What is the management approach for an adult patient with infectious diarrhoea?

Management of Infectious Diarrhea in Adults

The cornerstone of infectious diarrhea management is oral rehydration therapy with reduced osmolarity ORS, while empiric antibiotics should be avoided in most cases of acute watery diarrhea unless specific high-risk features are present. 1, 2

Rehydration: The Primary Intervention

Reduced osmolarity oral rehydration solution (ORS) is the first-line therapy for mild to moderate dehydration in adults with infectious diarrhea. 1, 2 This recommendation is based on strong evidence showing ORS is safer, less painful, less costly, and equally effective compared to IV fluids for patients who can tolerate oral intake. 3

Rehydration Algorithm:

Mild to Moderate Dehydration:

• Administer ORS until clinical dehydration is corrected (assess by thirst, orthostasis, decreased urination, dry mucous membranes). 1, 3
• Continue ORS to replace ongoing stool losses until diarrhea resolves. 1, 2

Severe Dehydration (shock, altered mental status, inability to tolerate oral intake):

• Start isotonic IV fluids (lactated Ringer's or normal saline) immediately. 1, 2
• Continue IV rehydration until pulse, perfusion, and mental status normalize. 1, 2
• Transition to ORS to replace remaining fluid deficit once patient is stabilized. 1, 2

Critical Pitfall: Do not neglect rehydration while focusing on antimicrobial therapy—dehydration is the primary cause of morbidity and mortality in infectious diarrhea. 2

Nutritional Management

Resume age-appropriate usual diet immediately during or after rehydration—do not withhold food. 1, 2, 3 Early realimentation prevents malnutrition and may actually reduce stool output. 4, 3 This represents a significant shift from older practices that recommended dietary restriction during diarrheal illness.

Antimicrobial Therapy: When to Treat

Empiric antimicrobial therapy is NOT recommended for most adults with acute watery diarrhea without recent international travel. 1, 2 This is a strong recommendation based on the fact that most acute diarrhea is viral and self-limited. 5

Specific Indications for Antimicrobial Therapy:

Consider antibiotics ONLY in these circumstances: 1, 2

• Immunocompromised patients with severe illness or bloody diarrhea 1, 2
• Recent international travelers with fever ≥38.5°C or signs of sepsis 2
• Bloody diarrhea with presumptive shigellosis 2
• Clinical features of sepsis with suspected enteric fever 2
• Severe dehydration requiring IV fluids with suspected bacterial etiology 2

Antibiotic Selection:

For infectious diarrhea when indicated, ciprofloxacin is FDA-approved for treatment of infectious diarrhea caused by enterotoxigenic E. coli, Campylobacter jejuni, Shigella species, and Salmonella typhi (typhoid fever). 6 However, local resistance patterns must guide empiric therapy choices, particularly for travelers from regions with high fluoroquinolone resistance. 2

Critical Contraindication:

Avoid antimicrobials in STEC O157 and other Shiga toxin 2-producing E. coli infections—they increase the risk of hemolytic uremic syndrome. 1, 2, 3 This is a strong recommendation with moderate-quality evidence.

Modify or discontinue antimicrobial treatment when a specific pathogen is identified. 1, 2

Adjunctive Therapies: Use With Caution

Antimotility Agents (Loperamide):

Loperamide may be given to immunocompetent adults with acute watery diarrhea ONLY after adequate hydration. 1, 2, 3

Absolute contraindications for loperamide: 1, 2, 3

• Any patient with bloody diarrhea
• Any patient with fever
• Suspected inflammatory diarrhea (risk of toxic megacolon)
• Age <18 years

Antiemetics:

Ondansetron may be given to facilitate oral rehydration in adults with significant vomiting, though the primary evidence supports use in children >4 years. 1, 2

Probiotics:

Probiotic preparations may be offered to reduce symptom severity and duration in immunocompetent adults, though the evidence quality is moderate. 1, 2 Probiotics can reduce mean diarrhea duration by approximately 25 hours. 4

Clinical Decision Algorithm

1. Assess hydration status (thirst, orthostasis, urine output, mental status, mucous membranes) 3

2. Initiate appropriate rehydration:

   • Mild-moderate: ORS 1, 3
   • Severe: IV fluids then transition to ORS 1, 2

3. Resume normal diet immediately 1, 3

4. Determine if antimicrobials are indicated:

   • NO for routine acute watery diarrhea 1, 2
   • YES only if high-risk features present (immunocompromised, sepsis, bloody diarrhea with shigellosis, international travel with fever ≥38.5°C) 2

5. Avoid antimotility agents unless patient is immunocompetent adult with non-bloody, non-febrile watery diarrhea who is adequately hydrated 1, 3

6. Replace ongoing losses with ORS until symptoms resolve 1, 2

Common Pitfalls to Avoid

• Using antimicrobials for routine acute watery diarrhea without high-risk features 2, 3
• Administering loperamide to patients with bloody or inflammatory diarrhea (risk of toxic megacolon) 1, 2
• Withholding food during diarrheal episodes (increases malnutrition risk) 2, 4
• Treating STEC infections with antibiotics (increases hemolytic uremic syndrome risk) 1, 2
• Focusing on antibiotics while neglecting rehydration (dehydration is the primary threat) 2

Special Considerations for Severe Illness

For patients requiring IV antibiotics due to suspected enteric fever with sepsis, obtain blood, stool, and urine cultures immediately before starting broad-spectrum IV antimicrobial therapy. 2 Transition to oral antibiotics once the patient is rehydrated with normalized vital signs and mental status. 2