Causes of diarrhea: infections of GI tract

Question 1

Common causes of food poisoning syndromes

Answer 1

• Food poisoning: ingestion of preformed toxin, rapid onset of illness (mostly N/V), usually short duration, rarely systemic signs (no fever), +/- diarrhea
• Toxins formed by: staph aureus, B cereus, C perfringes, ciguatera

Question 2

Pathogenesis of food poisoning: staph aureus and B cereus emetic disease

Answer 2

• Staph aureus: associated w/ mayonnaise-based foods left @ RT
• Enterotoxins are heat stable, resist hydrolysis by nzs
• Short incubation period (1-6 hrs)
• Diarrhea common (70%)
• B Cereus emetic disease: associated w/ re-heated rice
• Enterotoxins are heat stable, resist hydrolysis by nzs
• Short incubation period (1-6 hrs), lasts 8-10 hrs
• N/V, ab cramps, almost never diarrhea

Question 3

Pathogenesis of food poisoning: B cereus diarrheal disease and C perfringes

Answer 3

• B Cereus diarrheal disease: associated w/ meat and vegetables (requires ingestion of spores/bacteria)
• Bacteria grow in GI tract and produce heat labile toxin (similar to cholera toxin)
• Incubation period 9 hrs, lasts 20-36 hrs
• Sx: nausea, cramps, diarrhea (primary component), NO vomiting
• C perfringes: ingestion of spores in meat
• Produces heat labile enterotoxin
• Incubation period 8-24 hrs, lasts 24 hrs
• Sx: ab cramps and watery diarrhea

Question 4

Ciguatera poisoning and scombroid

Answer 4

• Ciguatera: toxin produces by dinoflagellates and concentrated in food chain (get it from eating fish)
• Sx: ab cramps, N/V, diarrhea, numbness/paresthesia of lips, tongue, throat
• Reversal of hot and cold temp sensation, sinus bradycardia, hypotension, cranial nerve palsies, respiratory paralysis
• Scombroid (histamine) fish poisoning: toxin produced by bacteria on flesh of fish

Question 5

Common causes of secretory diarrheas

Answer 5

• Secretory diarrhea: toxin-induced secretion of electrolytes/water
• No blood/mucous/inflammatory cells present
• Rx only oral rehydration
• Bacteria: vibrio cholera, ETEC, salmonella
• Viruses: rotavirus, norwalk-like viruses, adenoviruses
• Parasites: giardia, cryptosporidium

Question 6

Pathogenesis of secretory diarrhea 1

Answer 6

• Cholera: spread by ingestion of contaminated water/food
• Toxin activates AC, increasing secretion and decreasing absorption of electrolytes
• Sx: rice water diarrhea (w/ sweet or fishy odor), can be either mild or massive
• Rx: oral rehydration w/ water + salt + sugar
• Enterotoxigenic E Coli (ETEC): most common cause of traveler’s diarrhea (spread via food/water)
• Incubation period hrs-days, duration <5 days
• Toxin similar to cholera toxin

Question 7

Pathogenesis of secretory diarrhea 2

Answer 7

• EPEC (enteropathogenic E Coli) is a cause of infantile diarrhea
• EPEC spread via P2P and vomiting is more common
• Giardia: from drinking contaminated fresh water
• Produces foul-smelling diarrhea, Dx via antigen assays, Rx w/ metronidazole

Question 8

Causes of inflammatory diarrhea

Answer 8

• Inflammatory diarrhea: invasion of mucosa, characterized by bloody, mucous stool, ab cramping, tenesmus (feel the need to poop but colon is empty)
• Bacteria: campylobacter jejuni, EHEC (some other strains as well), salmonella (can also be non-inflammatory), shigella, yersinia, C diff
• Parasites: entamoeba histolytica

Question 9

E Coli: EHEC

Answer 9

• Enterohemorrhagic E Coli produces a shiga-toxin
• Cattle major source (undercooked beef)
• Can lead to HUS (2-8%): mostly extremes of age, characterized by microcytic hemolytic anemia, thrombocytopenia, renal failure (uremia)
• Other E Coli that cause inflammatory diarrhea: EAEC (infantile diarrhea and traveler’s diarrhea, causes a chronic diarrhea in HIV pts) EIEC (similar to shigella), DAEC (children in developing countries)

Question 10

C Diff

Answer 10

• Spread in hospital environment (spore former)
• Causes antibiotic-associated diarrhea and pseudomembranous colitis
• Produces enterotoxin, leading to hemorrhagic necrosis of intestinal wall and inflammation
• Clinical: Hx of antibiotics, ab pain, bloody diarrhea, fever

Question 11

Amebiasis (entamoeba histolytica)

Answer 11

• Protozoa, forms cysts in colon which survive in environment for weeks
• Fecal oral spread
• Clinical: colitis (fever, abdominal pain, dysentery), extraintestinal amebiasis (rare, usually liver abscess)