What is the recommended antibiotic treatment for a patient with infectious diarrhea, possibly caused by bacterial infections such as Clostridioides difficile or Giardia lamblia?

Antibiotic Treatment for Infectious Diarrhea

For most patients with acute infectious diarrhea, antibiotics are not recommended—the cornerstone of treatment is oral rehydration therapy, and empiric antibiotics should be reserved for specific high-risk scenarios including suspected Shigella with dysentery, recent international travelers with fever ≥38.5°C, immunocompromised patients with severe bloody diarrhea, or infants <3 months with suspected bacterial infection. 1

General Approach: When NOT to Use Antibiotics

• Acute watery diarrhea without recent international travel does not require empiric antimicrobial therapy as it is typically self-limiting and most often viral in origin 1, 2
• Immunocompetent children and adults with bloody diarrhea should NOT receive antibiotics while awaiting diagnostic results, with rare exceptions 1
• Asymptomatic contacts of patients with diarrhea should never receive empiric antibiotics 1

Critical Caveat: Avoid Antibiotics in STEC Infections

• Antimicrobial agents administered to patients with Shiga toxin-producing E. coli (STEC) infections may increase the risk of hemolytic uremic syndrome (HUS) 3
• This represents a potentially life-threatening complication where antibiotics worsen outcomes rather than improve them 3

When Antibiotics ARE Indicated

High-Risk Scenarios Requiring Empiric Therapy

• Recent international travelers with fever ≥38.5°C and/or signs of sepsis should receive empiric antibiotics immediately 1
• Immunocompromised patients with severe illness and bloody diarrhea require antibiotic treatment 1
• Infants <3 months of age with suspected bacterial etiology should be treated empirically 1
• Immunocompetent patients with documented fever, abdominal pain, bloody diarrhea, and bacillary dysentery presumptively due to Shigella should receive antibiotics 1

Pathogen-Specific Indications

• Shigellosis: Antibiotics are highly effective and recommended 2, 4
• Campylobacteriosis: Antibiotics are effective when used appropriately 2
• Cholera: Antimicrobial therapy is beneficial 4
• Enteric fever (typhoid): Requires empiric broad-spectrum antibiotics after collecting blood, stool, and urine cultures, then narrow therapy based on susceptibility results 1

Antibiotic Selection by Patient Population

Adults

• First-line options: Fluoroquinolones or azithromycin, with selection based on local susceptibility patterns and travel history 1
• The choice between these agents depends critically on regional resistance patterns, as resistance to fluoroquinolones has emerged in many areas 3

Children

• For infants <3 months or those with neurologic involvement: Third-generation cephalosporin 1
• For older children: Azithromycin based on local susceptibility patterns and travel history 1
• Furazolidone is an effective alternative but requires four times daily dosing for 7-10 days 5

Specific Pathogen Treatment

Clostridioides difficile

• For initial episode of nonsevere C. difficile infection: Oral vancomycin or oral fidaxomicin 6
• Metronidazole is no longer recommended as first-line therapy for adults 6
• Fecal microbiota transplantation is reasonable for patients with multiple recurrent episodes who have received appropriate antibiotic therapy for at least three episodes 6
• Critical warning: Antimotility agents and certain antibiotics can worsen C. difficile outcomes, potentially leading to severe complications including death 3

Giardia lamblia

• Metronidazole 5-7 day course cures >90% of individuals 5
• Single-dose tinidazole or ornidazole achieves similar cure rates 5
• Paromomycin may be used during early pregnancy because it is not systemically absorbed, though it is not always effective 5
• Resistant infections can usually be cured by prolonged combination therapy with a nitroimidazole plus quinacrine 5

Important Contraindications and Warnings

Antimotility Agents

• Loperamide should NOT be given to children <18 years of age with acute diarrhea 3, 1
• Avoid loperamide in suspected or proven inflammatory diarrhea or diarrhea with fever due to risk of toxic megacolon 3
• Deaths have been reported in 0.54% of children given loperamide, all occurring in children <3 years old 3
• Antimotility agents worsen clinical outcomes in shigellosis and STEC infections 3

Antibiotic-Related Risks

• Treatment of salmonellosis with antibiotics (including quinolones) can prolong the carrier state and increase clinical relapse rates 3
• Recent antimicrobial use increases susceptibility to resistant Salmonella infections 3
• Use of metronidazole or vancomycin for C. difficile enhances colonization with vancomycin-resistant enterococci 3

Treatment Modifications and Follow-Up

• Modify or discontinue antibiotics when a specific pathogen is identified to avoid unnecessary broad-spectrum coverage 1
• Consider non-infectious causes in patients with symptoms lasting ≥14 days 1
• Reassess fluid and electrolyte balance, nutritional status, and antibiotic efficacy in patients with persistent symptoms 1
• Follow-up stool testing is generally not recommended after symptom resolution except when required by local health authorities 1

The Foundation: Rehydration Therapy

• Oral rehydration solution (ORS) is the primary treatment for most infectious diarrhea and should be prioritized over antibiotics 1, 4
• Isotonic intravenous fluids (lactated Ringer's or normal saline) should be administered for severe dehydration, shock, altered mental status, or ORS failure 3
• Once rehydrated, resume age-appropriate diet immediately 3
• Human milk feeding should continue throughout the diarrheal episode in infants and children 3

Key Takeaway on Antibiotic Stewardship

Good antibiotic stewardship is a key strategy to decrease rates of C. difficile infection and prevent emergence of resistant strains 6. The shift away from empiric antibiotics for most infectious diarrhea reflects the recognition that inappropriate antibiotic use causes more harm than benefit through adverse effects, resistance development, and worsening of certain infections like STEC and C. difficile 3.