Vancomycin resistant Enterococci (VRE) are the second leading cause of HAIs among antimicrobial-resistant pathogens in the United States. VRE is labeled as a serious threat by the CDC, and it has shown to be a major pathogen especially in the ICU setting. Several sites have reported increasing rates of VRE, as well as resistance to antibiotics commonly used to treat VRE, prompting the VA Pharmacy Benefits Management Service to recommend VRE susceptibility to each of these antibiotics be confirmed prior to their use. As the prevalence of daptomycin resistance ranges from <1 to 20% in different U.S. institutions, we determined general susceptibility to daptomycin as well as these other agents at the Veterans Affairs Maryland Health Care System (VAMHCS).
Methods: A retrospective data analysis was performed on all VRE isolates obtained following the introduction of daptomycin in 2007 through August 31, 2014. Susceptibilities to daptomycin, linezolid, ampicillin, and quinupristin-dalfopristin were determined by BD Phoenix Epicenter System. Redundant cultures from the same patient and site within seven days, and those without a source identified were excluded.
670 VRE specimens were identified over the assigned period; 63 isolates were excluded, leaving 607 VRE isolates for inclusion in the analysis (including 403 E. faecium and 204 E. faecalis). The overall daptomycin resistance rate was 7.74%, with a higher percentage of E. faecium showing daptomycin resistance. The linezolid resistance rate was 2.14%, with a higher resistance rate among E. faecalis. Ampicillin was >99% non-susceptible among E. faecium, but only 4.85% resistant in E. faecalis. Quinupristin-dalfopristin showed that 2.48% of E. faecium, and 91.26% of E. faecium were resistant. There was a general trend of increasing daptomycin resistance from the start of this antibiotic’s availability at the institution.
Conclusion: There was higher than expected daptomycin resistance at the Baltimore VAMC over the preceding seven years, although not as high as has been reported at other individual sites. Our data support documentation of daptomycin and other antibiotic susceptibilities prior to treating VRE infections with these agents.