Infectious Enterocolitis (Bacterial and Viral) Flashcards
(48 cards)
What are the most common causes of traveler’s diarrhea?
- ETEC
- campylobacter jejuni
- salmonella
- shigella
Where does Vibrio cholerae come from?
(endemic areas/reservoirs and transmission)
endemic to India > Gulf of Mexico
reservoirs: shellfish
fecal-oral transmission:
-contaminated drinking water (think natural disasters)
-food
How are Vibrio cholerae infections typcially described?
- comma shaped, gram-negative
- oxidase-positive
- single, polar flagella
How does Vibrio cholerae cause disease?
Cholera toxin:
- enters cell via GM1
- toxin activates Gs protien -> activates adenylate cylcase -> increased cAMP -> CFTR activation
- increased in intraluminal chloride -> secretory diarrhea
What is the presentation of cholera?
(complications?)
- diarrhea; “rice-water” stools
- “fishy” smelling stool
- fever
- vomiting
Complications:
- severe dehydration
- hypotension/shock
How is cholera treated?
fluid replacement (typically sufficient w/o abx)
Where does Campylobacter jejuni come from?
(endemic areas/reservoirs and transmission)
- livestock act as reservoir (especially chicken)
- more pervalent in developed countries
Fecal-oral transmission:
- infected animal products (especially poultry)
- contaminated water
What is Campylobacter jejuni the most common cause of?
- most common cause of bacterial enterocolitis in developed countries
- common cause of “traveler’s diarrhea”
How are Campylobacter jejuni infections typcially described?
- comma shaped, gram-negative
- oxidase-positive
- single, polar flagella
How does Campylobacter jejuni cause disease?
Specific mechanism unclear
Virulence properties:
- toxin production (certain strains)
- invasion (certain strains)
- motility
- adherence
What is the presentation of campylobacter enteritis?
(complications?)
- influenza-like prodrome
- watery diarrhea
- bloody, inflammatory diarrhea (dysentery, associated with strains capable of mucosal invasion)
Complications:
- reactive arthritis (associated with HLA-B27)
- Guillian-Barré (0.1%; ascending, demylinating neuropathy -> parasthesia and weakness)
- erythema nodosum
How is campylobacter enteritis treated?
- self-limiting, treatment typically not needed
- abx in severe cases
Where do Shigella spp. come from?
(endemic areas/reservoirs and transmission)
- humans are only reservoir
- more prevalent in underdeveloped countries
Fecal-oral transmission:
- contaminated food
- contaminated water
How are Shigella spp. infections typcially described?
- gram-negative
- unencapsulated
- nonmotile
- facultative anaerobe
- green colonies (HE agar; vs. black colonies in similar appearing Salmonella)
- preferentailly infect left colon followed by ileum
How do Shigella spp. cause disease?
Shiga toxin:
-affects 60S ribosomal subunit, inhibiting protein synthesis -> enterocyte damage
Invasion:
- tropism for M cells
- can survive intracellularly, evading immune system
What is the presentation of shigellosis?
(complications?)
- watery diarrhea -> dysentery
- fever
- abdominal pain
Atypical presentatin:
-can mimic ulcerative colits in adults as waxing and waning diarrhea
Complications:
- uncommon triad of reactive arthiritis, urethritis, and conjunctivitis (associated with HLA-B27)
- HUS (associated with shiga toxin and EHEC shiga-like toxin)
- toxic megacolon
How is shigellosis treated?
- self-limiting (2-7 days), treatment typically not needed
- abx in severe cases
**antidiarrheals contraindicated, prolong symptoms and delay clearance of Shigella**
What causes Salmonelosis and where does it come from?
(endemic areas/reservoirs and transmission)
non-typhoidal salmonella, Salmonella enteritidis
- livestock act as reservoir (particularly chicken)
- prominent worldwide
Fecal-oral transmission:
-contaminated animal products (particularly poultry)
How are Salmonella enteritidis infections typcially described?
- gram-negative, w/ multiple flagella
- obligate pathogen
- acid-labile
- do not ferment lactose
- produces hyrdogen sulfide -> black colonies (HE agar; vs. green colonies in similar appearing Shigella)
How does Salmonella enteritidis cause disease?
Invasion:
- tropism for M cells
- can survive intracellularly, evading immune system
What is the presentation of salmonellosis?
(complications?)
-severe watery diarrhea -> dysentery
-severe vomiting
- fever
- abdominal pain
Complications (related to systemic infection):
- bacteremia/sepsis
- reactive artritis
How is salmonellosis treated?
- self-limiting (3-7 days), treatment typically not needed
- abx in systemic cases only as they prolong carrier state
What causes Typhoid fever and where does it come from?
(endemic areas/reservoirs and transmission)
- Salmonella enterica* (typhi/paratyphi)
- endemic to India, Mexico, and the Phillipines
- endemic populations tend to be infected with S. typhi
- visitors to endemic regions tend to be infected with S. paratyphi
- humans are only reservoir
Fecal-oral transmission:
- contact
- contaminated water
- contaminated food
How are Salmonella typhi/paratyphi infections typcially described?
- gram-negative, w/ multiple flagella
- obligate pathogen
- produces hyrdogen sulfide
- do not ferment lactose
- enlarged Peyer patches in distal ileum
-typhoid nodules in the liver (macrophage aggregates)
