Micro Unit 5 Review

Salmonella typhi

*Salmonella typhi is the causative agent of typhoid fever* -typhoid fever appears sporadically in the US with 200 to 400 cases reported/year -bacillus is ingested with food or water contaminated with feces -a small number of people chronically carry the bacilli in the gallbladder -bacilli are constantly released into the intestine and feces -*"Typhoid Mary"* was a well-known chronic carrier -infectious dose is 1,000 to 10,000 cells -the bacilli adhere to the mucosa of the small intestine and initiate a progressive, invasive infection -diagnosis based on the patient history and the presenting of symptoms -fever, abdominal pain, alternating diarrhea and constipation -ciprofloxacin or ceftriaxone are the drugs of choice -vaccines provide temporary protection for travelers and military personnel -animal salmonellosis -salmonelloses other than typhoid fever are termed *Salmonella food poisoning or gastroenteritis* -nontyphoidal salmonelloses are more prevalent than typhoid fever -40,000 to 50,000 cases/year -zoonotic in origin -Salmonella are normal intestinal flora in cattle, poultry, rodents and reptiles -animal products such as meat and milk can be easily contaminated -risks in eating poorly cooked beef or unpasteurized milk, ice cream and cheese -concern in food processing plants is the contamination of food by rodent droppings -eggs are a concern due the bacteria entering the egg while the shell is being formed in the chicken -poultry industry uses a probiotic containing a mixture of normal microbiota to spray on newly hatched chicks to colonize them -poultry and poultry-products should be handled with proper cleaning techniques and adequate cooking -wash your hands after handling reptiles or their cages -in the US, Salmonella causes the highest death rate among enteric pathogens, usually in elderly persons -marked by fever, vomiting, diarrhea, fluid loss, and mucosal lesions -*preventions* -adequate sanitation and proper hand washing -refrain from consuming unwashed fruits and vegetables, inadequately cooked meat and eggs, and unpasteurized milk -uncomplicated cases are handled with fluid and electrolyte replacement

Vibrio cholerae

*Vibrio cholera: the causative agent of cholera* -epidemiology of cholera -pathogen is free-living in certain endemic areas -transmission is influenced by season of the year and climate -warm, monsoon, alkaline and saline conditions favor growth -historically, outbreaks traced to large cargo ships that take on water in one port and release in another -one of the worst epidemics that occurred recently was in 2010, after an earthquake in Haiti -disruption to vital services and sanitation complicated control measures -in nonendemic areas such as the US, the microbe is spread by food and water contamination -pathogenesis of cholera -infectious dose is high (108 cells) -*vibrios* (curved rods) penetrate the mucosa of the small intestine -virulence due to the production of *cholera toxin* (enterotoxin) -cells shed large amounts of electrolytes (water follows) into the intestine -toxin stimulates the production of cAMP -disrupts membrane pumps leading to loss of electrolytes -symptoms begin abruptly with vomiting followed by secretory diarrhea -flecks of tissue debris in the stool leads to the description of "rice-water stool" -diarrhea reduces blood volume, acidosis from bicarbonate loss and potassium depletion -predispose patient to muscle cramps, severe thirst, flaccid skin and sunken eyes -young children can experience coma and convulsions -diagnosis and remedial measures -isolated and identified from stool samples -dark-field microscopy reveals characteristic curved cells -key to therapy is prompt replacement of water and electrolytes -*oral rehydration therapy* (ORT) -oral antibiotics such as doxycycline -*preventions* -proper sewage disposal -water purification -vaccines are available for travelers and people living in endemic areas

Streptococcus pyogenes (S. pyogenes)

*beta-hemolytic streptococci* -inhabits the throat, nasopharynx and occasionally the skin of humans -*most serious streptococcal pathogen of humans* -*transmission* through direct contact, droplets and fomites -incidence and types of infections are altered by climate, season and living conditions -skin infections occur more frequently in the warm temperatures of summer and fall -pharyngeal infections increase during the winter months -*skin infections* -*streptococcal impetigo* -burning, itching papules that break and form a highly contagious yellow crust -occurs in epidemics among school children -erysipelas is more invasive -spreads to the dermis and subcutaneous tissues -tender, red, puffy lesions have a sharp border that can burst and release fluid -*streptococcal pharyngitis or "strep throat"* involves pharyngeal mucous membranes -characterized by redness, edema and tenderness and swallowing is difficult and painful -purulent exudate over the tonsils, swollen lymph nodes and occasionally pus-filled abscesses on the tonsils -*systemic infections* -*scarlet fever* involves a strain of S. pyogenes that produces *erythrogenic toxin* -characterized by a high fever and a bright red rash ("strawberry" tongue) -streptococcal toxic shock syndrome is a severe and invasive infection -rapidly progresses to multiple organ failure (30% mortality rate) -long-term complications *(sequelae)* of Group A streptococcal infections -after a group A streptococcal infection, occasional long-term sequelae can occur -severe sore throats should be taken seriously due to these long-term complications -simple throat swab can be used to identify group A streptococci and antibiotics can be administered immediately -*two important sequelae* -*rheumatic fever* is an inflammatory condition of the joints and heart -in severe carditis, heart valve and muscle damage can occur -*acute glomerulonephritis* is a disease of the kidney -kidney cells are so damaged that they cannot filter blood -urine samples are abnormal with high levels of blood cells and protein -invasive group A streptococci and "flesh-eating" syndrome -*necrotizing fasciitis* is a complication of S. pyogenes and is the "flesh-eating disease" -these strains have special enzymes and toxins that increase their invasiveness -enzymes digest connective tissues and toxins kill epidermal and dermal tissues -Streptococcus agalactiae is an example from group B -normal microbiota from humans and other mammals -frequent cause of bovine mastitis -a resident in the human vagina, pharynx and large intestine -implicated in neonatal meningitis, wound and skin infections and endocarditis -most prevalent cause of neonatal pneumonia, sepsis and meningitis in the US and Europe -group D enterococci and groups C and G streptococci -Enterococcus sp. are normal inhabitants of the large intestine -enterococci are emerging as serious nosocomial opportunists -rising incidence of multidrug-resistant strains (vancomycin-resistant enterococci (VRE)) -groups C and G are frequently isolated from the human upper respiratory tract -cause bacteremia and disseminated infections in severely compromised patients -laboratory identification techniques -rapid cultivation and diagnosis that will ensure proper treatment and prevention methods are essential -rapid diagnostic test kits used in clinics or offices detect group A streptococci from pharyngeal swabs -CAMP reaction differentiates group B streptococci from groups A and D -*treatment and prevention* of group A, B and D streptococcal infections -groups A and B can be treated with penicillin -treating enterococcal infection requires combination therapy (ampicillin and gentamycin) -currently, a vaccine is not available -cell surface antigens and virulence factors -C carbohydrates -protect the bacterium from being dissolved by lysozyme -lysozyme is found in tears and saliva and targets the bacterial wall -lipoteichoic acid bound to fimbriae (adhesion) -M protein improves adherence and resists phagocytosis -capsule is involved in attachment and retards phagocytosis -C5a protease cleaves complement protein C5a -interferes with the chemotactic response of neutrophils -extracellular toxins -streptolysins (are hemolysins) target many cells and tissues (leukocytes, liver and heart muscle) -erythrogenic toxin is involved in scarlet fever -produces fever and a bright red rash -only lysogenic strains with viral genes can synthesize this toxin -some of the streptococcal toxins contribute to increased tissue injury by acting as superantigens -increase the stimulation of T cells that become overactive and release cytokines -leads to vascular injury (probable mechanism behind necrotizing fasciitis) -extracellular enzymes -streptokinase breaks down fibrin clots; may play a role in invasion -hyaluronidase breaks down intercellular cement allowing the spread into tissues -epidemiology and pathogenesis of Streptococcus pyogenes -transmission through direct contact, droplets and fomites -incidence and types of infections are altered by climate, season and living conditions -skin infections occur more frequently in the warm temperatures of summer and fall -pharyngeal infections increase during the winter months -cell surface antigens and virulence factors -C carbohydrates -protect the bacterium from being dissolved by lysozyme -lysozyme is found in tears and saliva and targets the bacterial wall -lipoteichoic acid bound to fimbriae (adhesion) -M protein improves adherence and resists phagocytosis -capsule is involved in attachment and retards phagocytosis -C5a protease cleaves complement protein C5a -interferes with the chemotactic response of neutrophils -extracellular toxins -streptolysins (are hemolysins) target many cells and tissues (leukocytes, liver and heart muscle) -erythrogenic toxin is involved in scarlet fever -produces fever and a bright red rash -only lysogenic strains with viral genes can synthesize this toxin -some of the streptococcal toxins contribute to increased tissue injury by acting as superantigens -increase the stimulation of T cells that become overactive and release cytokines -leads to vascular injury (probable mechanism behind necrotizing fasciitis) -extracellular enzymes -streptokinase breaks down fibrin clots; may play a role in invasion -hyaluronidase breaks down intercellular cement allowing the spread into tissues -epidemiology and pathogenesis of Streptococcus pyogenes -transmission through direct contact, droplets and fomites -incidence and types of infections are altered by climate, season and living conditions -skin infections occur more frequently in the warm temperatures of summer and fall -pharyngeal infections increase during the winter months -*cell surface antigens and virulence factors* -*C carbohydrates* -protect the bacterium from being dissolved by lysozyme -lysozyme is found in tears and saliva and targets the bacterial wall -lipoteichoic acid bound to fimbriae (adhesion) -*M protein* improves adherence and resists phagocytosis -*capsule* is involved in attachment and retards phagocytosis -*C5a protease* cleaves complement protein C5a -interferes with the chemotactic response of neutrophils -extracellular toxins -*streptolysins* (are hemolysins) target many cells and tissues (leukocytes, liver and heart muscle) -*erythrogenic toxin* is involved in scarlet fever -produces fever and a bright red rash -only lysogenic strains with viral genes can synthesize this toxin -some of the streptococcal toxins contribute to increased tissue injury by acting as superantigens -increase the stimulation of T cells that become overactive and release cytokines -leads to vascular injury (probable mechanism behind necrotizing fasciitis) -extracellular enzymes -*streptokinase* breaks down fibrin clots; may play a role in invasion -*hyaluronidase* breaks down intercellular cement allowing the spread into tissues

Neisseria meningitidis (N. meningitidis)

*commonly known as meningococcus* -associated with epidemic *cerebrospinal meningitis* -sporadic or epidemic incidence of occurrence is late winter and early spring -reservoirs are humans who harbor the microbe in the nasopharynx -*transmission* in crowded conditions with poor ventilation -day cares, military barracks and college dorms -highest risk groups are young children (6 to 36 months) and older children and young adults (10 to 20 years old) -acquired through close contact with secretions or droplets -bacteria enter the blood and can cross the blood-brain barrier, permeate the meninges and grow in cerebrospinal fluid -symptoms include fever, sore throat, stiff neck, convulsions and vomiting -meningococcemia is marked by the appearance of petechiae and ecchymoses on the skin or mucus membranes as a result of endotoxin-induced subcutaneous hemorrhage -damage to blood vessels triggers hemorrhage and coagulation leading to vascular damage -*petechiae* are small subcutaneous hemorrhages -*ecchymoses* are larger -immunity, treatment and prevention of meningococcal infection -most people have a natural immunity to the meningococcus -treatment of choice is a third generation cephalosporin (ceftriaxone) -broad-spectrum and crosses the blood-brain barrier -*prevention* -vaccination is recommended for all persons between 11 and 18 years of age -vaccination is also recommended for individuals in high-risk populations -students, military recruits and individuals exposed during outbreaks -*two vaccines* are currently available -*Menactra* (2 years to 55 years of age) and *Menomune* (older than 55 years) -*virulence* -capsule, adhesive fimbriae and IgA protease -lipopolysaccharide (endotoxin) is released from the cell when the microbe lyses

Discuss events that occur during primary tuberculosis.

*primary tuberculosis* -the minimum infectious dose for lung infection is approximately 10 cells -bacilli are phagocytized by alveolar macrophages and multiply within the cells (intracellular) -after 3 to 4 weeks, the immune system mounts a cell-mediated response against the bacilli -formation of specific infection sites called tubercles -tubercles are granulomas with a central core containing TB bacilli and macrophages -frequently the centers of the tubercles break down into a necrotic lesion (caseous necrosis) -response of T cells to tubercle proteins causes a cell-mediated response evident in the tuberculin reaction (diagnosis)

Staphylococcus aureus (S. aureus)

*the most serious staphylococcal organism* -common on humans and readily isolated from fomites -carriage occurs mostly in the anterior nares, in the skin, nasopharynx and intestine -predispositions to infections include -poor hygiene and nutrition and tissue injury -preexisting primary infections, diabetes mellitus and immunodeficiency states -third most common cause of infection in the newborn nursery and surgical wards -increase in community infections by strains of S. aureus called MRSA (methicillin-resistant S. aureus) -infections spread by contact with skin lesions; difficult to treat and control -*treatment of staphylococcal infections* -selection of a drug is dependent on culture and sensitivity testing of the staphylococcal isolates -MRSA may be treated (in combination therapy to reduce resistance) with *vancomycin*, daptomycin or ceftaroline -*synercid* is used in VISA and VRSA as a drug of last resort -*prevention* of staphylococcal infections -careful hygiene -adequate cleansing of surgical incisions and burns -proper handwashing -proper disposal of infectious dressings and discharges -isolation of individuals with open lesions -attention to indwelling catheters and needles -*virulence factors of Staphylococcus aureus* -*coagulase* clots and causes fibrin to be deposited around staphylococcal cells -helps stop the actions of host defenses such as phagocytosis -may promote adherence to host tissues -most staphylococcal organisms have coagulase and are coagulase-positive (diagnostic) -*hyaluronidase* is also called "spreading factor" and promotes invasion -digests intercellular cement that holds cells together allowing spread of the organism to underlying tissues -*staphylokinase* digests blood clots -*lipases* help the organism colonize oily skin surfaces -*nuclease* breaks down DNA -*penicillinase* inactivates penicillin which targets the bacterial cell wall (resistance) -*slime or capsules* contribute to biofilm formation in the body -binds organisms to surfaces and allows them to colonize catheters, artificial valves and other indwelling medical devices -*hemolysins* lyse red blood cells -alpha-toxin is the most important and lyses RBCs and damages leukocytes, renal tissue and heart and skeletal muscle -*leukocidins* damages cell membranes of neutrophils and macrophages causing lysis -*enterotoxins* are exotoxins that act in the gastrointestinal tract of humans -*exfoliative toxin* separates the epidermis from the dermis (causes skin to peel away) -responsible for staphylococcal *scalded skin syndrome* -*toxic shock syndrome toxin* (TSST) is associated with toxic shock -*the scope of staphylococcal disease* -disease ranges from localized to systemic infections -localized -*abscess* is a localized infection characterized by an inflamed, fibrous lesion enclosing a core of pus -localized cutaneous infections -*folliculitis* is an inflammation of a hair follicle -*furuncle* (boil) -*carbuncle* is a deeper lesion created by furuncles coalescing together -*impetigo* is characterized by epidermal swellings that that can break and peel away -miscellaneous systemic infections -in *osteomyelitis*, the pathogen becomes established in the highly vascular metaphyses of bone -abscess formation leads to necrosis or breakage of bony tissue -seen most frequently in growing children, adolescents and IV drug users -since the bacteria inhabit the nasopharynx, they can be aspirated into the lungs -cause a form of pneumonia involving multiple lung abscesses -most cases occur in infants and children suffering from cystic fibrosis and measles -this form of pneumonia is one of the most serious complications of influenza in the elderly -staphylococcal bacteremia causes a high mortality rate in hospitalized patients with chronic disease -origin is bacteria from infection sites or from colonized medical devices -in *endocarditis*, the organism colonizes the heart lining and is involved in valve destruction -meningitis can occur if the organism invades the brain -toxigenic staphylococcal disease -toxigenic disease can be presented as a toxemia (production of toxins in the body) or food intoxication (ingestion of toxin) -diseases associated with toxin production by S. aureus are food intoxication, scalded skin syndrome and toxic shock syndrome -*enterotoxins* are responsible for staphylococcal food poisoning -improperly prepared or stored potato salads and dressings are common food sources -*staphylococcal scalded skin syndrome* (SSSS) -toxin induces a bright red flush over the entire body -blisters and then causes a loss of the epidermis -majority of cases involve infants and children under the age of four -*toxic shock syndrome* was first identified in young women using vaginal tampons -tampons were ultra-absorbent and bound magnesium -in the absence of magnesium ions, S. aureus produces greater levels of exotoxins -tampon packages now contain a warning that the least-absorbent tampon that is effective should be used

Borrelia burgdorferii

-*Borrelia burgdorferii is linked to Lyme disease* -transmitted primarily by ticks from the genus Ixodes -the tick passes through a complex two year cycle that involves two principal hosts -larva or nymph stage of the tick feeds on the white-footed mouse and picks up the spirochete -the nymph form is most likely to bite humans -the adult tick reproductive phase of the cycle is completed on deer -the incidence of Lyme disease is increasing -greatest concentrations of Lyme disease are in areas with heavy mouse and deer populations -campers, hikers, backpackers and individuals living in newly developed communities near woodlands or forests are at highest risk -lesion (bull's eye) is called *erythema migrans* and occurs at the site of the bite -if not treated, can progress to a second stage -cardiac and neurological symptoms develop -polyarthritis can attack joints -diagnosis -ring-shaped (bull's eye) lesion -isolation of the spirochetes (blood) from the patient -serological tests such as ELISA -treatment with doxycycline and amoxicillin -avoidance of ticks -*DEET* -protective light-colored clothing, leggings and boots and stay on trails -properly remove ticks with forceps or fingers protected by gloves -possible to become infected by tick feces or body fluids

Bacillus anthracis (B. anthracis)

-*Bacillus anthracis is linked to anthrax* -anthrax is a zoonotic disease of herbivorous livestock (cattle, sheep and goats) -historically, Koch's model for developing his postulates and Pasteur (vaccination) -animals become infected while grazing on grass contaminated with endospores -the soil can become a long-term reservoir of infection for animal populations -recent cases in the US have occurred in textile workers handling imported animal hair or hides -human infections depend on the portal of entry -*human infections depend on the portal of entry* -*cutaneous anthrax* is caused by endospores entering the skin (cuts and abrasions) -most common and least dangerous form -produces a necrotic lesion called an *eschar* -*pulmonary anthrax* is associated with the inhalation of endospores -historically called woolsorter's disease -in the lungs, the endospores are phagocytosed and transported to lymph nodes -the endospores germinate and produce exotoxins that enter the circulatory system -toxins attach to the membranes of macrophages and gain entry through engulfment -toxins are highly lethal causing macrophage death and release of chemical mediators -effects include capillary thrombosis, cardiovascular shock and rapid death (if untreated) -*gastrointestinal anthrax* is rare -methods of anthrax control -active cases can be treated with ciprofloxacin, clindamycin or doxycycline -raxibacumab, a new drug approved by the FDA uses monoclonal antibodies -drug binds to one of the toxins secreted by B. anthracis keeping it from entering the cell -vaccines are used to protect livestock -*Biothrax* is a vaccine recommended for people in high-risk occupations or military personnel -*gas sterilization* of imported items containing animal hides, hair or bone -other bacillus species involved in human disease -Bacillus cereus is the cause of one type of food poisoning -multiplies readily in cooked foods such as rice, potato and meat dishes -endospores germinate and enterotoxins are released -ingestion of toxin-containing foods cause nausea, vomiting, cramps and diarrhea

Bartonella henselae

-*Bartonella henselae is the most common agent of cat-scratch fever* -acquired by scratches or bites from a cat -can be isolated in over 40% of cats, especially kittens -~25,000 cases/year in the U.S. (especially children 2 to 14 years old) -doxycycline, erythromycin and rifampin are effective therapies -prevention involves proper degermation of a cat bite or scratch

Bordatella pertussis

-*Bordatella pertussis is responsible for pertussis or whooping cough* -route of infection is direct contact with inhaled droplets or aerosols -~50% of cases occur in children between birth and four years of age -virulence factors -adhesion molecules that recognize and bind to ciliated respiratory epithelial cells -*pertussis toxin* results in increased mucus production -*tracheal cytotoxin* inhibits the movement of cilia on the epithelial cells of the respiratory tract -loss of ciliary cells leads to a buildup of mucus and blockage of the airways -initial stage is the *catarrhal stage* -marked by nasal drainage, congestion, sneezing and occasional coughing -*paroxysmal stage* is characterized by recurrent, persistent coughing -several abrupt, hacking coughs followed by a deep inhalation producing a "whoop" sound -acellular pertussis vaccine (aP) is part of the *DTaP vaccination* -current recommendations require administration of a Tdap booster called *Boostrix* recommended during early adolescence

Mycoplasma pneumoniae

-*most common agent of primary atypical pneumonia (walking pneumonia)* -transmitted by aerosol droplets -binds to specific receptors of the epithelial cells of the respiratory tract -lack of acute illness in most patients gives rise to the nickname of "walking pneumonia" -doxycycline and azithromycin inhibit mycoplasmal growth -do not stop the shedding of viable mycoplasmas -preventative measures -controlling contamination of fomites -avoiding contact with droplet nuclei -reducing aerosol dispersion

Borrelia hermsii

-*Borrelia hermsii is linked to tick-borne relapsing fever* -zoonosis; reservoirs include squirrels, chipmunks and other wild rodents -tick-borne relapsing fever occurs sporadically in the US -campers, backpackers and forestry personnel who frequent high elevations of western states -louse-borne relapsing fever occurs when famine, war or natural disasters are coupled with poor hygiene, crowding and inadequate medical attention -host is infected when lice are smashed and scratched into a wound or skin -pathogenesis and the nature of relapses -pathogenesis is similar in both tick- and louse-borne relapsing fever -the fever (in relapsing fever) follows a fluctuating course -explained by changes in the spirochetes and attempts of the immune system to control -the spirochetes change surface antigens during growth so previously produced antibodies lose effectiveness -cells with the new antigen type survive and new symptoms appear -new antibodies are formed but the spirochete cells change antigens so that the relapsing pattern continues -diagnosis, treatment and prevention -diagnosis involves patient history, clinical symptoms and presence of Borrelia in blood smears -except for pregnant women and young children, doxycycline or tetracycline is the treatment of choice -*prevention* depends on controlling rodents and avoiding tick bites -louse-borne relapsing fever can be controlled with improved hygiene

Brucella

-*Brucella* causes brucellosis (synonyms include *undulant fever and Bang disease)* -*zoonosis* transmitted to humans from infected animals or animal products -humans infected experience a severe febrile illness but not abortion -animal brucellosis results from infection of the placenta and fetus that can cause abortion -associated with occupational contact in slaughterhouses, livestock handling and the veterinary trade -infection through contact with blood, urine, placentas, and consumption of raw milk/cheese -Brucella enters through damaged skin or mucous membranes -virulence linked to ability to survive and grow inside macrophages -cardinal manifestation of human brucellosis is a fluctuating pattern of fever (undulant fever) -diagnosis -patient history -serological tests of the patient's blood -blood culture of the pathogen -*prevention* -testing and elimination of infected animals -quarantine of imported animals -pasteurization of milk -animal vaccines are available but vaccines for humans are ineffective or unsafe

Chlamydophila psittaci

-*Chlamydophila psittaci and ornithosis* -pneumonia-like illness transmitted by birds; "parrot" fever -zoonosis that is carried in a latent state in wild and domesticated birds -in the U.S., poultry have been subject to epidemics -transmitted to humans by contaminated feces and other discharges that become airborne and are inhaled -control includes quarantining imported birds and taking precautions in handling birds, feathers and droppings (care in cleaning cages)

Clostridium botulinum (C. botulinum)

-*Clostridium botulinum produces a severe intoxication usually from hand-bottled foods* -epidemiology of botulinum food poisoning (botulism) -intoxication usually associated with eating canned or preserved foods -modern techniques of food preservation and medical treatment have reduced incidence and fatality rates -often associated with low-acid vegetables such as green beans and corn -occasionally associated with meats, fish and dairy products -most outbreaks occur in home-processed foods -canned vegetables, smoked meats and cheese spreads -pathogenesis of botulism -endospores can survive if contaminated food is not properly bottled and steamed in a pressure cooker -proper temperature, pressure and time are required -infant and wound botulism -infant botulism is the most common type of botulism in the US (80 to 100 cases/year) -food sources could include raw honey or homemade baby food -the immature state of the neonatal intestine and resident microbes allow endospores to establish, germinate and release neurotoxin -babies exhibit the following symptoms -flaccid paralysis -have a weak suckling response -generalized loss of tone ("floppy baby syndrome") -respiratory complications -wound botulism -endospores enter through a wound or puncture -infection rate is highest in people who inject black tar heroin into the skin -*treatment and prevention of botulism* -education of proper methods of preserving and handling canned foods -pressure cookers should be tested for accuracy -home canners should be aware of the types of foods and conditions likely to cause botulism -addition of preservatives such as sodium nitrite, salt or vinegar -avoid bulging cans and bottles that look or smell spoiled -all home-bottled foods should be boiled for 10 minutes (toxin is heat-sensitive)

Clostridium difficile (C. difficile)

-*Clostridium difficile causes antibiotic-associated or pseudomembranous colitis* -second most common intestinal disease (after salmonellosis) in industrialized countries -many instances are traced to therapy with broad-spectrum antibiotics -origin for the term antibiotic-associated colitis -major cause of diarrhea in hospitals -able to superinfect the large intestine when the normal microbiota have been disrupted -enterotoxins trigger necrosis of the large intestine wall -predominant symptom is diarrhea -the colon becomes inflamed and gradually sloughs off loose, membrane-like patches -cecal perforation and death can occur -uncomplicated cases respond to withdrawal of antibiotics and fluid/electrolyte replacement -severe infections are treated with oral vancomycin or metronidazole -replacement cultures can help restore normal microbiota -fecal microbiota transplantation -feces from a healthy donor transferred by enema or colonoscopy directly to colon of patients suffering from C. difficile infections -immediate diagnosis is obtained by a rapid ELISA that detects toxins in fecal samples -clostridial food poisoning -Clostridium botulinum and Clostridium perfringens

Rickettsia rickettsii

-*Rocky Mountain Spotted Fever is caused by Rickettsia rickettsii* -transmitted by ticks -majority of cases concentrated in the Ozark and Appalachian mountain regions of the U.S. -occur most frequently in the spring and summer (tick vector is most active) -the dog tick (Dermacentor) is probably most responsible for transmission to humans -major vector in the southeast US -distinctive spotted rash within one to three days -grave manifestations are cardiovascular disruption including hypotension, thrombosis and hemorrhage -drug of choice is doxycycline -prevention is controlling the tick vector (wear light colored clothing, insect repellant such as DEET and stay on open trails)

Identify the functions of pertussis toxin and tracheal cytotoxin.

-*pertussis toxin* results in increased mucus production -*tracheal cytotoxin* inhibits the movement of cilia on the epithelial cells of the respiratory tract -loss of ciliary cells leads to a buildup of mucus and blockage of the airways

Clostridium perfringens (C. perfringens)

-*Clostridium perfringens is linked to gas gangrene/myonecrosis* -*factors* that predispose an individual to gangrene are injuries contaminated by endospores -surgical incisions -compound fractures -diabetic ulcers -septic abortions -puncture and gunshot wounds and crushing injuries -infection requires damaged or dead tissue that supplies growth factors and an anaerobic environment -stimulate endospore germination, rapid growth in the dead tissue and the release of exotoxins -*alpha-toxin* (lecithinase) causes red blood cell rupture, edema and tissue destruction -other virulence factors include collagenase, hyaluronidase and DNase -extent and symptoms of infection -*anaerobic cellulitis* is localized and does not spread into healthy tissue -bacteria spread in damaged tissue and produce toxins and gas -*true myonecrosis* is more destructive and mimics necrotizing fasciitis -toxins diffuse into healthy tissues and cause necrosis -disease can progress through an entire limb or body area, destroying tissue -the role of clostridia in infection and disease -two types of clostridial disease -wound and tissue infection -myonecrosis, antibiotic-associated colitis and tetanus -food intoxication -*treatment and prevention of gangrene* -immediate and rigorous cleaning and surgical repair of deep wounds, bedsores, compound fractures and infected incisions -*debridement* is the surgical removal of dead or damaged tissue -the preferred treatment is clindamycin, supplemented with penicillin -hyperbaric oxygen therapy can lessen the severity of the disease -extensive myonecrosis of a limb may require amputation

Clostridium tetani (C. tetani)

-*Clostridium tetani causes tetanus or lockjaw* -tetanus is a neuromuscular disease -endospores enter through puncture wounds, burns, the umbilicus, frostbite and crushed body parts -*neonatal tetanus* is the result of an infected umbilicus or circumcision -high in cultures that apply mud or dung to these sites to stop bleeding or as a customary ritual -the course of infection and disease -since the organism is a strict anaerobe, endospores cannot become established unless tissues are necrotic and poorly supplied with blood -these conditions favor germination of the endospore -*tetanospasmin* is a potent neurotoxin released by the vegetative cells -targets motor nerve endings and travels to the spinal cord -toxin binds to target sites on the spinal neurons and inhibits the proper release of neurotransmitters -inhibits proper skeletal muscle contraction -muscles are released from normal inhibition and contract uncontrollably -first symptoms are clenching of the jaw, followed in succession by arching of the back, flexion of the arms and extension of the legs -lockjaw confers *risus sardonicus* (sarcastic grin) -death is due to paralysis of respiratory muscles and respiratory failure -*treatment and prevention of tetanus* -antitoxin therapy with human tetanus immune globulin (TIG) -effective vaccine containing tetanus toxoid (DTaP) -childhood protection lasts about 10 years

Coxiella burnetii

-*Coxiella burnetii is the common agent of Q fever* -an intracellular parasite -humans acquire infection by environmental contamination and airborne spread -sources of infection include urine, feces, milk and airborne particles from infected animals -people at highest risk -farm workers and meat cutters -lab technicians and veterinarians -consumers of raw milk

Erysipelothrix rhusiopathiae (E. rhusiopathiae)

-*Erysipelothrix rhusiopathiae is a zoonotic pathogen* -gram positive regular non-spore forming bacilli -primary reservoir appears to be the tonsils of healthy pigs -persists for long periods of time in sewage, seawater, soils and foods -humans at greatest risk for infection are those who handle animals, carcasses and meats -butchers, veterinarians, slaughterhouse workers, fishermen and farmers -common portal of entry in human infections is an abrasion or scratch on the hand or arm -the disease is called *erysipeloid* -characterized by inflamed dark red lesions that burn and itch -*treatment is penicillin or erythromycin* -animal handlers can lower their risk by wearing gloves

Francisella tularensis

-*Francisella tularensis causes tularemia* -*zoonotic disease* -associated with the outbreak of disease in wild rabbits *("rabbit fever")* -vectors include ticks, biting flies, mites and mosquitos -in a majority of cases, infection results when the skin or eye is inoculated through contact with infected animals, animal products, contaminated water and dust -vector bites are also a frequent source of infection -intracellular pathogen that survives and spreads in macrophages to multiple sites -protection -live, attenuated vaccines -protective gloves, masks, and eyewear for lab workers and other occupationally exposed personnel

Legionella

-*Legionella is linked to legionellosis (Legionnaire's disease)* -organism is widely distributed in aqueous habitats -free-living amoebas in the water serve as a primary reservoir -human infections are commonly traced to tap water, cooling towers, spas, hot tubs, grocery store misters, misting systems and vaporizers -bacteria are released during aerosol formation -prevalent in males over the age of 50 years -nosocomial infections occur most often in elderly individuals hospitalized with diabetes, malignant disease, transplants, alcoholism and lung disease -noncommunicable -two major clinical forms of the disease -Legionnaire's disease is more severe -progresses to lung consolidation and impaired respiration and organ function -Pontiac fever does not lead to pneumonia and rarely causes death -diagnosed by symptoms and patient history -primarily treated with levofloxacin (quinolone that targets DNA gyrase) -control is difficult but chlorination and regular cleaning of artificial habitats

Leptospira

-*Leptospira and leptospirosis* -epidemiology and transmission of leptospirosis -zoonotic disease mainly found in the tropics -transmission occurs through contact of skin abrasions or mucous membranes with urine -spirochetes in the urine of infected animals -pathology of leptospirosis and host response -principal targets are the liver, kidneys, brain and eyes -two phases -leptospiremic phase -pathogen appears in the blood and CSF -immune phase -blood infection is cleared by natural defenses -marked by milder fever, headache due to leptospiral meningitis and Weil's syndrome -Weil's syndrome -characterized by kidney invasion, hepatic disease, jaundice, anemia and neurological disorders -diagnosis, treatment and prevention -dark-field microscopy of specimens, Leptospira culture and serological tests -macroscopic slide agglutination test -fast, specific and effective test used for screening -treatment with penicillin or doxycycline -vaccination for individuals with greater risk -combat troops training in jungle regions -animal care and livestock workers -wear protective footwear and clothing and avoid swimming or wading in natural waters used by animals

Listeria monocytogenes (L. monocytogenes)

-*Listeria monocytogenes is an emerging food-borne pathogen that causes listeriosis* -regular gram positive non-spore forming bacilli indicates that they stain uniformly and are not pleomorphic -morphology is coccobacilli to long filaments in palisades formation -resistant to cold, heat, salt, pH extremes and bile -*virulence factors* -replicates in the cytoplasm of the host cell after inducing its own phagocytosis -has the ability to move from cell to cell avoiding host immune responses -mature bacteria produce long *actin tails* which allow them to move from one cell to another -epidemiology and pathology of listeriosis -primary reservoir is soil or water (secondary sources are animals, plants and food) -cases of listeriosis are associated with ingesting contaminated dairy products, poultry and meats -aged cheeses from raw milk are a concern since the organism survives long storage and can grow during refrigeration -listeriosis is the third most prevalent cause of food-borne fatalities after salmonellosis and toxoplasmosis -outbreak in 2011 linked to cantaloupes (responsible for 33 deaths and one miscarriage) -predisposing factor seems to be the weakened condition of host defenses in the intestinal mucosa -studies have shown that immunocompetent individuals are rather resistant to infection -pregnant women are susceptible to infection -transmitted to the infant prenatally when the microbe crosses the placenta -transmitted to the infant perinatally through the birth canal -intrauterine infections are systemic and usually result in miscarriage and fetal death -diagnosis and control of listeriosis -cold enrichment can help isolate the pathogen but may take 4 weeks -rapid diagnostic kits using ELISA, immunofluorescence and DNA analysis are available for direct testing of foods -ampicillin and gentamicin are the first choice followed by trimethoprim/sulfamethoxazole -*prevention* -adequate pasteurization and thorough cooking of food that may be contaminated with animal feces

Mycobacterium tuberculosis (M. tuberculosis)

-*Mycobacterium is linked to tuberculosis and leprosy* commonly called the tubercle bacillus -epidemiology and transmission of tuberculosis -US cases show a strong correlation with age, sex and recent immigration history of the patient -highest case rates occur in people over 65 years of age as well as new immigrant populations from certain areas of SE Asia, Latin America, and Africa and in AIDS patients -transmitted by fine droplets of respiratory mucus suspended in the air -tubercle bacillus is very resistant; can stay viable for up to 8 months in aerosol particles -pronounced among people sharing closed, small rooms with limited access to fresh air -factors that affect a person's susceptibility -inadequate nutrition, debilitation of the immune system and lung damage -genetics and poor access to medical care -the course of infection and disease -humans are easily infected with the tubercle bacillus but are resistant to the disease -majority of TB cases (85%) are contained in the lungs -disseminated tubercle bacilli can give rise to tuberculosis in any organ of the body -initial infection and *primary tuberculosis* -the minimum infectious dose for lung infection is approximately 10 cells -bacilli are phagocytized by alveolar macrophages and multiply within the cells (intracellular) -after 3 to 4 weeks, the immune system mounts a cell-mediated response against the bacilli -formation of specific infection sites called *tubercles* -tubercles are granulomas with a central core containing TB bacilli and macrophages -frequently the centers of the tubercles break down into a necrotic lesion *(caseous necrosis)* -response of T cells to tubercle proteins causes a cell-mediated response evident in the tuberculin reaction (diagnosis) -*latent and recurrent tuberculosis* -bacilli can remain latent and can become activated weeks, months or years later -especially in individuals with weak immune systems -tubercles filled with masses of bacilli expand and drain into the bronchial tubes and upper respiratory tract -severe symptoms lead to gradual wasting of the body (an old name for TB was consumption) -*extrapulmonary tuberculosis* -bacilli can disseminate rapidly to other sites other than the lungs -organs most commonly involved are regional lymph nodes, kidneys, long bones, genital tract, brain and meninges -clinical methods for detecting tuberculosis -tuberculin skin test -delayed hypersensitivity reaction to tuberculoproteins -used to screen populations for the tuberculosis infection -is also called the *Mantoux test* -involves a local injection of purified protein derivative from M. tuberculosis -site is observed 48 to 72 hours for a red *induration* -chest X-rays -chest x-rays may be suggestive of (but are never diagnostic of) TB -primary tubercular infection presents several appearances -fine areas of infiltration -enlarged lymph nodes in the lower and central areas of the lungs -secondary tuberculosis show extensive infiltration in the upper lungs and bronchi and marked tubercles -acid-fast staining of sputum or other specimens may be used to detect Mycobacterium -cultural isolation and identification -M. tuberculosis is most accurately diagnosed by isolating and identifying the causative agent in pure culture -management and prevention of tuberculosis -treatment usually lasts for 6 to 24 months -combination therapy is used to reduce drug resistance -a one-pill regimen called Rifater is considered the best combination -contains isoniazid (INH), rifampin and pyrazinamide -in the hospital, the use of UV lamps in air conditioning systems and negative pressure rooms to isolate TB patients can help to control the spread of infection -*vaccine based on "bacilli Calmet-Guerin" (BCG)* -often given to children in countries that have high rates of tuberculosis -US does not have a high incidence as other countries -BCG vaccine is not generally recommended except among certain health professionals and military personnel who may be exposed to TB carriers -Mycobacterium is characterized by layered cell walls containing *mycolic acid* and waxes -high lipid content imparts acid-fastness -responsible for resistance of cells to drying, acids and various germicides -Mycobacterium tuberculosis is commonly called the tubercle bacillus -contain complex waxes and a *cord factor* that contribute to virulence by preventing the mycobacteria from being destroyed by lysosomes of macrophages after phagocytosis -allows persistence in the macrophages as *intracellular parasites*

Mycobacterium leprae (M. leprae)

-*Mycobacterium leprae is linked to leprosy (Hansen's Disease)* different from other mycobacteria by two ways -it is a strict parasite that has not been grown in artificial media or human tissue cultures -it is the slowest growing of all the species -leprosy is a progressive disease of the skin and peripheral nerves -epidemiology and transmission -incidence of the disease is declining due a worldwide control effort -in the US, reported cases number 50 to 100 per year -limited locales in Hawaii, Texas, Louisiana, Florida and California -armadillos harbor a mycobacterial species genetically identical to M. leprae and may develop a disease similar to leprosy -risk of contracting leprosy from armadillos is low -the leprosy bacillus is not very virulent -long-term household contact with leprotics, poor nutrition and crowded conditions increase the risk of infection -the course of infection and disease -usually macrophages successfully destroy the bacilli and there are no initial manifestations of infection -a weakened immune response can lead to intracellular survival of the pathogen -incubation period is usually 2 to 5 years -*tuberculoid leprosy* -characterized by shallow skin lesions -damage to nerves usually results in local loss of feeling and pain perception -*lepromatous leprosy* -responsible for the disfigurations commonly associated with leprosy -*lepromas* are caused by massive intracellular overgrowth of M. leprae -most severe effect of intermediate forms of leprosy is early damage to nerves that control muscles of the feet and hands -wasting of muscles and loss of control produce "drop foot" and "claw hands" -sensory damage can lead to trauma and loss of digits -diagnosing leprosy -*feather test* in endemic areas can be used to indicate a loss of sensation -numbness in the hands and feet, loss of heat and cold sensitivity, muscle weakness, thickened earlobes and chronic stuffy nose are additional evidences -laboratory diagnosis utilizes the *acid-fast stain* looking for acid-fast bacilli skin lesions, nasal discharges and tissue samples -*treatment and prevention of leprosy* -tuberculoid leprosy uses multidrug therapy with rifampin and dapsone (12 to 24 months) -lepromatous leprosy uses rifampin, dapsone and clofazimine (up to 2 years) -prevention requires surveillance, isolation of leprosy patients and chemoprophylaxis of healthy individuals in close contact with leprotics -infections by nontuberculous mycobacteria (NTM) -disseminated mycobacterial infection in AIDS -Mycobacterium avium complex (MAC) frequently cause secondary infections in AIDS patients -these common soil bacteria usually enter through the respiratory tract and rapidly disseminate in individuals with low immune ability -nontuberculous lung disease -pulmonary infections caused by commensal mycobacteria have symptoms like a milder form of tuberculosis but are not communicable -M. kansasii is endemic to the midwestern and southwestern US and parts of England -miscellaneous mycobacterial infections -M. marinum infection has been called swimming pool granuloma -a hazard of scraping against the rough concrete surfaces lining swimming pools

Shigella

-*Shigella causes shigellosis* -marked with abdominal cramps and frequent defecation of watery stool filled with mucus and blood -acquired primarily by eating fecally contaminated foods -quick guide to remember the sources -"feces transferred to food, fingers, flies, and sometimes fomites" (Five F's") -associated with lax sanitation, malnutrition and crowding -spread epidemically in day cares, prisons, mental institutions, nursing homes and military camps -*Shigella invades the large intestine rather than the small intestine (Salmonella)* -not as invasive as Salmonella -does not perforate the intestine or invade the bloodstream -instigates an inflammatory response that causes tissue destruction -the release of an endotoxin causes fever and an enterotoxin that damages the mucosa -Shigella dysenteriae produces an exotoxin called *Shiga toxin* -causes damage to nerve cells and the intestine as well as the kidneys -infection is treated by fluid replacement and oral drugs -prevention is essentially the same as for salmonellosis

Treponema pallidum

-*Treponema palladium: the spirochete of syphilis* -sexually transmitted -epidemiology and virulence factors of syphilis -human is the sole natural host and source -risk of an infection from an infected sexual partner is 12% to 30% -cases have more than doubled since 2000 -major contributors to this trend are gay and bisexual men in large urban areas -prostitutes and their contacts -IV drug abusers -individuals with syphilis often suffer concurrent infection with other STDs -pathogenesis and host response -acquired by direct contact with mucous membranes or abraded skin *treatment and prevention* -penicillin G -tetracycline and docycycline are less effective and indicated if penicillin allergy is documented -prevention includes abstinence, monogamous relationships and education -control relies on detection and treatment of sexual contacts of patients with syphilis

Yersenia pestis

-*Y. pestis is the nonenteric agent of bubonic plague* -nonenteric Yersinia pestis and plague -virulence factors -capsular and envelope proteins which protect against phagocytosis and allow intracellular growth -*coagulase* clots blood and is involved in clogging the esophagus of fleas and obstructing blood vessels in humans -epidemiology and life cycle of plague -exists naturally in many animal hosts throughout the world -persons most at risk include veterinarians and individuals living and working near forests and woodlands -epidemiology involves several types of vertebrate hosts and flea vectors -humans can develop plague through several means -contact with wild *(sylvatic plague)* or domesticated animals *(urban plague)* -contact with infected humans -animal reservoirs -long-term endemic reservoirs are rodents -harbor the organism but do not develop disease -the hosts spread the disease to other mammals called amplifying hosts -these hosts become infected and experience massive die-offs during epidemics -these hosts are the usual sources of human plague -*flea vectors* -flea ingests a blood meal from an infected animal; bacilli multiply in gut of flea -esophagus becomes blocked by coagulated blood and the flea cannot effectively feed -the flea jumps from animal to animal trying to get nourishment -humans can become infected by flea bites, handling infected animals, animal skins or meat and by inhaling droplets -pathology of plague -in *bubonic plague*, the bacillus multiplies in the flea bite, enters the lymph and is filtered by lymph nodes -infection causes necrosis and swelling of the node called a *bubo* -generally inguinal or axillary -*septicemic plague* is massive bacterial growth in the blood -intravascular coagulation, subcutaneous hemorrhage and purpura that may degenerate into necrosis and gangrene -this causes a visible darkening of the skin and is often called "black death" -*pneumonic plague* is localized in the lungs -highly contagious through sputum and aerosols; fatal if not treated -diagnosis, treatment and prevention -diagnosis -patient history including travel to endemic regions -symptoms -laboratory findings from bubo aspirates -treatment drug of choice is streptomycin -*preventions* include quarantines, controlling rodents and dusting rodent burrows with insecticides to kill fleas

Define and compare the three types of hemolysis associated with the streptococci.

-*alpha hemolysis* produces a partial hemolysis of red blood cells -greenish zones of hemolysis are produced -Streptococcus pneumoniae, viridans strep and group D are alpha hemolytic -*beta hemolysis* produces clear zones due to complete hemolysis of red blood cells -groups A, B and C demonstrate beta hemolysis -non-hemolytic is indicated as *gamma hemolysis* -many exist as microbiota of the oral cavity -others live in domestic animals, including pets and can colonize or infect humans

Compare coliforms to noncoliforms.

-*coliforms* ferment lactose rapidly and include E. coli -*noncoliforms* are either slow-lactose fermenting or non-lactose-fermenting bacteria

Identify the three forms of anthrax.

-*cutaneous anthrax* is caused by endospores entering the skin (cuts and abrasions) -most common and least dangerous form -produces a necrotic lesion called an *eschar* -*pulmonary anthrax* is associated with the inhalation of endospores -historically called woolsorter's disease -in the lungs, the endospores are phagocytosed and transported to lymph nodes -the endospores germinate and produce exotoxins that enter the circulatory system -toxins attach to the membranes of macrophages and gain entry through engulfment -toxins are highly lethal causing macrophage death and release of chemical mediators -effects include capillary thrombosis, cardiovascular shock and rapid death (if untreated) -*gastrointestinal anthrax* is rare

Compare the EBs and RBs of chlamydias.

-*elementary body* (EB) is the inactive, infectious form released from an infected host cell -shielded by a rigid, impervious envelope that ensures survival outside of host cell -*reticulate body* (RB) is not infectious and is actively dividing within the host cell -RBs are also energy parasites lacking enzyme systems for glucose catabolism and ATP production -possess ribosomes and have pathways for producing proteins, DNA and RNA

enterohemorrhagic E. coli O157:H7

-*enterohemorrhagic E. coli O157:H7 can lead to intestinal hemorrhage* -these bacteria owe much of their virulence to a cell wall receptor that fuses with host cell membrane -this type of E. coli has also acquired the *Shiga toxin* from Shigella -the toxin binds to ribosomes and disrupts protein synthesis -leads to death and shedding of the intestinal cells -a reservoir of E. coli is the intestines of cattle -can enter the food chain through contaminated beef, water and fresh vegetables -the infectious dose is small (100 cells) -commercially supplied hamburger can transmit E. coli because meat processing plants can mix meats from hundreds of sources -a single animal carrier can potentially contaminate thousands of pounds of beef -contaminant in vegetables, fruit drinks, and groundwater into which animal waste has seeped -symptoms and signs include gastroenteritis, dysentery, fever and acute abdominal pain -the more severe form of the disease is *hemolytic uremic syndrome* -caused by the effects of Shiga toxin in the blood and kidneys -leads to hemolysis and kidney damage and failure -children, the elderly and immunocompromised individuals are at highest risk -USDA has increased monitoring of fresh meats and sausages -testing for O157:H7 is randomly performed and is not required by slaughterhouses and meat suppliers -all fresh meats and poultry products have a small warning label (safe handling instructions) -miscellaneous infections caused by E. coli -causes 50% to 80% of UTIs in healthy people -more common in women -short urethras promote ascending infection to the urinary bladder -patients with bladder catheters are also at risk for E. coli urethritis -E. coli and the coliform count -E. coli is one of the indicator bacteria to monitor fecal contamination in water, food and dairy products

Identify the lesions associated with primary, secondary and tertiary syphilis.

-*primary syphilis* -appearance of a lesion called a *chancre* at the site of inoculation; contains viable spirochetes -begins as a small, red, hard bump that enlarges and breaks down leaving a shallow crater with firm margins -most chancres appear on the internal and external genitalia -can occur on the lips, nipples, on fingers or around the anus -chancre heals spontaneously without scarring; spirochete enters a period of systemic activity -*secondary syphilis* -after the chancre heals (average 6 weeks), the secondary stage appears -red or brown *rash* that breaks out on all skin surfaces, including the palms and soles -these lesions also contain viable spirochetes and disappear spontaneously in a few weeks -*latency and tertiary syphilis* -after resolution of secondary syphilis, about 30% of infections enter a latent period that can last 20 years or longer -tertiary syphilis is rare today because of widespread antibiotic use -lesion is a *gumma* which can develop in tissues such as the liver, skin, bone and cartilage -neurosyphilis can involve any part of the nervous system -affinity for blood vessels in the brain, cranial nerves and dorsal roots of the spinal cord -Argyll-Robertson pupil reaction -small pupils that do not react to light -most common sign indicating damage to the nerves that control the iris

Describe how tetanus toxin (tetanospasmin), botulin toxin and diptherotoxin work in the human body.

-*tetanospasmin* is a potent neurotoxin released by the vegetative cells -targets motor nerve endings and travels to the spinal cord -toxin binds to target sites on the spinal neurons and inhibits the proper release of neurotransmitters -inhibits proper skeletal muscle contraction -muscles are released from normal inhibition and contract uncontrollably -first symptoms are clenching of the jaw, followed in succession by arching of the back, flexion of the arms and extension of the legs -lockjaw confers *risus sardonicus* (sarcastic grin) -*botulinum toxin* is a potent exotoxin -this neurotoxin targets the neuromuscular junction of skeletal muscles -prevents the release of neurotransmitter (acetylcholine) -initial symptoms include neuromuscular symptoms -double vision, difficulty in swallowing and dizziness -later symptoms include muscular paralysis and respiratory failure -major determinant of pathogenicity is the production of *diphtherotoxin* -toxigenic strains of C. diphtheriae can produce this exotoxin from viral genes acquired during transduction -the main consequence of this cytotoxin is the arrest of protein synthesis -the local infection produces an inflammatory response, sore throat, nausea, vomiting, enlarged cervical lymph nodes and fever -complication is the production of a greenish-gray *pseudomembrane* that develops in the pharynx -if it forms in the airways, it can cause asphyxiation

Identify the two strains of Chlamydia trachomatis.

-*trachoma* strain attacks the mucus membranes of the eyes, lungs and genitourinary tract -*lymphogranuloma venerum* strain targets the lymphatic tissues of the genitalia

Identify the two types of leprosy.

-*tuberculoid leprosy* -characterized by shallow skin lesions -damage to nerves usually results in local loss of feeling and pain perception -*lepromatous leprosy* -responsible for the disfigurations commonly associated with leprosy -*lepromas* are caused by massive intracellular overgrowth of M. leprae -most severe effect of intermediate forms of leprosy is early damage to nerves that control muscles of the feet and hands -wasting of muscles and loss of control produce "drop foot" and "claw hands" -sensory damage can lead to trauma and loss of digits

Identify two important sequelae associated with S. pyogenes.

-*two important sequelae* -*rheumatic fever* is an inflammatory condition of the joints and heart -in severe carditis, heart valve and muscle damage can occur -*acute glomerulonephritis* is a disease of the kidney -kidney cells are so damaged that they cannot filter blood -urine samples are abnormal with high levels of blood cells and protein

Escherichia coli

-Escherichia coli is the best known coliform -*examples of pathogenic strains of E. coli* -*enterotoxigenic* E. coli -diarrheal illness linked to two exotoxins that stimulate secretion and fluid loss -*enteroinvasive* E. coli -inflammatory disease that involves invasion/ulceration of the mucosa of the large intestine -*enteropathogenic* E. coli -linked to a form of infantile diarrhea -*enterohemorrhagic* E. coli is commonly called E. coli O157:H7 -causes hemorrhagic colitis and may lead to *hemolytic uremic syndrome* (damage kidney) -clinical diseases of E. coli -pathogenic strains are frequent agents of infantile diarrhea -greatest single cause of mortality among babies -rate of infection is higher in crowded tropical regions -poor sanitation -contaminated water supplies -adults carry pathogenic strains to which they have developed immunity -immature, nonimmune neonatal intestine has no protection -enterotoxigenic strains are linked to 70% of travel-associated gastrointestinal diseases -"Montezuma's revenge" and "Delhi belly" -traveler's pick up virulent strains while eating or drinking contaminated food/water -Pepto-Bismol helps to counteract the enterotoxin and also provides an antimicrobic effect

Identify the three complex surface antigens that are important in pathogenicity and immune responses in the enterics.

-H is the flagellar antigen -K is the capsule and/or fimbrial antigen -O is the somatic or cell wall antigen -not all species carry the H and K antigens but all have the O antigen -the O antigen is LPS implicated in endotoxic shock -antigens are identified by serotyping -specific antibodies are mixed in a culture to measure the degree of agglutination or precipitation -pathogenesis of enterics is linked to endotoxins, exotoxins, capsules, fimbriae and adhesion molecules

Haemophilus influenza

-Haemophilus means blood-loving -this organism requires factors released by lysed RBCs for energy metabolism -is the agent for *acute bacterial meningitis* in humans (primarily caused by the b serotype) -transmitted by close contact with nose and throat discharges -treated with third generation cephalosporins -*Hib vaccine* is recommended for children -*Haemophilus aegypticus is a primary agent of acute communicable conjunctivitis (pinkeye)* -spread through contaminated fingers and shared personal items -also spread by gnats and flies -treated with antibiotic eyedrops -Haemophilus ducreyi is the agent of *chancroid* which is a STD -Haemophilus parainfluenzae is involved in infective endocarditis in adults who have underlying congenital or rheumatic heart disease

Identify several ways that tuberculosis can be detected.

-clinical methods for detecting tuberculosis -*tuberculin skin test* -delayed hypersensitivity reaction to tuberculoproteins -used to screen populations for the tuberculosis infection -is also called the *Mantoux test* -involves a local injection of purified protein derivative from M. tuberculosis -site is observed 48 to 72 hours for a red *induration* -chest X-rays -chest x-rays may be suggestive of (but are never diagnostic of) TB -primary tubercular infection presents several appearances -fine areas of infiltration -enlarged lymph nodes in the lower and central areas of the lungs -secondary tuberculosis show extensive infiltration in the upper lungs and bronchi and marked tubercles -acid-fast staining of sputum or other specimens may be used to detect Mycobacterium -cultural isolation and identification -M. tuberculosis is most accurately diagnosed by isolating and identifying the causative agent in pure culture

Identify some of the major steps and organisms involved in the formation of plaque and dental caries.

-dental caries is the most common human disease -sugar, microbes and acid are all required in the initiation of dental caries -*plaque* and dental caries formation -tooth surface develops a thin layer of adhesive salivary glycoproteins (acquired pellicle) -the pellicle presents a potential substrate upon which certain bacteria can attach (biofilm) -fibers of proteins, antibodies, salivary enzymes and bacterial debris adhere to the pellicle -earliest colonizers are Streptococcus organisms which can adhere to the outer pellicle -form the initial base of plaque -cell-cell signaling and coaggregation with additional colonists adding to biofilm -rod-shaped Actinomyces are common in this stage -Streptococcus species secrete fructans and glucans that add bulk to the biofilm -if plaque is allowed to remain, other bacteria will aggregate creating a denser mat of plaque -initial damage to enamel occurs when streptococci ferment sugars in plaque to acids -acids etch or weaken the enamel surface resulting in dental caries

Chlamydia trachomatis

-diseases of Chlamydia trachomatis -EBs are transmitted through contact with secretions -two human strains -*trachoma* strain attacks the mucus membranes of the eyes, lungs and genitourinary tract -*ocular trachoma* is a major cause of blindness in certain parts of the world -transmission favored by contaminated fingers, fomites, flies, and a hot, dry climate -inflammation of the conjunctiva is followed by an infiltration of lymphocytes and macrophages into infected area -as cells accumulate, they impart a pebbled (rough) appearance to the inner part of the upper eyelid -a vascular pseudomembrane of exudate and inflammatory leukocytes forms over the cornea (called a pannus) -early treatment with azithromycin is highly effective -inclusion conjunctivitis is acquired through contact with secretions of an infected genitourinary tract -infantile conjunctivitis develops 5 to 12 days after a baby has passed through the birth canal of an infected mother -initial signs are conjunctival irritation, redness and a profuse adherent exudate -routine eye prophylaxis of all newborns (as for gonococcal infection) -*lymphogranuloma venerum* strain targets the lymphatic tissues of the genitalia -is sexually transmitted -70% of infected women harbor the bacterium asymptomatically (10% of males) -chlamydiosis is the most prevalent bacterial disease -virulent strains of Chlamydia that chronically infect the genitourinary tract results in a severe disease called lymphogranuloma venerum -enters through nicks or breaks in the perigenital skin or mucus membranes -forms a small painless vesicular lesion -lymph nodes near the lesion fill with granuloma cells and they enlarge -become firm and tender bubos -can cause lymphatic obstruction leading to deforming edema of the genitalia and anus -identification, treatment and prevention of chlamydiosis -immunofluorescent staining of specimens and PCR are commonly used in identification -methods useful in diagnosing inclusion conjunctivitis are Giemsa or iodine stains -most effectively treated with drugs that act intracellularly (such as doxycycline or azithromycin) -prevention of sexually transmitted chlamydial diseases -includes abstinence, monogamy and education

Compare gingivitis and periodontitis.

-initial signs of *gingivitis* are swelling, loss of normal contour, redness, and bleeding -spaces of pockets of varying depth also develop between the tooth and gingiva -persistence leads to a more serious disease called *periodontitis* -involves loss of the periodontal ligament and produces deeper pockets -results in bone resorption resulting in loosening of the tooth in its socket (tooth can be lost)

Corynebacterium diptheriae (C. diptheriae)

-irregular non-spore-forming bacteria tend to be pleomorphic and stain unevenly -possess mycolic acids and a unique type of peptidoglycan in the cell wall -rod-shaped with many pleomorphic variations; palisade arrangements -epidemiology of diphtheria -many populations harbor a reservoir of healthy carriers so the potential for diphtheria is constantly present -pathology of diphtheria -exposure results from close contact with droplets from human carriers -occasional exposure from fomites or contaminated milk -clinical disease has two stages -local infection by C. diphtheriae -toxin production and toxemia -common location of primary infection is the upper respiratory tract -cutaneous diphtheria usually starts as a secondary infection producing ulcerations that are slow to heal -diphtherotoxin and toxemia -major determinant of pathogenicity is the production of *diphtherotoxin* -toxigenic strains of C. diphtheriae can produce this exotoxin from viral genes acquired during transduction -the main consequence of this cytotoxin is the arrest of protein synthesis -the local infection produces an inflammatory response, sore throat, nausea, vomiting, enlarged cervical lymph nodes and fever -complication is the production of a greenish-gray *pseudomembrane* that develops in the pharynx -if it forms in the airways, it can cause asphyxiation -the most dangerous systemic complication is toxemia -toxin is carried to certain target organs, primarily the heart and nerves -causes myocarditis and abnormal EKG patterns in the heart -muscle weakness and paralysis can result from cranial and peripheral nerve involvement -diagnostic methods for Corynebacterium -initial diagnosis may be based on the presence of the pseudomembrane -simple stain reveals pleomorphic granulated (metachromatic granules) cells -Elek test is an assay that relies on antibodies to detect toxins -important to differentiate C. diphtheriae from other "diphtheroids" -C. xerosis lives in the eye, skin and mucous membranes -occasional opportunist in eye and postoperative infections -C. pseudodiphtheriticum is a normal inhabitant of the human nasopharynx -can colonize natural and artificial heart valves -*treatment and prevention of diphtheria* -toxemia is treated with DAT (diphtheria antitoxin) derived from horses -prevention of diphtheria with a series of vaccinations with toxoids (DTaP) -this vaccine also prevents against tetanus and pertussis

Identify people most at risk of developing a Pseudomonas infection.

-most common nosocomial infections occur in compromised patients -individuals with severe burns, neoplastic disease, cystic fibrosis and premature birth -healthy people are subject to outbreaks of skin rashes, UTIs and ear infections from community hot tubs and swimming pools -bath sponges and wash cloths serve as a common reservoir (rubbed into the skin produce a rash)

Identify the most important complication associated with viridans streptococci.

-most important complication of viridans streptococcal infection is *subacute endocarditis*

Propionibacterium

-most prominent species is P. acnes, a common resident of the pilosebaceous glands of the skin -relationship with acne lesions of adolescence -acne is a complex disease also influenced by genetic and hormonal factors -occasionally involved in infections of the eye and artificial joints

Identify the group of organisms that are "membrane" parasites.

-mycoplasmas are sometimes called "membrane" parasites -acquire certain necessary lipids from host cell membranes

Identify why rickettsias are termed "energy parasites".

-obligate parasitism originates from the inability to metabolize AMP (precursor to ADP and ATP) -have to obtain ATP (energy) from their host; they are "energy parasites"

Compare petechiae to ecchymoses.

-petechiae are small subcutaneous hemorrhages -ecchymoses are larger

Identify the importance of urease to H. pylori.

-produce *urease* which converts urea into ammonia and bicarbonate (neutralize stomach acid)

Describe the mechanism of action of the cholera toxin.

-virulence due to the production of *cholera toxin* (enterotoxin) -cells shed large amounts of electrolytes (water follows) into the intestine -toxin stimulates the production of cAMP -disrupts membrane pumps leading to loss of electrolytes -symptoms begin abruptly with vomiting followed by secretory diarrhea -flecks of tissue debris in the stool leads to the description of "rice-water stool" -diarrhea reduces blood volume, acidosis from bicarbonate loss and potassium depletion

Streptococcus pneumonuia (S. pneumonia)

also referred to as the pneumococcus -involved in the majority of bacterial pneumonias (primarily affects immunocompromised patients) -major cause of meningitis in adults and otitis media in young children -alpha-hemolysis -*pathogenic strains have capsules as the major virulence factor (retard phagocytosis)* -epidemiology and pathology of S. pneumoniae -direct contact with respiratory secretions or droplets from carriers -predisposing factors -old age -season (infection rate is higher in the winter) -other lung diseases or viral infections that weaken body defenses -living in close proximity to infected individuals -pathology of Streptococcus pneumoniae -in the lungs, pneumococci multiply and induce an inflammatory response -marked by exudation of fluid into the lungs -in *lobar pneumonia*, this fluid accumulates in the alveoli along with red and white blood cells and the patient can actually "drown" in their secretions -if the mixture of exudate, cells and bacteria solidify, a condition called consolidation occurs -symptoms are chills, fever, shaking and rapid breathing -patient can experience severe pain, cyanosis and a cough that produces a bloody sputum -*otitis media* is a middle ear infection caused by S. pneumoniae -occurs readily in children since the Eustachian tube is short and more horizontal -healthy people have high natural resistance to the pneumococcus -mucus and ciliary responses of the respiratory tract help remove transients -alveolar macrophages are involved if the capsule is coated with opsonins in the presence of complement -*treatment and prevention* of pneumococcal infections -treatment of choice has been penicillin -~15% of isolates are termed DRSP have shown multidrug resistance -alternate drugs include cephalosporins, sulfonamides and quinolones -prevention involves two vaccines -Pneumovax consists of capsular antigens from 23 of the most common serotypes -indicated for older adults and at-risk populations -pneumococcal conjugate vaccine (Prevnar) -recommended for children (2 to 59 months) -preventive therapy for otitis media and meningitis

Identify the two stages associated with whooping cough.

initial stage is the *catarrhal stage* -marked by nasal drainage, congestion, sneezing and occasional coughing -*paroxysmal stage* is characterized by recurrent, persistent coughing -several abrupt, hacking coughs followed by a deep inhalation producing a "whoop" sound

What selective media is used to isolate S. aureus?

isolated on selective media such as *mannitol salt agar*

Neisseria gonorrhoeae (gonococcus)

cells are bean-shaped and paired -cells have LPS and capsules can be found on pathogenic strains -sexually transmitted -most cases occur in young adults with multiple sex partners -most infectious when transferred by direct contact -infection is asymptomatic in ~10% of males and 50% of females -in males, painful urination and a purulent discharge -scar tissue formation in the spermatic ducts can result in infertility -in females, bloody vaginal discharge and painful urination -characterized by fever, abdominal pain and tenderness -*pelvic inflammatory disease (PID)* -scar tissue formation can block fallopian tubes leading to sterility and ectopic pregnancies -extragenital gonococcal infections in adults -anal intercourse can lead to proctitis -oral sex can lead to gingivitis and pharyngitis -careless personal hygiene can lead to self-inoculation of the eyes (conjunctivitis) -gonococcal infections in children -*ophthalmia neonatorum* can result from an infant being infected during birth -untreated may lead to blindness -antibiotics, silver nitrate or other antiseptics are placed in the conjunctival sac of newborn babies -clinical diagnosis and control of gonococcal infections -gram stain -gram-negative diplococci in neutrophils from urethral, vaginal, cervical or eye exudates -in 2010, 27.2% of isolates were resistant to penicillin, tetracycline and ciprofloxacin -a large proportion of N. gonorrhoeae infections are complicated by a concurrent STD such as chlamydiosis -*treatment consists* of a cephalosporin (N. gonorrhoeae) and a doxycycline (chlamydial infection) -reportable infectious disease -follow-up involves tracking sexual partners to offer prophylactic antibiotic therapy -*control/prevention* -abstinence or monogamous relationships -education programs -safer sex practices such as the use of condom -*factors contributing to pathogenicity* -fimbriae promote attachment of cocci to each other and invasion and infection of epithelial tissue -fimbriae also slow phagocytosis -*IgA protease* cleaves secretory IgA (antibody) found on mucosal surfaces

Identify the three diseases associated with the DTaP vaccine.

diptheria, tetanus and pertussis

What selectve media is used to isolate Neisseria?

grown on Thayer-Martin media or *chocolate agar*

Identify and compare the three pathologic types of plague.

pathology of plague -in *bubonic plague*, the bacillus multiplies in the flea bite, enters the lymph and is filtered by lymph nodes -infection causes necrosis and swelling of the node called a *bubo* -generally inguinal or axillary -*septicemic plague* is massive bacterial growth in the blood -intravascular coagulation, subcutaneous hemorrhage and purpura that may degenerate into necrosis and gangrene -this causes a visible darkening of the skin and is often called "black death" -*pneumonic plague* is localized in the lungs -highly contagious through sputum and aerosols; fatal if not treated

Helicobacter pylori

primary habitat is the human stomach -*implicated in 90% of stomach and duodenal ulcers* -an apparent cofactor in a common type of stomach cancer called adenocarcinoma -probably transmitted person to person by oral-oral or fecal-oral route -spread by houseflies acting as mechanical vectors -proposed that the disease is a zoonosis transmitted from an animal reservoir -in the stomach, the organism bores through the mucosa and attaches to epithelial cells -one receptor specific for Helicobacter is the same receptor as type O blood -accounts for the higher rate of ulcers in people with type O blood -produce urease which converts urea into ammonia and bicarbonate (neutralize stomach acid) -isolated from biopsy specimens -urea breath test -tablet containing urea (and some minimally radioactive carbon) is swallowed - if H. pylori is present, exhaled radioactive carbon dioxide can be measured -newest recommended therapy is two to four week of clarithromycin to eliminate the bacterial infection along with stomach acid inhibitors

viridans streptococci

the most numerous and widespread inhabitants of the oral cavity -not highly invasive -entrance usually occurs through dental or surgical instrumentation and manipulation -chewing hard candy or brushing teeth can provide a portal of entry -most important complication of viridans streptococcal infection is *subacute endocarditis* -blood-borne bacteria target heart lining or valves -colonization leads to vegetations (thick biofilms) that can be released into the blood which can travel to the brain or lungs damaging these organs (emboli) -individuals with preexisting heart conditions are given prophylactic antibiotics prior to dental or surgical procedures -*dental caries* -viridans strep produce slime layers that adhere to tooth structure -plaque is formed and can be coinfected with other bacteria producing dental disease

Identify the virulence factors associated with Yersenia pestis.

virulence factors -capsular and envelope proteins which protect against phagocytosis and allow intracellular growth -*coagulase* clots blood and is involved in clogging the esophagus of fleas and obstructing blood vessels in humans