Gastrointestinal Infections Part I Flashcards
What is gastroenteritis?
Irritated GI system
What is a symptom of diarrhea?
Small intestines not absorbing secreted fluid and electrolytes
What is dysentery?
Invasion of large intestine resulting in bloody and purulent stool
What causes diarrhea?
Increased secretion
Decreased absorption
What is food-associated infection?
Multiplication of the organism in the body
What is food poisoning?
Microbial toxins in contaminated food
What do enterotoxins do?
Stimulate intestinal secretion (diarrhea)
How does cholera work?
B subunit binds GM1
Endocytosis
A subunit crosses ER membrane
A subunit transfers ACP ribosyl group from NAD to stimulatory G protein
G protein activates adenylate cyclase
Adenylate cyclase activates PKA using cAMP
CFTR is phosphorylated by PKA secreting Cl-
How are E. coli strains differentiated by their antigens?
Somatic (O)
Flagellar (H)
Capsule (K)
Most common E, coli strain in the United States?
Enterohemorrhagic
O157:H7
What does ETEC produce?
Enterotoxins (causing watery diarrhea)
What codes for enterotoxins in ETEC?
Plasmid
What does ETEC mimic?
Cholera toxin
What does ETEC cause?
Purely secretory diarrhea (no bloody stool or inflammation)
What does ETEC stand for?
Enterotoxigenc E coli
What does EPEC stand for?
Enteropathogenic E coli
What does EPEC cause?
Diarrhea in infants and young children sometimes bloody
EHEC stands for:
Enterohemorrhagic
What does EHEC encode for?
Shiga-like cytotoxin
How does EHEC shiga-like cytotoxin work?
Cleaves adenine off rRNA halting protein synthesis
What can EHEC cause?
Local necrosis and inflammation (hemorrhagic colitis) Kidney damage (hemolytic-uremic syndrome)
What medium can test for EHEC?
Sorbitol MacConkey: non-fermentation of sorbitol makes the strain stand out
EIEC invasive or non-invasive?
Invasive
What does EAEC do when attaching to cells?
Aggregates
What is unique about E. coli bacteria?
Cannot kill all E. coli with antibiotics
What part of the colon does shigella invade?
Descending and sigmoid colon
What does shigella cause?
Bloody stool
Intestinal necrosis
Campylobacter gram stain:
Gram-negative
What diarrhea does Campylobacter cause?
Watery stool
What is campylobacter associated with?
Guillain-Barrie syndrome due to cross-reactive antibodies (no antibiotics necessary)
Gram stain for Vibrio cholera:
Gram negative
What is the vibrio cholera flagellum arrangement?
Monotrichous
Cholera stool:
Watery cloudy stool with mucus blebs (rice soup)
Main treatment of cholera?
IV rehydration
Where does Yersinia enterocolitica infect?
Ileum causing necrosis and bloody stool
Where is Vibrio parahaemolyticus found in concentration?
Shellfish (filter feeders)
Best diagnosis for Helicobacter pylori?
Carbon isotope-labeled urea for breath test (C 13 or 14)
What does H. pylori do?
Creates ammonia
Reaction H. pylori does:
CH4NO2 -> CO2 + NH3
Why don’t you use clindamycin against C. diff?
It is effective against all anaerobes except C. diff making it the predominate species
Antibiotics for C. diff?
Metronidazole
Vancomycin
How to tell if it’s C. diff?
PCR for toxin B gene
How to treat C. diff?
Fecal microbiota transplantation
Where can you catch Clostridium perfringens?
Fecal bacteria that contaminate MEAT
Where do Bacillus cereus spores germinate?
Cooked rice
How do staphylococcal enterotoxins work?
Give you food poisoning through toxins that work on the CNS (cytokines)to induce vomiting
What does botulism do?
Blocks the release of acetylcholine in the neuromuscular junction leading to flaccid paralysis
Treatment for botulism?
Animal-derived antitoxin
