Infectious Diarrhea and Diarrhea Self-Study Flashcards
What is the definition of diarrhea?
Passage of abnormally liquid / unformed stool at increased frequency
or
Stool weight exceeds 200 grams/day (made mostly of water)
What is acute vs persistent vs chronic diarrhea?
Acute: <2 weeks
Persistent: 2-4 weeks
Chronic: >4 weeks
What most commonly causes diarrhea and what is on the differential?
Infectious agents more than 90% of the time
Differential: Med-induced or poison-induced Ischemic colitis Diverticulitis IBD
What pathogens cause watery diarrhea via entertoxins and usually involve upper small bowel?
Vibrio cholerae
ETEC
Bacillus cereus - reheated rice
Clostridium perfringens
What pathogens interfere with absorption to cause watery diarrhea?
Giardia Cryptosporidium - esp. immunocompromised EPEC Rotavirus Norovirus
What are the most common causes of inflammatory diarrhea in the US?
Campylobacter
Salmonella enteriditis (non-typhoid)
Clostridium difficile
EHEC - in pediatrics
What are other important causes of inflammatory diarrhea worldwide?
Shigella
Entamoeba histolytica
Salmonella typhi
What diarrheal pathogens commonly spread systemically via bacteremia?
Typhoid
Non-typhoidal Salmonella
Which Salmonella / Shigella strains have an animal reservoir?
Only non-typhoid Salmonella (most common in US, normally spread by poultry)
Salmonella typhi / paratyphi and Shigella species are human only
What cells does Salmonella typhi spread to and what is it’s main virulence factor?
Invades thru M cells then lives intracellularly in macrophages and reticuloendothelial system, including liver and spleen.
Virulence factor includes a Type III secretion system from a Salmonella pathogenicity island which translocates proteins from its intracellular vacuole into the macrophage cytoplasm, preventing maturation of mature phagolysosome.
What are important intestinal consequences of Salmonella typhi and why?
Host immunologic reaction may contribute to necrosis of Peyer’s patches in severe disease:
Intestinal hemorrhage and/or perforation (distal ileum) are feared complications
What are the stages of Typhoid fever?
Early constipation or diarrhea for 1-2 weeks (BEFORE fever)
Flu-like symptoms begin by end of first week
Second week - high fever, often with loss of diarrhea, and appearance of rose spots, hepatosplenomegaly, and relative bradycardia
3rd-4th week: Systemic complications
What are the systemic complications of typhoid fever?
Bacteremia may cause:
- Meningitis
- Liver abscess
- Septic joints / osteoarthritis
- Endocarditis
- Mycotic aneurysms in atherosclerotic plaques
- Immune-complex glomerulonephritis
How is typhoid fever usually diagnosed?
Blood cultures are usually first.
Cultures of stool, urine, rose spots, and bone marrow may also be positive
What’s the treatment for typhoid fever?
Fluoroquinolones (flower in sketchy) or ceftriaxone
What are common reservoirs for nontyphoidal Salmonella?
Birds, poultry, and REPTILES (pet reptiles)