ACUTE INFECTIOUS DISEASE Flashcards
- passage of abnormally liquid or unformed stools at an increased frequency
- Stool weight >200 g/day
DIARRHEA
TWO COMMON CONDITIONS, USUALLY ASSOCIATED
WITH THE PASSAGE OF STOOL TOTALING <200 G/D
|. Pseudodiarrhea
2. Fecal Incontinence
- frequent passage of small volumes of |
- often associated with rectal urgency, tenesmus, or a feeling of incomplete evacuation
- accompanies IBS or proctitis
PSEUDODIARRHEA
- involuntary discharge of rectal contents
- most often caused by neuromuscular disorders or structural anorectal problems
FECAL INCONTINENCE
DURATION OF DIARRHEA
- acute if <2 weeks
- persistent if 2-4 weeks
- chronic if >4 weeks in duration.
- > 90% of cases of acute diarrhea are caused by infectious agents vomiting, fever, and abdominal pain.
- 10% are caused by medications, toxic ingestions, ischemia, food indiscretions, and other conditions.
sACUTE DIARRHEA
PATHOGENIC MECHANISMS OF ACUTE DIARRHEA
- INOCULUM SIZE
- ADHERENCE
- TOXIN PRODUCTION
- INVASION
INOCULUM SIZE: 10-100 bacteria or cysts
Shigella, enterohemorrhagic Escherichia coli, Giardia lamblia, or Entamoeba
INOCULUM SIZE
105-108
Vibrio organism
INOCULUM SIZE:
The infective dose varies widely, depending on the species, host and food vehicle
Salmonella
ADHERENCE
specific surface adhesins, including the toxin-coregulated pilus
V. cholerae
ADHERENCE
produces an adherence protein called colonization factor antigen
Enterotoxigenic E. coli
ADHERENCE
produce virulence determinants
Enteropathogenic/Enterohemorrhagic E. coli
TOXIN PRODUCTION
cause watery diarrhea by acting directly on secretory mechanisms in the intestinal mucosa.
Enterotoxin
TOXIN PRODUCTION
cause destruction of mucosal cells and associated inflammatory diarrhea
Cytotoxins
TOXIN PRODUCTION
which act directly on the central or peripheral nervous system
Neurotoxins
- prototypical enterotoxin
- heterodimeric protein composed of one A and five B subunits
Cholera toxin
Cholera toxin contains the enzymatic activity of the toxin
A subunit
Cholera toxin binds holotoxin to the enterocyte surface receptor, the ganglioside GMI, increase in cAMP
B subunit pentamer
similar to cholera toxin and causes secretory diarrhea by the same mechanism.
heat-labile enterotoxin (LT)
one form of which causes diarrhea by activation of guanylate cyclase and elevation of intracellular cGMP
heat-stable enterotoxin (ST)
- destroy intestinal mucosal cells and produce the syndrome of dysentery
- Shigella dysenteriae type |, Vibrio parahaemolyticus,
and Clostridium difficile.
BACTERIAL CYTOTOXINS
produce potent cytotoxins and have been associated with outbreaks of hemorrhagic colitis and hemolytic-uremic syndrome
S. dysenteriae type I and Shiga toxin-producing strains of E. coli
- usually produced by bacteria outside the host and therefore cause symptoms soon after ingestion
- which act on the central nervous system to produce vomiting.
- staphylococcal and Bacillus cereus toxins
Neurotoxins
