Common GI Infections Flashcards
What type of diarrhea is caused by infections in the
- Small intestine
- Large intestine
- Watery and/or malabsorptive diarrhea
2. Inflammatory diarrhea
Diarrhea definition
3 or more loose stools per day
“Stool that conforms to the shape of its container”
3 physiological causes of diarrhea
More fluid secreted into the lumen than the gut can absorb (secretory or osmotic) Normal secretion but impaired absorption (malabsorptive) Inflamed mucosa (leakage of fluid plus impaired absorption, frequently with pus/blood)
How can you tell the difference between 1. Secretory 2. Osmotic 3. Malabsorptive 4. Inflammatory diarrhea?
- Typically water, minimal fever, continues with fasting/diet
- Due to overingestion of osmotic agents
- Frequently with foul smell/gas (fermentation of nonabsorbable sugars) and/or greasy stools
- Fever, bloody stool, WBCs in stool
Where is the time cut off for chronic diarrhea?
> 14 days
Secretory infectious bacteria
Caused by bacteria that adhere to but do not damage the intestinal epithelium
They secrete toxins that turn on fluid secretion
Can overwhelm the ability of the gut to absorb fluid, leading to massive intestinal fluid losses
2 steps in the management of watery diarrhea
Volume repletion (oral rehydration preferred, can give IV if unconscious) Antibiotics (but all infections are self limited)
Malabsorptive diarrheal infections
Infection of small intestine, leading to villus blunting
Mild inflammation = increased secretion
Damaged villi = impaired absorption
Ex: Giardia, E. coli, Norovirus
Inflammatory enterocolitis
Refers to bacteria (or amoeba) that attach to and invade the small and/or large intestinal epithelia
Symptoms: diarrhea with blood and/or pus, fever, cramps, prostration
Dystenery
A disease characterized by severe diarrhea with passage of mucus and blood and usually caused by infection
A type of inflammatory colitis
Can have tenesmus
Tenesmus
Sensation of having to poop, then you go but you still feel like you need to
From swelling in the rectal mucosa
5 common causes of dysentery
Non-typhoidal Salmonella Campylobacter jejuni Shigella spp. Entamoeba histolytica Clostridium difficile (sort of)
How is dysentery transmitted
Through food/water, fomites, or direct person-to-person
How is 1. Shigella 2. Salmonella 3. Campylobacter spread?
- Person to person (low number of organisms needed for infection)
2 and 3. Through food and water
Shigella
Gram negative rod
4 subspecies, almost identical to E. coli
Invades epithelial cells directly leading to cell death
Classic cause of bacillary dysentery
S. dysenteriae 1 also expresses a shigatoxin that can lead to HUS
Infections from fecal contamination of food or water
Oral rehydration and antibiotics are used for eradication (antibiotics not really needed)
Non-typhoidal Salmonella
Gram negative rod
One species but many serovars
Frequent colonizer of poultry and meats, can be spread by food preparers
Mild nonspecific diarrhea to dysentery
Self limited
Risk of bacteremia and metastatic disease in specific hosts
Campylobacter jejuni
Gram negative "gull wing" rod Colonizer of poultry Seldom spread person to person Mild diarrhea to dysentery Almost never fatal Increasing antibiotic resistance
Entamoeba histolytica
Protozoan
Very infectious (spread person to person)
Can be asymptomatic, have invasive colitis/dysentery, and/or metastatic infection (liver abscess)
Typical: fever, bloody diarrhea, tenesmus but can be nonspecific
Diagnose off microscopy or antigen testing
4 ways to diagnose dysentery (and which one is the gold standard)
Clinical diagnosis based on blood/mucus/pus in stool, fever, +/- tenesmus
Fecal WBCs
Fecal calprotectin or lactoferrin
Gold standard: Stool culture
Infectious proctitis
Infection limited to the rectum
Sexually-transmitted through receptive anal intercourse
Symptoms usually minimal (itching, discharge)
Can be severe (HSV, certain serotypes of chlamydia)
Generally treated like their genital counterparts
Hemorrhagic colitis
Caused by EHEC or STEC (Stx 1 and Stx 2)
Most common strain O157:H7
Symptoms: afebrile, bloody diarrhea, severe abdominal pain
Major complication is hemolytic-uremic syndrome (especially in children and the elderly)
Diarrhea self-limited in <10 days, HUS typically follows
Hemolytic-uremic syndrome
Caused by systemic Stx2 > 1 (shiga toxin from E coli)
Triad of: intravascular hemolysis, acute kidney injury, thrombocytopenia)
Neurologic sequelae (coma, stoke) may occur
Permanent renal damage in 25-50%
STEC
Shiga-toxin producing E coli
3 principles of treatment for hemorrhagic colitis
Avoid anti-perstaltic agents (they increase HUS risk)
Antibiotics are not recommended (keep toxins in bacteria)
Supportive care and monitoring for HUS
Clostridium difficile
Gram +, spore forming anaerobe
Survives in meat
Endemic in health care settings
Infection typically occurs after antibiotic exposure in hospital
After depletion of commensal anaerobic bacteria the spores germinate
Makes 2 toxins: TcdA and TcdB (cause cell death and inflammation in the colonic epithelium)
Symptoms range from mild diarrhea to fulminant, fatal colitis with shock
What does the colon look like with C diff infection
Pseudomembranous colitis
Highly inflamed
Looks like membranes but they are exudates - can scrape them off but will bleed
Treatment of C diff infections
Vancomycin PO
Alternative: fidaxomicin (expensive)
Mild disease: can use metronidazole PO only if vanco is too expensive
When is stool testing most useful
In outbreaks
Immune compromised patients
Those with bloody stools
When CDI is suspected
