What is the treatment for a patient with a coagulase-negative staphylococcus (CoNS) infection associated with a medical device?

Treatment of CoNS Device-Associated Infection

Remove the infected device immediately and treat with systemic antibiotics—device removal is the cornerstone of successful therapy, as antibiotics alone cannot eradicate biofilm-embedded organisms.

Device Removal Strategy

Complete device removal is mandatory for cure. The type and timing depend on the specific device:

Intravascular Catheters

• Remove the catheter immediately for catheter-related bloodstream infection (CRBSI), as biofilm formation prevents antibiotic penetration and leads to treatment failure 1
• Percutaneous removal is preferred over surgical extraction for cardiovascular implantable electronic devices (CIEDs), though this requires experienced operators at high-volume centers with cardiothoracic surgery backup 1
• For CIED infections, do not delay device removal regardless of when antimicrobial therapy is initiated 1
• Never attempt guidewire exchange in the setting of active infection—this has unacceptably high failure rates 2

Prosthetic Valves and Cardiac Devices

• Early surgical intervention is often lifesaving, particularly for prosthetic valve endocarditis (PVE) within 12 months of implantation or when aortic valve prostheses are involved 1
• Percutaneous lead extraction can safely remove leads with vegetations >2 cm, though decisions should account for patient-specific factors and operator experience 1

Empiric Antibiotic Selection

Start vancomycin immediately as empiric therapy because most CoNS are methicillin-resistant and vancomycin provides reliable coverage 1, 3

• Target vancomycin trough concentrations of 10-20 μg/mL 1
• For hemodialysis patients, dose vancomycin at 20 mg/kg after each dialysis session 2
• Switch to cefazolin or nafcillin only if the isolate is oxacillin-susceptible AND the patient demonstrates clear clinical response 1, 3

Definitive Antibiotic Regimens

For Prosthetic Valve Endocarditis (Oxacillin-Resistant CoNS)

Vancomycin + rifampin + gentamicin is the recommended triple therapy:

• Vancomycin 30 mg/kg/24h IV divided every 12 hours for ≥6 weeks 1
• Rifampin 900 mg/24h IV or PO divided every 8 hours for ≥6 weeks 1
• Gentamicin 3 mg/kg/24h IV/IM divided every 8-12 hours for 2 weeks only 1

Critical caveat: Administer gentamicin in close temporal proximity to vancomycin dosing to maximize synergy 1

For Prosthetic Valve Endocarditis (Oxacillin-Susceptible CoNS)

• Nafcillin or oxacillin 12 g/24h IV divided every 4 hours for ≥6 weeks 1
• Plus rifampin 900 mg/24h for ≥6 weeks 1
• Plus gentamicin 3 mg/kg/24h for 2 weeks 1
• Substitute cefazolin for non-immediate penicillin allergies; use vancomycin for immediate-type hypersensitivity 1

For Catheter-Related Bloodstream Infection (Device Removed)

Treat for 5-7 days if uncomplicated (no endovascular hardware, no metastatic infection, catheter removed) 1, 2, 3

• Extend to 10-14 days if signs of complicated infection are present 1, 2
• Extend to 4-6 weeks if bacteremia persists >24 hours after device removal despite appropriate antibiotics 1, 2

For Catheter-Related Bloodstream Infection (Device Retained)

Treat for 10-14 days with systemic antibiotics plus antibiotic lock therapy if attempting catheter salvage 1, 3

Major pitfall: Never attempt antibiotic lock therapy when systemic antibiotics have already failed—this approach has a 50% failure rate even in ideal circumstances and is contraindicated with persistent bacteremia 2

For CIED Pocket Infections

• 7-10 days after device removal if presentation is device erosion without inflammation 1
• 10-14 days if inflammatory changes are present at the pocket site 1
• At least 2 weeks of parenteral therapy for patients with documented bloodstream infection 1
• 4 weeks of parenteral therapy if blood cultures remain positive >24 hours after device removal, even with negative echocardiography 1

Resistance Considerations

Aminoglycoside Resistance

• If CoNS are gentamicin-resistant, substitute an aminoglycoside to which the organism is susceptible 1
• If resistant to all aminoglycosides, substitute a fluoroquinolone if the isolate is susceptible (though fluoroquinolone resistance can emerge during therapy) 1

Rifampin Resistance

• CoNS may develop rifampin resistance during therapy for PVE 1
• Retest all organisms recovered from surgical specimens or from bacteriologic relapse for complete susceptibility profiles 1

Emerging Daptomycin Resistance

• Daptomycin non-susceptible CoNS can emerge in cardiovascular device infections, particularly after prior vancomycin and daptomycin exposure with inadequate debridement 4

Post-Treatment Monitoring

Obtain repeat blood cultures 2-3 days after device removal to confirm clearance 2, 3

• Consider transesophageal echocardiography if bacteremia persists >72 hours after device removal 2
• Assess for tunnel infection, pocket abscess, or septic thrombophlebitis 2

Device Replacement Timing

Wait until blood cultures are negative before placing a new permanent device 2, 5

• Place temporary catheters at a different anatomical site (contralateral side preferred) 1, 2
• Ensure adequate debridement and infection control at all sites before new device placement 1

Special Considerations

Staphylococcus lugdunensis

Manage identically to S. aureus infections due to its propensity for endocarditis and metastatic complications—this requires device removal and 4-6 weeks of antimicrobial therapy 1, 3

AV Graft Infections

• Infected grafts at the AV anastomosis require immediate surgical resection 5
• Graft infections require 6 weeks of antibiotic therapy, initiated with vancomycin plus an aminoglycoside 5

Distinguishing True Infection from Contamination

• Multiple positive blood cultures from different sites strongly indicate true infection rather than contamination 1, 3
• Differential time to positivity ≥2 hours between catheter and peripheral cultures is highly sensitive and specific for catheter-related bacteremia 3
• If only one of four blood culture bottles is positive in a clinically stable patient with no signs of sepsis, this likely represents contamination and no treatment is needed 5

Common Pitfalls to Avoid

• Never continue antibiotics hoping for delayed response if bacteremia persists 48-72 hours—this mandates immediate device removal 2
• Never attempt antibiotic lock therapy as salvage after systemic antibiotic failure 2
• Never exchange catheters over a guidewire in the setting of active infection 2
• Do not underestimate CoNS virulence—these organisms form therapy-refractory biofilms and have poor treatment success rates even with appropriate management (only 47% success in prosthetic joint infections) 6