Cefepime Coverage of Gram-Positive Cocci in Clusters
Cefepime provides adequate coverage for methicillin-susceptible Staphylococcus aureus (MSSA) but has NO activity against methicillin-resistant Staphylococcus aureus (MRSA), which are the Gram-positive cocci in clusters you're asking about. 1
Spectrum Against Staphylococcal Species
MSSA Coverage
- Cefepime is active against methicillin-susceptible S. aureus and is recommended by IDSA/ATS guidelines for empiric coverage when MRSA is not suspected. 2, 3
- Cefepime is approximately 4-fold more active than ceftazidime against MSSA, achieving 100% susceptibility in vitro. 3
- The FDA label explicitly lists S. aureus (methicillin-susceptible isolates only) as a pathogen for which cefepime has demonstrated clinical efficacy. 1
- When MRSA coverage is not needed, cefepime monotherapy provides adequate MSSA coverage for hospital-acquired pneumonia, febrile neutropenia, and other serious infections. 2, 4
MRSA - No Coverage
- Most isolates of methicillin-resistant staphylococci are resistant to cefepime. 1
- The FDA label and multiple guidelines explicitly state that cefepime is inactive against MRSA. 1, 5
- When MRSA is suspected based on risk factors (prior IV antibiotics within 90 days, ICU with >20-25% MRSA prevalence, known MRSA colonization), vancomycin or linezolid must be added to cefepime. 2
Clinical Application Algorithm
When to Use Cefepime Alone for GPC in Clusters:
- Gram stain shows GPC in clusters AND local MRSA prevalence is <20% AND patient has no MRSA risk factors (no IV antibiotics in past 90 days, no prior MRSA colonization, no severe sepsis/shock). 2
- Confirmed MSSA infection on culture results - continue cefepime or de-escalate to narrower agents like oxacillin, nafcillin, or cefazolin for definitive therapy. 2
When to Add Anti-MRSA Coverage to Cefepime:
- ICU setting where >20-25% of S. aureus respiratory isolates are MRSA. 2
- Patient received IV antibiotics within the prior 90 days. 2
- Suspected catheter-related infection, skin/soft tissue infection, or hemodynamic instability/septic shock. 2, 4
- Prior influenza, end-stage renal disease, or injection drug use (community-acquired MRSA risk factors). 2
- Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) or linezolid 600 mg IV every 12 hours. 2
Common Pitfalls
- Do not assume cefepime covers all staphylococci - the methicillin resistance status is critical. 1, 5
- Gram stain showing GPC in clusters from tracheal aspirate or adequate sputum is the best indicator for S. aureus, but blood culture findings are less reliable due to contamination risk. 2
- If vancomycin is added empirically and cultures show no MRSA or gram-positive infection, discontinue vancomycin within 24-48 hours to avoid nephrotoxicity and resistance selection. 4
- Cefepime has poor activity against enterococci - if enterococcal coverage is needed (e.g., intra-abdominal infections), add ampicillin. 2, 1