Ch. 20 - The Gram-Negative Bacilli of Medical Importance

True Pathogens

Haemophilus influenzae, Legionella pneumophila, Bordetella pertussis, Francisella tularensis, Yersinia pestis, Shigella Salmonella typhi

E. coli can cause __________.

Hemolytic Uremic Syndrome

E. coli can cause

acute diarrhea, UTIs, and Hemolytic Uremic Syndrome (O157:H7)

The flea is the vector that carries the Yersinia bacterium from animal to animal, causing _______ plague. pneumonic bubonic septicemic drug resistant

bubonic

The main distinction between the coliforms and noncoliforms is the ability to utilize _______ as a nutrient. lactose citrate glucose eosin

lactose

What are some noncoliform Lactose-Negative Enterics?

• Proteus • Morganella • Providencia • Salmonella • Shigella

Shigella causes:

• Shigellosis - incapacitating dysentery • S. dysenteriae, S. sonnei, S. flexneri, and S. boydii • Human parasites • Invades villus of large intestine, does not perforate intestine or invade blood • Enters Peyer's patches instigate inflammatory response; endotoxin and exotoxins -> rice-water stools

Characteristics of Pseudomonas

• Small gram-negative rods with a single polar flagellum • Free living: Primarily in soil, sea water, and fresh water; also colonize plants and animals • Important decomposers and bioremediators • Frequent contaminants in homes and clinical settings • Use aerobic respiration; do not ferment carbohydrates • Produce oxidase and catalase • Many produce water soluble pigments

Characteristics of Brucella

• Tiny gram-negative coccobacilli • 2 species: Brucella abortus (cattle), Brucella suis (pigs)

Salmonella and Shigella

• well-developed virulence factors, primary pathogens, not normal human flora • Associated with GI tract infections, including epidemics

Brucella causes:

- Brucellosis, aka malta fever, undulant fever, and Bang disease - a zoonosis transmitted to humans from infected animals

Antigenic Structures and Virulence Factors

- Complex surface antigens contribute to pathogenicity and trigger immune response • H: flagellar Ag • K: capsule and/or fimbrial Ag • O: somatic or cell wall Ag - all have • Endotoxin • Exotoxins

Please choose all features which allow Francisella tularensis to be an exemplary pathogen. - The symptomology can include relapses of the infection. - Very few bacterial cells can produce the disease. - The bacterium has the ability to spread to adjacent tissues because of enzymes that destroy the integrity of the tissues. - The bacterium can live within macrophages, and therefore be carried to locations around the body as the WBCs move.

- The symptomology can include relapses of the infection. - Very few bacterial cells can produce the disease. - The bacterium can live within macrophages, and therefore be carried to locations around the body as the WBCs move.

Infection Cycle of Yersinia pestis

- amplifying host: humans can be infected by it - endemic reservoir hosts: other animals can get infected by it but humans can't

Salmonella enteritidis

- causes GI tract infections and intoxifications - includes 1,700 different serotypes based on variation on O, H, and Vi - Flagellated; survive outside the host - Resistant to chemicals - bile and dyes • Salmonelloses other than typhoid fever are called enteric fevers, Salmonella food poisoning, and gastroenteritis • usually less severe than typhoid fever but more prevalent • zoonotic in origin but humans can become carriers - Cattle, poultry, rodents, reptiles, animal, and dairy products - Fomites contaminated with animal intestinal flora

Pertussis/whooping cough

- communicable childhood affliction - Acute respiratory syndrome - Often severe, life-threatening complications in babies - Loss of ciliary mechanism leads to buildup of mucus and blockage of the airways - Vaccine: DTaP (acellular vaccine contains toxoid and other Ags

Francisella tularensis

- considered to be one of the most infectious bacterial species due to an extremely small infectious dose - complex life cycle involves numerous animal reservoirs and arthropod vectors

Yersinia enterocolitica

- domestic and wild animals, fish, fruits, vegetables, and water - bacteria enter small intestinal mucosa, some enter lymphatic and survive in phagocytes; inflammation of ileum can mimic appendicitis

Characteristics of Facultative anaerobes

- grow best in air - ferment glucose - oxidase negative - catalase positive - 2 groups: coliforms (ferment lactose) and non-coliforms (do not ferment lactose)

Endotoxins

- heat-stable toxin associated withthe outer membranes of certain gram-negative bacteria - released only when the cells are disrupted - less potent and less specific than exotoxins

Yersinia pseudotuberculosis

- infection similar to Y. enterocolitica, more lymph node inflammation

Salmonella typhi

- most serious pathogen of the genus - cause of typhoid fever - human host - can also cause Septicemia - usually transmitted by indirect oral-fecal route

Characteristics of Klebsiella pneumoniae

- opportunistic Coliforms - normal inhabitant of respiratory tract, - large capsule - cause of nosocomial pneumonia, meningitis, bacteremia, wound infections, and UTIs - becoming more resistant to antibiotics: serious nosocomial agent

S. cholerae-suis

- zoonosis of swine

Characteristics of Proteus and its relatives

-reservoir: saprobes in soil, manure, sewage, polluted water; commensals of humans and animals - Proteus sp. : • highly motile - swarms on moist agar in • involved in UTI, wound infections, pneumonia, septicemia, and infant diarrhea

Progression of whooping cough symptoms, starting with infection

1. Destruction of ciliated epithelial cells along respiratory tract 2. Buildup of mucus along respiratory tract 3. Congestion and sneezing 4. Sudden coughs with gasping breath intake

Acinetobacter baumanii

A common pathogen in the military, particularly those having been in the Middle East. Transmitted by contact or objects, this bacterial infection can be severe, and to make matters worse, it is resistant to drugs. Other similar bacteria to Pseudomonas (in modes of operation as well as pathogenicity) are Burkholderia and Stenotrophomonas.

Please select possible transmission method(s) for Legionella pneumophila. Whirlpool spas Humidifiers Water droplets or aerosol, released by air-conditioning units Respiratory therapy equipment All of these

All of these

Please choose the feature of Pseudomonas that makes it a difficult organism to control in a hospital environment. - An endotoxin - A capsule - The ability to utilize all sorts of nutrients - An anaerobic bacterium - Antibiotic resistance

Antibiotic resistance

Shigella can cause ______________.

Bacillary dysentery

The Family Enterobacteriaceae is divided into:

Coliforms and Noncoliforms

_________________ E. coli, aka E. coli O157:H7, has been highly publicized because of its role in foodborne illness.

Enterhemorrhagic

_____________________ E. coli invades and causes ulceration of the large intestine similar to that seen with Shigella infection.

Enteroinvasive

___________________ E. coli targets infants, but the pathogenesis of this strain is not well understood.

Enteropathogenic

_____________________ E. coli mimics cholera by producing two toxins that increase secretion and fluid loss from the intestine.

Enterotoxigenic

T/F. The common virulence factor for all gram-negative bacteria is the exotoxin, lipopolysaccharide, which forms the outer layer of the cell wall.

FALSE (endotoxin)

Please select all answers that explain the high incidence of Salmonella foodborne illness. Bagged spinach is often implicated in Salmonella outbreaks because the water used to wash the spinach may be contaminated. Fowl are notorious for harboring Salmonella. Fast-food chains often keep their foods under hot lights to keep the food warm, but this doesn't kill the Salmonella. Eggs are a good growth medium for Salmonella. People using the public toilets, particularly when not washing hands, easily spread Salmonella.

Fowl are notorious for harboring Salmonella. Eggs are a good growth medium for Salmonella.

Please select all of the tests which can be used for the identification of the common enteric bacteria in the Enterobacteriaceae family. Glucose use Salt resistance Nitrate test Endotoxin production Oxidase test

Glucose use, Nitrate test, Oxidase test

Please select the answer that explains how humans most commonly contract plague. Humans eat contaminated meat after a hunting trip. Humans drink contaminated water when camping. Certain flea species prefer humans to other hosts. Humans are accidental hosts when they get between the flea and its preferred rodent hosts.

Humans are accidental hosts when they get between the flea and its preferred rodent hosts.

Please select the answer that differentiates between typhoidal and non-typhoidal salmonelloses. If the organism moves into the blood and replicates Which host cells the bacterium parasitizes The immune status of the host The age of the host The sex of the host

If the organism moves into the blood and replicates

Please select the disease that Haemophilus bacteria do not cause. Conjunctivitis Meningitis Sexually transmitted disease Endocarditis Influenza

Influenza

Please choose the answer that indicates the significance of E. coli O157:H7 to test your understanding of this organism. Its role in foodborne illness outbreaks has prompted random testing and required labeling of meat products. It is the most common opportunistic pathogen in the hospital setting. It has been linked to various forms of cancer and autoimmune diseases. It is the only strain of E. coli that produces the toxin that causes endotoxic shock.

Its role in foodborne illness outbreaks has prompted random testing and required labeling of meat products.

The nonenteric Yersinia pestis causes:

Plague

Please select the genus which represents an opportunistic noncoliform. Shigella Salmonella Bordetella Yersinia Proteus

Proteus

Opportunistic species

Proteus vulgaris, Serratia marcesens, Pasteurella multocida, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter, Acinetobacter baumanii True

Difference between Salmonella and Shigella

Slamonella = motile, makes H2S from sulfur-containing amino acids Shigella = non-motile

Please choose the feature which allows Brucella to be an exemplary pathogen. The bacterium is transported by blood around the body. The bacterium produces a very potent exotoxin, allowing it to destroy host cells. The bacterium has the ability to spread to adjacent tissues because of enzymes that destroy the integrity of the tissues. The bacterium can live within macrophages, and therefore, it can be carried to locations around the body as the WBCs move.

The bacterium can live within macrophages, and therefore, it can be carried to locations around the body as the WBCs move.

Please select the statement which explains why it is important to be able to differentiate between the coliform and noncoliform members of the Enterobacteriaceae family. The coliforms and noncoliforms are treated with completely different antibiotics. The coliforms are transmitted human-to-human, while the noncoliforms are not. Coliforms are found in humans, while the noncoliforms are associated with animals. Coliforms are gram-negative while noncoliforms are gram-positive. The noncoliform bacteria are the true pathogens of this family, while the coliforms are opportunistic pathogens.

The noncoliform bacteria are the true pathogens of this family, while the coliforms are opportunistic pathogens.

Please select the answer that explains how the E. coli O157:H7 strain can have a large systemic effect. The bacterium replicates within blood. It attacks the central nervous system, which controls all parts of the body. The toxin produced by the bacteria is spread by blood, disrupting protein synthesis within cells of the body. The bacterium replicates within lymph nodes, located all over the body.

The toxin produced by the bacteria is spread by blood, disrupting protein synthesis within cells of the body.

Please select the explanation for why the members of the bacterial family Enterobacteriaceae are commonly pathogenic to humans. Humans contact these bacteria easily from soil. This family of bacteria commonly inhabits the human body as normal flora. As air contaminants, these bacteria easily are transmitted by respiratory route. Humans have no inherited resistance to these bacteria. Animals have these bacteria as normal flora, and since humans and animals are in close contact, the bacteria are easily transmitted to humans.

This family of bacteria commonly inhabits the human body as normal flora.

Please select the explanation for why the E. coli 0157:H7 is such a potent pathogen. This strain of E. coli is very drug resistant. This strain of E. coli makes an extra toxin in addition to its endotoxin. This strain of E. coli is encapsulated, making it impossible to destroy by phagocytosis. This strain of E. coli is infectious in very small numbers of cells.

This strain of E. coli makes an extra toxin in addition to its endotoxin.

Salmonella can cause ___________.

Typhoid fever

Enterobacter sp.

UTI's, surgical wounds

Please choose the high-risk population for contracting brucellosis. Farmer Nurse Veterinarian Day care teacher Plumber

Veterinarian Brucellosis is an occupational disease, associated with slaughterhouses, livestock handling, and veterinary work. In animals, the infection may result in an abortion, but in humans, it is a febrile blood infection. It is sometimes called undulant fever because of the fluctuating fever.

The main pathogens of enteric Yersinia are:

Yersinia enterocolitica and Yersinia pseudotuberculosis

Pseudomonas aeruginosa can cause

burn infections, corneal ulcers, meningitis, endocarditis, complication of cystic fibrosis, urinary tract infections

Haemophilus influenzae can cause:

conjunctivitis, meningitis

The O antigen of Enterobacteriaceae cell walls consists of lipopolysaccharide, which has a lipid portion referred to as _________. endotoxin exotoxin hemolysin leukocidin

endotoxin

Escherichia coli is the most prevalent _____________ bacillus

enteric

How is Shigellosis treated?

fluid replacement and ciprofloxacin and sulfamethoxazole /trimethoprim (SXT

Bordetella and Legionella are mainly _______________ pathogens

human

Noncoliforms are lactose _________ and include the true pathogenic genera _____________ and _____________.

negative; Salmonella; Shigella

Pseudomonas and Burkholderia are ________________ pathogens

opportunistic

Citrobacter sp.

opportunistic UTI's and bacteremia

Bordetella pertussis causes:

pertussis or whooping cough

Coliforms are lactose _________ and include _____________

positive; E. coli

Serratia marcescens

produces a red pigment; causes pneumonia, burn and wound infections, septicemia and meningitis

Pseudomona aeruginosa can be transmitted to healthy individuals through community ____________________.

swimming pools and hot tubs

Klebsiella pneumoniae can cause:

wound infections, Meningitis, Pneumonia, Urinary Tract Infection

Proteus spp. can cause:

wound infections, pneumonia, Urinary Tract Infection

Brucella and Francisella are __________ pathogens

zoonotic

Characteristics of Pseudomonas aeruginosa

• Common inhabitant of soil and water • Intestinal resident in 10% normal people • Resistant to soaps, dyes, quaternary ammonium disinfectants, drugs, drying • Frequent contaminant of ventilators, IV solutions, anesthesia equipment • Opportunistic pathogen • Common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosis • Complications include pneumonia, UTI, abscesses, otitis, and corneal disease • Endocarditis, meningitis, bronchopneumonia • Grapelike odor and greenish-blue pigment (pyocyanin) ;• Multidrug resistant

Diagnosis, Treatment, and Prevention of Plague

• Diagnosis depends on history, symptoms, and lab findings from aspiration of buboes • Treatment: streptomycin, tetracycline, or chloramphenicol • Killed or attenuated vaccine available • Prevention by quarantine and control of rodent population in human habitats

Characteristics of Enterobacteriaceae Family

• Enteric facultative anaerobic Gram negative bacilli • Large family of small, non-spore-forming rods • Many members inhabit soil, water, decaying matter, and are common occupants of large bowel of animals including humans • Most frequent cause of diarrhea through enterotoxins • Enterics, along with Pseudomonas sp., account for almost 50% of nosocomial infections

What are the 4 pathogenic strains of E. coli?

• Enterotoxigenic E. coli (ETEC): causes severe diarrhea; tourista • Enteroinvasive E. coli (EIEC): causes inflammatory disease of the large intestine • Enteropathogenic E. coli (EPEC): linked to wasting form infantile diarrhea • Enterohemorrhagic E. coli, O157:H7 strain (EHEC): causes hemorrhagic uremic syndrome; high mortality rate for children and elderly; Jack-in-the-Box killer

Brucellosis

• Fluctuating pattern of fever: weeks to a year • Combination of tetracycline + rifampin or streptomycin • Animal vaccine available • Potential bioweapon

Pathology of Plague

• ID 3-50 bacilli • Bubonic: bacillus multiplies in flea bite, enters lymph, causes necrosis and swelling called a bubo in groin or axilla • Septicemic: progression to massive bacterial growth; virulence factors cause intravascular coagulation subcutaneous hemorrhage and purpura - black plague • Pneumonic: infection localized to lungs, highly contagious; fatal without treatment

Characteristics of Aerobic Gram-Negative Nonenteric Bacilli

• Large, diverse group of non-spore-forming bacteria • Wide range of habitats: large intestines (enteric), zoonotic, respiratory, soil, water • Most are not medically important; some are true pathogens, some are opportunists • All have outer membrane lipopolysaccharide of the cell wall: endotoxin

Characteristics of Bordetella pertussis

• Minute, encapsulated coccobacillus • Reservoir: apparently healthy carriers • Transmission: direct contact or inhalation of aerosols and droplets during coughing • Virulence factors: receptors that recognize and bind to ciliated respiratory epithelial cells; toxins that destroy and dislodge ciliated cells • children under four are most likely group for infection

Characteristics of E. coli

• Most common aerobic and non-fastidious bacterium in gut • 150 strains • Most strains are not highly infectious, but some have developed virulence through plasmid transfer, others are opportunists • Pathogenic strains frequent agents of infantile diarrhea: greatest cause of mortality among babies • Causes ~70% of traveler's diarrhea • Causes 50-80% UTI • Coliform count: indicator of fecal contamination in water

Yersinia pestis

• Nonenteric • Tiny, gram-negative rod, unusual bipolar staining and capsules • Virulence factors: capsular and envelope proteins protect against phagocytosis and foster intracellular growth; Coagulase, Endotoxin, Murine toxin • Transmission: contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans • Reservoir: in 200 species of mammals; rodents, without causing disease • Flea vectors - bacteria replicates in gut, coagulase causes blood clotting that blocks the esophagus; flea becomes ravenous

What are some oxidase-positive nonenteric pathogens?

• Pasteurella multocida • Haemophilus influenzae • H. aegyptius • H. ducreyi • H. parainfluenzae • H. aphrophilus

Characteristics of Haemophilus

• Tiny Gram-negative pleomorphic rods • Fastidious, sensitive to drying, temperature extremes, and disinfectants • Require enriched media for growth: chocolate agar - Growth factors: hemin & NAD • Diseases:: Some species are normal colonists of upper respiratory tract or vagina (H. parainfluenzae, H. ducreyi) - Others are virulent species responsible for childhood meningitis, and chancroid

Pasteurella multocida

• Zoonotic genus; normal flora in animals - especially cats and dogs • Opportunistic infections • Animal bites or scratches cause local abscess that can spread to joints, bones, and lymph nodes • Immunocompromised are at risk for septicemia and complications • Treatment: penicillin and tetracycline

Characteristicss of Haemophilus influenzae

• can cause a severe infection in infants and toddlers • may result in lifelong disability or death • Disease - acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, and bronchitis • transmitted by nasal and throat discharged causing sporadic meningitis cases in day care and family settings • vaccine available for worst serotype - Hib

Typhoid Fever

• transmission: S. typhi; fecal/oral; ingestion of fecally contaminated food or water • Asymptomatic carriers: some chronic carriers shed bacilli from gallbladder • Bacilli adhere to small intestine, cause invasive diarrhea septicemia • Treatment: chloramphenicol or sulfamethoxazole /trimethoprim (SXT) • 2 vaccines for temporary protection