What is the recommended antibiotic treatment for an adult patient with fever and diarrhea (loose stools)?

Antibiotic Treatment for Fever and Loose Stools in Adults

For an adult with fever and loose stools, azithromycin 500-1000 mg as a single dose is the preferred first-line antibiotic, but only if specific high-risk features are present—otherwise, most cases should be managed with rehydration alone without antibiotics. 1

When to Withhold Antibiotics

Most adults with acute diarrhea and fever do NOT need antibiotics. 1, 2 The following scenarios should be managed with aggressive rehydration only:

• Simple acute watery diarrhea with low-grade fever in otherwise healthy adults without recent international travel 3, 1
• Absence of dysentery features (high fever >38.5°C, bloody stools, severe abdominal cramps, tenesmus) 3
• No signs of sepsis or severe systemic illness 3, 2

Critical caveat: Never give antibiotics if STEC (Shiga toxin-producing E. coli) is suspected, as this increases the risk of hemolytic uremic syndrome. 3, 1, 2

When Antibiotics Are Indicated

Empiric antibiotic therapy should be initiated in the following specific scenarios:

• Bacillary dysentery pattern: High fever (>38.5°C documented in medical setting) + bloody diarrhea + severe abdominal cramps + tenesmus, presumed to be Shigella 3, 1
• Recent international travel with body temperature ≥38.5°C and/or signs of sepsis 3, 1
• Immunocompromised patients with severe illness and bloody diarrhea 3, 2
• Clinical features of enteric fever/sepsis: These patients need broad-spectrum IV antibiotics immediately after obtaining blood, stool, and urine cultures 3, 2

Recommended Antibiotic Regimens

First-Line: Azithromycin

Azithromycin is the preferred empiric antibiotic for bacterial diarrhea in most clinical scenarios. 1, 4

• Acute watery diarrhea with fever: 500 mg single dose 1, 4
• Febrile diarrhea/dysentery (bloody stools): 1000 mg single dose 1, 4

Azithromycin is superior to fluoroquinolones because of increasing fluoroquinolone resistance, particularly among Campylobacter species in Southeast Asia and other regions. 1, 4 The drug achieves excellent tissue penetration and intracellular accumulation, with a long elimination half-life allowing single-dose or short-course therapy. 5, 6

Alternative: Fluoroquinolones (with caution)

Fluoroquinolones such as ciprofloxacin (750 mg single dose) or levofloxacin (500 mg single dose) may be used only if local hospital surveillance data shows ≥90% susceptibility of E. coli to quinolones. 3, 1, 4

Do NOT use fluoroquinolones if:

• Travel history includes Southeast Asia (high fluoroquinolone-resistant Campylobacter) 1
• Local resistance patterns are unknown 1
• Patient is a child (fluoroquinolones contraindicated in pediatrics) 1, 2

Antibiotics to Avoid

• Trimethoprim-sulfamethoxazole: High resistance rates among common pathogens 1
• Ampicillin-sulbactam: High resistance among community-acquired E. coli 1

Adjunctive Therapy with Loperamide

Loperamide can be combined with antibiotics in immunocompetent adults with acute watery diarrhea to reduce symptom severity and duration. 3, 1, 4 However, absolutely avoid loperamide in:

• Children <18 years 1, 2
• Patients with bloody diarrhea or dysentery 1, 2
• Fever or suspected inflammatory diarrhea 1, 2
• Suspected toxic megacolon 1, 2

Rehydration Remains the Cornerstone

Aggressive rehydration must never be neglected, even when antibiotics are indicated. 3, 2 Antibiotics are adjunctive therapy only. 3

• Maintain adequate fluid intake guided by thirst 3
• Use drinks containing glucose (lemonades, fruit juices) or electrolyte-rich soups 3
• Oral rehydration solutions are not essential in otherwise healthy adults but should be used for moderate dehydration 3, 2
• IV fluids are required for severe dehydration, shock, or altered mental status 2

When to Seek Medical Intervention

Patients should seek immediate medical attention if: 3

• No improvement within 48 hours 3
• Symptoms worsen or overall condition deteriorates 3
• Development of severe vomiting, dehydration, persistent high fever, abdominal distension, or frank blood in stools 3

Algorithm for Decision-Making

1. Assess severity: Check for fever >38.5°C, bloody stools, signs of sepsis, recent international travel, immunocompromised status 3, 1, 2

2. Rule out STEC: If suspected (especially in outbreak settings or after consuming undercooked beef), withhold antibiotics 3, 1, 2

3. If high-risk features present: Start azithromycin 500-1000 mg single dose (dose depends on severity) 1, 4

4. If no high-risk features: Manage with rehydration alone, avoid antibiotics 1, 2

5. Consider loperamide: Only if watery diarrhea without fever/blood in immunocompetent adults 1, 2

6. Modify therapy: When culture results return, adjust or discontinue antibiotics based on pathogen identification 2