In an adult with suspected bacterial enterocolitis who requires antibiotics (e.g., severe illness, high fever, dysentery, immunocompromise), what is the recommended empiric therapy?

Recommended Antibiotics for Suspected Bacterial Enterocolitis

For adults with suspected bacterial enterocolitis requiring empiric therapy, use either ciprofloxacin 500 mg orally twice daily or azithromycin 1000 mg as a single dose, with the choice depending on local fluoroquinolone resistance patterns and recent travel history. 1

When to Initiate Empiric Antibiotics

Empiric antimicrobial therapy is not routinely recommended for most cases of bloody diarrhea while awaiting diagnostic results 1. However, specific clinical scenarios mandate immediate treatment:

Clear Indications for Empiric Therapy:

• Bacillary dysentery syndrome: Frequent scant bloody stools, documented fever in a medical setting, abdominal pain, and tenesmus presumptively due to Shigella 1
• Recent international travel with body temperature ≥38.5°C and/or signs of sepsis 1
• Immunocompromised patients with severe illness and bloody diarrhea 1
• Infants <3 months of age with suspicion of bacterial etiology 1

Do NOT Use Empiric Antibiotics:

• Asymptomatic contacts of patients with bloody diarrhea 1
• Most immunocompetent adults and children with acute watery diarrhea without recent international travel 1
• Any suspected STEC O157 or Shiga toxin 2-producing E. coli infection (antibiotics may precipitate hemolytic uremic syndrome) 1

Empiric Antibiotic Regimens

Adults:

First-line options (choose based on local resistance patterns and travel history):

• Ciprofloxacin 500 mg orally every 12 hours for 5-7 days 1, 2
• Azithromycin 1000 mg as a single oral dose 1, 3

Critical caveat: Due to increasing E. coli resistance to fluoroquinolones, check local susceptibility patterns before using ciprofloxacin 1, 4. If the patient has traveled to regions with high fluoroquinolone resistance (e.g., South Asia), azithromycin is preferred 1.

Children:

• Azithromycin (dose based on local susceptibility patterns and travel history) 1
• Third-generation cephalosporin for infants <3 months or those with neurologic involvement 1

Immunocompromised Patients:

For severe illness with bloody diarrhea, empiric broad-spectrum therapy should be considered 1. In neutropenic enterocolitis specifically:

• Monotherapy with anti-pseudomonal β-lactam (piperacillin-tazobactam) OR carbapenem (meropenem, imipenem-cilastatin, or doripenem) 4
• Conservative antibiotic management succeeds in 86% of neutropenic enterocolitis cases with median resolution in 6-8 days 4

Special Clinical Scenarios

Enteric Fever (Suspected Typhoid):

Patients with clinical features of sepsis and suspected enteric fever require:

• Broad-spectrum empiric therapy after obtaining blood, stool, and urine cultures 1
• Narrow therapy once susceptibility results are available 1
• If no isolate is available, tailor antibiotics to susceptibility patterns from the acquisition setting 1

Healthcare-Associated Enterocolitis:

Empiric therapy should be driven by local microbiologic results and may require multidrug regimens with expanded gram-negative coverage 1:

• Imipenem-cilastatin, meropenem, doripenem, or piperacillin-tazobactam 1
• Cefepime or ceftazidime in combination with metronidazole 1

Duration of Therapy

• Standard duration: 5-7 days for infectious diarrhea 2
• Continue at least 2 days after signs and symptoms resolve 2
• Modify or discontinue when a specific organism is identified and targeted therapy is appropriate 1

Critical Pitfalls to Avoid

1. Never use antibiotics for suspected STEC infections that produce Shiga toxin 2, as this increases risk of hemolytic uremic syndrome 1

2. Do not use ampicillin-sulbactam due to high resistance rates among community-acquired E. coli 1

3. Avoid cefotetan and clindamycin due to increasing Bacteroides fragilis group resistance 1

4. Do not routinely cover enterococci in community-acquired infections 1

5. Avoid empiric antifungal therapy for community-acquired intra-abdominal infections unless Candida is grown from cultures 1

6. Check fluoroquinolone resistance patterns before empiric use, as E. coli resistance is increasing globally 1, 4

Supportive Care

Regardless of antibiotic use, all patients require:

• Reduced osmolarity oral rehydration solution (ORS) as first-line therapy for mild to moderate dehydration 1
• Intravenous isotonic fluids (lactated Ringer's or normal saline) for severe dehydration, shock, or altered mental status 1