| Infectious Agent
|
Characteristics
|
Reservoir
|
Common Mode of Transmission
|
Pathogenesis
|
| E. coli (ETEC) |
- Gram-negative rod||
- Humans and animals||
- Fecal-oral route
- Contaminated ground beed, unpasteurized mild, cheese, vegetables, or water||
- Enterotoxin-mediated: secretion of heat-labile toxin (LT) and heat-stable toxin (ST)
|
| Campylobacter jejuni |
- Gram-negative rod||
- Humans and animals||
- Fecal-oral route*Contaminated meat, unpasteurized mild, cheese, vegetables, or water*Exposure to infected animals||
- Enterotoxin-mediated: secretion of cholera-like enterotoxin
|
| Shigella spp. |
- Gram-negative rod||
- Humans only||
- Fecal-oral route*Contaminated meat and pork, unpasteurized mild, cheese, vegetables, or water||
- Low inoculum sufficient for infection (resistant to gastric acid)*Enterotoxin-mediated: secretion of Shiga toxin
- Invasion of macrophages and induction of cellular apoptosis
- Intracellular spread by actin polymerization processes (rocket propulsion)
|
| Salmonella spp. |
- Gram-negative rod||
- S. typhi: Humans only
- Other Salmonella spp.: Humans and animals||
- Fecal-oral route
- Contaminated raw egg shells, poultry, unpasteurized mild, cheese, vegetables, or water||
- High inoculum sufficient for infection (inactivated by gastric acid)
- Vi capsule endotoxin prevents opsonization and lysis
- Spread through the reticuloendothelial system
|
| Norovirus |
- Positive-sense, single-stranded RNA virus||
- Humans and animals||
- Fecal-oral route
- Contaminated food, vegetables, and water
- Fomites
- Aerosol exposure||
- Virus uses P2 subdomain for binding and HBGA for attachment on host cell
|
| Rotavirus |
- Double-stranded RNA virus||
- Humans and animals||
- Fecal-oral route
- Fomites||
- Poorly understood pathogenesis
- Viral replication in villous epithelium of host small intestine
|
| Giardia lamblia |
- Anerobic, flagellated protozoan parasite||
- Humans and animals||
- Ingestion of cysts in water or uncooked foods
- Fecal-oral route||
- Attaches to the epithelium by a ventral adhesive disc, and reproduces via binary fission
- Usually luminal infection, no hematogenous spread
|
| Entamoeba histolytica |
- Anaerobic parasitic protozoan with pseudopods||
- Humans*Rare (but present) in animals||
- Ingestion of cysts in water*Fecal-oral route||
- Excystation in the small intestine and migration to the large intestine
- Luminal and extraluminal infection, hematogenous spread common
|
| Cryptosporidium |
- Spore-forming parasite||*Humans and animals||
- Ingestion of oocytes in water*Fecal-oral route||
- Minimally invasive, surface-level mucosal inflammation
- Usually luminal infection, potential to infect biliary tree
|