This study describes
coagulase-negative staphylococcal (CoNS)
infective endocarditis (IE) epidemiology at our institution, the
antibiotic susceptibility profile, and the influence of
vancomycin minimum inhibitory concentration (MIC) on patient outcomes. One hundred and three adults with definite IE admitted to an 850-bed tertiary care hospital in Barcelona from 1995-2008 were prospectively included in the cohort. We observed that CoNS IE was an important cause of community-acquired and healthcare-associated IE; one-third of patients involved native valves. Staphylococcus epidermidis was the most frequent species, methicillin-resistant in 52% of patients. CoNS frozen isolates were available in 88 patients.
Vancomycin MICs of 2.0 μg/mL were common; almost all cases were found among S. epidermidis isolates and did not increase over time. Eighty-five patients were treated either with
cloxacillin or
vancomycin: 38 patients (Group 1) were treated with
cloxacillin, and 47 received
vancomycin; of these 47, 27 had CoNS isolates with a
vancomycin MIC <2.0 μg/mL (Group 2), 20 had isolates with a
vancomycin MIC ≥ 2.0 μg/mL (Group 3). One-year mortality was 21%, 48%, and 65% in Groups 1, 2, and 3, respectively (P = 0.003). After adjusting for confounders and taking Group 2 as a reference,
methicillin-susceptibility was associated with lower 1-year mortality (OR 0.12, 95% CI 0.02-0.55), and
vancomycin MIC ≥ 2.0 μg/mL showed a trend to higher 1-year mortality (OR 3.7, 95% CI 0.9-15.2; P=0.069). Other independent variables associated with 1-year mortality were
heart failure (OR 6.2, 95% CI 1.5-25.2) and pacemaker lead IE (OR 0.1, 95%CI 0.02-0.51). In conclusion, methicillin-resistant S.epidermidis was the leading cause of CoNS IE, and patients receiving
vancomycin had higher mortality rates than those receiving
cloxacillin; mortality was higher among patients having isolates with
vancomycin MICs ≥ 2.0 μg/mL.