Prognostic factors associated with 30-day in-hospital mortality in coagulase-negative Staphylococcus bacteraemia: no impact of vancomycin minimum inhibitory concentration.

Background: The impact of a minimum inhibitory concentration (MIC) of vancomycin ≥2 mg/L on mortality and the potential benefit of new antistaphylococcal treatments in coagulase-negative Staphylococcus (CoNS) bacteraemia remain unknown. We assessed the impact of vancomycin MIC on 30-day in-hospital mortality and identified factors independently associated with 30-day in-hospital mortality.

Methods: All patients presenting significant CoNS bacteraemia in the university hospital of Reims, between 01 January 2008 and 31 December 2012, were included. Data were retrospectively extracted from the patient records. Vancomycin MIC was assessed using the E-test method, and antimicrobial susceptibility testing was performed in accordance with the recommendations of the Antibiogram Committee of the French Microbiology Society. Cox's Proportional Hazards model was used for multivariate analysis.

Results: Two hundred and sixty-nine patients (mean age 61.2 ± 15.7 years) were included. Foreign material was present in 92% of patients and 78.4% of isolated methicillin-resistant strains had vancomycin MIC ≥2 mg/l. Thirty-day in-hospital mortality was 16%. There was no association between vancomycin MIC ≥2 mg/l and 30-day in-hospital mortality (adjusted Hazard Ratio (aHR) = .80, 95% confidence interval (95%CI) [.30-2.19], p = .67). Factors independently associated with 30-day in-hospital mortality were age ≥75 vs. ≤60 years (aHR =3.72, 95%CI [1.39-9.97], p = .009), absence of active antibiotic treatment (aHR =5.52, 95%CI [1.13-26.87], p = .03) and acute renal failure (aHR =4.45, 95%CI [2.08-9.56], p < .0001). Removal of an infected device had a protective effect against 30-day in-hospital mortality (aHR = .23, 95%CI [.11-.48], p < .0001).

Conclusions: These results suggest that CoNS bacteraemia should be managed by removal of the infected device and antibiotic treatment such as vancomycin.