What is a recommended oral antibiotic regimen for common bacterial infections?

Recommended Oral Antibiotic Regimens for Common Bacterial Infections

For most common bacterial infections, the choice of oral antibiotic depends on the specific infection site and likely pathogens, with shorter courses now preferred based on recent evidence to minimize resistance and adverse effects while maintaining efficacy.

Urinary Tract Infections

Uncomplicated Cystitis (Women)

• Nitrofurantoin 5 days is a first-line option 1
• TMP-SMX for 3 days is equally effective when susceptibility is known 1
• Fosfomycin single dose provides convenient alternative therapy 1
• Avoid fluoroquinolones as empiric therapy due to adverse effect profile and resistance concerns 1

Uncomplicated Pyelonephritis

• Fluoroquinolones (ciprofloxacin or levofloxacin) for 5-7 days are highly effective with clinical cure rates exceeding 93% 1
• TMP-SMX for 14 days is appropriate when susceptibility testing confirms sensitivity, though clinical cure rates are lower (85%) compared to fluoroquinolones (96%) 1
• The 5-day fluoroquinolone course has proven noninferior to 10-day courses in recent trials 1

Respiratory Tract Infections

Community-Acquired Pneumonia

• Treatment duration should be 5 days for patients who achieve clinical stability (no fever for 48 hours) 1
• Levofloxacin 750 mg daily for 5 days is as effective as 500 mg daily for 10 days, with 90.9% clinical success rates 2
• For atypical pathogens (Mycoplasma, Chlamydophila), levofloxacin achieves 96% success rates 2
• Levofloxacin is effective against multi-drug resistant Streptococcus pneumoniae with 95% clinical success 2

Acute Bacterial Sinusitis

• Levofloxacin 750 mg daily for 5 days achieves 91.4% clinical success 2
• Amoxicillin-clavulanate is first-line for maxillary sinusitis 1
• Second-generation cephalosporins (cefuroxime-axetil) or third-generation (cefpodoxime-proxetil) are alternatives 1
• Reserve fluoroquinolones (levofloxacin, moxifloxacin) for frontal, ethmoidal, or sphenoidal sinusitis or first-line treatment failures 1
• Treatment duration is typically 7-10 days, though some agents are effective in 5 days 1

Skin and Soft Tissue Infections

Nonpurulent Cellulitis

• 5-6 day antibiotic course is adequate for patients with close follow-up 1
• Cephalexin 500 mg four times daily is first-line for methicillin-susceptible Staphylococcus aureus 1
• Dicloxacillin 500 mg four times daily is the oral agent of choice for MSSA 1
• Clindamycin 300-450 mg three times daily covers both streptococci and MSSA 1
• For MRSA: TMP-SMZ 1-2 double-strength tablets twice daily or doxycycline 100 mg twice daily 1

Impetigo

• Dicloxacillin or cephalexin for 7 days depending on clinical response 1
• Mupirocin ointment three times daily for limited lesions 1
• Amoxicillin-clavulanate 875/125 mg twice daily is an alternative 1

Animal Bites

• Amoxicillin-clavulanate is the oral treatment of choice for both dog and cat bites 1
• Doxycycline 100 mg twice daily has excellent activity against Pasteurella multocida from animal bites 1
• Moxifloxacin or levofloxacin 400 mg daily covers Pasteurella but misses some anaerobes 1

Human Bites

• Amoxicillin-clavulanate is first-line therapy 1
• Doxycycline 100 mg twice daily is an alternative with good coverage of Eikenella corrodens 1
• Avoid cephalosporins as monotherapy since they miss Eikenella corrodens 1

Gastrointestinal Infections

Salmonella/Shigella Species

• Ciprofloxacin 20-40 mg/kg/day divided every 12 hours (maximum 750 mg per dose) is effective 1
• Treatment duration typically 7 days for enteric fever with rapid defervescence (median 4 days) 3

Important Caveats

Fluoroquinolone Use: While highly effective, fluoroquinolones should not be used as first-line empiric therapy for most infections due to adverse effect profiles and the need to preserve their efficacy 1. They are appropriate when susceptibility is documented or for specific indications like complicated UTIs and severe sinusitis 1.

Pediatric Considerations: Fluoroquinolones are generally contraindicated in children under 18 years, though they may be used for specific indications like UTIs caused by resistant organisms when alternatives are inadequate 1. Tetracyclines should be avoided in children under 8 years 1.

Resistance Patterns: Always consider local resistance patterns when selecting empiric therapy. TMP-SMX should not be used empirically if local resistance exceeds 20% 1. Fluoroquinolone resistance in E. coli remains below 7% in most pediatric centers but is increasing 1.

Treatment Duration: Shorter courses are now preferred for most infections to reduce adverse effects and resistance development while maintaining efficacy 1. The traditional approach of treating "until neutrophil recovery" or using arbitrary 10-14 day courses has been replaced by evidence-based shorter durations 1.