What is the best antibiotic for Acute Gastroenteritis (AGE)?

Best Antibiotic for Acute Gastroenteritis (AGE)

Azithromycin 500 mg once daily for 3 days is the best first-line antibiotic for bacterial acute gastroenteritis requiring treatment, with superior coverage of the most common pathogens (Campylobacter and Shigella) and lower resistance rates compared to fluoroquinolones. 1

When Antibiotics Are Actually Indicated

Most cases of AGE do not require antibiotics—the majority are viral and self-limited. 1, 2 Antibiotics should be reserved for specific high-risk scenarios:

Clear Indications for Treatment:

• 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 3, 1
• Infants under 3 months with suspected bacterial diarrhea 3
• Signs of sepsis or bacteremia 3
• Travelers' diarrhea significantly affecting daily activities 1

Do NOT Treat:

• Mild, self-limited diarrhea in immunocompetent patients 1
• Asymptomatic carriers (except Salmonella Typhi in food handlers/healthcare workers) 1
• Uncomplicated non-typhoidal Salmonella gastroenteritis in immunocompetent patients 1

First-Line Empiric Treatment

Azithromycin is the preferred empiric antibiotic when treatment is indicated before culture results are available. 1, 4, 2

Why Azithromycin:

• Excellent coverage of Campylobacter (the most common bacterial cause requiring treatment) 1
• Excellent coverage of Shigella 1, 4
• Fluoroquinolone resistance in Campylobacter has reached 19%, making azithromycin superior 1
• Well-tolerated in both adults and children 2

Dosing:

• Adults: Azithromycin 500 mg once daily for 3 days 1
• Children: Azithromycin is the preferred antibiotic for pediatric bacterial gastroenteritis 1, 2

Pathogen-Specific Treatment (When Culture Results Available)

Shigella:

• First-line: Azithromycin 500 mg once daily 1, 4, 2
• Alternative: Fluoroquinolones 1
• Always treat proven or strongly suspected shigellosis promptly 4, 2

Campylobacter jejuni:

• First-line: Azithromycin 500 mg once daily 1, 2
• Alternative: Fluoroquinolones (but note 19% resistance) 1
• Treatment most effective when started early in the disease course 4, 2

Non-typhoidal Salmonella:

• Uncomplicated cases in immunocompetent patients: NO antibiotics (prolongs carrier state) 1, 2
• Severe disease or high-risk patients: Ciprofloxacin 500 mg twice daily PO or 400 mg twice daily IV 1
• Alternative: Ceftriaxone 2g IV daily 3, 2
• Bacteremia: Ceftriaxone 2g IV daily plus ciprofloxacin 3

Yersinia:

• Bacteremia: Ceftriaxone 2g IV daily plus gentamicin 5 mg/kg IV daily 3
• Severe cases: Ceftriaxone may be used 3

Treatment Duration

Standard duration is 3 days for most bacterial gastroenteritis, continuing until clinical signs resolve. 1 Immunocompromised patients may require longer duration based on clinical response. 1

Critical Pitfalls to Avoid

Never Use Antibiotics For:

• Viral gastroenteritis (norovirus, rotavirus, adenovirus)—antibiotics are completely ineffective 3
• Parasitic causes (Giardia, Cryptosporidium, Cyclospora)—require specific antiparasitic agents 3
• Mild self-limited diarrhea in healthy adults—increases resistance and prolongs carrier state 1

Never Combine With:

• Antimotility agents (loperamide) in children <18 years or any patient with bloody diarrhea or fever 1

Empiric Treatment Caution:

• Empirical treatment without bacteriological documentation should be avoided in most cases 2
• Only 30% of empiric treatments in primary care follow guideline recommendations, compared to 99% of targeted treatments 5

Supportive Care Is Primary

Rehydration takes priority over antibiotics in all cases:

• Oral rehydration solution (ORS) for mild-moderate dehydration 1
• IV fluids for severe dehydration, shock, or altered mental status 1