Enteric Bacteria Flashcards
What are the characteristics of secretory diarrhea?
- no WBC or RBC present
- large, watery volume
- nausea & vomiting
- afebrile
- example: cholera
What are the characteristics of inflammatory diarrhea?
- WBC present
- fever
- example: shigella
What are the characteristics of E coli?
- gram - bacilli
- facultative anaerobe
- serogroups -> O=LPS, H = flagella, K= capsule
What are the pathotypes of E coli?
- enterotoxigenic (ETEC)
- enteropathogenic (EPEC)
- enterohemorrhagic (EHEC)
What are the characteristics of ETEC?
- endemic in developing countries -> traveler’s diarrhea
- transmission: fecal-oral
- symptoms: watery diarrhea, nausea, vomiting, no RBCs or WBCs
What are the virulence factors/pathogenesis of ETEC?
- heat stabile (ST) toxin -> increased cGMP
- heat labile (LT) toxin -> increased cAMP
What are the characteristics of EPEC?
- endemic in underdeveloped countries
- symtpoms: water diarrhea, malabsorption, no RBCs or WBCs
What are the virulence factors/pathogenesis of EPEC?
- type 3 secretion system -> Tir
- injects effectors directly from bacterial cytoplasm into host cytoplasm via injection pore
- only in gram - bacteria
What are the characteristics of EHEC?
- predominantly in developed nations -> cattle & undercooked beef
- most common stereotype -> O157:H7
- symptoms: watery diarrhea -> bloody
- cramps
- +/- fever
What are the virulence factors/pathogenesis of EHEC?
- virulence -> shiga-like toxin
1. pathogenesis of A/E lesion
2. T3 secretion system injects shiga-like toxin
3. inhibition of host cell protein snthesis
4. cell death
5. dissemination = hemolytic uremic syndrome
What is the diagnosis & treatment of E coli?
- MacConkey agar: selective -> gram - bacteria; differential -> E coli (lactose +) turn pink
- sorbitol-MacConkey (SMAC): used if EHEC suspected; O157 is sorbitol negative (other strains are positive)
What are the characteristics of vibrio cholerae?
- gram - curved bacilli
- polar flagellum
- facultative anaerobe
- transmission -> water supply, marine environment, fresh seafood
How much bacteria is needed to produce a vibrio cholerae infection?
> 1 million
What is the virulence factor & symptoms of vibrio cholerae?
- virulence -> cholera toxin (increased cAMP= increased Cl- transport)
- symptoms: acute onset of watery stools, rice water stools, low fever, little pain
What is the diagnosis & treatment of virbio cholerae?
- diagnosis: blood & MacConkey agar
- prevention: oral vaccine
- treatment: supportive therapy & antibiotics
What is the pathogenesis of & diseases of the salmonella subspecies typhi?
- reservoir: humans
- infectious dose: about 1000
- pathogenesis: macrophages ingest & carry organisms via lymph & blood
- disease: enteric fever & septicemia
What is the pathogenesis of & diseases of the salmonella subspecies non-typhi?
- reservoir: humans, animals, feed, eggs, dair, water
- infectious disease: 10 ^ 6
- pathogenesis:invade cells lining the lumen
- disease: non-bloody diarrhea
What is the diagnosis & treatment of salmonella?
- diagnosis: differential on XLD agar + stereotyping & lactose negative
- prevention: S. typhi vaccine
- treatment for non-typhi: antibiotics NOT recommended
- treatment for typhi: fluoroquinolones, cephalosporin
What is the diagnosis & treatment for shigella?
- diagnosis: differential on XLD agar
- treatment
1. replacement of fluids & electrolytes
2. antibiotics indicated insevere cases
3. antidiarrheals are contraindicated
What is the epidemiology of shigella?
- 1-3 day incubation period; subsides in 10 days
- transmission/origin: human disease in children; fecal-oral route
- < 200 bacteria needed to produce
What are the virulence factors and diseases of shigella?
- virulence: invasins & shiga toxin
- disease: shigellosis -> frequent bloody diarrhea, tenesmus, cramps, small stools, fever, hemolytic uremic syndrome
What are the characteristics of campylobacter jejuni?
- gram - bacilli, thin, curved
- polar flagellum
- reservoir: wild/domestic animals
- transmission: contaminated food/water & direct contact with carrier animal
What bacteria is the most common cause of bacterial gastroenteritis in the US?
campylobacter jejuni
What are the virulence factors & symptoms of campylobacter jejuni?
- virulence: adhesins, cytotoxin, enterotoxin
- symptoms: rapid onset of watery to bloody diarrhea & Guillain-Barre syndrome
What is the diagnosis & treatment of campylobacter jejuni?
- diagnosis: gull wing shaped cells & campy agar
- treatment: replacement of fluids + electrolytes & antibiotics indicated in severe cases
