycoplasrna pneumoniae and Streptococcus pneumoniae. The organism frequently produces β-lactamase, and so penicillins and cephalosporins are less effective. Prevention involves reducing cigarette and alcohol consumption, eliminating aerosols from water sources, and reducing the incidence of Legionella in hospital water supplies by using high temperatures and hyperchlorination. There is no vaccine.

S. agalactiae

B Beta Bacitracin-resistant; hippurate hydrolyzed

Bacillus cereus

B. cereus is the most important pathogen, with gastroenteritis, ocular infections, and intravenous catheter-related sepsis the diseases. In immunocompromised patients, including sepsis, meningitis, pneumonia, and wound infections . Certain populations are at increased risk for B. cereus infection, including cancer patients, neonates, intravenous drug users, and patients with a history of trauma, surgery, or catheterization. Gastroenteritis caused by B. cereus is mediated by one of two enterotoxins . The heat-stable, proteolysis-resistant enterotoxin causes the emetic form of the disease(rice), and the heat-labile enterotoxin causes the diarrheal form (meat vegetable)of the disease. Spores of Bacillus cereus on grains ( rice ) survive steaming and rapid frying. The spores germinate when rice is kept warm for many hours (re-heated fried rice). Clinical Findings: There are 2 syndromes: (1) short incubation period ( 3 hours ) with nausea and vomiting and similar to Staphylococcal food poisoning. (2)long incubation period ( 18 hours ) with watery, non-bloody diarrhea and toxin resembles same as that of cholera toxin; i.e., it adds adenosine diphosphate-ribose, a process called ADP-ribosylation, to a G protein, which stimulates adenylate cyclase and leads to an increased concentration of cyclic adenosine monophosphate (AMP) within the enterocyte. Prevention: Cooked rice should NOT be kept at room temperature or warm for long periods.

Pathogenesis of anthrax

Based on the production of 2 exotoxins, collectively known as anthrax toxin. The two exotoxins, edema factor and lethal factor, each consist of two proteins in an A-B subunit configuration. The B, or binding, subunit in each of the two exotoxins is protective antigen. The A, or active, subunit has enzymatic activity. Protective antigen forms pores in the human cell membrane that allows edema factor and lethal factor to enter the cell. The name protective antigen refers to the fact that antibody against this protein protects against disease. Edema factor, an exotoxin, is an adenylate cyclase that causes an increase in the intracellular concentration of cyclic AMP. This causes an outpouring of fluid from the cell into the extracellular space, which manifests as edema. (Note the similarity of action to that of cholera toxin.) Lethal factor is a protease that cleaves the phosphokinase that activates the mitogen-activated protein kinase (MAPK) signal transduction pathway. This pathway controls the growth of human cells, and cleavage of the phosphokinase inhibits cell growth.

Drug resistance are mediated

Beta-lactamase production: β-lactamase (penicillinase) inactiviates penicillin by splitting the beta-lactam ring action mediated by the plasmid. The same plasmid may carry genes resistance for multiple drug. Lack of penicillin-binding proteins: some staphylococcus strain lack the receptor on their surface hence MRSA. This reaction is mediated by the bacterial chromosome MecA gene (oxacillin)encodes these alterted PBPS. The most common strain of MRSA in the united states is the "USA300"strain. Daptomycin, Trimethoprim-sulfamethoxazole,Clindamycin, A combination of two streptogramins, Quinupristin-dalfopristin.

Staphylococcus

Blood Agar S. aureus - β haemolysis clear, colorless. Other staph - nonhaemolytic

Bordetella pertussis Laboratory Diagnosis

Bordet Gengou contains high percentage of blood to inactivate inhibitors in the agar.(Cotton swabs contains fattyacids that are toxic to B.pertusis.Calcium alginate or Darcon fibre). The sputum specimen was also cultured on Regan-Lowe medium and incubated in room air at 358C. After 72 h small shiny colonies were observed. Direct fluorescent antibody stain for Bordetella pertussis The DFA stain used fluoroscein isothiocyanate conjugate produced by Difco(Detroit, Mich.) for B. pertussis and B. parapertussis diluted1:900 prior to use. It was counterstained with Evans blue stain. The positive controls were B. pertussis and B. parapertussis, and the negative control was Escherichia coli. Immunoglobulin G (IgG) and IgA antibody titers to filamentous hemagglutinin (FHA) and pertussis toxin (PT), can be performed Polymerase chain reaction-based tests are highly specific and sensitive

Gram-Positive Cocci

Both staphylococci and streptococci are gram-positive cocci, non motile, do not form spores but they are distinguished by two main criteria. (1) Microscopically, staphylococci appear in grapelike clusters, whereas streptococci are in chains. (2) Biochemically, staphylococci produce catalase (ie, they degrade hydrogen peroxide), whereas streptococci do not. Definitive method for defining a bacterial species are -DNA/DNA hybridization.

Pathogenesis of C. botulinum

Botulinum toxin is absorbed from the gut and carried via the blood to peripheral nerve synapses, where it blocks release of acetylcholine.(flaccid )

Gram-Negative Rods Related to Animal Sources (ZoonoticOrganisms)

Brucella species, Francisella tularemis, Yersinia pestis, and Pasteurella multocida

Animal sources

Brucella, Francisella, Pasteurella, Yersinia

BRUCELLOSIS Clinical finding

Brucellosis may be either acute or chronic. Fever is the most common symptom and sign of brucellosis. Fever can be associated with a relative bradycardia. Fever of unknown origin (FUO) is a common initial diagnosis in patients in areas of low endemicity. It is associated with chills in almost 80% of cases Constitutional symptoms include anorexia, asthenia, fatigue, weakness, and malaise and are very common (>90% of cases). Musculoskeletal ,Multi organ invovlement. Bone and joint symptoms include arthralgias, low back pain, spine and joint pain, and, rarely, joint swelling. These symptoms affect as many as 55% of patients. Gastrointestinal symptoms, present in 50% of patients, include abdominal pain, constipation, diarrhea, and vomiting Neurologic symptoms can include weakness, dizziness, unsteadiness of gait, depression, and urinary retention. Respiratory symptoms of cough and dyspnea are present in as many as 19% of persons; however, these symptoms are rarely associated with active pulmonary involvement. Pleuritic chest pain may affect patients with underlying empyema. Elevated ESR, c-reactive protein. Elevated transaminase, Anaemia Fatalities (0-3%) generally are due to endocarditis.

BRUCELLOSIS(undulant fever)

Brucellosis may be seen in any age group, but it still involves young and middle aged adults more frequently. (California,Texas, travel to mexico) Brucella are Gram-negative, nonmotile, coccobacilli. They are strict aerobes and grow very slowly (fastidious) on blood agar. In the host, they live as facultative intracellular pathogens. Brucellosis is primarily a disease of animals and it affects organs rich in the sugar erythritol (breast, uterus, epididymis, etc.). The organism localizes in these animal organs and cause infertility, sterility,mastitis, abortion or resides as carriage. Humans in closed contact with infected animals (slaughterhouse workers, veterinarians, farmers, dairy workers) are at risk of developing undulant fever. Brucella species, particularly B. melitensis and B. suis, are potential agents of biological terrorism. There are 100-200 cases of brucellosis seen in the US, although the worldwide incidence is estimated at 500,000 Four different species of Brucella are known to infect humans: B. abortus (cattle), B. suis (swine), B. melitensis (goats/sheep and B. canis (dogs). Although brucellosis has been eradicated in most developed countries through animal vaccination, it persists many underdeveloped and developing countries.

Yersinia pestis Clinical Findings

Bubonic plague, which is the most frequent form, begins with pain and swelling of the lymph nodes draining the site of the flea bite and systemic symptoms such as high fever, myalgias, and prostration. The affected nodes enlarge and become exquisitely tender. These buboes are an early characteristic finding. Septic shock and pneumonia are the main life-threatening subsequent events. Pneumonic plague can arise either from inhalation of an aerosol or from septic emboli that reach the lungs. Untreated bubonic plague is fatal in approximately half of the cases, and untreated pneumonic plague is invariably fatal.

PSEUDOMONAS Non fermenters

Burkholderia cepacia Complex Pulmonary infections: Range from colonization to bronchopneumonia primary in patients with cystic fibrosis or chronic granulomatous disease Opportunistic infections: Urinary tract infections in catheterized patients; bacteria in immunocompromised patients with contaminated intravascular catheters Burkholderia pseudomallei Pulmonary infections: Can range from asymptomatic colonization to abscess formation Stenotrophomonas maltophilia -ubiquitous environmental organism. Opportunistic infections: A variety of infections (most commonly pulmonary and urinary tract) in immunocompromised patients previously exposed to broad-spectrum antimicrobial therapy . Acinetobacter species Pulmonary infections: Opportunistic pathogen in patients receiving respiratory therapy. Moraxella species Pulmonary infections: Tracheobronchitis or bronchopneumonia in patients with chronic pulmonary diseases (most commonly caused by M. catarrhalis)

Clostridium difficile

C. difficile causes antibiotic-associated pseudomembranous colitis. C. difficile is the most common nosocomial cause of diarrhea. It is transmitted by the fecal-oral route. The hands of hospital personnel are important intermediaries. Antibiotics suppress drug-sensitive members of the normal flora, allowing C. difficile to multiply and produce exotoxins A and B. Both exotoxin A are enzyme that glucosylate (add glucose to) a G protein involved in actin filament polymerization. Exotoxin B (cytotoxin )causes depolymerization of the actin, resulting in a loss of cytoskeletal integrity, apoptosis, and death of the enterocytes. Clindamycin,second-and third-generation cephalosporins,cancer chemotherapy recognized as a cause of pseudomembranous colitis. C. difficile rarely invades the intestinal mucosa. The diarrhea is usually not bloody, and neutrophils are found in the stool in about half of the cases. Fever and abdominal cramping often occur pseudomembranes are visualized by sigmoidoscopy. Toxic megacolon can occur, and surgical resection of the colon may be necessary Detection of the exotoxins in stool filtrates. 1. enzyme-linked immunosorbent assay (ELISA) using known antibody to the exotoxins. The ELISA tests are rapid but are less sensitive than the cytotoxicity test. 2.In the cytotoxicity test, human cells in culture are exposed to the exotoxin in the stool filtrate and the death of the cells is observed. This test is more sensitive and specific but requires 24-48 hours' incubation time. The causative antibiotic should be withdrawn. Oral metronidazole or vancomycin should be given and fluids replaced.

Clostridium perfringens

C. perfingens causes two distinct diseases, gas gangrene(myonecrosis, necrotizing fasciitis) and food poisoning, depending on the route of entry into the body. Gas gangrene is associated with war wounds,automobile and motorcycle accidents, and septic abortions (endometritis). Gas gangrene is also caused by Clostridium histolyticum, Clostridium septicum, Clostridium novyi, and Clostridium sordellii. (C. sordellii also causes toxic shock syndrome in postpartum and postabortion woman.) rare case of necrotizing pneumonia, empyema, and septic shock caused by Clostridium perfringens. Organisms grow in traumatized tissue (especially muscle) and produce a variety of toxins. The most important is alpha toxin (lecithinase), which damages cell membranes, including those of erythrocytes, resulting in hemolysis. Degradative enzymes produce gas in tissues. Clinical Findings Pain, edema, and cellulitis occur in the wound area. Crepitation indicates the presence of gas in tissues. Hemolysis and jaundice are common, as are blood-tinged exudates. Shock and death can ensue. Mortality rates are high. The organisms are cultured anaerobically (Robertson's cooked meat )and then identified by sugar fermentation reactions and organic acid production. Egg yolk agar is used to demonstrate the presence of the lecithinase. C.perfringens colonies exhibit a double zone of hemolysis on blood agar. Food poisoning is the second disease caused by C. perfringens. The mode of action of the enterotoxin is the same as that of the enterotoxin of S. aureus; ie, it acts as a superantigen. The disease has an 8- to 16-hour incubation period and is characterized by watery diarrhea with cramps and little vomiting. It resolves in 24 hours.

Clostridium tetani

C. tetani causes tetanus (lockjaw). Spores are widespread in soil. The portal of entry is usually a wound site, eg, where a nail penetrates the foot,but the spores can also be introduced during "skin-popping," a technique used by drug addicts to inject drugs into the skin. Germination of spores is favored by necrotic tissue and poor blood supply in the wound. Neonatal tetanus, in which the bacteria enters through a contaminated umbilicus or circumcision wound, is a major problem in some developing countries.

Clostridium tetani Laboratory Diagnosis

C. tetani produces a terminal spore, ie, a spore at the end of the rod. This gives the organism the characteristic appearance of a "tennis racket."

CAMPYLOBACTER

Campylobacter jejuni is a frequent cause of enterocolitis, especially in children. C. fetus subspecies fetus Campylobacters are curved, gram-negative rods with polar flagella("gull's wings"). They are microaerophilic, growing best in 5% oxygen rather than in the 20% present in the atmosphere. C. jejuni grows well at 42°C.

Haemophilus Determinants of Pathogenicity:

Capsular polysaccharide - H. influenzae contain phosphoribosylribitol phosphate (PRP). Capsular (PRP) has antiphagocytic properties and is the prime virulence factor for H. influenzae type B. Membrane lipo oligosaccharide - may play a role in bacterial attachment, invasiveness, and paralysis of the ciliated respiratory epithelium. IgA protease inactivate secretory antibodies. The usual portal of entry for all strains of Haemophilus is the upper respiratory tract, particularly the nasopharynx. H. influenzae type b penetrates the nasopharyngeal epithelium and damages the epithelium, spreads either directly or haemotogenously to the meninges.

SYSTEMIC INFECTION

Capsule and the endotoxin, play a more prominent role in the pathogenesis of systemic, rather than intestinal tract, disease. The capsular polysaccharide interferes with phagocytosis, thereby enhancing the organism's ability to cause infections in various organs. For example, E. coli strains that cause neonatal meningitis usually have a specific capsular type called the K1 antigen. The endotoxin of E. coli is the cell wall lipopolysaccharide, which causes several features of gram-negative sepsis such as fever, hypotension, and disseminated intravascular coagulation.

Determinants of pathogenicity

Capsule. The capsular polysaccharide has antiphagocytic properties. Pili Lipopolysaccharide (LPS, endotoxin) - most potent endotoxins which causes fever,shock. IgA proteases.---meningitidis produce IgA proteases, which cleave IgA at the hinge region.IgA protease enzyme protects bacteria against the effects of secretory IgA. People with complement deficiencies, have an increased incidence of meningococcal bacteremia. Complement C6-C9-fixing IgM and IgG antibodies can promote bacterial elimination from circulation and tissues.

The Breath Test

Carbon-14-urea Breath Test You swallow a capsule or drink water which contains one microCurie of C14-urea. You provide the breath sample usually by blowing up a small balloon or blowing bubbles in a small bottle of collection liquid

URINARY TRACT INFECTIONS

Certain O serotypes of E. coli preferentially cause urinary tract infections. These uropathic strains are characterized by pili with adhesin proteins that bind to specific receptors on the urinary tract epithelium. The binding site on these receptors consists of dimers of galactose (Gal-Gal dimers). The motility of E. coli may aid its ability to ascend the urethra into the bladder and ascend the ureter into the kidney.

Necrotizing fascitis

Characterized by extensive fascial and subcutaneous tissue necrosis, Predisposing factors: Concurrent infection with other bacteria,Delayed or inappropriate treatment,

N. meningitides Control and Prevention

Chemoprophylaxis: Therapy with rifampin or ciprofloxacin is recommended for individuals with close patient contact. Immunoprophylaxis:There are two kinds of meningococcal vaccine in the U.S. Meningococcal conjugate vaccine (MCV4) is the preferred vaccine for people 55 years of age and younger. Conjugate vaccines: made with A and C polysaccharides and a nontoxic mutant of diphtheria toxin are currently begin evaluated with the hopes that these vaccines will be more immunogenic and effective, even in infants. Meningococcal polysaccharide vaccine (MPSV4) has been available since the 1970s. It is the only meningo-coccal vaccine licensed for people older than 55.

Anthrax Prevention and Treatment

Ciprofloxacin and doxycycline are the antibiotics of choice. Human vaccine is available. People at high risk can be immunized with cell-free vaccine containing purified protective antigen as immunogen. The vaccine is weakly immunogenic, and six doses of vaccine over an 18-month period are given. Annual boosters are also given to maintain protection. Incinerating animals that die of anthrax, rather than burying them, will prevent the soil from becoming contaminated with spores.

H. influenzae type b

Clinical disease: Meningitis: H. influenzae capsulated type b Most frequently seen in children between 6 month and 2 years. Risk groups: Non immunized patients with a history of head trauma, otitis media, hypogammaglobulinemia, or sickle cell anemia. Laboratory diagnosis: Gram stain of sputum or CSF, gram negative coccobacillus. Culture on chocolate agar with two growth factors addition of two components, heme (factor X) and NAD (factor V), for adequate energy production.

Clinical Findings of C. botulinum

Clinical picture:-Descending weakness and paralysis, including diplopia,dysphagia, and respiratory muscle failure, are seen. Two special clinical forms occur: (1) wound botulism:-In the United States,drug abuse, especially skin-popping with black tar heroin. (2) infant botulism, in which the organisms grow in the gut and produce toxins. Ingestion of honey containing the organism is implicated in transmission of infant botulism. Affected infants develop weakness or paralysis and may need respiratory support but usually recover spontaneously.

CLOSTRIDIUM

Clostridium. This genus was defined by the following properties: (1) Presence of endospores, (2) Strict anaerobic metabolism, (3) Gram-positive cell wall structure. There are four medically important species: Clostridium tetani,& Clostridium botulinum, Clostridiurn perfringens (which causes either gas gangrene or food poisoning), and Clostridium difficile.

Vibrio cholerae Laboratory Diagnosis

Colorless colonies on MacConkey's agar because lactose is fermented slowly. The organism is oxidase-positive, which distinguishes it from members of the Enterobacteriaceae. On TSI agar, an acid slant and an acid butt with out gas or H2S are seen because the organism ferments sucrose. TCBS(THIOSULPHATE CITRATE BILESALT SUCROSE ) -selective media for vibrios. Produces yellow colony

Shigella LAB DIAGNOSIS

Confirmation of the organism as Shigella and determination of its group are done by slide agglutination. One important adjunct to laboratory diagnosis is a methylene blue stain of a fecal sample to determine whether neutrophils are present. Invasive organism such as Shigella, Salmonella, or Campylobacter (Certain viruses and the parasite Entamoeba histolytica can also cause diarrhea without PMNs in the stool.)

NON-SPORE-FORMING GRAM- POSITIVE RODS

Corynebacterium diphtheriae and Listeria monocytogenes. C. diphtheriae causes diphtheria. Other Corynebacterium species (diphtheroids) are implicated in opportunistic infections. The bacillus was first observed and described by klebs, but was first cultivated by Loeffler hence known as Klebs- Loeffler bacillus (K.L.B).

OXIDASE TEST

Cytochrome oxidase is an enzyme found in some bacteria that transfers electrons to oxygen, the final electron acceptor in some electron transport chains. Thus, the enzyme oxidizes reduced cytochrome c to make this transfer of energy. Presence of cytochrome oxidase can be detected through the use of an Oxidase Disk(phenylene-di-amine) which acts as an electron donator to cytochrome oxidase. If the bacteria oxidize the disk(redox dye) (remove electrons) the disk will turn purple, indicating a positive test.

E. faecalis

D Alpha or beta or none Growth in 6.5% NaCl3

S. bovis

D Alpha or none No growth in 6.5% NaCl

Prevention

Despite the efficacy of antimicrobial drug treatment, the mortality rate is high in elderly (ie, persons older than 65 years), immunocompromised (especially splenectomized), or debilitated persons. Such persons should be immunized with the polyvalent (23-type) polysaccharide vaccine. The vaccine is safe and fairly effective and provides long-lasting (at least 5 years) protection. A booster dose is recommended for (1) people over the age of 65 who received the vaccine more than 5 years ago and who were less than 65 when they received the vaccine and (2) people between the ages of 2 and 64 who are asplenic, HIV-infected, receiving cancer chemotherapy, or receiving immunosuppressive drugs to prevent transplant rejection. Oral penicillin is given to young children with hypogammaglobulinemia or splenectomy because such children are prone to pneumococcal infections and respond poorly to the vaccine. A different pneumococcal vaccine containing pneumococcal polysaccharide coupled (conjugated) to a carrier protein (diphtheria toxoid) is given to children under the age of 2 years. This "conjugate" vaccine is effective in young children in preventing both bacteremic infections, such as meningitis, and mucosal infections, such as otitis media.

BRUCELLOSIS Diagnosis

Diagnosis is based on prolonged (at least a week) presence of undulating fever or malta fever, myalgia, arthralgia and the history of exposure (contact with animals or consumption of unprocessed material from infected animals). Definitive diagnosis can be made by culturing blood samples on blood enriched media. (fastidious) The (fastidious) organisms grow very slowly (4-6 weeks in blood culture). B. abortus but not other Brucella grow better in 5% CO2 atmosphere. On blood agar, they produce white glistening colonies. Serology can be used to further confirm the diagnosis.

Epidemiology of CAMPYLOBACTER

Domestic animals such as cattle, chickens, and dogs serve as a source of the organisms for humans. Transmission is usually fecal-oral. Food and water contaminated with animal feces is the major source of human infection. Foods, such as poultry, meat, and unpasteurized milk, are commonly involved. Puppies with diarrhea are a common source for children. C. jejuni is a major cause of diarrhea in the United States.

Entero

EPEC destroys the brush border microvilli, and becomes firmly attached through a pedestal consisting of actin and actin binding proteins. ETEC bind loosely via fimbriae, secrete toxins (like Cholera toxins) into the gut that then gain entry into the cell without disruption of cytoskeleton C. EIEC, gains entry into the cell, escaping from the immune system by digesting the phagolyosome. EIEC can grow and divide in the cell cytoplasm and gain entry to neighbouring cells by bursting through and digesting membranes. D. EHEC, operates like EPEC, but in addition Shiga toxins are liberated that the epithelial cells take up in coated pits and taken to the Golgi. The toxins then travel from Golgi to the E.R. where they destroy ribosomes by the removal of a single adenine residue from the 28SrRNA. This results in the death of the cell.

PATHOGENS BOTH WITHIN & OUTSIDE THE ENTERIC TRACT ESCHERICHIA

ESCHERICHIA E. coli is the most common cause of urinary tract infection and gram-negative rod sepsis. It is one of the two important causes of neonatal meningitis and the agent most frequently associated with "traveler's diarrhea," a watery diarrhea. Some strains of E. coli are enterohemorrhagic and cause bloody diarrhea. E. coli ferments lactose,

Neonatal Meningitis

Early onset type that develops a few days after birth is accompanied by sepsis, pneumonia and high mortality. Late onset type disease comes on in 2 to 6 weeks with symptoms of meningitis - fever vomiting and seizures The main predisposing factor is prolonged (longer than 18 hours) rupture of the membranes in women who are colonized with the organism. Children born prior to 37 weeks' gestation have a greatly increased risk of disease. Also, children whose mothers who lack antibody to group B streptococci and who consequently are born without transplacentally acquired IgG have a high rate of neonatal sepsis caused by this organism. Because most cases occur in the hospital, personnel must be aware of the risk of passively transmitting this pathogens, especially in the neonatal and surgical units.

Corynebacterium diphtheriae Document toxin production

Elek test -precipition lines A PCR assay for the presence of the toxin gene in the organism isolated from the patient can also be used. The treatment of choice is antitoxin, which should be given immediately on the basis of clinical impression. DTP vaccine should be given at 2, 4, and 6 months of age, with boosters at 1 and 6 years of age.

PSEUDOMONAS virulence factors:-

Endotoxin, exotoxins, and enzymes. Its endotoxin, causes sepsis and septic shock. Exotoxin A, which causes tissue necrosis. It inhibits eukaryotic protein synthesis by the same mechanism as diphtheria exotoxin, namely, ADP-ribosylation of elongation factor 2. Enzymes, such as elastase and proteases, which are histotoxic and facilitate invasion of the organism into the bloodstream. Pyocyanin damages the cilia and mucosal cells of the respiratory tract. Strains of P. aeruginosa that have a "type III secretion system" are significantly more virulent, this secretion system transfers the exotoxin from the bacterium directly into the adjacent human cell, which allows the toxin to avoid neutralizing antibody.

Clinical Findings CAMPYLOBACTER

Enterocolitis, caused primarily by C. jejuni, begins as acute watery, foul-smelling diarrhea followed by bloody stools accompanied by fever and severe abdominal pain. Ten or more stools per day. Self limiting in 3-5 days. After an average incubation period of three days (range one to seven days), the disease starts in one of two ways. Most commonly, the first symptoms include abrupt onset of abdominal pain and diarrhea, making the intestinal nature of the illness obvious. However, in about one-third of cases, a prodromal period of fever and malaise without gastrointestinal symptoms occurs Systemic infections, most commonly bacteremia, are caused by C. intestinalis. The symptoms of bacteremia, eg, fever and malaise, are associated with no specific physical findings. Chronic bacteremia with relapses that can persist for several months occurring in an immunocompromised host

Rheumatic fever

Epidemiology: R.F is most prevalent in children and adolescents proper treatment of streptococcal pharyngitis has reduced the incidence of rheumatic fever 2 major criteria or 2 minor criteria with 1 major criteria Serologic test: raised titer of antistreptolysin O( ASO), elevated ESR. Treatment: Non steroidal anti inflammatory drugs (aspirin). Prevention of recurrences: Prophylactic penicillin for the rest of their lives.

N. meningitides Diagnosis

Examination of C.S.F.----Leucocytosis, elevated protein concentration and low sugar concentration. gram stain → morphology. Rapid diagnostics tests → based on the agglutination of latex particles coated with antibodies to the most common bacteria. Blood culture: In cases of suspected bacterial meningitis, blood cultures are obtained because the organisms most likely reached the meanings through the blood stream. Treatment: Penicillin,Ceftriaxone,Chloramphenicol

N. meningitides Clinical disease

Febrile illness Severe headache, fever, stiff neck. Acute meningococcemia → systemic infection with N. meningitides. Waterhouse Friderichsen syd---high fever, shock, DIC, wide spread purpura, thrombocytopenia, adrenal insufficiency. Epidemiology: Transmission → N. meningitides is transmitted by respiratory secretions and is highly contagious. High transmission rates are found in day-care centers and military barracks.

HIPPURATE TEST

For sodium hippurate hydrolysis performed by some Streps Dispense 0.5 ml of distilled water into a tube. ASEPTICALLY add one hippurate disk. Emulsify a large loopful of inoculum in the water. Add a tight cap. Incubate at 300-370 C for 2 hours. Add 5 drops of ninhydrin reagent after incubation, shaking gently. Reincubate the tube for 10-15 minutes, no more than 30 minutes, and note color. Sodium hippurate, when hydrolyzed, is broken down to benzoic acid and glycine. The ninhydrin reacts with glycine to form ammonia, a purple color. A dark purple is a strong +, a light purple is a weak +.

FRANCISELLA

Francisella tularensis subsp. novicida isolated from a human in Arizona using multiple DNA-based approaches Francisella tularensis causes tularemia.(bacteria in the blood stream-circulating). F .tularensis is a small, pleomorphic gram-negative rod. It has a single serologic type. There are two biotypes, A and B, which are distinguished primarily on their virulence and epidemiology. Type A is more virulent and found primarily in U.S whereas type B is less virulent and found primarily in Europe. F. tularensis is endemic in animals in every state, but most human cases occur in the rural areas of Arkansas and Missouri. It has been isolated from more than 100 different species of wild animals, the most important of which are rabbits, deer, and a variety of rodents. The bacteria are transmitted among these animals by vectors such as ticks, mites, and lice, especially the Dermacentor ticks that feed on the blood of wild rabbits. The tick maintains the chain of transmission by passing the bacteria to its offspring by the transovarian route. In this process, the bacteria are passed through ovum, larva, and nymph stages to adult ticks capable of transmitting the infection. Humans are accidental "dead-end" hosts who acquire the infection most often by being bitten by the vector or by having skin contact with the animal during removal of the hide. Rarely, the organism is ingested in infected meat, causing gastrointestinal tularemia, or is inhaled, causing pneumonia. F. tularensis is unique in that it can penetrate the unbroken skin. The main type of tularemia in the United States is tick-borne tularemia from a rabbit reservoir.

Clinical Findings of HELICOBACTER

Gastritis and peptic ulcer are characterized by recurrent pain in the upper abdomen, frequently accompanied by bleeding into the gastrointestinal tract. Laboratory Diagnosis The organism can be seen on Gram-stained smears of biopsy specimens of the gastric mucosa. Urease production is the basis for a noninvasive diagnostic test called the "urea breath" test. In this test, radiolabeled urea is ingested. If the organism is present, urease will cleave the ingested urea, radiolabeled CO 2 is evolved, and the radioactivity is detected in the breath.

N. gonorrhoeae

Gonococci, like meningococci, cause disease only in humans. The organism is usually transmitted sexually; newborns can be infected during birth. Gonorrhea is usually symptomatic in men but often asymptomatic in women. Genital tract infections are the most common source of the organism, but anorectal and pharyngeal infections are important sources as well. Sexual intercourse From mother to infant during child birth Acquired form inanimate objects (e.g. solid towels)

Genus Neisseria

Gram negative cocci, Kidney bean shaped, often seen as (diplococci) Aerobic, oxidase-positive. Grow best on chocolate agar supplemented with solubilized starch under increased CO2 tension at 37* C.

Lab Investigation

Gram stain. Culture on blood agar →β haemolysis, yellow colon. Mannitol salt agar. Coagulase test. Antibiogram: drugs - penicillin, erythromycin, on salt mueller hinton agar/using 1 µg oxacillin disc incubating at room temperature Mupirocin is effective topically. Vancomycin ---MIC- 2µg/ml. A combination of two streptogramins, quinupristin-dalfopristrin (synercid ) can be used for VISA

Laboratory Diagnosis

Gram-stained smears are useless in streptococcal pharyngitis because viridans streptococci are members of the normal flora and cannot be visually distinguished from the pathogenic S. pyogenes. Cultures of swabs from the pharynx or lesion on blood agar plates show small, translucent beta-hemolytic colonies in 18-48 hours. If inhibited by bacitracin disk, they are likely to be group A streptococci. Group B streptococci are characterized by their ability to hydrolyze hippurate and by the production of a protein that causes enhanced hemolysis on sheep blood agar when combined with beta-hemolysin of S. aureus (CAMP test).

Pharyngitis

Group A streptococci are the most common bacterial cause of pharyngitis and tonsillitis They adhere to pharyngeal epithelium via pili covered with lipoteichoic acid and M protein. Many strains have a hyaluronic acid capsule that is antiphagocytic. Symptoms: Sore throat accompanied by fever, headache. The organism multiplies in the tonsils or pharyngeal mucous membranes causing redness, edema, enlargement and extreme tenderness that makes swallowing difficult and painful. → Purulent exudates over the tonsils, swollen cervical lymph nodes and occasionally white, pus filled nodes on the tonsils. Pre school children may complain of a headache and abdominal pain instead of a sore throat.

Christie,Atkins, Munch-peterson

Group B streptococci produce a diffusible, heat-stable protein (CAMP factor) that enhances β-hemolysis of Staphylococcus aureus. S. aureus produces sphingomyelinase C, which can bind to erythrocyte membranes. When exposed to the group B CAMP factor, the cells undergo hemolysis.

Haemophilus Satellitism:

H. influenzae may grow on blood agar plates if S. aureus is simultaneously seeded. Blood agar - factor X S. aureus provides factor V

HAEMOPHILUS

H. influenzae used to be the leading cause of meningitis in young children, but the use of the highly effective "conjugate" vaccine has greatly reduced the incidence of meningitis caused by this organism. It is still an important cause of upper respiratory tract infections (otitis media, sinusitis, and epiglottitis) and sepsis in children. It also causes pneumonia in adult, particulary in those with chronic obstructive lung disease. H. influenzae is a small gram-negative rod (coccobacillus) with a polysaccharide capsule. It is one of the three important encapsulated pyogens, along with the pneumococcus and the meningococcus. Serologic typing is based on the antigenicity of the capsular polysaccharride. Of the six serotypes, type b causes most of the severe, invasive diseases, such as meningitis and sepsis. The type b capsule is composed of polyribitol phosphate.

Gram-Negative Rods Related to the Respiratory Tract

Haemophilus Bordetella LEGIONELLA

Respiratory tract

Haemophilus, Legionella, Bordetella

HELICOBACTER

Helicobacter pylori causes gastritis and peptic ulcers. Infection with H. pylori is a risk factor for type I gastric carcinoma and is linked to mucosal-associated lymphoid tissue (MALT) lymphomas. Helicobacters are curved gram-negative rods similar in appearance to campylobacters, DIFFERENCE Helicobacters are strongly urease-positive, whereas campylobacters are urease-negative. H. pylori attaches to the mucus-secreting cells of the gastric mucosa. The production of large amounts of ammonia from urea by the organism's urease, coupled with an inflammatory response, leads to damage to the mucosa. Loss of the protective mucus coating predisposes to gastritis and peptic ulcer. The ammonia also neutralizes stomach acid, allowing the organism to survive. The natural habitat of H. pylori is the human stomach, and it is probably acquired by ingestion. However, it has not been isolated from stool, food, water, or animals. Person-to-person transmission probably occurs, because there is clustering of infection within families. The rate of infection with H. pylori in developing countries is very high, a finding that is in accord with the high rate of gastric carcinoma in those countries.

staphylococci Transmission

Humans are the reservoir for staphylococci. The nose is the main site of colonization of S. aureus Hand contact is an important mode of transmission and handwashing decreases transmission. S. aureus is also found in the vagina of approximately 5% of women, which predisposes them to toxic shock syndrome. Additional sources of staphylococcal infection are shedding from human lesions and fomites such as towels and clothing contaminated by these lesions. Disease caused by S. aureus is favored by a heavily contaminated environment (e.g., family members with boils) and a compromised immune system. Reduced humoral immunity, including low levels of antibody, complement, or neutrophils, especially predisposes to staphylococcal infections. Diabetes and intravenous drug use predispose to infections by S. aureus. Patients with chronic granulomatous disease (CGD), a disease characterized by a defect in the ability of neutrophils to kill bacteria, are especially prone to S. aureus infections .

CAMPYLOBACTER ID

If the patient has diarrhea, a stool specimen is cultured on a blood agar plate containing antibiotics that inhibit most other fecal flora. Campy medium or skirrow agar(Skirrow's agar: peptone and soy protein base agar supplemented with lysed horse blood and vancomycin (inhibits Gram-positives), polymyxin B (antifungal), and trimethoprim (broad spectrum). The plate is incubated at 42°C in a microaerophilic atmosphere containing 5% oxygen and 10% carbon dioxide, which favors the growth of C. jejuni. It is identified by failure to grow at 25°C, oxidase positivity, and sensitivity to nalidixic acid. C. intestinalis is confirmed by its failure to grow at 42°C, its ability to grow at 25°C, and its resistance to nalidixic acid.

PATHOGENS OUTSIDE THE ENTERIC TRACT

KLEBSIELLA-ENTEROBACTER-SERRATIA These organisms are usually opportunistic pathogens that cause nosocomial infections, especially pneumonia and urinary tract infections. Klebsiella pneumoniae is an important respiratory tract pathogen outside hospitals as well. K. pneumoniae, Enterobacter cloacae, and Serratia marcescens are the species most often involved in human infections. They are frequently found in the large intestine but are also present in soil and water. These organisms have very similar properties and are usually distinguished on the basis of several biochemical reactions and motility. K. pneumoniae has a very large capsule, which gives its colonies a striking mucoid appearance

LISTERIA MONOCYTOGENES

L. monocytogenes is a small gram-positive rod arranged in V- or L-shaped formations similar to corynebacteria. The organism exhibits an unusual tumbling(Motile at 22 0C but not at 37 0C). L. monocytogenes causes meningitis and sepsis in newborns and immunocompromised adults especially renal transplant patient. It also causes outbreaks of febrile gastroenteritis. L. monocytogenes is a facultative intracellular pathogen that can grow in macrophages,epithelial cells, and cultured fibroblasts. Listeria grows well at cold temperatures. "cold enhancement." Colonies on a blood agar plate produce a narrow zone of beta-hemolysis that resembles the hemolysis of some streptococci. (distinguishes it from the corynebacteria) Listeria uses the cellular machinery to move around inside the host cell: it induces directed polymerization of actin by the ActA transmembrane protein, thus pushing the bacterial cell around. Listeria monocytogenes, for example, encodes virulence genes which are thermoregulated. The expression of virulence factor is optimal at 37 degrees Celsius and is controlled by a transcriptional activator, PrfA, whose expression is thermoregulated by the , PrfA thermoregulated UTR element. At low temperatures, the PrfA transcript is not translated due to structural elements near the ribosome binding site. As the bacteria infect the host, the temperature of the host melts the structure and allows translation initiation for the virulent genes. To invade, Listeria induces macrophage phagocytic uptake by displaying D-galactose in their teichoic acids that are then bound by the macrophage 's polysaccharide receptors . Other important adhesins are the internalins. Once phagocytosed, the bacterium is encapsulated by the host cell's acidic phagolysosome organelle. Listeria, however, escapes the phagolysosome by lysing the vacuole's entire membrane with secreted hemolysin, now characterized as the exotoxin listeriolysin O. The bacteria then replicate inside the host cell's cytoplasm.

LEGIONELLA

L. pneumophila (and other legionellae) causes pneumonia, both in the community and hospitalized immunocompromised patients. The genus is named after the famous outbreak of pneumonia among people attending the American Legion convention in Philadelphia in 1976 (legionnaires' disease). Legionellae are gram-negative rods that stain faintly with the standard Gram stain. They do, however, have a gram-negative type of cell wall, and increasing the time of the safranin counterstain enhances visibility. Legionellae in lung biopsy sections are stain by special methods, such as the Dieterle silver impregnation stain, are used to visualize the organisms. The organism's requirement for a high concentration of iron and cysteine; culture media supplemented with these nutrients will support growth. L. pneumophila causes approximately 90% of pneumonia attributed to legionellae.

FRANCISELLA Laboratory Diagnosis

Laboratory Diagnosis ---special Cysteine-containing medium required for growth is not usually available. Growth on chocolate, Thayer-Martin, and horse blood agar: 1-3 mm, gray-white to bluish-gray with a smooth flat surface at 48-72 hrs The most frequently used diagnostic method is the agglutination test with acute- and convalescent-phase serum samples. Fluorescent-antibody staining of infected tissue can be used if available. Multi-locus Sequence Typing (MLST), which is effective at assigning unknown isolates of F. tularensis.

LEGIONELLA Pathogenesis

Legionellae are associated chiefly with environmental water sources such as air conditioners and water-cooling towers. Out breaks of pneumonia in hospitals have been attributed to the presence of the organism in water taps, sinks, and showers. The portal of entry is the respiratory tract, and pathologic changes occur primarily in the lung. However, in severe cases, bacteremia occurs accompanied by damage to the vascular endothelium in multiple organs, especially the brain and kidneys. The major virulence factor of the organism is lipopolysaccharide (endotoxin). The typical candidate for legionnaires' disease is an older man who smokes and consumes substantial amounts of alcohol. Patients with AIDS, cancer, or transplants (especially renal transplants) or patients being treated with corticosteroids are predisposed to legionella pneumonia, which indicates that cell-mediated immunity is the most important defense mechanism.

Pathogenesis of S.pneumonia

Lipoteichoic acid, which activates complement and induces inflammatory cytokine production, contributes to the inflammatory response and to the septic shock syndrome that occurs in immunocomprised individuals. Pneumococci produce lgA protease that enhances the organism's ability ,to colonize the mucosa of the upper respiratory tract. Pneumococci multiply in tissues and cause inflammation. When they reach alveoli, there is outpouring of fluid and red and white blood cells, resulting in consolidation of the lung.

LISTERIA MONOCYTOGENES Pathogenesis

Listeria infections occur primarily in two clinical settings: (1) in the fetus or newborn as a result of transmission across the placenta or during delivery. (2) in immunosuppressed adults, especially renal transplant patients,on chemotherapy, chronic illness. The organism is distributed worldwide in animals, plants, and soil. From these reservoirs, it is transmitted to humans primarily by ingestion of unpasteurized milk products, undercooked meat, and raw vegetables. Contact with domestic farm animals and their feces is also an important source. In the United States, listeriosis is primarily a food-borne disease associated with eating unpasteurized cheese and delicatessen meats.

Pathogenesis of CAMPYLOBACTER

Low infectious dose (as few as 500) Adhesion, motility,and invasion. Invades mucosa of colon, destroying mucosal surface;blood and pus in stools inflammatory diarrhea. Multiple genome sequences have defined conserved and hypervariable loci in the C. jejuni genome. Interaction of C. jejuni with eukaryotic cells results in numerous signal transduction changes and release of proinflammatory cytokines Rarely penetrates to cause septicemia.

Clinical Importance of Staphylococcus infection

MRSA-nafcillin resistance staphylococcus aureus Strains of S. aureus with intermediate resistance (so-called VISA strains) Importance : One of the emerging hospital acquired infection or nosocomial infection (infection acquiring during stay in hospital after 24 hours) Especially in: 1. ICU (Intensive Care Unit) where patient stay for longer time, already disturb immune system/numerous device 2. Neonatal ward: causing sepsis. Carrier: healthy and unhealthy carrier Nasal carrier (doctor, nurse, attendant) Precaution: Isolation of the patient Diagnosis: In case of sepsis → blood culture

BACTEROIDES & PREVOTELLA

Members of the genus Bacteroides are the most common cause of serious anaerobic infections, eg, sepsis, peritonitis, and abscesses. Bacteroides fragilis is the most frequent pathogen. Bacteroides and Prevotella species are part of the normal flora, infections are endogenous, usually a rising from a break in a mucosal surface, and are not communicable. These organisms cause a variety of infections, such as local abscesses at the site of a mucosal break, metastatic abscesses by hematogenous spread to distant organs, or lung abscesses by aspiration of oral flora. Predisposing factors such as surgery, trauma, and chronic disease play an important role in pathogenesis. Local tissue necrosis, impaired blood supply, and growth of facultative anaerobes at the site contribute to anaerobic infections. The polysaccharide capsule of B. fragilis is an important virulence factor. Many of the symptoms of Bacteroides sepsis resemble those of sepsis caused by bacteria with endotoxin, but the lipopolysaccharide of Bacteroides is chemically different (lipid A lack phosphate )from the typical endotoxin. Bacteroides species can be isolated anaerobically on blood agar plates containing kanamycin and vancomycin Identified by biochemical reactions (eg, sugar fermentations)

Methicillin-resistant S. aureus (MRSA) or nafcillin-resistant S. aureus (NRSA).

More than 90% of S. aureus strains contain plasmids that encode -lactamase, the enzyme that degrades many, but not all, penicillins. Some strains of S. aureus are resistant to the -lactamase-resistant penicillins, such as methicillin and nafcillin, by virtue of changes in the penicillin-binding protein in their cell membrane. These strains are commonly known as methicillin-resistant S. aureus (MRSA) or nafcillin-resistant S. aureus (NRSA). Rare strains called vancomycin-intermediate S. aureus (VISA), with reduced sensitivity to vancomycin, have emerged, as having strains fully resistant to vancomycin.

Gamma (enterococcus)

Most strains remain susceptible to penicillin, ampicillin, and vancomycin. DRUG RESISTANCE: Strains resistant to β-lactams, aminoglycosides and, increasingly, vancomycin . Vancomycin-Resistant Enterococcus faecium in Hospitalized Children quinupristin-dalfopristin, linezolid, daptomycin. Strep.bovis clinically significant, because strains that cause bacteremia have a prominent association with occult malignancy of the colon.

N. meningitidis (meningococci)

N. meningitidis, one of the most virulent human pathogens, causative agent of meningitis. Humans are the only natural hosts for meningococci. The organisms are transmitted by airborne droplets; Meningococci are divided into at least 13 serologic groups on the basis of the antigenicity of their capsular polysaccharides.

S. pneumoniae

NA Alpha Bile-soluble; inhibited by optochin

Viridans group

NA Alpha Not bile-soluble; not inhibited by optochin

S. pneumoniae tests

On blood agar: Alpha haemolysis Biochemical reactions: Ferments several sugars, forming acid only fermentation is tested in Hiss's serum water or serum agar slopes Fermentation of inulin by Pneumococci is a useful test for differentiating them from streptococci. Pneumococci are bile soluble. few drops of 10% sodium deoxycholate solution are added to 1 ml of overnight broth culture. The culture clears due to the lysis of the cocci.

SALMONELLA 3 vaccine

Oral ty21a Parenteral heat killed S.typhi (no longer used) Parenteral ViCPS polysaccharide capsular vaccine

Yersina outer proteins

Other factors that contribute to the extraordinary pathogenicity of Y. pestis are a group of virulence factors collectively called Yops (Yersina outer proteins). These are injected into the human cell via type III secretion systems (Type III secretion systems, which are found in various gram-negative organisms, are specialized for the export of virulence factors delivered directly to host cells) and inhibit phagocytosis and cytokine production by macrophages and neutrophils. For example, one of the Yops proteins (YopJ) is a protease that cleaves two signal transduction pathway proteins required for the induction of tumor necrosis factor synthesis. This inhibits the activation of our host defenses and contributes to the ability of the organism to replicate rapidly within the infected individual.

PSEUDOMONAS Clinical Findings

P. aeruginosa can cause infections virtually anywhere in the body, but urinary tract infections, pneumonia (especially in cystic fibrosis patients), and wound infections (especially burns) predominate. From these sites, the organism can enter the blood, causing sepsis. The bacteria can spread to the skin, where they cause black, necrotic lesions called ecthyma gangrenosum. It is an important cause of endocarditis in intravenous drug users. Severe external otitis (malignant otitis externa) and other skin lesions (eg, folliculitis) occur in users of swimming pools and hot tubs in which the chlorination is inadequate. P. aeruginosa is the most common cause of osteochondritis of the foot in those who sustain puncture wounds through the soles of gym shoes. Corneal infections caused by P. aeruginosa are seen in contact lens users.

PSEUDOMONAS Laboratory Diagnosis

P. aeruginosa grows as non-lactose- fermenting (colorless) colonies on MacConkey's or EMB agar. It is oxidase-positive. A typical metallic sheen of the growth on TSI agar, coupled with the blue-green pigment on ordinary nutrient agar and a fruity aroma, is sufficient to make a presumptive diagnosis

PSEUDOMONAS Lab Diagnosis

P. aeruginosa produces two pigments useful in clinical and laboratory diagnosis: (1) pyocyanin, which can color the pus in a wound blue; and (2) pyoverdin (fluorescein), a yellow-green pigment that fluoresces under ultraviolet light, a property that can be used in the early detection of skin infection in burns patients. In the laboratory, these pigments diffuse into the agar, imparting a blue-green color that is useful in identification. P. aeruginosa is the only species of Pseudomonas that synthesizes pyocyanin.

Haemophilus test and treatment

Particle agglutination test: latex particles coated with anti H. influenzae type b antibody are most frequently used. Treatment Ampicillin plus chloramphenicol or Thrid generation cephalosporin. Prophylaxis: The vaccine contains the capsular polysaccharide of H. influenzae type b conjugated to diphtheria toxoid or other carrier protein.

PASTEURELLA

Pasteurella multocida causes wound infections associated with cat and dog bites. Is a short, encapsulated gram-negative rod that exhibits bipolar staining. The organism is part of the normal flora in the mouths of many animals, particularly domestic cats and dogs, and is transmitted by biting. Capsule and endotoxin is present in the cell wall are a virulence factor. A rapidly spreading cellulitis at the site of an animal bite is indicative of P. multocida infection. The incubation period is brief, usually less than 24 hours. Osteomyelitis can complicate cat bites in particular, because cats' sharp, pointed teeth can implant the organism under the periosteum. Laboratory Diagnosis :-culture of a sample from the wound site. Treatment :-Penicillin G is the treatment of choice. People who have been bitten by a cat should be given ampicillin to prevent P. multocida infection. Animal bites, especially cat bites, should not be sutured.

N. gonorrhoeae Determinants of pathogenicity

Pili → helps in bacterial adherence to host cells. Two virulence factors in the cell wall are a.LOS lipooligosaccharide (a modified form of endotoxin) and the b. outer membrane proteins. Outer membrane protein I (por ) → associated with serum resistance, invasion and disseminated infection. Outer membrane protein II → opa proteins (opacity) → primary virulence factors of N. gonorrhoeae, mediates attachment to mucosal cells and have antiphagocytic properties. Outer membrane protein III-protects bacteria from bactericidal antibodies. Peptidoglycan , IgA protease, Β-lactamase Antibodies directed against these bacterial components are bactericidal in the presence of complement. antigenic variation is present ― hence no immunity. Persons with a deficiency of the late-acting complement components (C6-C9) are at risk for disseminated infections, as are women during menses and pregnancy) Disseminated infections usually arise from asymptomatic infections.

S. pneumoniae

Pneumococci are normal inhabitants of the upper respiratory tract of human beings. They are the single most prevalent bacterial agent in pneumonia(community acquired ). particularly young and old after damage to upper respiratory tract *e.g. following viral infection bacteremia meningitis middle ear infections (otitis media). Pneumococci are gram-positive lancet-shaped cocci arranged in pairs (diplococci) or short chains. (The term "lancet-shaped" means that the diplococci are oval they are lysed by bile or deoxycholate and their growth is inhibited by optochin.

K. pneumoniae

Pneumonia caused by Klebsiella, which produces a thick, bloody sputum ("currant-jelly" sputum) and can progress to necrosis and abscess formation. Urinary tract infection - catheter-related from fecal contaimation. Septicemia .

BRUCELLOSIS Prevention and treatment

Prolonged treatment with rifampin, or drugs which penetrates cells with streptomycin or tetracyclin is used to treat human Brucella infections. The control measures include animal vaccination and avoidance of infected material.

PSEUDOMONAS

Pseudomonas aeruginosa causes infections (eg, sepsis, pneumonia, and urinary tract infections) primarily in patients with lowered host defenses. (Pseudomonas aeruginosa is also known as Burkholderia aeruginosa.) Pseudomonas cepacia (renamed Burkholderia cepacia) and Pseudomonas maltophilia now called Stenotrophomonas maltophilia(oxidase -negative ) also cause these infections, but much less frequently. Pseudomonas pseudomallei, the cause of melioidosis, Pseudomonas are gram-negative rods That resemble the members of the Enterobacteriaceae but differ in that they are strict aerobes; ie, they derive their energy only by oxidation of sugars rather than by fermentation. Because they do not ferment glucose, they are called non-fermenters, in contrast to the members of the Enterobacteriaceae, which do ferment glucose. Oxidation involves electron transport by cytochrome c; ie, they are oxidase-positive. Pseudomonas are able to grow in water containing only traces of nutrients, eg, tap water, and this favors their persistence in the hospital environment. P. aeruginosa and P. cepacia have a remarkable ability to with stand disinfectants; this accounts in part for their role in hospital-acquired infections. They have been found growing in hexachlorophene-containing soap solutions, in antiseptics, and in detergents.

Laboratory diagnosis

Rapid diagnostic tests----latex agglutination Culture and isolation Quellung reaction-using antisera capsule "fixed" visible microscopically. Therapy S. pneumoniae most strains susceptible to penicillin resistance is common

Nonsuppurative sequelae

Rheumatic fever Glomerulonephritis Rheumatic fever follows primary infection by group A β. Haemolytic streptococci. The fever and glomerulonephritis result from cross-reactive autoimmunity triggered by the host's response to the microbe or to tissue damage inflicted by streptococcal toxins and extracellular factor. Rheumatic fever follows a streptococcal throat infection and characterized by carditis, (myocardium, heart valves), arthritis (large joints), chorea (uncontrolled involuntary movements).

Coagulase test

S. aureus produces coagulase, an enzyme like protein that clots by activating prothrombin to form thrombin . Thrombin then catalyzes the activation of fibrogen to form the fibrin clot in oxalated or citrated plasma. Procedure: 0.5 ml of 1 in 10 dilution of rabbit plasma is taken + 0.5 ml of the inoculum If plasma develop a lump -- +ve (S. aureus.) If plasma develop liquid -- -ve (S. epidermis)

Clinical Findings Enterobacter and Serratia

S. marcescens produces red-pigmented colonies. Urinary tract infections and pneumonia are the usual clinical entities associated with these three bacteria, but bacteremia and secondary spread to other areas such as the meninges occur.

Cell wall of S.aureus

Several important components and antigens. 1).Protein A. Is the major protein in the cellwall 2).Teichoic acids . 3).S.aureus have polysaccharide microcapsule which prevents phagocytosis. 4).Have a surface receptors for specific bacteriophage 5). The peptidoglycan of S. aureus has endotoxin-like properties; (1) Protein A is the major protein in the cell wall. It is an important virulence factor because it binds to the Fc portion of IgG at the complement-binding site, thereby preventing the activation of complement. As a consequence, no C3b is produced, and the opsonization and phagocytosis of the organisms are greatly reduced. (2) Teichoic acids are polymers of ribitol phosphate. They mediate adherence of the staphylococci to mucosal cells and play a role in the induction of septic shock. (3) Surface receptors for specific staphylococcal bacteriophages permit the "phage typing" of strains for epidemiologic purposes. Teichoic acids make up part of these receptors. (4) Polysaccharide capsule is also an important virulence factor. Most strains of S. aureus are coated with a small amount of polysaccharide capsule (microcapsule) that is antiphagocytic. There are 11 serotypes based on antigenicity of the capsular polysaccharide. (5) The peptidoglycan of S. aureus has endotoxin- like properties; ie, it can stimulate macrophages to produce cytokines and can activate the complement and coagulation cascades. This explains the ability of S. aureus to cause the clinical findings of septic shock yet not possess endotoxin.

Shigella Pathogenesis

Shiga toxin: Produced by S. dysenteriae,type 1 Three activities:neurotoxic,cytotoxic,enterotoxic AB component toxin is internalized in human cells; inhibits protein synthesis by clipping 60 ribosomal subunit.

PATHOGENS PRIMARILY WITHIN THE ENTERIC TRACT

Shigella species cause enterocolitis (dysentery). Shigellae are non-lactose-fermenting, gram-negative rods that can be distinguished from salmonellae by three criteria: they produce no gas from the fermentation of glucose, they do not produce H2S, and they are nonmotile. All shigellae have O antigens (polysaccharide) in their cell walls, and these antigens are used to divide the genus into four groups: A, B, C, and D.

Pathogenesis & Epidemiology Shigella

Shigellae are the most effective pathogens among the enteric bacteria. They have a very low ID50. Shigellosis is only a human disease, ie, there is no animal reservoir. The organism is transmitted by the fecal-oral route. The four F's--fingers, flies, food, and feces-are the principal factors in transmission. Food- borne outbreaks out number water-borne outbreaks by 2 to 1. Outbreaks occur in day-care nurseries and in mental hospitals, where fecal-oral transmission is likely to occur. Shigella, which cause disease almost exclusively in the gastrointestinal tract, produce bloody diarrhea (dysentery) by invading the cells of the mucosa of the distal ileum and colon. Local inflammation accompanied by ulceration occurs, but the organisms rarely penetrate through the wall or enter the bloodstream, unlike salmonellae. Although some strains produce an enterotoxin (called Shiga toxin), invasion is the critical factor in pathogenesis. Endotoxin triggers inflammation. No H antigens . Shigellae invade M cells (membrane ruffling and macropinocytosis); get into the cytoplasm,replicate and then polymerize actin jet trails to go laterally without going back out into the extracellular milieu. This produces very shallow ulcers and rarely causes invasion of blood vessels

Yersinia pestis Laboratory Diagnosis

Smear and culture of blood or pus from the bubo is the best diagnostic procedure. Great care must be taken by the physician during aspiration of the pus and by laboratory workers doing the culture not to create an aerosol that might transmit the infection. Giemsa or Wayson stain reveals the typical safety-pin appearance of the organism better than does Gram stain. Fluorescent-antibody staining can be used to identify the organism in tissues. A rise in antibody titer to the envelope antigen can be useful retrospectively.

ENTEROBACTERIACEAE Laboratory Diagnosis

Specimens are usually inoculated onto two media, a Blood agar plate and a selective differential medium such as MacConkey's agar or eosin-methylene blue (EMB) agar. is based on lactose fermentation, which is the most important metabolic criterion used in the identification of these organisms On these media, the non-lactose fermenters, eg, Salmonella and Shigella, form colorless colonies, whereas the lactose fermenters, eg, E. coli, form colored colonies. The selective effect of the media in suppressing unwanted gram-positive organisms is exerted by bile salts or bacteriostatic dyes in the agar. Motility Some of these organisms is their motility, which is dependent on the presence of flagella. Proteus species are very motile and characteristically swarm over the blood agar plate, obscuring the colonies of other organisms. Motility is also an important diagnostic criterion in the differentiation of Enterobacter cloacae, which is motile, from Klebsiella pneumoniae, which is nonmotile.

Laboratory Diagnosis

Specimens suspected of containing enteric gram-negative rods, such as E. coli, are grown initially on a blood agar plate and on a differential medium, such as EMB agar or MacConkey's agar. E. coli, which ferments lactose, forms pink colonies, (1) it produces indole from tryptophan, (2) it decarboxylates lysine, (3) it uses acetate as its only source of carbon, and (4) it is motile. E. coli O157:H7 does not ferment sorbitol, which serves as an important criterion that distinguishes it from other strains of E. coli..

Erysipelas

Spreading infections of the skin or mucous membranes, are usually seen on the face but now more commonly on leg.( D.D Erysipelothrix rhusiopathiae)

LEGIONELLA Laboratory Diagnosis

Sputum Gram stains reveal many neutrophils (leucocytosis of 25,000 cells/mm3, but no bacteria. The organism fails to grow on ordinary media in a culture of sputum or blood, but it will grow on Buffered charcoal-yeast agar, a special medium supplemented with iron and cysteine. Diagnosis usually depends on a significant increase in antibody titer in convalescent- phase serum by the indirect immunofluorescence assay. Detection of L. pneumophila antigens in the urine is a rapid means of making a diagnosis. If tissue is available, it is possible to demonstrate Legionella antigens in infected lung tissue by using fluorescent-antibody staining.

Resistance

Staphylococci are among the more resistant of non-sporing bacteria. 1. Can tolerate temperature 60ofor 30 minutes therefore the thermal death point is 62o for 30 minutes 2. Some strains grow in the presence of 10-15% Nacl - these factors have significance in food preservation 3. Drug resistant: staphylococcus originally it was sensitive to penicillin in pre- antibiotics era. Later during the antibiotic are due to indiscriminate use of the drug in hospital. They emerged the penicillin resistance strains methicillin resistance strain.

Str. agalactiae

Str. Agalactiae: Normal flora of humans and other mammals and may be isolated in clinical specimens from diseased human tissue. Group B streptococcus (GBS) has assumed great clinical importance as the single most common cause of neonatal meningitis in the west & also causes puerperal, wound and skin infections and endocarditis. Group B streptococcus - Normal flora of the vagina. It can be transferred to the infant during delivery. In some newborns, these bacteria become part of normal flora without infection, but infants with inadequate phagocytic defenses or deficient passive immunity are vulnerable forms of clinical disease

PSEUDOMONAS pathogenesis

Strains of P.aeruginosa isolated from cystic fibrosis patients have a prominent slime layer (glycocalyx), which gives their colonies a very mucoid appearance. The slime layer mediates adherence of the organism to mucous membranes of the respiratory tract and prevents antibody from binding to the organism. P. aeruginosa is found chiefly in soil and water, although approximately 10% of people carry it in the normal flora of the colon. It is found on the skin in moist areas and can colonize the upper respiratory tract of hospitalized patients. Its ability to grow in simple aqueous solutions has resulted in contamination of respiratory therapy and anesthesia equipment, intravenous fluids, and even distilled water. P. aeruginosa is primarily an opportunistic pathogen that causes infections in hospitalized patients, eg, those with extensive burns, in whom the skin host defenses are destroyed; in those with chronic respiratory disease (eg, cystic fibrosis), in whom the normal clearance mechanisms are impaired; in those who are immunosuppressed; in those with neutrophil counts of less than 500/µL; and in those with indwelling catheters. It causes 10-20% of hospital-acquired infections and, in many hospitals, is the most common cause of gram- negative nosocomial pneumonia.

Streptococcus viridans

Strep. Viridans are the most numerous and widespread residents of the oral cavity (gingival, cheeks, tongue, saliva) and are also found in the nasopharynx, genital tract, and skin. These species can cause serious systemic infections their entrance into tissue usually occurs through dental or surgical instumentation. The most important complication of all viridans streptococcal infections is sub acute endocarditis.

STREPTOCOCCAL

Streptococci cause a wide variety of infections. ФS. pyogenes (group A β-h-streptococcus) is the leading bacterial cause of pharyngitis and cellulitis. It is also the inciting factor of two important immunologic diseases, namely, rheumatic fever and acute glomerulonephritis. Ф Streptococcus agalactiae (group B streptococcus) is the leading cause of neonatal sepsis and meningitis. Ф Enterococcus faecalis is an important cause of hospital-acquired urinary tract infections and endocarditis. (Ab resistence) Ф Viridans group streptococci are the most common cause of endocarditis. Ф Streptococcus bovis also causes endocarditis.

FRANCISELLA Treatment

Streptomycin is the drug of choice. Prevention Prevention involves avoiding both being bitten by ticks and handling wild animals.

Clostridium tetani Clinical disease

Strong muscle spasms (spastic paralysis, tetany). lockjaw (trismus) masseter muscles due to rigid contraction of the jaw muscles, which prevents the mouth from opening; a characteristic grimace known as risus sardonicus; an exaggerated reflexes. Opisthotonos, a pronounced arching of the back due to spasm of the strong extensor muscles of the back, is often seen.

Pneumonia

Symptoms: Chills, rapid breathing and fever. pain in the chest wall, cyanosis (due to compromised 02 exchange) Cough - rusty colored (blood). Complication: Pneumococcal bacteremia and meningitis Meningitis: In children pneumococci also causes meningitis one route of entry is through respiratory tract and other by otitis media (middle ear infections) otitis media is the third most common childhood disease in the United States.

BRUCELLOSIS (undulant fever) body response

The bacteria are engulfed by neutrophils and monocytes and localize in the regional lymph nodes, where they proliferate intracellularly. If the Brucella organisms are not destroyed or contained in the lymph nodes, the bacteria are released from the lymph nodes resulting in septicemia. The organisms migrate to other lympho-reticular organs (spleen, bone marrow, liver, testes) producing granulomas and/or micro abscesses

Bile solubility test

The bile solubility test is based on the presences of an autolytic amidase that cleaves the bond between alanine and muramic acid in the peptidoglycan. The amidase is activated by surface active agents such as bile or bile salts, resulting in lysis of the organisms. The test should be carried out at neutral pH using deoxycholate and live young cells in saline suspension.

LEGIONELLA Clinical Findings

The clinical picture can vary from a mild influenza like illness to a severe pneumonia accompanied by mental confusion, nonbloody diarrhea, proteinuria, and microscopic hematuria. Although cough is a prominent symptom, sputum is frequently scanty and nonpurulent. Hyponatremia (serum sodium _< 130 mEq/L) is an important laboratory finding. Most cases resolve spontaneously in 7-10 days, but in older or immunocompromised patients, the infection can be fatal. Legionellosis is an atypical pneumonia and must be distinguished from other similar pneumonias such as Mycoplasma pneumonia, viral pneumonia, psittacosis, and Q fever. Pontiac fever is a mild, flu like form of Legionella infection that does not result in pneumonia. The name "Pontiac" is derived from the city in Michigan that was the site of an outbreak in 1968.

INTESTINAL TRACT INFECTION

The first step is the adherence of the organism to the cells of the jejunum and ileum by means of pili that protrude from the bacterial surface. Once attached, the bacteria synthesize enterotoxins (exotoxins that act in the enteric tract), which act on the cells of the jejunum and ileum to cause diarrhea. Enterotoxigenic strains of E. coli can produce either or 'both of two enterotoxins. (1) The high-molecular-weight, heat-labile toxin (LT) acts by stimulating adenylate cyclase. Both LT and cholera toxin act by catalyzing the addition of adenosine diphosphate-rlbose, a process called ADP-ribosylation, to the G protein that stimulates the cyclase. The resultant increase in intracellular cyclic adenosine monophosphate (AMP) concentration stimulates cyclic AMP- dependent protein kinase, causing an outpouring of fluid, potassium, and chloride from the enterocytes. (2) The other enterotoxin is a low-molecular-weight, -'heat-stable toxin (ST), which stimulates guanylate cyclase. Certain enterohemorrhagic strains of E. coli, O157:H7 serotype, also cause bloody diarrhea but do not cause inflammation; therefore, no neutrophils are found in the stool. These O157:H7 strains produce verotoxin, so called because it is toxic to Vero (monkey) cells in culture and presumably to the cells lining the colon. These toxins are also called Shiga-like toxins because they are very similar to those produced by Shigella species. Vero- toxin acts by removing an adenine from the large (28S) ribosomal RNA, thereby stopping protein synthesis. These O157:H7 strains are associated with out- breaks of diarrhea following ingestion of undercooked hamburger at fast-food restaurants Also, direct contact with animals, eg, visits to farms and petting zoos, have resulted in bloody diarrhea caused by O 157:H7 strains. Some patients with bloody diarrhea caused by O 157:H7 strains also have a life-threatening complication called hemolytic-uremic syndrome, which occurs when verotoxin enters the bloodstream. This syndrome consists of hemolytic anemia, thrombocytopenia, and acute renal failure. The hemolytic anemia and renal failure occur because there are receptors for verotoxin on the surface of the endothelium of small blood vessels and on the surface of kidney epithelium. Death of the endothelial cells of small blood vessels results in a microangiopathic hemolytic anemia in which the red cells passing through the damaged area become grossly distorted (schistocytes) and then lyse. Thrombocytopenia occurs because platelets adhere to the damaged endothelial surface

Triple Sugar Iron Agar

The important components of this medium are ferrous sulfate and the three sugars glucose, lactose, and sucrose. The glucose is present in one-tenth the concentration of the other two sugars. The medium in the tube has a solid, poorly oxygenated area on the bottom, called the butt, and an angled, well-oxygenated area on top, called the slant. The organism is inoculated into the butt and across the surface of the slant, The interpretation of the test results is as follows: (1) If lactose (or sucrose) is fermented, a large amount of acid is produced, which turns the phenol red indicator yellow both *********** and on the slant. Some organisms generate gases, which produce bubbles ***********. (2) If lactose is not fermented but the small amount of glucose is, the oxygen-deficient butt will be yellow, but on the slant the acid will be oxidized to CO2 and H20 by the organism and the slant will be red (neutral or alkaline). (3) If neither lactose nor glucose fermented, both the butt and the slant will be red.The slant can become a deeper red-purple (more alkaline) as a result of the production of ammonia from the oxidative deamination of amino acids. (4) If H2S is produced, the black color of ferrous sulfide is seen

Urea Agar

The important components of this medium are urea and the pH indicator phenol red. If the organism produces urease, the urea is hydrolyzed to NH3 and co2. Ammonia turns the medium alkaline, and the color of the phenol red changes from light orange to reddish purple. The important organisms that are urease-positive are Proteus species and Klebsiella pneumoniae.

Bordetella Complication of vaccine

The killed vaccine is no longer recommended in the United States because it is suspected of causing various side effects, including postvaccine encephalopathy at a rate of about one case per million doses administered. The killed vaccine is in use in many countries other than the United States.

Medical importance staph

The medical importance of staphylococcus are: Staphylococcus aureus (pyogens) Staphylococcus epidermidis (albus) Staphylococcus saprophyticus. Staphylococcus epidermidis can cause endocarditis and prosthetic joint infections. Staphylococcus saprophyticus causes urinary tract infections.

Clostridium tetani Pathogenesis

The organism begins to elaborate toxin, which binds to peripheral nerve endings, is internalized, and travels via retrograde intra- axonal transport to the spinal cord, where it interferes with the activity of the inhibitory interneurons. C. tetani produces a potential neurotoxin,tetanospasmin inhibits the release of inhibitory transmitters, causing spastic paralysis

FRANCISELLA Pathogenesis

The organism enters through the skin, forming an ulcer at the site in most cases. It then localizes to the cells of the reticuloendothelial system, and granulomas are formed. Caseation necrosis and abscesses can also occur. Symptoms are caused primarily by endotoxin. Clinical Findings:- Presentation can vary from sudden onset of an influenza like syndrome to prolonged onset of a low-grade fever and adenopathy. Approximately 75% of cases are the "ulceroglandular" type, in which the site of entry ulcerates and the regional lymph nodes are swollen and painful. Other, less frequent forms of tularemia include glandular, oculoglandular, typhoidal, gastrointestinal, and pulmonary. Disease usually confers lifelong immunity

Pathogenesis & Epidemiology PROTEUS-PROVIDENCIA-MORGANELLA

The organisms are present in the human colon as well as in soil and water. Their tendency to cause urinary colon and to colonization of the urethra, especially in women. The vigorous motility of Proteus organisms may contribute to their ability to invade the urinary tract. Production of the enzyme urease is an important feature of the pathogenesis of urinary tract infections by this group. Urease hydrolyzes the urea in urine to form ammonia, which raises the pH and encourages the formation of stones (calculi) called "struvite" composed of magnesium ammonium phosphate. Stones in the urinary tract obstruct urine flow, damage urinary epithelium, and serve as a nidus for recurrent infection by trapping bacteria within the stone. Because alkaline urine also favors growth of the organisms and more extensive renal damage, treatment involves keeping the urine at a low pH.

Fitz-Hugh-Curtis syndrome

The symptoms are an acute onset, upper right-quadrant abdominal pain and tenderness aggravated by breathing, coughing or movement, and referred to the right shoulder following an episode of PID. Enlargement of the liver with hepatic tenderness and right upper quadrant pain. Laparoscopy may reveal "violin string" adhesions. Fitz-Hugh-Curtis

The Indole Test

The test organism is inoculated into tryptone broth, a rich source of the amino acid tryptophan. Indole positive bacteria such as Escherichia coli produce tryptophanase, an enzyme that cleaves tryptophan, producing indole and other products. When Kovac's reagent (p-dimethylaminobenzaldehyde) is added to a broth with indole in it, a dark pink color develops. The indole test must be read by 48 hours of incubation because the indole can be further degraded if prolonged incubation occurs. The acidic pH produced by Escherichia coli limits its growth.

Toxic shock syndrome

The toxin enters the bloodstream, causing a toxemia. Blood cultures typically do not grow S. aureus. TSST is a superantigen and causes toxic shock by stimulating the release of large amounts of IL-1, IL-2, and tumor necrosis factor (TNF) Approximately 5-25% of isolates of S. aureus carry the gene for TSST. Toxic shock occurs in people who do not have antibody against TSST.

Beta-hemolytic streptococci

There are two important antigens of beta-hemolytic streptococci: (1) C carbohydrate determines the group of beta- hemolytic streptococci. It is located in the cell wall. C substance and cytoplasmic membrane antigens - plays a important pathogenic role in the nonsuppurative sequelae of streptococcal infections. These molecules are structurally similar to human tissue antigens, particularly those of heart, kidneys and joints. Consequently, an immune response directed against group A strep may become auto-reactive and contributes to development of endocarditis, glomerulonephritis, or arthritis. (2) M protein is the most important virulence factor and determines the type of group A beta-hemolytic streptococci. It protrudes from the outer surface of the cell and interferes with ingestion by phagocytes; ie, it is antiphagocytic. Antibody to M protein provides type- specific immunity. There are approximately 100 serotypes based on the M protein, which explains why multiple infections with S. pyogenes can occur.

Clinical Findings K. pneumoniae

There are two other species of Klebsiella that cause unusual human infections rarely seen in the United States. Klebsiella ozaenae is associated with atrophic rhinitis, and Klebsiella rhinoscleromatis causes a destructive granuloma of the nose and pharynx.

Prevention of B. pertusis

There are two vaccines: 1.an acellular vaccine containing purified proteins from the organism and 2. a killed vaccine containing inactivated B. pertussis organisms. The acellular vaccine consisting of five antigens purified from the organism is now used in the United States. The main immunogen in this vaccine is inactivated pertussis toxin (pertussis toxoid). The toxoid in the vaccine is pertussis toxin that has been inactivated genetically by introducing two amino acid changes that eliminates its ADP-ribosylating activity but retains its antigenicity. It is the first vaccine to contain a genetically inactivated toxoid. The other pertussis antigens in the vaccine are filamentous hemagglutinin, pertactin, and fimbrae types 2 and 3. The acellular vaccine has fewer side effects than the killed vaccine. The pertussis vaccine is usually given combined with diphtheria and tetanus toxoids (DTaP) in three doses beginning at 2 months of age. A booster at 12-15 months of age and another at the time of entering school are recommended. Because outbreaks have occurred during the years 2000-2003, especially among teenagers, a booster for those between 10 and 18 years old is recommended. This vaccine, called Boostrix, contains diphtheria and tetanus toxoids also. A second vaccine called Adacel also contains diphtheria and tetanus toxoids and is approved for use not only in adolescents but in adults up to the age of 64.

PROTEUS-PROVIDENCIA-MORGANELLA

These organisms primarily cause urinary tract infections, both community and hospital-acquired. These gram-negative rods are distinguished from other members of the Enterobacteriaceae by their ability to produce the enzyme phenylalanine deaminase. In addition, they produce the enzyme urease, which cleaves urea to form NH 3 and CO 2. Certain species are very motile and produce a striking swarming effect on blood agar, characterized by expanding rings (waves) of organisms over the surface of the agar. Phenylalanine deaminase medium tests the ability of an organism to produce the enzyme deaminase. This enzyme removes the amine group from the amino acid phenylalanine and releases the amine group as free ammonia. As a result of this reaction, phenylpyruvic acid is also produced. When 10% ferric chloride is added to phenylalanine medium inoculated with Proteus mirabilis, the presence of phenylpyruvic acid causes the media to turn dark green. This is a positive result. When 10% ferric chloride is added to phenylalanine deaminase medium inoculated with Staphylococcus aureus, no color change occurs. This is a negative result. The cell wall O antigens of certain strains of Proteus, such as OX-2, OX-19, and OX-K, cross-react with antigens of several species of rickettsiae. These Proteus antigens can be used in laboratory tests to detect the presence of antibodies against certain rickettsiae in patients' serum. This test, called the Weil-Felix reaction

Laboratory Diagnosis PROTEUS-PROVIDENCIA-MORGANELLA

These organisms usually are highly motile and produce a "swarming" overgrowth on blood agar. Growth on blood agar containing phenylethyl alcohol inhibits swarming, thus allowing isolated colonies of Proteus and other organisms to be obtained. They produce non-lactose-fermenting (colorless) colonies on Mac conkey . P.mirabilis is indole-negative, P.vulgaris are indole-positive,

Cultural Characteristics

They grow on ordinary media at optimum temp 37* and pH 7.4 - 7.6 They are aerobes and facultative anaerobes Nutrient agar: The colonies are large, round,opaque and easily emulsified. Most strains produce carotenoid pigment called staphyloxanthin that imparts a golden color to its colonies. S. aureus - golden yellow pigment ( this pigments inactivates superoxides and other oxygen reactive species with in neutrophils) S. albus - white colonies

Str. agalactiae in adult

This organism also causes such infections as pneumonia, endocarditis, arthritis, and osteomyelitis in adults. Postpartum endometritis also occurs. Diabetes is the main predisposing factor for adult group B streptococcal infections. Lab finding:-Bacitracin-resistant Hippurate hydrolyzed - test that's done to identify this pathogen

Scarlet fever

Throat infection may lead to scarlet fever. Scarlet fever caused by S. pyogens carrying a prophage that codes for erythrogenic toxin. Systemic spread of this toxin result in high fever and a bright red, diffuse rash over the face, trunk, inner arms and legs, and even the tongue (strawberry tongue) within 10 days the rash and fever usually disappear, often accompanied by desquamation of the epidermis. Many a time pharyngitis and scarlet fever are mild and uncomplicated but occasionally they elicit an inflammatory reaction that leads to rheumatic fever.

Clostridium botulinum

Transmission :-Spores, widespread in soil, contaminate vegetables and meats. When these foods are canned or vacuum-packed without adequate sterilization, spores survive and germinate in the anaerobic environment. Toxin is produced within the canned food and ingested preformed. The highest-risk foods are (1) alkaline vegetables such as green beans, peppers, and mushrooms and (2) smoked fish. The toxin is relatively heat-labile; it is inactivated by boiling for several minutes. Thus, disease can be prevented by sufficient cooking.

Yersinia pestis treatment & prevention

Treatment :- A combination of streptomycin and tetracycline, although streptomycin alone can be used. Prevention :-Controlling the spread of rats in urban areas, preventing rats from entering the country A patient with plague must be placed in strict isolation (quarantine) for 72 hours after antibiotic therapy is started. Only close contacts need receive prophylactic tetracycline, but all contacts should be observed for fever. Reporting a case of plague to the public health authorities is mandatory. A vaccine consisting of formalin-killed organisms provides partial protection against bubonic but not pneumonic plague.

Vibrioparahaemolyticus

V. parahaemolyticus is a marine organism transmitted by ingestion of raw or undercooked seafood, especially shellfish such as oysters. It is a major cause of diarrhea in Japan, where raw fish is eaten in large quantities, but is an infrequent pathogen in the United States, although several outbreaks have occurred aboard cruise ships in the Caribbean. an enterotoxin similar to choleragen is secreted and limited invasion sometimes occurs. The clinical picture caused by V. parahaemolyticus varies from mild to quite severe watery diarrhea, nausea and vomiting, abdominal cramps, and fever. The illness is self-limited, lasting about 3 days. V. parahaemolyticus is distinguished from V. cholerae mainly on the basis of growth in NaCl: V. parahaemolyticus grows in 8% NaCl solution (as befits a marine organism), whereas V. cholerae does not. No specific treatment is indicated, because the disease is relatively mild and self-limited. Disease can be prevented by proper refrigeration and cooking of seafood. V. parahaemolyticus serotype O6:K18,

Vibrio

Vibrio cholerae, the major pathogen in this genus, is the cause of cholera. Vibrio parahaemolyticus causes diarrhea associated with eating raw or improperly cooked seafood. Vibrio vulnificus causes cellulitis and sepsis. Vibrios are curved, comma-shaped gram-negative rods. V. cholerae is divided into two groups according to the nature of its O cell wall antigen. Members of the O1 group cause epidemic disease whereas non-O1 organisms either cause sporadic disease or are nonpathogens. The O1 organisms have two biotypes, El Tor and Cholerae, and 3 serotypes, called Ogawa, lnaba, and Hikojima. V. parahaemolyticus and V. vulnificus are marine organisms; they live primarily in the ocean, especially in warm salt water. They are halophilic; ie, they require a high NaCl concentration to grow.

Vibrio cholerae Clinical Findings

Watery diarrhea in large volumes is the hallmark of cholera. There are no red blood cells or white blood cells in the stool. Rice-water stool is the term often applied to the nonbloody effluent. The loss of fluid and electrolytes leads to cardiac and renal failure. Acidosis and hypokalemia also occur as a result of loss of bicarbonate and potassium in the stool. The mortality rate without treatment is 40%.

BRUCELLOSIS escapes immune system

While in the phagolysosome, B. abortus releases 5'-guanosine and adenine which are capable of inhibiting the degranulation of peroxidase-containing granules and thus inhibit the myeloperoxidase-peroxide-halide system of bacterial killing. The intracellular persistence of bacteria results in granuloma formation in the reticuloendothelial system organs and tissue damage due to hypersensitivity reactions, mostly type-IV.(non caseating granuloma)

Bordetella pertussis Clinical Findings

Whooping cough that begins with mild upper respiratory tract symptoms followed by a severe paroxysmal cough, which lasts from 1 to 4 weeks. The paroxysmal pattern is characterized by a series of hacking coughs, accompanied by production of copious amounts of mucus, that end with an inspiratory "whoop" as air rushes past the narrowed glottis. Although central nervous system anoxia and exhaustion can occur as a result of the severe coughing, death is due mainly to pneumonia. In the correct clinical setting, adults with a cough lasting several weeks (often called the 100-day cough) should be evaluated for infection with B. pertussis.

Yersinia enterocolitica

Y. enterocolitica and Y. pseudotuberculosis are gram-negative, oval rods that are larger than Yersinia pestis. These organisms are transmitted to humans by contamination of food with the excreta of domestic animals such as dogs, cats, and cattle.

Yersinia enterocolitica & Yersinia pseudotuberculosis

Y. enterocolitica causes enterocolitis that is clinically clinically indistinguishable from that caused by Salmonella or Shigella. Both Y. enterocolitica and Y. pseudotuberculosis can cause mesenteric adenitis that clinically resembles acute appendicitis. Septicemia ass/ c- blood transfusion (cold storage favours reliplication ) Rarely, these organisms are involved in bacteremia or abscesses of the liver or spleen, mainly in persons with underlying disease. Yersinia infection is associated with two autoimmune diseases: reactive arthritis and Reiter's syndrome. Other enteric pathogens such as Salmonella, Shigella, and Campylobacter also trigger these diseases.

Yersinia enterocolitica & Yersinia pseudotuberculosis Lab Diagnosis

Y. enterocolitica is usually isolated from stool specimens and forms a lactose-negative colony on Mac-Conkey's agar oxidase negative , catalase positive ,fermenters glucose . It grows better at 25°C than at 37°C; most biochemical test results are positive at 25°C and negative at 37°C. Incubation of a stool sample at 4°C for I week, a technique called "cold enrichment," increases the frequency of recovery of the Y. enterocolitica . Enterocolitis and mesenteric adenitis caused by the organisms do not require treatment. In cases of bacteremia or abscess, either trimethoprim-sulfamethoxazole or ciprofloxacin is usually effective. There are no preventive measures except to guard against contamination of food by the excreta of domestic animals.

YERSINIA

Yersinia pestis is the cause of plague, also known as the black death, the scourge of the Middle Ages. Yersinia enterocolitica and Yersinia pseudotuberculosis,

Cutaneous anthrax Clinical Findings

a painless ulcer filled with blue-black edema fluid. Rupture of this lesion will reveal a black eshar at the base surrounded by a zone of induration. This lesion is called a malignant pustule. Local edema is striking. Untreated cases progress to bacteremia and death

Yersinia pestis

a small gram-negative rod that exhibits bipolar staining; ie, it resembles a safety pin, with a central clear area. Freshly isolated organisms possess a capsule composed of a polysaccharide-protein complex. It is one of the most virulent bacteria known and has a strikingly low ID50; ie, 1 to 10 organisms are capable of causing disease. The plague bacillus has been endemic in the wild rodents of Europe and Asia for thousands of years but entered North America in the early 1900s, probably carried by a rat that jumped ship at a California port. It is now endemic in the wild rodents in the western United States, although 99% of cases of occur in South-east Asia. The enzootic (sylvatic) cycle consists of transmission among wild rodents by fleas. In the United States, prairie dogs are the main reservoir (don't kill, just grow). Rodents are relatively resistant to disease; most are asymptomatic. Humans are accidental hosts, and cases of plague in this country occur as a result of being bitten by a flea that is part of the enzootic ( sylvatic) cycle. The urban cycle, which does not occur in the United States, consists of transmission of the bacteria among urban rats, with the rat flea as vector. This cycle predominates during times of poor sanitation, eg, wartime, when rats proliferate and come in contact with the fleas in the sylvatic cycle. The flea ingests the bacteria while taking a blood meal from a bacteremic rodent. The blood clots in the flea's stomach as a result of the action of the enzyme coagulase, which is made by the bacteria. The bacteria are trapped in the fibrin and proliferate to large numbers. The mass of organisms and fibrin block the proventriculus of the flea's intestinal tract, and during its next blood meal the flea regurgitates the organisms into the next animal. Because the proventriculus is blocked, the flea gets no nutrition, becomes hungrier, loses its natural host selectivity for rodents, and more readily bites a human The organisms inoculated at the time of the bite spread to the regional lymph nodes, which become swollen and tender. These swollen lymph nodes are the buboes buboes (keep enlarging until bursting) that have led to the name bubonic plague. The organisms can reach high concentrations in the blood and disseminate to form abscesses in many organs. The endotoxin-related symptoms, including disseminated intravascular coagulation and cutaneous hemorrhages (cause of death), probably were the genesis of the term black death. In addition to the sylvatic and urban cycles of transmission, respiratory droplet transmission of the organism from patients with pneumonic plague can occur. The organism has several factors that contribute to its virulence: (1) the envelope capsular antigen, called F-l, which protects against phagocytosis; (2) endotoxin; (3) an exotoxin; The action of the exotoxin is unknown. and two proteins known as (4) V antigen and (5) W antigen. The V and W antigens allow the organism to survive and grow intracellularly, but their mode of action is unknown

Gamma (enterococcus) Group D:

a. Enterococci b. Non-enterococci i.e S.bovis Enterococci: sp E. faecalis. E. faecium Cell wall with group-specific antigen (group D glycerol teichoic acid) . Urinary tract infection: Dyuria and pyuria most commonly in hospitalized patients with an indwelling urinary catheter and receiving broad-spectrum cephalosporin antibiotics. Peritonitis: Abdominal swelling and tenderness after abdominal trauma or surgery; patients are typically acutely ill, febrile, and with positive blood cultures Endocarditis: Infection of the heart endothelium or valves; associated with persistent bacteremia; can present acutely or chronically

Biochemical reactions

a.Catalase test:- Staph -- catalase + Strept- catalase -ve b.mannitol --S. aureus- ferments mannitol C. Coagulase: S. aureus coagulase +ve Other coagulase -ve (Surgical wound infection with in 2- days ). Latex test for staphylococci, to distinguish S.aureus from other staphylococci contains latex particle coated with antibodies that bind coagulase.

Septicemia

accounts for only about 5-10% of Salmonella infections and occurs in one of two settings: a patient with an underlying chronic disease such as sickle cell anemia or cancer or a child with enterocolitis. The septic course is more than that seen with many other gram-negative rods. Bacteremia results in the seeding of many organs, with osteomyelitis, pneumonia, and meningitis as the most common sequelae. Osteomyelitis in a child with sickle cell anemia is an important example of this type of salmonella infection. Previously damaged tissues, such as infarcts and aneurysms, especially aortic aneurysms, are the most frequent sites of metastatic abscesses. Salmonella are also an important cause of vascular graft infections.

Pathogenesis: N. gonorrhoeae

adhere to the surface of epithelial cells, particularly those of the urethra, genital tract, rectum, and throat. Eventually the bacteria invade the epithelial cells and penetrate the submucosal space, causing a suppurative infection, later disseminates. For example, in men → from mucosa of the external portions of the urogenital tract to the prostate and epididymis. In women → paracervical glands, fallopian tubes and to peritoneal cavity.

In typhoid

and other enteric fevers, infection begins in the small intestine but few gastrointestinal symptoms occur. The organisms enter, multiply in the mononuclear phagocytes of Peyer's patches, and then spread to the phagocytes of the liver, gallbladder, and spleen. This leads to bacteremia, which is associated with the onset of fever and other symptoms, probably caused by endotoxin. Survival and growth of the organism within phagosomes in phagocytic cells are a striking feature of this disease, as is the predilection for invasion of the gallbladder, which can result in establishment of the carrier state and excretion of the bacteria in the feces for long periods.

S. pneumoniae Capsules

are virulence factors; ie they interfere with phagocytosis and favor invasiveness. Specific antibody to the capsule opsonizes the organism, facilitates phagocytosis, and promotes resistance. Such antibody develops in humans as a result either of infection (asymptomatic or clinical) or of administration of polysaccharide vaccine. Capsular polysaccharide elicits primarily a B-cell (ie, T-independent) response.

N. meningitides Pathogenesis

attaches to the cells of the nasopharynx following inhalation of contaminated droplets. In a nonimmune, susceptible host, it invades locally, disseminates hematogenously, and reaches the meninges → primary tissue → proliferate, causing inflammation.

Pyoderma and impetigo

burning, itchy papules that break and form a highly contagious yellow crust seen in poor hygiene people and over crowded living conditions.

B. abortus and B. canis

cause a mild suppurative febrile infection whereas B. suis causes a more severe suppurative infection which can lead to destruction of the lymphoreticular organs and kidney.

Staphylococcus aureus

causes abscesses,various pyogenic infections (eg, endocarditis, septic arthritis, and osteomyelitis), food poisoning, and toxic shock syndrome. It is one of the most common causes of hospital- acquired pneumonia, septicemia, and surgical-wound infections.

H. aegyptius, also called the Koch-Weeks bacillus

causes an acute, purulent conjunctivitis. This contagious organism is associated with epidemics, particularly during the warm months of the year. H. aegyptius also causes Brazilian Purpuric Fever Haemophilus ducreyi, the agent of chancroid,

STAPHYLOCOCCUS AUREUS description

causes disease both by producing toxins and by inducing pyogenic inflammation. The three clinically important exotoxins are enterotoxin, toxic shock syndrome toxin, and exfoliatin. (1) Enterotoxin causes food poisoning characterized by prominent vomiting and watery, nonbloody diarrhea. It acts as a superantigen within the gastrointestinal tract to stimulate the release of large amounts of interleukin-1 (IL-1) and interleukin-2 (IL-2) from macrophages and helper T cells, respectively. The prominent vomiting appears to be caused by cytokines released from the lymphoid cells, which stimulate the enteric nervous system to activate the vomiting center in the brain . Enterotoxin (preformed ) is fairly heat-resistant and therefore is usually not inactivated by brief cooking. It is resistant to stomach acid and to enzymes in the stomach and jejunum. There are six immunologic types of enterotoxin,types A-E Saltyfoods, custard pastries,potato salad,canned meats. 2) Toxic shock syndrome toxin (TSST) causes toxic shock, especially in tampon-using menstruating women or in individuals with wound infections. (nasal packing )desquamating rash, fever,hypotension. Toxic shock also occurs in patients with nasal packing used to stop bleeding from the nose. TSST is produced locally by S. aureus in the vagina, nose, or other infected site. (3) Exfoliatin causes "scalded skin" syndrome in young children. It is "epidermolytic" and acts as a serine protease that cleaves desmoglein in desmosomes, leading to the separation of the epidermis at the granular cell layer. cytolysis and inflammation are not present * (4) Several toxins can kill leukocytes (leukocidins) and cause necrosis of tissues in vivo. Of these, the most important is alpha toxin, which causes marked necrosis of the skin and hemolysis. The cytotoxic effect of alpha toxin is attributed to the formation of holes in the cell membrane and the consequent loss of low-molecular- weight substances from the damaged cell. A second toxin, P-V leukocidin, also kills white blood cells by damaging cell membranes. (in 21 st century, increase in community -acquired necrotizing pneumonia, typically caused by MRSA specificially related to panton - valentine -leukocidin ) (5) The enzymes include coagulase, fibrinolysin, hyaluronidase, proteases, nucleases, and lipases (helps in invasion of normal healthy skin). Coagulase, by clotting plasma, serves to wall off the infected site, thereby retarding the migration of neutrophils into the site. Staphylokinase is a fibrinolysin that can lyse thrombi.

E. coli Pathogenesis

causes urinary tract infections is the patient's own colonic flora that colonizes the urogenital area. The source of the E. coli that causes neonatal meningitis is the mother's birth canal; the infection is acquired during birth. In contrast, the E. coli that causes traveler's diarrhea is acquired by ingestion of food or water contaminated with human feces. Note that the main reservoir of enterohemorrhagic E. coli O157 is cattle and the organism is acquired in undercooked meat.

Bordetella pertussis

causes whooping cough Bordetella pertussis small gram negative coccobaccilli. B. pertussis, a pathogen only for humans, is transmitted by airborne droplets produced during the severe coughing episodes. The organisms attach to the ciliated epithelium of the upper respiratory tract but do not invade the underlying tissue. Decreased cilia activity followed by death of the ciliated epithelial cells are important aspects of pathogenesis. Pertussis is a highly contagious disease that occurs primarily in infants and young children. Several factors play a role in the pathogenesis: (1) Attachment of the organism to the cilia of the epithelial cells is mediated by a protein on the pili called filamentous hemagglutinin. Antibody against the filamentous hemagglutinin inhibits attachment and protects against disease. (2) Pertussis toxin stimulates adenylate cyclase by catalyzing the addition of adenosine diphosphate ribose, a process called ADP-ribosylation, to the inhibitory subunit of the G protein complex (Gi protein). This results in prolonged stimulation of adenylate cyclase and a consequent rise in cyclic adenosine monophosphate (AMP) and in cyclic AMP-dependent protein kinase activity. The toxin also has a domain that mediates its binding to receptors on the surface of respiratory tract epithelial cells. pertussis toxin also causes a striking lymphocytosis in the blood of patients with pertussis. The toxin inhibits signal transduction by chemokine receptors, resulting in a failure of lymphocytes to enter lymphoid tissue such as the spleen and lymph nodes. Because the lymphocytes do not enter lymphoid tissue, there is an increase in their number in the blood . (3) The organisms also synthesize and export adenylate cyclase. This enzyme, when taken up by phagocytic cells can inhibit their bactericidal activity. Bacterial mutants that lack cyclase activity are avirulent. (4) Tracheal cytotoxin is a fragment of the bacterial peptidoglycan that damages ciliated cells of respiratory tract. Tracheal cytotoxin appears to act in concert with endotoxin to induce nitric oxide, which kills the ciliated epithelial cells.

Enterocolitis is

characterized by an invasion of the epithelial and subepithelial tissue of the small and large intestines. Strains that do not invade do not cause disease. The organisms penetrate both through and between the mucosal cells into the lamina propria, with resulting inflammation and diarrhea. A polymorphonuclear leukocyte response limits the infection to the gut and the adjacent mesenteric lymph nodes; bacteremia is infrequent in enterocolitis. In contrast to Shigella enterocolitis, in which the infectious dose is very small (on the order of 10 organisms), the dose of Salmonella required is much higher, at least 100,000 organisms. Various properties of salmonellae and shigellae are compared in . Gastric acid is an important host defense; gastrectomy or use of antacids lowers the infectious dose significantly.

STAPHYLOCOCCUS AUREUS:Kawasaki syd

disease of unknown etiology resemble toxic shock syd KS is a vasculitis involving small and medium size arteries, especially the coronary arteries. Clinically , characterized by a high fever of at least 5 days ;bilateral non purulent conjunctivitis ;lesions of the lips and erythema of the oropharynx A diffuse erythematous, maculopapular rash; erythema and edema of the hands and feet that often ends with desquamation ; and cervical lymphadenopathy. Common in children of asian ancestry,certain MHC alleles may predispose to the disease High dose of immunglobins -reduces fever and other symptoms

Other sexually transmitted infections,

eg, syphilis and nongonococcal urethritis caused by Chlamydia trachomatis, can coexist with gonorrhea; therefore, appropriate diagnostic and therapeutic measures must be taken. Ceftriaxone or Fluroquinolones (e.g.) ciprofloxacin The prevention of gonorrhea involves the use of condoms and the prompt treatment of symptomatic patients and their contacts. Cases of gonorrhea must be reported to the public health department to ensure proper follow-up. Gonococcal conjunctivitis in newborns is prevented most often by the use of erythromycin ointment. The genus Neisseria is one of several in the family Neisseriaceae. A separate genus contains the organism Moraxella catarrhalis, which is part of the normal throat flora but can cause such respiratory tract infections as sinusitis, otitis media, bronchitis, and pneumonia. M. catarrhalis and members of other genera, such as Branhamella, Kingella, and Acinetobacter

Group D Streptococci hydrolyze

esculin in the presence of bile; ie, they produce a black pigment on bile-esculin agar. The group D organisms are further subdivided: the enterococci grow in hypertonic (6.5%) NaCI, whereas the nonenterococci do not.

Corynebacterium diphtheriae

gram-positive rods that appear club-shaped (wider at one end) and are arranged in palisades or in V- or L-shaped formations. Humans are the only natural host of C. diphtheriae. Both toxigenic and nontoxigenic organisms reside in the upper respiratory tract and are transmitted by air-borne droplets. Although exotoxin production is essential for pathogenesis, invasiveness is also necessary because the organism must first establish and maintain itself in the throat. The toxin affects all eukaryotic cells regardless of tissue type. Diphtheria toxin inhibits protein synthesis by ADP-ribosylation of elongation factor 2 (EF-2). The DNA that codes for diphtheria toxin is part of the genetic material of a temperate'bacteriophage. During the lysogenic phase of viral growth, the DNA of this virus integrates into the bacterial chromosome and the toxin is synthesized. C. diphtheriae cells that are not lysogenized by this phage do not produce exotoxin and are nonpathogenic Thick, gray, adherent pseudomembrane over the tonsils and throat fever, sore throat, and cervical adenopathy. Clinical Findings Prominent complications: (1) Airway obstruction (2) Myocarditis accompanied by arrhythmias and circulatory collapse Cutaneous diphtheria causes ulcerating painless lesions covered by a gray membrane. A throat swab should be cultured on Loffler's medium, Tellurite plate, and a blood agar plate.

Rapid tests that provide a diagnosis

in approximately 10 minutes. Specific antigens from the group A streptococci are extracted from the throat swab with certain enzymes and are reacted with antibody to these antigens bound to latex particles. Agglutination of the colored latex particles occurs if group A streptococci are present in the throat swab. A rapid test is also available for the detection of group B streptococci in vaginal and rectal samples. It detects the DNA of the organism and results can be obtained in approximately 1 hour.

Enterobacter and Serratia

infections are clearly related to hospitalization, especially to invasive procedures such as intravenous catheterization, respiratory intubation, and urinary tract manipulations. In addition, outbreaks of Serratia pneumonia have been associated with contamination of the water in respiratory therapy devices. Prior to the extensive use of these procedures, S. marcescens was a harmless organism most frequently isolated from environmental sources such as water.

The epidemiology of Salmonella

infections is related to the ingestion of food and water contaminated by human and animal wastes. The most frequent animal source is poultry and eggs, but meat products that are inadequately cooked have been implicated as well. Dogs other pets, including turtles, snakes, lizards, and iguanas, are additional sources.

Vibrio vulnificus

is also a marine organism; ie, it is found in warm salt waters such as the Caribbean sea. It causes severe skin and sofi tissue infections (cellulitis), especially in shellfish handlers, who often sustain skin wounds. It can also cause a rapidly fatal septicemia in immunocom-promised people who have eaten raw shellfish containing the organism. Hemorrhagic bullae in the skin often occur in patients with sepsis caused by V. vulnificus. Chronic liver disease, eg, cirrhosis, predisposes to severe infections. The recommended treatment is doxycycline.

The diagnosis of botulism

is confirmed if the organism is isolated or toxin activity is demonstrated Botulinum toxin is demonstrable in uneaten food and the patient's serum by mouse protection tests. ELISA PCR Treatment :-Trivalent antitoxin (types A, B, and E) is given, along with respiratory support. The antitoxin is made in horses, and serum sickness occurs in about 15% of antiserum recipients. Prevention :- Proper sterilization of all canned and vacuum-packed foods is essential. Food must be adequately cooked to inactivate the toxin. Swollen cans must be discarded (clostridial proteolytic enzymes form gas, which swells cans).

Pathogenesis & Epidemiology ENTERIC TRACT

is most likely to be a primary, nonopportunistic pathogen; this property is related to its antiphagocytic capsule. Although this organism is a primary pathogen, patients with K pneumoniae infections frequently have predisposing conditions such as advanced age, chronic respiratory disease, diabetes, or alcoholism. The organism is carried in the respiratory tract of about 10% of healthy people, who are prone to pneumonia if host defenses are lowered

Clinical Findings E. coli

is the leading cause of community-acquired urinary tract infections. These occur primarily in women; this finding is attributed to three features that facilitate ascending infection into the bladder, namely, a short urethra, the proximity of the urethra to the anus, and colonization of the vagina by members of the fecal flora. It is also the most frequent cause of nosocomial (hospital-acquired) urinary tract infections, which occur equally frequently in both men and women and are associated with the use of in-dwelling urinary catheters. is also a major cause, along with the group B streptococci, of meningitis and sepsis in neonates. Exposure of the newborn to E. coli and group B streptococci occurs during birth as a result of colonization of the vagina by these organisms in approximately 25% of pregnant women. Infection with enterohemorrhagic E. coli (EHEC), on the other hand, results in a dysentery like syndrome characterized by bloody diarrhea, abdominal cramping, and fever similar to that caused by Shigella. The O157:H7 strains of E. coli also cause bloody diarrhea, which can be complicated by hemolytic-uremic syndrome. This syndrome is characterized by kidney failure, hemolytic anemia, and thrombocytopenia.

Vibrio cholerae

is transmitted by fecal contamination of water and food, primarily from human sources. Human carriers are frequently asymptomatic and include individuals who are either in the incubation period or convalescing. The main animal reservoirs are marine shell- fish, such as shrimp and oysters. Ingestion of these without adequate cooking can transmit the disease. A major epidemic of cholera, which spanned the 1960s and 1970s, began in Southeast Asia and spread over three continents to areas of Africa, Europe, and the rest of Asia. A pandemic of cholera began in Peru in 1991 and has spread to many countries in Central and South America. The organism isolated most frequently was the El Tor biotype of O 1 V. cholerae, usually of the Ogawa serotype. The factors that predispose to epidemics are poor sanitation, malnutrition, overcrowding, and inadequate medical services. The pathogenesis of cholera is dependent on colonization of the small intestine by the organism and secretion of enterotoxin. For colonization to occur, large numbers of bacteria must be ingested because the organism is particularly sensitive to stomach acid. Persons with little or no stomach acid, such as those taking antacids or those who have had gastrectomy, are much more susceptible. Adherence to the cells of the brush border of the gut, which is a requirement for colonization, is related to secretion of the bacterial enzyme mucinase, which dissolves the protective glycoprotein coating over the intestinal cells. After adhering, the organism multiplies and secretes an enterotoxin called choleragen. This exotoxin can reproduce the symptoms of cholera even in the absence of the vibrio organisms. Choleragen consists of an A (active) subunit and a B (binding) subunit. The B sub-unit, which is a pentamer composed of five identical proteins, binds to a ganglioside receptor on the surface of the enterocyte. The A subunit is inserted into the cytosol, where it catalyzes the addition of ADP-ribose to the G s protein (G s is the stimulatory G protein). This locks the G s protein in the "on" position, which causes the persistent stimulation of adenylate cyclase. The resulting overproduction of cyclic AMP stimulates secretion of chloride ions and water, leading to a massive watery diarrhea without inflammatory cells. Morbidity and death are due to dehydration and electrolyte imbalance. However, if treatment is instituted promptly, the disease runs a self-limited course in up to 7 days. The genes for cholera toxin and other virulence factors are carried on a single-stranded DNA bacteriophage called CTX. Lysogenic conversion of non-toxin- producing strains to toxin-producing ones can occur when the CTX phage transduces these genes. The pili that attach the organism to the gut mucosa are the receptors for the phage. Non-O1 V. cholerae is an occasional cause of diarrhea associated with eating shellfish obtained from the coastal waters of the United States.

Enterobacteriaceae

large family of gram negative rods found primarily in the colon of humans and other animals, many as part of the normal flora. Four metabolic processes: (1) They are all facultative anaerobes; (2) They all ferment glucose (fermentation of other sugars varies); (3) None have cytochrome c oxidase (ie, they are oxidase-negative ---reagent-Tetramethyl-p-phenylenediamine ); and (4) They reduce Nitrates to Nitrites as part of their energy-generating processes.

Group A streptococci

produce three important inflammation-related enzymes. (1) Hyaluronidase degrades hyaluronic acid, which is the ground substance of subcutaneous tissue. Hyaluronidase is known as spreading factor because it facilitates the rapid spread of S. pyogenes in skin infections (cellulitis). (2) Streptokinase (fibrinolysin) activates plasminogen to form plasmin, which dissolves fibrin in clots, thrombi, and emboli facilitates spread of bacteria in tissues. Can be used to lyse thrombi in the coronary arteries of heart attack patients. (3) DNase (streptodornase) A----D depolymerizes DNA in pus or necrotic tissue. Antibody to DNase B develops during pyoderma; this can be used for diagnostic purposes (acute glomerulonephritis ). (Streptokinase-streptodornase mixtures applied as a skin test give a positive reaction in most adults, indicating normal cell-mediated immunity.)

ENTEROBACTERIACEAE Antigens

several members of the Enterobacte-riaceae, especially Salmonella and Shigella, are important; they are used for identification purposes both in the clinical laboratory and in epidemiologic investigations. The three surface antigens are as follows: (1) The cell wall antigen (also known as the somatic, or O, antigen) is the outer polysaccharide portion of the lipopolysaccharide . The O antigen, which is composed of repeating oligosaccharides consisting of three or four sugars repeated 15 or 20 times, is the basis for the serologic typing of many enteric rods. The number of different O antigens is very large; eg, there are approximately 1500 types of Salmonella and 150 types of E. coli. (2) The H antigen is on the flagellar protein. Only flagellated organisms, such as Escherichia and Salmonella, have H antigens,. The H antigens of certain Salmonella species are unusual because the organisms can reversibly alternate between two types of H antigens called phase 1 and phase 2. The organisms may use this change in antigenicity to evade the immune response. (3) The capsular or K polysaccharide antigen is particularly prominent in heavily encapsulated organisms such as Klebsiella. The K antigen is identified by the quellung (capsular swelling) reaction in the presence of specific antisera. In S.typhi, the cause of typhoid fever, it is called the Vi (or virulence) antigen.

SALMONELLA

species cause enterocolitis, enteric fevers such as typhoid fever, and septicemia with metastatic infections such as osteomyelitis. They are one of the most common causes of bacterial enterocolitis in the United States. - are gram-negative rods that do not ferment lactose but do produce H2S--features that are used in their laboratory identification. Their antigens---cell wall O, flagellar H, and capsular Vi (virulence)--are important for taxonomic and epidemiologic purposes. The O antigens, which are the outer polysaccharides of the cell wall, are used to subdivide the salmonellae into groups A-I. There are two forms of the H antigens, phases 1 and 2. Only one of the two H proteins is synthesized at any one time, depending on which gene sequence is in the correct alignment for transcription into mRNA. The Vi antigens (capsular polysaccharides) are antiphagocytic and are an important virulence factor for S. typhi, the agent of typhoid fever. Ewing divides the genus into three species: 1.S. typhi, 2.Salmonella choleraesuis, and 3.Salmonella enteritidis.

Strains of S. pyogenes

that produce certain class1M protein types are rheumatogenic, ie, cause primarily rheumatic fever, Where as strains of S. pyogenes that produce other M protein types are nephritogenic, ie, cause primarily acute glomerulonephritis. Although M protein is the main antiphagocytic component of S. pyogenes, the organism also has a polysaccharide capsule that plays a role in retarding phagocytosis.

B. melitensis is

the cause of most severe prolonged recurring disease. The bacteria enter the human host through the mucous membranes of the oropharynx (ingestion/inhalation routes), through abraded skin, or through the conjunctiva. Usually infection occurs by direct contact with infected material, although it may also occur by ingestion of milk or milk products.

Haemophilus (Unencapsulated)

therefore untypeable strains can also cause disease, especially diseases of the upper respiratory tract such as sinusitis and otitis media, but are usually noninvasive.

Gastrointestinal infection

with C. jejuni is associated with Guillain-Barr syndrome, the most common cause of acute neuromuscular paralysis. Guillain-Barrie syndrome is an autoimmune disease attributed to the formation of antibodies against C. jejuni that cross-react with antigens on neurons. Campylobacter is also associated with two other autoimmune diseases: reactive arthritis and Reiter's syndrome