Management of Coagulase-Negative Staphylococcus (CoNS) Bacteremia
Critical First Step: Determine if This Represents True Infection or Contamination
Do not initiate vancomycin therapy based solely on a single positive blood culture for CoNS—this likely represents contamination and unnecessary vancomycin use promotes resistance. 1
Criteria for True CoNS Bacteremia vs. Contamination
- At least 2 blood cultures positive for CoNS within 48-72 hours is the minimum threshold to consider true bacteremia 2, 3
- If only 1 of 2 blood cultures drawn simultaneously is positive for CoNS, this is highly likely contamination and vancomycin should be withheld 1
- The algorithm with best sensitivity (62%) and specificity (91%) requires: either ≥2 positive blood cultures within 5 days OR 1 positive culture PLUS clinical evidence of infection (abnormal WBC, fever, or hypotension) 3
Additional Clinical Context Supporting True Infection
- Presence of indwelling central venous catheter or other prosthetic device 1, 2
- Signs of sepsis syndrome (fever, hypotension, tachycardia) 3
- Neutropenia 3
- Recent healthcare exposure, hemodialysis, chronic wounds, or long-term care facility residence 1, 2
If True CoNS Bacteremia is Confirmed: Initiate Treatment
Empirical Antibiotic Therapy
Vancomycin remains the appropriate empirical therapy for confirmed CoNS bacteremia, as 58-87% of CoNS isolates are methicillin-resistant. 2, 4
- Vancomycin dosing: 40 mg/kg/day IV divided every 8-12 hours (maximum 2 g daily) 2
- Vancomycin covers both methicillin-susceptible and methicillin-resistant CoNS 1, 5
- Despite concerns about vancomycin MIC creep, recent data shows vancomycin MICs for CoNS have actually decreased over time, and vancomycin remains effective 6
Duration of Therapy
- Uncomplicated CoNS bacteremia: 10-14 days of antimicrobial therapy if prompt clinical response and no complications 1
- Complicated infection (septic thrombosis, endocarditis, osteomyelitis): 4-8 weeks depending on site 1
- Reassess therapy at 48-72 hours when final susceptibilities are available 2
Device Management
Remove or replace central venous catheters and arterial lines if multiple blood cultures are positive for CoNS. 1, 2
- Catheter retention is associated with persistent bacteremia 1
- In adults and children (except neonates), catheter removal is recommended when CoNS bacteremia is confirmed 1
De-escalation Strategy
Once susceptibilities return:
- If methicillin-susceptible CoNS: Consider switching from vancomycin to nafcillin, oxacillin, or cefazolin (beta-lactams are more rapidly bactericidal than vancomycin for susceptible organisms) 1
- If methicillin-resistant: Continue vancomycin for full treatment course 1, 2
Monitoring Requirements
- Vancomycin trough levels should be monitored, especially in patients with renal impairment 2
- Target trough: 15-20 mcg/mL for serious infections 2
- Repeat blood cultures to document clearance of bacteremia 1
Common Pitfalls to Avoid
- Treating single positive blood cultures for CoNS without confirmation—this leads to unnecessary vancomycin exposure and promotes resistance 1, 2
- Continuing vancomycin empirically when cultures remain negative for beta-lactam-resistant organisms 1
- Failing to remove infected catheters—this prolongs bacteremia and increases complications 1
- Delaying appropriate therapy when true CoNS bacteremia is confirmed—while CoNS is less virulent than S. aureus, delayed treatment can still lead to complications including endocarditis 1, 2
Special Populations
Neonates and Infants
- Empirical vancomycin for CoNS bacteremia in infants showed no survival benefit compared to delayed therapy (started 1-3 days after culture) 7
- However, delayed therapy resulted in 1 day longer duration of bacteremia 7
- Clinical judgment regarding severity of illness should guide timing of vancomycin initiation 7