GI Infections

Pathogens commonly responsible for infectious diarrhea

  • Vibrio Cholerae
  • E. Coli (ETEC, EIEC, EAEC, EPEC, EHEC)
  • 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

 

Etiology

Antibiotic(s)

Salmonella (nontyphoid)

Ciprofloxacin, ceftriaxone or azithromycin

Shigella

Same as Salmonella

Campylobacter

Erythromycin or other macrolide

Staphylococcus aureus

Not Recommended

E. Coli

Supportive

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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