First-Line Antibiotic for Proctitis and Enteritis
For acute bacterial proctitis and enteritis in adults, empiric treatment with a fluoroquinolone (ciprofloxacin) or azithromycin is recommended, with the choice depending on local resistance patterns and travel history.
Pathogen-Specific Approach
The choice of empiric antibiotic should be guided by the most likely causative organisms and local resistance patterns:
For Shigella (Most Common in Bacterial Enteritis)
- Ciprofloxacin or another fluoroquinolone is first-line 1
- Azithromycin is an effective alternative, particularly important given emerging fluoroquinolone resistance 1, 2
- Two randomized controlled trials established this as the treatment of choice 1
For Campylobacter
- Azithromycin has become the drug of choice due to increasing fluoroquinolone resistance (19%) 1
- This represents a shift from previous fluoroquinolone preference 3
For Salmonella
- Ciprofloxacin is preferred for immunocompromised patients 1
- Alternatives include TMP-SMZ or amoxicillin based on susceptibility 1
- For bacteremia: combination of ceftriaxone plus ciprofloxacin to avoid initial treatment failure before resistance results are available 1
For Yersinia
- Fluoroquinolone, TMP-SMZ, or doxycycline 1
- For severe disease: third-generation cephalosporin combined with gentamicin 1
Clinical Decision Algorithm
When to Treat Empirically 2:
Treat immediately if:
- Infants <3 months with suspected bacterial etiology
- Fever documented in medical setting + abdominal pain + bloody diarrhea + bacillary dysentery (frequent scant bloody stools, fever, cramps, tenesmus) presumptively due to Shigella
- Recent international travel with temperature ≥38.5°C and/or signs of sepsis
- Immunocompromised patients with severe illness and bloody diarrhea
Do NOT treat empirically:
- Immunocompetent adults with bloody diarrhea without the above features 2
- Mild to moderate cases in immunocompetent patients may not require antibiotics 1
Practical Prescribing Recommendations
Adult Empiric Therapy 2:
- Ciprofloxacin (if local E. coli susceptibility ≥90%)
- Azithromycin (preferred if fluoroquinolone resistance suspected or recent travel to areas with high resistance)
Pediatric Empiric Therapy 2:
- Third-generation cephalosporin for infants <3 months and those with neurologic involvement
- Azithromycin for older children, depending on local patterns and travel history
Critical Resistance Considerations
Major pitfall: Fluoroquinolone resistance is increasing significantly:
- Quinolone-resistant E. coli has become common in many communities 4
- Campylobacter shows 19% fluoroquinolone resistance 1
- Do not use quinolones unless hospital surveys indicate ≥90% E. coli susceptibility 4
Emerging trend: Several studies now recommend azithromycin as preferred empiric therapy in regions with documented fluoroquinolone resistance 3, particularly given its effectiveness against both Campylobacter and Salmonella.
What NOT to Use
- Ampicillin: Only 36% of Shigella isolates remain sensitive 5
- TMP-SMZ: Only 26% of Shigella isolates remain sensitive 5
- These agents should be reserved for targeted therapy after susceptibility testing
Modification After Culture Results
Always modify or discontinue antimicrobial treatment when a clinically plausible organism is identified 2. This allows de-escalation to narrower-spectrum, organism-specific therapy and reduces unnecessary antibiotic exposure.