Does Ancef (cefazolin) cover Staphylococcus infections?

Cefazolin Coverage for Staphylococcus Infections

Yes, Ancef (cefazolin) effectively covers methicillin-susceptible Staphylococcus aureus (MSSA) infections and is recommended as a first-line treatment option for these infections. 1

Efficacy Against Staphylococcus

Cefazolin demonstrates excellent activity against:

• Methicillin-susceptible Staphylococcus aureus (MSSA)
• Staphylococcus epidermidis (methicillin-susceptible strains)
• Other methicillin-susceptible staphylococcal species 2

However, it's important to note that:

• Methicillin-resistant staphylococci (MRSA) are uniformly resistant to cefazolin 2
• Some MSSA strains may exhibit the cefazolin inoculum effect (CzIE), though the clinical significance remains uncertain 1, 3

Clinical Applications

Cefazolin is recommended for:

1. Native valve endocarditis caused by MSSA:

   • 4-6 weeks of treatment
   • Alternative to anti-staphylococcal penicillins (ASPs) in patients without type 1 penicillin allergies 1

2. Bacteremia and other serious MSSA infections:

   • Multiple studies show cefazolin is as effective as ASPs for MSSA bacteremia
   • Associated with lower mortality (OR 0.69) and clinical failure rates (OR 0.56) compared to ASPs 4
   • Twice-daily dosing has been shown effective for serious MSSA infections in outpatient settings 5

3. Surgical prophylaxis (particularly for procedures where staphylococcal coverage is important)

Safety Profile

Cefazolin offers several advantages over anti-staphylococcal penicillins:

• Lower rates of nephrotoxicity (OR 0.36)
• Lower rates of hepatotoxicity (OR 0.12)
• Fewer adverse events leading to discontinuation (OR 0.24) 4
• Better overall safety profile 1, 4

Clinical Considerations and Caveats

1. Cefazolin Inoculum Effect (CzIE):

   • Some MSSA strains show increased MICs at higher bacterial loads
   • Resistance to clindamycin or erythromycin may predict CzIE positivity
   • Cefazolin can likely be used safely if the isolate is susceptible to clindamycin or erythromycin 3

2. MRSA Coverage:

   • Cefazolin does NOT cover MRSA infections
   • If MRSA is suspected or confirmed, alternative agents like vancomycin or daptomycin should be used 1

3. Dosing for Serious Infections:

   • For serious infections: 2g IV every 8 hours (6g/day)
   • Adjust for renal function as needed 1

Evidence Quality

Multiple high-quality studies support cefazolin's efficacy against MSSA:

• Large retrospective cohort studies show equivalent or superior outcomes compared to ASPs 6
• Meta-analyses demonstrate reduced mortality and fewer adverse effects compared to ASPs 4
• Specific studies for conditions like spinal epidural abscesses show equivalent efficacy 7

In summary, cefazolin is an excellent choice for treating MSSA infections with a favorable safety profile compared to anti-staphylococcal penicillins, but it should not be used for MRSA infections.