Vancomycin-resistant enterococci with reduced daptomycin susceptibility in Singapore: prevalence and associated factors

Prevalence of vancomycin-resistant enterococci (VRE) and use of daptomycin are increasing in Asia. To determine the prevalence of daptomycin non-susceptible enterococci (DNSE) and understand factors associated with reduced daptomycin susceptibility in VRE, we conducted a case-control study in a 1600-bed adult tertiary hospital in Singapore. All VRE isolates from inpatients in 2012 were tested for daptomycin susceptibility. Patients with VRE isolates of daptomycin minimum inhibitory concentration (MIC) 3 mu g/ml were classified as daptomycin-reduced susceptible VRE (DRS-VRE) and those with daptomycin MIC <3 mu g/ml classified as daptomycin-susceptible VRE (DS-VRE). Medical records were reviewed for clinical and epidemiological data. None of 243 VRE isolates had MIC >4 mu g/ml (DNSE). About half (135, 55%) had reduced susceptibility to daptomycin (MIC 3-4 mu g/ml). None in the DS-VRE group had prior exposure to daptomycin. After adjusting for age, gender, comorbidity, hospitalization duration, surgical history, indwelling device use, and duration of antibiotic exposure in the prior 3 months, >1 movement between wards [odds ratio (OR) 0<bold></bold>35, 95% confidence interval (CI) 0<bold></bold>16-0<bold></bold>74, P = 0<bold></bold>006] and minocycline resistance (OR 0<bold></bold>45, 95% CI 0<bold></bold>25-0<bold></bold>84, P = 0<bold></bold>011) were independently associated with DRS-VRE. Our study suggests that daptomycin exposure, >1 movement between wards, and resistance to minocycline, were associated with reduced daptomycin susceptibility in VRE.