Determination of Risk Factors Associated With Isolation of Linezolid-Resistant Strains of Vancomycin-Resistant Enterococcus

Abstract

objective. To identify independent risk factors associated with isolation of linezolid-resistant, vancomycin-resistant Enterococcus (VRE).design. A retrospective, case-case-control study.setting. A tertiary care, academic medical center.methods. VRE isolates from clinical cultures were retrospectively analyzed for linezolid resistance during our 18-month study period. Clinical data were obtained from electronic patient records, and the risk factors associated with isolation of linezolid-resistant VRE were determined by comparison of 2 case groups with a control group.results. A total of 20% of the VRE isolates analyzed during the study period were linezolid resistant, and resistant isolates were most commonly recovered from the urine (40% of resistant isolates). Risk factors found to be associated with isolation of linezolid-resistant VRE were peripheral vascular disease and/or the receipt of a solid organ transplant, total parenteral nutrition, piperacillin-tazobactam, and/ or cefepime. Only 25% of patients from whom linezolid-resistant VRE was isolated had previous linezolid exposure, and in the multivariate model this was not found to be a risk factor associated with the isolation of linezolid-resistant VRE.conclusions. The results of this analysis suggest that there is horizontal transmission of linezolid-resistant VRE in our institution and highlight the need for improved infection control measures. Furthermore, the high incidence of linezolid-resistant VRE demands a reassessment of our empirical antibiotic selection for patients infected with VRE.

Epidemiological Interpretation of Studies Examining the Effect of Antibiotic Usage on Resistance

“…To overcome the limitations inherent in the two different types of control groups, two variations on the case-control design have been developed: case-case-control (23,33,(111)(112)(113)(114)(115)(116)(117)(118)(119)(120) and casecontrol-control (121-126). As described by Kaye et al (40), a casecase-control study involves two separate analyses: (i) a comparison of cases with a resistant strain of an organism to controls uninfected by that organism and (ii) a comparison of cases with a susceptible strain of the organism to those same controls.…”

Treatment of Resistant Enterococcal Urinary Tract Infections

“…An open-label, nonrandomized study showed linezolid to cause microbiologic eradication rate of 85% in VR E. faecalis bacteremia [56]. Reports of linezolid resistance among VRE isolates are emerging, with up to 20% resistance being reported in certain institutions, commonly among urine isolates [57].…”

Multicenter Study of High-Dose Daptomycin for Treatment of Enterococcal Infections

“…Studies evaluating linezolid for the treatment of vancomycin-resistant E. faecium bloodstream infection (BSI) have revealed clinical success frequencies ranging from 58% to 78% (7,8). However, reports of linezolid resistance in VRE have emerged, with an incidence as high as 20% (9). Moreover, prolonged treatment with linezolid can lead to myelosuppression, including neutropenia, thrombocytopenia, and anemia, which are frequent comorbid conditions already present in many patients with VRE infections (6,10).…”