Treatment of Gram-Positive Cocci in Blood and Coagulase-Negative Staphylococcus in Urine
Yes, cefazolin and vancomycin can be used together to treat a patient with gram-positive cocci in the blood and coagulase-negative Staphylococcus in the urine, with cefazolin being preferred for methicillin-susceptible strains and vancomycin for methicillin-resistant strains. 1
Treatment Algorithm
Initial Empiric Therapy
- Start with vancomycin plus cefazolin while awaiting full culture and susceptibility results 1
- This combination provides coverage for both methicillin-resistant and methicillin-susceptible staphylococci 2
- The empiric combination approach reduces mortality risk compared to vancomycin alone when treating potential staphylococcal bacteremia 2
Once Susceptibility Results Are Available
- For methicillin-susceptible staphylococci: De-escalate to cefazolin alone (preferred agent) 1, 2
- For methicillin-resistant staphylococci: Continue vancomycin alone 1
- For mixed infections: Consider continuing both agents if both methicillin-resistant and methicillin-susceptible organisms are present in different sites 1
Dosing Recommendations
Vancomycin Dosing
- Standard dosing: Based on weight and renal function 3
- For hemodialysis patients: 20 mg/kg loading dose followed by 500 mg during subsequent dialysis sessions 1
- Monitor serum levels to maintain therapeutic concentrations and minimize toxicity 3, 4
Cefazolin Dosing
- Standard dosing: Based on weight and renal function 5
- For hemodialysis patients: 20 mg/kg IV after each dialysis session 1
- Adjust dose in patients with impaired renal function to prevent seizures 5
Clinical Considerations
Benefits of Combination Therapy
- The empirical combination of vancomycin and a β-lactam (cefazolin) for staphylococcal bacteremia may improve clinical outcomes 2
- Provides broader coverage while awaiting final culture results 1, 2
- Reduces risk of treatment failure if the organism is methicillin-susceptible but treated only with vancomycin 2
Catheter-Related Considerations
- If infection is catheter-related, consider antibiotic lock therapy in addition to systemic antibiotics 1
- For catheter lock solutions: cefazolin (5.0 mg/mL) is preferred for methicillin-susceptible staphylococci; vancomycin (5.0 mg/mL) for methicillin-resistant staphylococci 1, 6
Important Caveats and Pitfalls
- Do not continue unnecessary vancomycin: If cultures confirm methicillin-susceptible staphylococci only, discontinue vancomycin to reduce toxicity risk and prevent resistance development 2, 7
- Monitor for drug interactions: Probenecid may decrease renal tubular secretion of cephalosporins, resulting in increased blood levels 5
- Watch for nephrotoxicity: Combined therapy may increase risk of kidney injury, particularly in elderly or those with baseline renal impairment 3, 5
- Be alert for emerging resistance: Coagulase-negative staphylococci can develop vancomycin resistance, particularly during prolonged therapy 8
- Consider local resistance patterns: In units with low prevalence of methicillin-resistant staphylococci, cefazolin alone may be appropriate for initial empiric therapy 1