GI Infections

Pathogens commonly responsible for infectious diarrhea

  • Vibrio Cholerae
  • Shigella
  • Salmonella
  • Campylobacter
  • Staph aureus
  • Yersinia
  • Clostridium difficile

Risk factors for and sources of contamination responsible for gastrointestinal infections

  • Risk factors:  antibiotic exposure, inadequate refrigeration, recent travel to high risk areas, immunosuppressed, poor personal hygiene, disruption of normal defense barrier mechanisms, a regional outbreak of food or water-borne illness
  • Sources of contamination (fecal to oral transmission):  drinking water, ice cubes, unpeeled fruits & veggies, raw seafood, undercooked meat

Measures useful in preventing GI infections

  • Nonpharmacological prevention strategies:  good hygiene (wash hands), cook meat well (especially ground beef), don’t drink unpasteurized milk, avoid or refrigerate unpasteurized fruit juices, refrigerate eggs & dairy products
    • In high risk areas: boil/chlorinate/iodinate water, peel fruits/vegetables prior to eating, know where your ice comes from

Antimicrobial regimens for prevention and/or treatment of common GI infections

  • Prevention strategies for “Travelers Diarrhea”:
    • Any of the following (start 1 day prior to travelling & continue for 2 days after returning)
      • Cipro 500mg qd
      • Rifaximin 525 mg qd-qid
      • Bismuth subsalicylate 2 ts w/ meals & hs
Antibiotic Treatment Options




Salmonella (nontyphoid)

Ciprofloxacin, ceftriaxone or azithromycin


Same as Salmonella


Erythromycin or other macrolide

Staphylococcus aureus

Not Recommended

E. Coli


Vibrio Cholera

Ciprofloxacin, azithromycin

Clostridium difficile Associated Colitis

  • Iatrogenic infection spread via the fecal to oral route (gram + spore forming anaerobe)
  • Prevention:  use soap & water
  • Demonstrates resistance to fluoroquinalones & cephalosporins
  • Patients may become symptomatic days or weeks after their antibiotic exposure (promoted  by an alteration in normal GI flora secondary to antibiotic exposure)
    • Antibiotics frequently responsible for this condition:  Ampicillin, Amox, Cephalosporins, Clindamycin, Fluroquinalones
      • Less frequently tetracyclines, sulfonamides, trimethoprim (Bactrim), erythromycins, aminoglycosides, bacitracin, metronidazole, vancomycin
    • Other risk factors:  elderly, recent bowel surgery, ischemic bowel, malnutrition, chemo, shock
  • Diagnosis is based off a serum or stool assay for Clostridium difficile toxin
  • Prevention: wash hands w/ non-alcohol based hand sanitizers (use soap), clean room furniture w/ bleach, isolate the patient, probiotics
  • Treatment:  stop the offending agent, maintain fluids/electrolytes, may use the following antibiotics:
    • mild to moderate disease:
      • Metronidazole (drug of choice for CDAD) 500 mg po TID x 10-14 days
        • Alternative:  Vanco 125-500 mg PO QID
    • Severe disease (pseudomembraneous colitis, leukocytosis, acute renal failure, hypotension):
      • Vanco 125-500 mg QID for 10-14 days   +   metronidazole 500 mg TID-QID
    • For patients w/ toxic megacolon:
      • Metronidazole 500 mg QID for 10-14 days
        • Or Vanco 500-1000mg q 4-12 h
    • 10-20% of patients will relapse w/in 1-3 weeks after discontinuing the initial regimen  (after relapsing once you are more likely to have multiple relapses)
      • Mild relapses usually resolve on their own w/o antibiotics
      • 1st  relapse:  use same approach as initial trxt
      • 2nd relapse:  tapering dose of vanco
      • 3rd relapse:  vanco x 14 days followed by rifixamin x 14 days

Cryptosporidiosis can also cause infectious diarrhea:

  • Protozoa that is a common cause of diarrhea in patients with HIV that’s transmitted via the fecal to oral route & characterized by abdominal pain, fever & watery diarrhea
  • Treatment:  paromomycin or spiramycin

Rotovirus is another common cause of infectious diarrhea that most commonly affects kids 6 mo-2 years old from October to April.  Treatment is supportive
Oral rehydrating solution treatment should contain Na, K, Cl, Bicarb, & glucose   (ex. Ricelyte, pedialyte, etc)
Empiric treatment  (none of the following are indicated w/ dysentry diarrhea):

  • loperamide (imodium):  as long as it’s not associated w/ bloody diarrhea
  • Diphenoxylate/atropine (lomotil)
  • A Quinalone (Cipro, ofloxacin, etc)
  • Rifixamin (xifaxin) 200 mg po TID

Signs/symptoms & complications:  secretory or dysentery diarrhea, abdominal cramping & extension, nausea, dehydration, electrolyte disturbances, malaise, fever, mucous/bloody diarrhea, renal failure, hemolytic uremic syndrome (renal failure, hemolytic anemia, thrombocytopenia)
Diagnosis:  stool cultures– inspection for ova & parasites, fecal leukocytes & clostridium difficile toxin

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