| Bacterial |
| Campylobacter | Proven in dysentery and sepsis, possibly effective in enteritis | Azithromycin (Zithromax), 500 mg once per day for 3 to 5 days | Erythromycin, 500 mg four times per day for 3 to 5 days | Consider prolonged treatment if the patient is immunocompromised |
| Ciprofloxacin (Cipro), 500 mg twice per day for 5 to7 days |
| Clostridium difficile | Proven | Metronidazole (Flagyl), 500 mg three times per day for 10 days | Vancomycin, 125 mg four times per day for 10 days | If an antimicrobial agent is causing the diarrhea, it should be discontinued if possible |
| Enteropathogenic/enteroinvasive Escherichia coli | Possible | Ciprofloxacin, 500 mg twice per day for 3 days | TMP/SMX DS, 160/800 mg twice per day for 3 days | — |
| Enterotoxigenic E. coli | Proven | Ciprofloxacin, 500 mg twice per day for 3 days | TMP/SMX DS, 160/800 mg twice per day for 3 days | Enterotoxigenic E. coli is the most common cause of traveler's diarrhea |
| Azithromycin, 500 mg per day for 3 days |
| Salmonella, non-Typhi species | Doubtful in enteritis; proven in severe infection, sepsis, or dysentery | — | Options for severe disease: Ciprofloxacin, 500 mg twice per day for 5 to 7 days | In addition to patients with severe disease, it is appropriate to treat patients younger than 12 months or older than 50 years, and patients with a prosthesis, valvular heart disease, severe atherosclerosis, malignancy, or uremia |
| TMP/SMX DS, 160/800 mg twice per day for 5 to 7 days |
| Azithromycin, 500 mg per day for 5 to 7 days | Patients who are immunocompromised should be treated for 14 days |
| Shiga toxin–producing E. coli | Controversial | No treatment | No treatment | The role of antibiotics is unclear; they are generally avoided because of their association with hemolytic uremic syndrome |
| Antimotility agents should be avoided |
| Shigella | Proven in dysentery | Ciprofloxacin, 500 mg twice per day for 3 days, or 2-g single dose | Azithromycin, 500 mg twice per day for 3 days | Use of TMP/SMX is limited because of resistance |
| TMP/SMX DS, 160/800 mg twice per day for 5 days | Patients who are immunocompromised should be treated for 7 to 10 days |
| Ceftriaxone (Rocephin), 2- to 4-g single dose | |
| Vibrio cholerae | Proven | Doxycycline, 300-mg single dose | Azithromycin, 1-g single dose | Doxycycline and tetracycline are not recommended in children because of possible tooth discoloration |
| Tetracycline, 500 mg four times per day for 3 days |
| TMP/SMX DS, 160/800 mg twice per day for 3 days |
| Yersinia | Not needed in mild disease or enteritis, proven in severe disease or bacteremia | — | Options for severe disease: | — |
| Doxycycline combined with an aminoglycoside |
| TMP/SMX DS, 160/800 mg twice per day for 5 days |
| Ciprofloxacin, 500 mg twice per day for 7 to 10 days |
| Protozoal |
| Cryptosporidium | Possible | Therapy may not be necessary in immunocompetent patients with mild disease or in patients with AIDS who have a CD4 cell count greater than 150 cells per mm3 | Option for severe disease: Nitazoxanide (Alinia), 500 mg twice per day for 3 days (may offer longer treatment for refractory cases in patients with AIDS) | Highly active antiretroviral therapy, which achieves immune reconstitution, is adequate to eradicate intestinal disease in patients with AIDS |
| Cyclospora or Isospora | Proven | TMP/SMX DS, 160/800 mg twice per day for 7 to 10 days | — | — |
| AIDS or immunosuppression: TMP/SMX DS, 160/800 mg twice to four times per day for 10 to 14 days, then three times weekly for maintenance |
| Entamoeba histolytica | Proven | Metronidazole, 750 mg three times per day for 5 to 10 days, plus paromomycin, 25 to 35 mg per kg per day in 3 divided doses for 5 to 10 days | Tinidazole (Tindamax), 2 g per day for 3 days, plus paromomycin, 25 to 35 mg per kg per day in 3 divided doses for 5 to 10 days | If the patient has severe disease or extraintestinal infection, including hepatic abscess, serology will be positive |
| Giardia | Proven | Metronidazole, 250 to 750 mg three times per day for 7 to 10 days | Tinidazole, 2-g single dose | Relapses may occur |
| Microsporida | Proven | Albendazole (Albenza), 400 mg twice per day for 3 weeks | — | Highly active antiretroviral therapy, which achieves immune reconstitution, is adequate to eradicate intestinal disease in patients with AIDS |
