What antibiotics are recommended for treating bacterial enteritis?

Antibiotic Treatment for Bacterial Enteritis

For most cases of bacterial enteritis, antibiotics are NOT routinely recommended unless the patient has severe disease, invasive infection, or specific high-risk features. 1

When to Treat with Antibiotics

Treat with antibiotics if any of the following are present:

• Severe or invasive disease (high fever, bloody diarrhea, systemic toxicity) 1
• Immunocompromised patients (HIV, transplant recipients, chemotherapy patients) 1
• Extremes of age (neonates up to 3 months, adults >50 years with suspected atherosclerosis) 1
• Underlying conditions (cardiac valvular disease, prosthetic joints, significant vascular grafts) 1
• Specific pathogens identified (Shigella, Campylobacter with severe symptoms, Salmonella Typhi/Paratyphi) 1

Pathogen-Specific Antibiotic Recommendations

Campylobacter Species

Azithromycin 500 mg once daily for 3 days is the first-line treatment 1, 2. Fluoroquinolones (ciprofloxacin) are alternatives but should be avoided due to high resistance rates (19% or higher) 1, 2. Treatment is most effective when started early in the disease course 3.

Shigella Species

Azithromycin 500 mg once daily for 3 days OR ciprofloxacin 500 mg twice daily for 3 days 1. However, avoid fluoroquinolones if the ciprofloxacin MIC is ≥0.12 μg/mL, even if reported as susceptible 1. Azithromycin is increasingly preferred due to rising fluoroquinolone resistance 2, 4.

Non-typhoidal Salmonella

Antibiotics are usually NOT indicated for uncomplicated gastroenteritis 1. Treatment paradoxically may prolong fecal shedding 3.

Treat only if:

• Patient has risk factors listed above (immunocompromised, extremes of age, cardiac disease) 1
• Bacteremia is documented 1

If treatment is indicated:

• First-line: Ciprofloxacin 500 mg twice daily OR ceftriaxone 2 g once daily 1
• For bacteremia: Ceftriaxone 2 g once daily PLUS ciprofloxacin 500 mg twice daily initially, then de-escalate based on susceptibility 1

Salmonella Typhi or Paratyphi (Enteric Fever)

Ceftriaxone 2 g once daily OR ciprofloxacin 500 mg twice daily for 7-14 days 1, 5. Azithromycin 500 mg once daily for 14 days is an alternative 1, 6, but is associated with slower fever clearance and prolonged bacteremia compared to ciprofloxacin 6. A 7-day course of ciprofloxacin achieves rapid defervescence (median 4 days) 5.

Yersinia enterocolitica

Ciprofloxacin 500 mg twice daily OR levofloxacin 500 mg once daily 1. Alternatives include TMP-SMX 160/800 mg twice daily or doxycycline 100 mg twice daily 1. For bacteremia, use ceftriaxone 2 g once daily plus gentamicin 5 mg/kg once daily 1.

Clostridium difficile

Oral vancomycin 125 mg four times daily for 10 days for severe disease 1. Fidaxomicin is an alternative (not for children <18 years) 1. Metronidazole 500 mg three times daily for 10 days is acceptable for non-severe disease in children and as a second-line option in adults who cannot access vancomycin 1.

Empirical Treatment for Acute Watery Diarrhea (Traveler's Diarrhea)

Azithromycin 1000 mg single dose for febrile diarrhea/dysentery OR 500 mg single dose for non-febrile acute watery diarrhea 2. This is now preferred over fluoroquinolones due to widespread Campylobacter resistance 2.

Alternative regimens:

• Levofloxacin 500 mg single dose (for acute watery diarrhea) or 500 mg once daily for 3 days (for dysentery) 2
• Ciprofloxacin 750 mg single dose (for acute watery diarrhea) or 500 mg twice daily for 3 days (for dysentery) 2
• Rifaximin 200 mg three times daily for 3 days (only for non-invasive disease without fever or blood) 2

Loperamide can be added to antibiotic therapy to further reduce symptoms and duration, but should not be used alone in invasive disease 2.

Critical Pitfalls to Avoid

• Do not use fluoroquinolones empirically in areas with high Campylobacter resistance (>10% resistance rates) 2
• Do not treat uncomplicated non-typhoidal Salmonella gastroenteritis in immunocompetent patients, as this may prolong carriage 1, 3
• Do not use antiperistaltic agents or opiates in patients with suspected or confirmed C. difficile infection 1
• Avoid fluoroquinolones if the patient has received quinolone therapy within 3 months due to likely resistance 1
• Treatment is most effective when initiated within 48 hours of symptom onset for bacterial enteritis 3
• Do not assume azithromycin dosing for enteric fever is optimal at standard doses—it shows delayed treatment response compared to ciprofloxacin despite in vitro susceptibility 6

Duration of Therapy

Most bacterial enteritis requires 3-7 days of treatment 1, 2. Single-dose therapy is effective for traveler's diarrhea 2. Enteric fever requires 7-14 days 1, 5. C. difficile requires 10 days minimum 1.