Vancomycin-resistant Enterococci with Reduced Daptomycin Susceptibility in Singapore: Prevalence and Associated Factors
Daptomycin-nonsusceptible Enterococcus (DNSE) is an emerging clinical and public health problem. In the United States, DNSE infections with and without prior daptomycin exposure have been reported.
In Singapore, daptomycin utilization has increased over the years, but little is known about the epidemiology of DNSE. Our study aims to determine the prevalence of DNSE and understand the factors associated with reduced daptomycin susceptibility.
We conducted a case-control study in 1600-bed Tan Tock Seng Hospital in Singapore. All vancomycin-resistant Enterococcus (VRE) isolates from inpatients from Jan 1 thru Dec 31, 2012 were tested for daptomycin susceptibility using the Etest.
Cases were defined as VREs with daptomycin minimum inhibitory concentration (MIC) >=3 µg/mL [daptomycin reduced susceptible VRE, DRS-VRE], and controls were VREs with daptomycin MIC < 3 µg/mL [daptomycin susceptible VRE, DS-VRE] . Medical records were reviewed for clinical and epidemiological data. To compare the differences in covariates between the groups, odds ratios and 95% confidence intervals were computed. A multiple logistic regression model was used to control for confounding.
None of the 243 VRE-colonized/infected patients had DNSE (MIC >4). About half (135, 55%) had reduced susceptibility to daptomycin (DRS-VRE). None of the DS-VRE and only 3% of DRS-VRE had prior exposure to daptomycin. Patients who had more than 1 movement between wards (OR 0.57, 95% CI 0.33-0.98), a longer duration of cephalosporin exposure (OR 0.941, 95% CI 0.888-0.998), or minocycline resistance (OR 0.49, 95% CI 0.28-0.85), were less likely to have DRS-VRE.
After adjusting for age, gender, comorbidity, hospitalization duration, surgical history, indwelling device use, and duration of aminoglycoside, carbapenem, cephalosporin, daptomycin, fluoroquinolone, penicillin, polymyxin B, and vancomycin use in the past 3 months, more than 1 movement between wards (Adj OR 0.35, 95% CI 0.16-0.74) and minocycline resistance (Adj OR 0.45, 95% CI 0.25-0.84) were independently associated with DRS-VRE.
No DNSE was observed, but 55% of VREs had reduced daptomycin susceptibility. More than 1 movement between wards and minocycline resistance were negatively associated with DRS-VRE. Further research is needed to understand the reasons for these associations.
M. K. Win, None
W. Lee, None
P. Krishnan, None