What is the typical treatment for common bacterial infections with antibiotics?

Antibiotic Treatment for Common Bacterial Infections

For most common bacterial infections, treatment should be guided by infection site, severity, and local resistance patterns, with preference for narrow-spectrum agents from the WHO Access group when appropriate.

Respiratory Tract Infections

Community-Acquired Pneumonia

• Low-severity patients: Amoxicillin monotherapy is the recommended first-line empirical treatment 1
• Moderate-severity patients: Combination of amoxicillin plus a macrolide (azithromycin or clarithromycin) 1
• High-severity patients: Beta-lactam/beta-lactamase inhibitor (amoxicillin-clavulanate or piperacillin-tazobactam) plus a macrolide 1
• Suspected Pseudomonas aeruginosa: Piperacillin-tazobactam or carbapenem combined with ciprofloxacin or levofloxacin 1

Acute Bacterial Rhinosinusitis

• First-line options (predicted 83-92% efficacy): High-dose amoxicillin (4 g/day in adults), amoxicillin-clavulanate, cefpodoxime proxetil, cefuroxime axetil, or cefdinir 2
• Respiratory fluoroquinolones (predicted 90-92% efficacy): Levofloxacin, moxifloxacin, or gatifloxacin for treatment failures or high-risk patients 2
• Macrolides (azithromycin, clarithromycin) have lower predicted efficacy (77-81%) and should be reserved for penicillin-allergic patients 2

Chronic Bronchitis Exacerbations

• Simple exacerbations: Antibiotic therapy not immediately recommended unless fever >38°C persists >3 days 2
• Chronic obstructive bronchitis with FEV1 35-80%: Treat only if ≥2 of 3 Anthonisen criteria present (increased dyspnea, sputum volume, sputum purulence) 2
• First-line antibiotics: Amoxicillin, first-generation cephalosporins, macrolides, or doxycycline for infrequent exacerbations 2
• Second-line antibiotics: Amoxicillin-clavulanate, cefuroxime-axetil, cefpodoxime-proxetil, or respiratory fluoroquinolones (levofloxacin, moxifloxacin) for frequent exacerbations (≥4/year) or FEV1 <35% 2

Urinary Tract Infections

Uncomplicated Cystitis

• Nitrofurantoin for 5 days is a first-line option 2
• Trimethoprim-sulfamethoxazole (TMP-SMX) for 3 days when local resistance <20% 2
• Single-dose fosfomycin is an alternative 2
• Fluoroquinolones should be reserved for patients with resistant organisms due to adverse effect profile 2

Pyelonephritis

• Fluoroquinolones for 5-7 days when susceptibility is known (clinical cure rates >93%) 2
• TMP-SMX for 14 days only with documented susceptibility (92% cure rate for susceptible strains) 2
• Empirical TMP-SMX is not recommended without culture due to high resistance rates 2
• A 7-day course of TMP-SMX may be effective for susceptible E. coli pyelonephritis 2

Skin and Soft Tissue Infections

Nonpurulent Cellulitis

• 5-6 day course of antibiotics active against streptococci for patients with close follow-up 2
• Oral options: Dicloxacillin, cefalexin, or clindamycin 2
• Parenteral options: Cefazolin or nafcillin 2
• Doxycycline or TMP-SMX are alternatives 2

MRSA Skin Infections

• Oral therapy: Clindamycin, doxycycline, or TMP-SMX 2
• Parenteral therapy: Vancomycin, linezolid, or daptomycin 2
• Ceftaroline is an alternative for severe infections 2

Diabetic Wound Infections

• Mild infections: Dicloxacillin, clindamycin, cefalexin, levofloxacin, or amoxicillin-clavulanate 2
• Moderate-to-severe infections: Levofloxacin, ceftriaxone, ampicillin-sulbactam, moxifloxacin, ertapenem, or tigecycline 2
• Add vancomycin, linezolid, or daptomycin if MRSA suspected 2

Bite Wounds

• Animal bites (oral): Amoxicillin-clavulanate 2
• Animal bites (IV): Ampicillin-sulbactam, piperacillin-tazobactam, or second/third-generation cephalosporins 2
• Human bites: Amoxicillin-clavulanate or ampicillin-sulbactam; carbapenems for severe cases 2

Multidrug-Resistant Organisms

Carbapenem-Resistant Enterobacterales (CRE)

• Bloodstream infections: Ceftazidime-avibactam 2.5g IV q8h, meropenem-vaborbactam 4g IV q8h, or imipenem-cilastatin-relebactam 1.25g IV q6h for 7-14 days 2
• Alternative: Colistin 5mg/kg IV loading dose plus tigecycline 100mg loading then 50mg q12h 2
• UTIs: Same agents as bloodstream infections, or aminoglycosides (gentamicin 5-7mg/kg/day or amikacin 15mg/kg/day) for 5-7 days 2

Carbapenem-Resistant Pseudomonas aeruginosa (CRPA)

• Susceptible to other agents: Piperacillin 3-4g IV q6h, ceftazidime 2g IV q8h, cefepime 2g IV q8-12h, or fluoroquinolones for 5-14 days 2
• Difficult-to-treat strains: Ceftolozane-tazobactam 1.5-3g IV q8h, ceftazidime-avibactam 2.5g IV q8h, or colistin-based therapy 2

Critical Administration Principles

Beta-Lactam Optimization

• Maintain plasma concentrations >MIC for ≥70% of dosing interval in critically ill patients 1
• Extended infusion (3-4 hours) for cefepime, piperacillin-tazobactam, meropenem, and doripenem when MIC is high 1
• Continuous infusion should be considered for carbapenems, ceftazidime, and piperacillin-tazobactam in severe infections with pharmacodynamic failure risk 1

Vancomycin Administration

• Loading dose followed by continuous infusion to achieve early target concentrations 1
• Therapeutic drug monitoring is essential 1

Treatment Duration Principles

Shorter courses are as effective as longer courses for many infections and reduce antibiotic resistance 3:

• Community-acquired pneumonia: 5-7 days for most cases
• Uncomplicated cystitis: 3-5 days depending on agent
• Pyelonephritis: 5-7 days with fluoroquinolones
• Cellulitis: 5-6 days
• Complicated intra-abdominal infections: 5-10 days

De-escalation Strategy

• Re-evaluate within 48-72 hours based on clinical status and microbiological results 1
• Procalcitonin <0.5 ng/mL or >80% decrease from peak supports discontinuation in lower respiratory tract infections 1
• Narrow to targeted monotherapy when pathogen identified 1

Common Pitfalls

• Avoid empirical fluoroquinolones for uncomplicated cystitis due to adverse effects and resistance concerns 2
• Do not use TMP-SMX empirically for pyelonephritis without susceptibility data due to high resistance rates 2
• Avoid tigecycline monotherapy for pneumonia; use only in combination if MIC ≤2 mg/L 2
• Do not prescribe antibiotics for simple chronic bronchitis exacerbations without fever >38°C for >3 days 2
• Approximately 50% of ICU patients receiving antibiotics lack confirmed infections, highlighting need for stewardship 4