Viral & Bacterial Causes of Gastroenteritis Flashcards
This bacteria is halophilic and grows at low temperatures. It is the most severe form of enteritis and may harm a fetus. How is it spread?
Listeria - food-borne via cheese, ice cream, lunch meats
What is the leading cause of sporadic viral gastroenteritis and outbreaks?
Norovirus
What bacteria is responsible for causing enteric fever?
Salmonella Typhi
What agar may be used to differentiate Shigella & Salmonella?
Hektoen agar - Salmonella produces H2S, while Shigella does not
While this pathogen is not the leading cause of bacterial gastroenteritis, it does cause the most hospitalizations.
Listeria
With enteric fever, bacteria survive and replicate within macrophages and cause bacteremia. What organ is chronically infected?
Gallbladder
True/False. E. coli does not ferment lactose.
False. E. coli ferments lactose, but Shigella does not.
What is the mechanism of the cholera toxin?
AB toxin - increases cAMP, stimulates PKA, Cl- influx, watery diarrhea
Infection with this bacteria presents with “rice-water stool.”
Vibrio cholerae
What is the most common type of Shigella seen in the USA?
Shigella sonnei
What complications are associated with C. jejuni infection?
Guillain-Bare Syndrome, reactive arthritis
This bacteria is responsible for the most cases of foodborne gastroenteritis in the USA.
Salmonella, STEC, Listeria
Infection with this bacteria is associated with coastal water contaminated with sewage, raw oysters, and shellfish.
Vibrio cholerae & parahaemolyticus
What is the most severe complication of STEC?
Hemolytic uremic syndrome (renal failure, thrombocytopenia, hemolytic anemia)
These subtypes of V. cholerae cause clinical cholera.
O1 & O139 - all other subtypes cause vibriosis
What agar may be used to differentiate STEC?
Sorbitol MacConkey Agar - STEC does not ferment sorbitol
This type of Shigella produces a Shiga-like toxin.
Shigella dysenteriae
This gastroenteritis-causing bacteria has bipolar staining, grows at colder temperatures, and may mimic appendicitis.
Yersinia enterocoltica & pseudotuberculosis
STEC is most associated with what sources?
Livestock and petting zoos, contaminated beef
This bacterial cause of gastroenteritis is most associated with nursing homes, daycare, etc.
Shigella spp.
What virulence factor is most responsible for STEC infection?
Intimin - bacterial adhesion molecule
What virulence factors are associated with Listeria?
Listeriolysin O - enables escape from phagolysosomes
Act A - rearrangement of actin for motility
True/False. Doxycycline should be used to treat STEC.
False - this can cause overwhelming toxin release. The infection must run its course.
This bacteria does not ferment lactose or produce H2S.
Shigella spp.
This dsRNA is most common to cause gastroenteritis in children <5.
Rotavirus
What subtype of E. coli produces the Shiga-like toxin?
O157:H7 (STEC)
What are the characteristics of norovirus?
+ssRNA, naked, icosahedral
Bacillus cereus products both a heat-stable and labile enterotoxin. How does the presentation of infection with these toxins differ?
Heat-stable - emetic form, rice, vomiting, intoxication
Heat-labile - diarrheal form, meats, diarrhea, infection
What Rotavirus proteins are targets for vaccines?
VP4 & VP7
H. pylori persists within the stomach and is associated with peptic ulcers and adenocarcinoma. What are its characteristics?
Spiral G- rod, corkscrew motility, microaerophilic, urease +
This E. coli subtype is the leading cause of traveler’s diarrhea.
Enterotoxigenic E. Coli (ETEC)
This bacteria is microaerophilic and capnophilic and spreads via undercooked chicken.
C. jejuni
Staph aureus can cause gastroenteritis via enterotoxin A, causing vomiting. What foods are associated with intoxication?
Processed meats, dairy products, mayonnaise-based salads
What Rotavirus protein functions as an enterotoxin?
NSP4
Salmonella gastroenteritis is most associated with what causes?
Undercooked chicken, raw eggs, reptiles (small turtles)
This bacteria is a major cause of diarrhea in hospitals and is associated with antibiotic-acquired gastroenteritis.
C. difficile
This bacteria is a leading cause of inflammatory diarrhea in the USA.
C. jejuni
Vomiting as a symptom of gastroenteritis generally indicates what type of infection?
Viral infection - except Staph aureus & Bacillus cereus, which produce enterotoxins that induce vomting