Agent
Brief clinical tidbits
Treatment
Campylobacter, Shigella, Salmonella, Yersinia
Invasive diarrhea characterized by fever, bloody stools
TMP/SMX or fluoroquinolone for 3 days (may reduce duration of shedding); see below for more information regarding Campylobacter
Enterotoxigenic E. coli, Campylobacter, Salmonella, Shigella, Aeromonas, Vibrio, Bacteroides
Traveler’s diarrhea: watery diarrhea, ± abdominal cramps, N/V, tenesmus
TMP/SMX or fluoroquinolone for 3 days may reduce duration of illness by 2–3 days
Shigella
Severe dysentery with fever, bloody diarrhea
TMP/SMX or fluoroquinolone two times a day for 3 days
Vibrio cholera
“Rice-water stools,” severe diarrhea
Doxycycline 300 mg × 1 dose, or TMP/SMX two times a day for 3 days or fluoroquinolone × 1 dose
Campylobacter
Associated with Guillain-Barre, inflammatory bowel disease and reactive arthritis. Causes acute watery diarrhea
Azithromycin 500 mg a day for 3 days
Salmonella
Treat specific patient populations (see below)
TMP/SMX or fluoroquinolone two times a day for 5–7 days
Listeria
Treat specific patient populations (see below)
Ampicillin
C. difficile
See below
Metronidazole 500 mg orally three times a day for 10–14 days or vancomycin 125 mg orally four times a day for 10–14 days
Table 18.2
Antibiotic choices for specific protozoal agents
Agent | Brief clinical tidbits | Treatment |
|---|---|---|
Giardia | Persistent diarrhea after exposure to untreated water; relapses may occur due to misdiagnosis | Metronizadole 750 mg three times a day for 7–10 days |
Entamoeba histolytica | Severe disease may result in hepatic abscess | Metronizadole 750 mg three times a day for 5–10 days in addition to paromomycin 25–35 mg/kg in three divided doses for 5–10 days |
Cryptosporidium | Therapy may be required in immunosuppressed patients but may not be necessary in immunocompetent patients with mild disease and those patients with HIV who have a CD4 count >150 cells/mm3 | Nitazoxanide 500 mg two times a day for 3 days for severe disease |
Cyclospora or Isospora | Requires longer therapy in HIV or immunosuppressed | TMP/SMX two times per day for 7–10 days (2–4 times per day for 10–14 days for HIV or immunosuppressed) |
Microsporidia | In patients with AIDS, highly active retroviral therapy may be adequate to eradicate intestinal disease | Albendazole 400 mg two times per day for 3 weeks |
Pitfalls
- 1.
Treating patients who have bloody diarrhea with abdominal pain and no fever and relevant history of eating raw ground beef or seed sprouts with antibiotics:
- (a)
There is a risk of hemolytic-uremic syndrome.
- (b)
Treatment with antibiotics does not improve O157 illness.
- (a)
- 2.
Treatment of Yersinia. These patients present with “pseudoappendicitis” with right lower quadrant abdominal pain along with the watery diarrhea. Treatment is only required for immunocompromised patients.
- 3.
Routine treatment of Salmonella. These patients may present acutely ill with fever and muscle aches and pains, and it typically is human-to-human transmission. Treatment is recommended for those patients who are:
- (a)
Immunocompromised
- (b)
Are at the extremes of age
- (c)
Have persistent, severe diarrhea
- (d)
Have severe illness, including sepsis
- (e)
Have a history of valvular heart disease
- (a)
- 4.
Routine treatment of Listeria. Unless pregnant or immunocompromised – in which case the disease may be severe – patients typically have mild systemic symptoms.
18.9.2 Treatment of Clostridium Difficile
This organism deserves special mention as it is one of the more serious causes of diarrhea affecting patients. Prior antibiotic use (including fluoroquinolones, clindamycin, penicillins, and cephalosporins) eliminates normal gut flora allowing for colonization by C. difficile. The diarrhea caused by C. difficile is severe, with up to 15 bowel movements per day with associated abdominal pain and cramping. Many patients may have a systemic reaction, with fever, tachycardia, and tachypnea depending on level of dehydration and overall illness. Complications of C. difficile infection include toxic megacolon, which is an abnormal dilation of the colon that is seen on imaging studies. Those patients who do not respond to medical management may require urgent surgical consultation due to the high risk of perforation.
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