Common Broad-Spectrum Antibiotics in Clinical Practice
The most commonly used broad-spectrum antibiotics include piperacillin-tazobactam, third-generation cephalosporins (ceftriaxone, cefotaxime), carbapenems (meropenem, imipenem), and fluoroquinolones (ciprofloxacin, levofloxacin), with selection based on infection site, severity, and local resistance patterns. 1
Intra-Abdominal Infections
Mild to Moderate Community-Acquired
- First-line options: Amoxicillin-clavulanate or ampicillin + gentamicin + metronidazole 1
- Alternative regimens: Ciprofloxacin + metronidazole, or cefotaxime/ceftriaxone + metronidazole 1
- These narrower-spectrum agents are preferred to preserve broader agents for resistant organisms 1
Severe or High-Risk Infections
- Preferred agents: Cefotaxime or ceftriaxone + metronidazole, piperacillin-tazobactam 1
- Alternative options: Meropenem, ampicillin + gentamicin + metronidazole 1
- For nosocomial infections requiring Pseudomonas coverage: meropenem, imipenem-cilastatin, or piperacillin-tazobactam 1
Skin and Soft Tissue Infections
Necrotizing Fasciitis
- Recommended regimens: Vancomycin or linezolid PLUS piperacillin-tazobactam or a carbapenem 1
- Alternative: Ceftriaxone + metronidazole 1
Surgical Site Infections (Intestinal/Genitourinary Origin)
- Single-drug options: Piperacillin-tazobactam, carbapenems (imipenem, meropenem, ertapenem) 1
- Combination regimens: Ceftriaxone + metronidazole, or fluoroquinolone (ciprofloxacin/levofloxacin) + metronidazole 1
Animal/Human Bites
- Oral treatment: Amoxicillin-clavulanate 1
- IV treatment: Ampicillin-sulbactam, piperacillin-tazobactam, second/third-generation cephalosporins (cefuroxime, ceftriaxone, cefotaxime), carbapenems 1
Hospital-Acquired and Ventilator-Associated Pneumonia
Low-Risk Patients (No MRSA Risk Factors)
- Monotherapy options: Piperacillin-tazobactam 4.5g IV q6h, cefepime 2g IV q8h, levofloxacin 750mg IV daily, imipenem 500mg IV q6h, or meropenem 1g IV q8h 1
High-Risk or Recent Antibiotic Use
- Dual therapy required: Two antipseudomonal agents from different classes (avoid two β-lactams) 1
- Options include: Piperacillin-tazobactam, cefepime, ceftazidime, levofloxacin, ciprofloxacin, imipenem, meropenem, aminoglycosides (amikacin, gentamicin, tobramycin), or aztreonam 1
- PLUS MRSA coverage: Vancomycin 15mg/kg IV q8-12h (target trough 15-20 mg/mL) or linezolid 600mg IV q12h 1
Febrile Neutropenia
High-Risk Patients
- Monotherapy options: Cefepime, carbapenems (imipenem-cilastatin or meropenem), or piperacillin-tazobactam 1
- These are preferred over aminoglycoside combinations due to fewer adverse events and similar efficacy 1
- Ceftazidime is no longer reliable for empirical monotherapy due to decreasing potency against gram-negatives and poor gram-positive coverage 1
Low-Risk Patients (Outpatient Consideration)
- Oral regimen: Ciprofloxacin + amoxicillin-clavulanate 1
- Patients receiving fluoroquinolone prophylaxis should NOT receive fluoroquinolone empiric therapy 1
Key Clinical Considerations
Pseudomonas coverage is essential when treating nosocomial infections, structural lung disease (bronchiectasis, cystic fibrosis), or high-risk intra-abdominal infections 1. Agents with reliable antipseudomonal activity include piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, and carbapenems 1.
Carbapenem selection: Meropenem is preferred over other carbapenems for most infections due to broader coverage and lower seizure risk, making it suitable for meningitis 1, 2. Ertapenem lacks Pseudomonas coverage and should only be used for community-acquired infections 1.
Piperacillin-tazobactam carries nephrotoxicity risk in critically ill patients (odds ratio 1.7), requiring careful monitoring 3. Diarrhea occurs in 11-20% of patients, with C. difficile infection possible 3.
Duration of therapy: For complicated intra-abdominal infections with adequate source control, limit antibiotics to 3-5 days postoperatively 1. Prolonged courses beyond this offer no additional benefit 1.
Local resistance patterns must guide final selection, particularly for nosocomial infections where ESBL-producing organisms, MRSA, and resistant Pseudomonas are concerns 1.