What is the recommended treatment for coagulase-negative staph (CoNS) infections?

Treatment of Coagulase-Negative Staphylococcal (CoNS) Infections

For CoNS infections, vancomycin remains the empiric drug of choice, but you should switch to a beta-lactam (nafcillin, oxacillin, or cefazolin) if the isolate proves susceptible to methicillin. 1

Initial Empiric Therapy

• Start with vancomycin empirically because most CoNS are methicillin-resistant, particularly in healthcare-associated infections 1, 2
• Target vancomycin trough levels of 10-15 mg/L for most CoNS infections 1
• Vancomycin remains appropriate empiric therapy despite concerns about MIC creep—recent data shows no difference in clinical outcomes between isolates with MICs <2 μg/mL versus ≥2 μg/mL 3, 4

De-escalation Strategy

• If susceptibility testing shows methicillin susceptibility, immediately switch to a semisynthetic penicillin (nafcillin, oxacillin, or flucloxacillin) because beta-lactams are superior to vancomycin for susceptible organisms 1, 2
• First-generation cephalosporins like cefazolin are acceptable alternatives for patients with non-immediate penicillin allergies 1

Treatment Duration Based on Clinical Scenario

Uncomplicated Catheter-Related Bloodstream Infection

• If the catheter is removed: treat for 5-7 days with systemic antibiotics 1
• If a non-tunneled catheter is retained: treat for 10-14 days with systemic antibiotics plus antibiotic lock therapy 1
• If a tunneled catheter or implantable device is retained: treat for 7 days of systemic therapy plus 14 days of antibiotic lock therapy 1

Prosthetic Valve Endocarditis (PVE)

• Treat for a minimum of 6 weeks with vancomycin plus rifampin, adding gentamicin for the first 2 weeks 1
• Vancomycin dosing: 30 mg/kg/day IV in 2 divided doses, targeting trough 10-20 μg/mL 1
• Rifampin: 900 mg/day IV or PO in 3 divided doses 1
• Gentamicin: 3 mg/kg/day IV/IM in 2-3 divided doses for first 2 weeks only 1
• If gentamicin-resistant, substitute with an aminoglycoside to which the organism is susceptible, or consider a fluoroquinolone if susceptible 1

Native Valve Endocarditis

• Treat for 6 weeks with vancomycin (if methicillin-resistant) or a beta-lactam (if susceptible) 1
• Combination therapy with aminoglycosides is not routinely recommended for native valve CoNS endocarditis 1

Critical Pitfalls to Avoid

• Do not use vancomycin for single positive blood cultures when contamination is likely—this is the most common scenario where vancomycin is inappropriately prescribed 1
• Do not continue vancomycin if repeat cultures are negative—CoNS are common contaminants and require ≥2 positive cultures within 48 hours to confirm true bacteremia 1, 4
• Do not use combination therapy with vancomycin plus gentamicin or rifampin for routine CoNS infections—reserve combinations for prosthetic valve endocarditis only 1
• Persistent fever or positive cultures after 72 hours of appropriate therapy mandates catheter removal—do not continue conservative management 1

When Catheter Removal is Mandatory

• Remove the catheter immediately if: persistent bacteremia after 72 hours of appropriate antibiotics, septic thrombophlebitis, endocarditis, tunnel infection, or pocket infection of implantable devices 1
• Treatment failure (persistent fever, positive cultures, or relapse after antibiotic discontinuation) is an absolute indication for catheter removal 1

Alternative Agents (When Vancomycin Cannot Be Used)

• Linezolid is an alternative for vancomycin-intolerant patients, though significantly more expensive 5
• Daptomycin may be considered for complicated infections, though data for CoNS are limited compared to S. aureus 2
• Do not use rifampin or fusidic acid as monotherapy—resistance develops rapidly 2