What is the first-line antibiotic choice for acute gastroenteritis from food poisoning?

First-Line Antibiotic Choice for Acute Gastroenteritis from Food Poisoning

For acute gastroenteritis from food poisoning, most cases do not require antibiotics—hydration is the primary treatment—but when antibiotics are indicated (dysentery, severe illness, or high-risk patients), azithromycin is the preferred first-line agent, with ciprofloxacin as an alternative in regions with low fluoroquinolone resistance. 1, 2

When Antibiotics Are Actually Indicated

The critical first decision is whether antibiotics are needed at all:

• Most acute gastroenteritis does NOT require antibiotics, as the majority of cases are viral or self-limited bacterial infections where rehydration is sufficient 3, 4
• Antibiotics are indicated for: dysentery (bloody diarrhea with fever), severe/incapacitating illness, immunocompromised patients, or when specific pathogens like Shigella, Campylobacter, or Vibrio cholerae are suspected 1, 5
• Avoid empiric antibiotics in mild watery diarrhea without fever or blood, as this promotes resistance without clinical benefit 3

First-Line Antibiotic: Azithromycin

Azithromycin is the preferred empiric first-line antibiotic for moderate-to-severe bacterial gastroenteritis:

Dosing Options:

• Single 1000 mg dose (preferred for compliance) OR 500 mg daily for 3 days 1, 2
• The single-dose regimen offers equivalent efficacy with better adherence 1

Why Azithromycin is First-Line:

• Superior for Campylobacter infections: 100% clinical and bacteriological cure rates versus fluoroquinolone failures in high-resistance areas 1, 2
• Effective for Shigella infections: demonstrates excellent cure rates as first-line treatment 1, 5
• Critical in Southeast Asia and other high-resistance regions: fluoroquinolone resistance exceeds 85-90% for Campylobacter, making azithromycin clearly superior 1
• Broader coverage: effective against enteroinvasive E. coli, Aeromonas, Plesiomonas, and Yersinia enterocolitica 2

Combination Therapy:

• Azithromycin plus loperamide reduces illness duration dramatically (from 59 hours to <12 hours in moderate-to-severe cases) 1
• Loperamide dosing: 4 mg initially, then 2 mg after each liquid stool, maximum 16 mg/24 hours 1, 2
• Avoid loperamide in children <18 years, inflammatory diarrhea with fever, or suspected toxic megacolon 3

Second-Line Alternative: Fluoroquinolones

Ciprofloxacin remains an option but with important caveats:

• The 2024 WHO guidelines and 2017 IDSA guidelines list ciprofloxacin as first-choice for invasive bacterial diarrhea in areas with low resistance 3
• However, increasing fluoroquinolone resistance (particularly for Campylobacter) limits its utility in many regions 1, 2
• Serious adverse effects include tendon rupture, C. difficile infection, and QT prolongation 2
• Use ciprofloxacin only when azithromycin is unavailable or contraindicated, and local resistance patterns support its use 3

Pathogen-Specific Considerations

Shigella infections:

• Azithromycin is first-line 1, 5
• Avoid fluoroquinolones due to inferior outcomes compared to β-lactams for confirmed Shigella 3

Campylobacter infections:

• Azithromycin is superior to fluoroquinolones, especially in severe cases during the initial phase 1, 5

Salmonella infections:

• Most cases do not require antibiotics unless severe or in high-risk patients (infants <3 months, elderly, immunocompromised) 5, 4
• When indicated: ceftriaxone or ciprofloxacin (based on susceptibility) 5, 4

Vibrio cholerae (cholera):

• Azithromycin is more effective than fluoroquinolones 3
• Doxycycline is an alternative second-choice 3

What NOT to Use

• Co-trimoxazole (trimethoprim-sulfamethoxazole): increasing resistance compromises efficacy 3
• Macrolides other than azithromycin (erythromycin): widespread bacterial resistance 3
• Ampicillin, tetracyclines (except doxycycline for cholera): no longer recommended due to resistance 3

Critical Caveats and Pitfalls

• Do not use antibiotics for non-bloody, non-febrile diarrhea—watchful waiting with symptom relief is appropriate 3
• Obtain stool cultures before antibiotics when possible, though empiric therapy is warranted in severe cases 2, 4
• Geographic resistance patterns matter: azithromycin should be the default in Southeast Asia regardless of severity 1
• Avoid antacids with azithromycin: aluminum or magnesium-containing antacids reduce absorption 2
• Immunocompromised patients: consider empiric antibacterial treatment even for less severe illness 1