What is the recommended antibiotic regimen for infective Acute Gastroenteritis (AGE) of bacterial origin?

Antibiotic Treatment for Bacterial Acute Gastroenteritis

Most cases of acute gastroenteritis do not require antibiotics, but when bacterial infection is confirmed or strongly suspected with severe symptoms, azithromycin 500 mg once daily for 3 days is the preferred first-line antibiotic for empiric treatment. 1

When to Treat with Antibiotics

Antibiotics are indicated only in specific clinical scenarios, not for routine gastroenteritis 2:

• Severe illness with high fever, bloody diarrhea, or signs of systemic toxicity 1
• Immunocompromised patients including those with neutropenia, HIV/AIDS, or on immunosuppressive therapy 2, 1
• Confirmed bacterial pathogens requiring treatment (Shigella, severe Campylobacter, invasive Salmonella) 3, 4
• Travelers' diarrhea significantly affecting daily activities 1

Critical caveat: Never give antibiotics for suspected STEC O157:H7 (E. coli) infections, as this increases the risk of hemolytic uremic syndrome 1.

First-Line Empiric Treatment

When empiric treatment is warranted before culture results:

• Azithromycin 500 mg once daily for 3 days (or 1000 mg single dose for severe cases) 1
• This is preferred due to excellent coverage of Campylobacter (which has 19% fluoroquinolone resistance) and Shigella 2, 3

Alternative option:

• Ciprofloxacin 500 mg twice daily for 3 days (or 750 mg once daily) 1
• Use only if Campylobacter is unlikely or local resistance patterns favor fluoroquinolones 5

Pathogen-Specific Treatment

Shigella

• Azithromycin 500 mg once daily IV/PO 2, 1
• Fluoroquinolones (ciprofloxacin 500 mg twice daily or levofloxacin 500 mg once daily) are alternatives 2
• Treatment is mandatory for all confirmed cases due to high transmissibility 3, 4

Campylobacter

• Azithromycin 500 mg once daily IV/PO 2, 1
• Fluoroquinolones are alternatives but have 19% resistance rates 2
• Only treat if diagnosed early (within 3-4 days of symptom onset) or severe disease 3, 4

Non-typhoidal Salmonella

For uncomplicated gastroenteritis: No antibiotics needed in immunocompetent patients 2, 3

For severe disease or high-risk patients:

• Ciprofloxacin 500 mg twice daily PO or 400 mg twice daily IV 2, 1
• Alternatives: Levofloxacin 500 mg once daily, amoxicillin 500 mg three times daily, or TMP-SMZ 160/800 mg twice daily (based on susceptibility) 2

For bacteremia:

• Ceftriaxone 2 g once daily IV plus ciprofloxacin 500 mg twice daily IV 2
• Start combination therapy and de-escalate once resistance data available 2

Yersinia

• Fluoroquinolone (ciprofloxacin 500 mg twice daily or levofloxacin 500 mg once daily) 2
• Alternatives: TMP-SMZ 160/800 mg twice daily or doxycycline 100 mg twice daily 2

For bacteremia:

• Ceftriaxone 2 g once daily IV plus gentamicin 5 mg/kg once daily IV 2

Treatment Duration

• Standard duration: 3 days for most bacterial gastroenteritis 1, 3
• Continue until clinical signs resolve (normalization of temperature, WBC count, return of GI function) 2
• If symptoms persist after 5-7 days, investigate for complications rather than extending antibiotics 2

Special Populations

Immunocompromised Patients

• Lower threshold for initiating antibiotics 1
• Consider broader coverage and longer duration 2
• Linezolid 600 mg every 12 hours for VRE enterococcal infections 2

Children

• Azithromycin is the preferred antibiotic for pediatric bacterial gastroenteritis requiring treatment 1, 3
• Avoid fluoroquinolones in children unless no alternatives exist 3, 4

What NOT to Do

• Do not treat asymptomatic carriers except for Salmonella Typhi in food handlers or healthcare workers 2
• Do not use antimotility agents (loperamide) in children <18 years or in any patient with bloody diarrhea or fever 2
• Do not give empiric antibiotics for mild, self-limited diarrhea in immunocompetent patients 2, 3, 5
• Do not substitute empiric treatment for proper hydration, which remains the cornerstone of management 2

Supportive Care Priorities

Antibiotics are adjunctive; rehydration is primary 2:

• Oral rehydration solution (ORS) for mild-moderate dehydration 2
• IV fluids (lactated Ringer's or normal saline) for severe dehydration, shock, or altered mental status 2
• Continue normal diet once rehydrated 2
• Probiotics may reduce symptom duration in immunocompetent patients 2