Flashcards in GI Infections Deck (48):
Most common bacterial causes of acute diarrhea
salmonella, shingella, campylobacter, E. coli
Salmonella risk factors
antacid use, prior abx use, depressed immune function
How do we get Salmonella
contracted via contaminated food, mostly meat and milk products, undercooked chicken products.
Dx of Salmonella
monocytes in the stool (2+ PMNs) (RBCs-rare)
A aerobic gram neg. bacillus; motile, does not ferment lactose; acid sensitive
How and where does Salmonella infect?
attach to epithelial cells in SI and colon
gram neg bacillus, nonmotile, does not ferment lactose
How and where does Shigella infect?
surface proteins that induce cellular ingestion, uses surface hemolysin to lyse the phagosome membrane and escape into the cytoplasm where it induces actin rocket tails to propel it. First takes up residence in SI then invades colon.
Symptoms of Salmonella
can cause bacteremia, enters mesenteric LN and causes classic enteric fever
How does Shigella spread?
cell to cell, produces cytotoxic Shiga toxin and induces premature cell death (does not enter the blood stream)
Which cause of acute infectious diarrhea is acid resistant?
How is Shigella transmitted?
fecal oral route (only in humans); children in day cares have high incidence of infection
commoa shaped gram neg rod; paired in a seagull shape. ACID SENSITIVE
How and where does Campylobacter infect?
Ingested by monocytes, surviving in the gut for 6-7 days. Once intracellular it induces cell death and tissue necrosis and intense inflammatory reaction which allows it to enter the blood stream.
How is Campylobacter transmitted?
It commonly infects poultry (10x more common in chicken than Salmonella)
enterotoxigenic strains of E. coli. Colonize the small bowel and produce a cholera like or heat stable toxin.
ETEC is found
in developing countries: water is contaminated w/ human sewage
stimulates secretion of chloride, causing watery diarrhea
Ciprofloxacin or Levofloxacin
Which E coli is a main cause of travelers diarrhea?
produces verotoxins or shiga like cytotoxins that inhibit protein synthesis and cause cell death
EHEC is found
in industrialized nations, associated with undercooked beef or unpasturized milk (Cattle is primary resevior)
toxin damages endothelium in the bowel and glomeruli, causing hemorrhagic inflammatory colitis and hemolytic uremic syndrome
no tx; avoid anti motility drugs (increase toxin release and worsen hemolytic uremic syndrome). Supportive Care ONLY
V. Cholera toxin
gains entry to small bowel when host ingests contaminated water or food. (NEUTRALIZED BY STOMACH ACID) Attaches to small intestine and creates cholera toxin. Endotoxin binds to specific receptor in bowel mucosa that activates adenylate cyclase causing an increase in cAMP, elevated cAMP in turn promotes secretion of chloride and water causing voluminous watery diarrhea
a/w cholera. an aggregation of bacteria surrounded by a protective biofilm, that blocks killing by chlorine and other disinfectants
acute diarrhea (lasts less than 14 days), abdominal pain, diffuse pain and tenesmus
Clinical manifestations of enteric fever caused by s. typhi and s. paratyphi
Watery Diarrhea Etiologies:
ETEC and Vibrio
Bloody Diarrhe Etiologies:
Shingella, Campylobacter, EHEC
Tx of Shingella
Tx of Salmonella
Tx of Campylobacter
Tx of V. cholera
Tx of C. diffe
spore forming, gram negative rod that produces watery diarrhea. Releases 2 toxins (A and B) that bind to and kill cells in the bowel wall. There is a third toxin, binary toxin, that is a/w severe disease.
Pathogenesis of C. Diffe
Forms shallow ulcers and pseudomembranes seen on colonoscopy (or CT)
C. Diffe is most associated with....
Abx diarrhea, specifically clindamycin
How does C. Diffe spread?
Person to person
Signs and symptoms of C. Diffe
crampy bilateral lower abdominal pain that is decreased after a BM, low grade fever, mild peripheral leukocytes, TOXIC MEGACOLON, thumbprinting is seen
Dx of C Diffe
Cytotoxicity assay, ELIZA can detect toxin A and B
What is the most common form of infectious diarrhea
What causes viral diarrhea?
The disease is caused primarily by four viral groups:
Norovirus (“Norwalk”), Rotavirus, Enteric adenovirus 40, 41, Astrovirus. For these etiologies no PMNs found in stool.
blunts intestinal villi, causes mild malabsorption, is resistant to chlorine, is spread by contaminated water (including swimming pools), and primarily infects adults
Causes lactase deficiency, and primarily infects infants. Resists hand washing. Peaks in winter
Enteric adenovirus diarrhea
Infects infants and young children; peaks in summer months
Infects children in pediatric wards & elderly in nursing homes