161. Microbial Pathogens GI Tract Flashcards
Differences b/w Inflammatory and Non-inflammatory Diarrhea
Inflammatory:
- Mucus/blood in stool
- Leukocytes and RBC on microscopic examination
- due to local tissue destruction by pathogen invading intestinal mucusa
- fever
- longer incubation period (2-4 days)
Non-inflammatory:
- watery/loose stools w/o mucus/blood
- No leukocytes or RBCs on microscopic exam
- most often TOXIN-mediated or caused by viruses
- no fever
- shorter incubation period (1-2 days)
Vibrios spp.
- difference b/w Vibrio cholerae, parahemolyticus, and vulnificus
- type of bacteria
- habitat and spread
V. Cholerae pathogenicity, disease, dx, tx, prevention
GNR, live in salt water, spread via contaminated water.
Parahemolyticus: causes GE following undercooked seafood
Vulnificus: causes GE, wound infections, bacteremia
Cholerae: causes cholera epidemics (serogroup O1)
Pathogenicity: need large amount ingestion (most killed by stomach), colonize small intestine (TCP - toxin coregulated pili help bacterial aggregation)
Cholera Toxin: A-B toxin (B binding for endocytosis; A causes ADP-ribosylating activity of adenylate cyclase = increases cAMP = activates CFTR = Cl secretion, less Na uptake = SECRETORY DIARRHEA)
cholera: severe dehydration due to secretory diarrhea (mucus flecks), absent fever
Source: contaminated water, raw shellfish
dx: culture on TCBS agar
Tx: Rapid replacement of fluid/electrolytes, ABx shorten sx duration (macrolides, ciprofloxacin)
Prevention: oral live attenuated vaccine, purified drinking water, cooking seafood
ETEC
- type of bacteria
- disease
- pathogenicity
GN bacilli, part of enterobacteriaceae
disease: 50% of Traveler’s Diarrhea cases
Heat Labile Toxin (LT): AB Toxin (like cholera), stimulates adenylate cyclase in gut epithelial cells
Heat Stable Toxin (ST): stimulates guanylate cyclase in gut epithelial cells
Clostridium perfringens
- type of bacteria
- source
- disease
- tx
Anaerobic G+ Bacillus
Source: contaminated meat/poultry
Disease: diarrhea with severe abd cramping, self-limiting (6-12 hr incubation - short)
tx: no Abx therapy b/c self-limiting usually
Bacillus cereus
- type of bacteria
- pathogenicity
- disease
- source
- tx
G+ rod, facultative anaerobe (grow in both)
2 toxins: 1. Toxin like ETEC LT - shorter incubation causing diarrhea - ADP ribosylates/cAMP
2. Toxin like staph enterotoxin - vomiting, short incubation period (1-5hrs)
disease: WATERY DIARRHEA, vomiting
Source: Slowly-cooled rice (resistant to boiling/reheating)
Tx: no abx bc usually limited to less than 24 hrs
Staph aureus
- type of bacteria
- pathogenicity
- disease
- source
- tx
G+ cocci in clusters
Five enterotoxins A, B, C, D, E (usually premade in source = short incubation period)
Disease: Vomiting»_space; Diarrhea, 10-24 hrs
Source: ham, poultry, egg, dairy, baked goods, casseroles
tx: abx no use b/c illness due to preformed toxin
Rotavirus
- type of infection
- sx
- Dx
- prevention
dsRNA virus, common worldwide (most infected by 3yo, 30-50% cases of diarrhea requiring hospitalization)
sx: Vomiting followed by diarrhea, fever (even though noninflammatory), respiratory sx
dx: stool ELISA, latex agglutination tests
prevention: two oral attenuated vaccines! RotaTeq and Rotarix
seasonal! (chicago -peak in feb)
Norovirus
- transmission
- sx
- dx
- tx
Trans: fecal-oral, contaminated food/water
Sx: Stomach flu - N/V/D, low-grade fever
Dx: ELISA, PCR
Tx: not necessary, only 24-48hrs
Giardia Lamblia
- type of infection
- transmission
- pathogenicity
- sx
- dx
- tx
Unicellular parasite - trophozoite and cyst forms
Trans: through water (campers), food, person-person (fecal oral)
Path: adheres to epithelium of small intestine - causing malabsorption
sx last 1-4weeks (subacute): diarrhea, flatulence, abd bloating/cramping
dx: Examine stool, ELISA, NAATs
Tx: Metronidazole, tinidazole, nitazoxanide
Cryptosporidium spp.
- type of infection
- transmission
- source
- sx
- dx
- tx
Unicellular parasite
trans: fecal-oral route
source: domestic animal reservoir
sx: acute self-limited diarrhea; immunocompromised get chronic diarrhea and malabsorption
dx: acid-fast stain of stool!!!, direct IF ab stain, PCR
Tx: usually not necessary (nitazoxanide in immunocompromised)
Shigella spp.
- type of bacteria
- pathogenicity
- transmission
- disease
- dx
- tx
- prevention
GNR (related to E Coli)
P: tolerates stomach acid (need only small number ingested)
Invade colon - inflammatory response - diarrhea
Bacteria transcytose through M Cells - type III secretion system and escape vacuoles - move through cells with actin (like Listeria)
Shiga toxin: assoc with HUS
trans: 5F’s (fingers food flied feces fomites)
disease: mild watery diarrhea, bacillary dysentery (painful defecation with blood and pus), fever
dx: stool culture
tx: fluoroquinolone, azithromycin
Prevention: good sanitation, proper cooking of food
Salmonella enterica
- type of bacteria
- disease
- source
GN bacillus
cause of food-poisoning epidemics
source: chicken and eggs
Campylobacter jejuni
- type of bacteria
- disease
- source
- dx
- tx
- rare complication
Curved GN rod (sea-gull appearance on gram stain)
bloody diarrhea
source: ingestion of contaminated food (often poultry)
dx: gram stain stool, NAATs
tx: only SEVERE infections (macrolides/fluoroquinolones)
rare complication: Guillan-Barre Syndrome - ascending neuropathy with paresthesias/weakness/paralysis
EHEC
- type of bacteria
- sx
- assoc
GNrod
Sx: bloody diarrhea, crampy abd pain, none-lowgrade fever
assoc: HUS (worry!): hemolytic anemia, decreased platelets, renal failure, CNS dysfx
Peak in summer: BBQs, undercooked food
Yersinia enterocolitica
- type of bacteria
- disease
GNR
Food poisoning that invades and disseminates to bloodstream!
Leads to enlargement of mesenteric LNs (abd pain) and bacteremia!
