What is the recommended antibiotic treatment for a bacterial infection?

Recommended Antibiotic Treatment for Bacterial Infections

The choice of antibiotic depends critically on the infection site and severity, but for most common bacterial infections, narrow-spectrum agents should be prioritized first-line, with amoxicillin or amoxicillin-clavulanate serving as the backbone for respiratory and many other infections, while fluoroquinolones and broad-spectrum agents should be reserved for severe disease or treatment failures. 1

Respiratory Tract Infections

Community-Acquired Pneumonia (CAP)

• For mild to moderate CAP: Amoxicillin is the reference treatment for pneumococcal pneumonia, dosed at 80-100 mg/kg/day in children or standard adult dosing 1
• Treatment duration: 5 days is sufficient for most patients who achieve clinical stability (afebrile for 48 hours), which is as effective as longer courses with fewer adverse events 1
• For atypical pathogens (Mycoplasma, Chlamydia): Macrolides (azithromycin, clarithromycin) are appropriate first-line agents 1
• For severe CAP or treatment failure: Levofloxacin 750mg daily for 5 days or moxifloxacin provides excellent coverage against both typical and atypical pathogens 1

Acute Bacterial Rhinosinusitis

• Mild disease without recent antibiotic use: Amoxicillin 1.5-4g/day (higher doses for resistant pathogens or moderate disease) 1
• Moderate disease or recent antibiotic exposure: Amoxicillin-clavulanate (4g/250mg formulation) or respiratory fluoroquinolones (levofloxacin, moxifloxacin) 1
• Treatment duration: 5-7 days for uncomplicated cases 1
• β-lactam allergic patients: Respiratory fluoroquinolones are preferred over macrolides due to 20-25% bacterial failure rates with macrolides 1

Acute Bronchitis/COPD Exacerbations

• Children under 3 years with fever >38.5°C for >3 days: Beta-lactams (amoxicillin, amoxicillin-clavulanate, cefuroxime-axetil, or cefpodoxime-proxetil) 1
• Children over 3 years: Macrolides are appropriate 1
• Duration: 5-8 days 1

Urinary Tract Infections

Uncomplicated Cystitis (Women)

• First-line options: Nitrofurantoin for 5 days, trimethoprim-sulfamethoxazole (TMP-SMX) for 3 days, or fosfomycin as a single dose 1
• Avoid fluoroquinolones for empiric treatment due to adverse effect profile; reserve for resistant organisms 1

Uncomplicated Pyelonephritis

• Fluoroquinolone-susceptible organisms: Levofloxacin or ciprofloxacin for 5-7 days (not 10 days) 1
• When fluoroquinolone resistance is concern: TMP-SMX for 14 days based on susceptibility testing 1
• Critical caveat: TMP-SMX should not be used empirically without culture confirmation due to resistance concerns 1

Skin and Soft Tissue Infections

Impetigo and Purulent Infections

• Methicillin-susceptible Staphylococcus aureus: Dicloxacillin, cefazolin, or cefalexin 1
• MRSA suspected or confirmed: Vancomycin, linezolid, clindamycin, daptomycin, or TMP-SMX 1
• Non-purulent infections: Benzylpenicillin, phenoxymethylpenicillin, or clindamycin 1

Necrotizing Fasciitis

• Empiric therapy: Vancomycin or linezolid PLUS piperacillin-tazobactam or a carbapenem, OR ceftriaxone plus metronidazole 1

Bite Wounds

• Animal bites (oral): Amoxicillin-clavulanate 1
• Animal bites (IV): Ampicillin-sulbactam or piperacillin-tazobactam 1
• Human bites: Amoxicillin-clavulanate or ampicillin-sulbactam; carbapenems for multidrug-resistant organisms 1

Diabetic Foot Infections

• Mild infections: Dicloxacillin, clindamycin, cefalexin, or levofloxacin 1
• MRSA suspected: TMP-SMX 1
• Moderate to severe: Levofloxacin, ceftriaxone, ampicillin-sulbactam, moxifloxacin, or ertapenem 1
• MRSA in severe disease: Add linezolid, daptomycin, or vancomycin 1
• Pseudomonas coverage needed: Piperacillin-tazobactam, ceftazidime, cefepime, or carbapenems 1

Intra-Abdominal Infections

Mild to Moderate Community-Acquired

• First-line: Amoxicillin-clavulanate 1
• Alternative: Ampicillin + gentamicin + metronidazole 1
• Second-line: Ciprofloxacin + metronidazole OR cefotaxime/ceftriaxone + metronidazole 1

Severe Infections

• First-line: Cefotaxime or ceftriaxone + metronidazole, OR piperacillin-tazobactam 1
• Second-line: Ampicillin + gentamicin + metronidazole, OR meropenem 1
• Add ampicillin if enterococcal coverage is needed with regimens that don't cover it (e.g., ceftriaxone-metronidazole) 1

Critical Principles for Antibiotic Selection

Duration Optimization

• Shorter courses are non-inferior for most common infections when patients achieve clinical stability, with reduced adverse events and resistance selection 1, 2
• Default to shorter durations rather than traditional 10-day courses unless specific indications require longer treatment 1

Resistance Considerations

• Recent antibiotic use (within 4-6 weeks) is a major risk factor for resistant organisms and should prompt broader-spectrum choices 1
• High-dose amoxicillin (4g/day) is advantageous in areas with high penicillin-resistant S. pneumoniae prevalence 1
• Fluoroquinolone resistance is increasing in Enterobacteriaceae, limiting their empiric use 1

Common Pitfalls to Avoid

• Do not use macrolides, TMP-SMX, or doxycycline for respiratory infections when β-lactams are appropriate, as bacterial failure rates reach 20-25% 1
• Reassess diagnosis if patients fail appropriate antibiotics rather than reflexively extending duration 1
• Avoid empiric broad-spectrum agents (carbapenems, anti-pseudomonal agents) unless severe sepsis, healthcare-associated infection, or documented resistance 1