Daptomycin and tigecycline susceptibility of vancomycin resistant enterococci isolated from rectal swab cultures

Abstract

The increased incidence of infections by vancomycin-resistant Entero-coccus (VRE) causes an accumulation of patients who are either colonized with VRE or flagged as potentially colonized with VRE. Since such patients require precautionary isolation upon admission to a hospital, rapid methods to establish VRE coloniza-tion status would improve patient care and optimize hospital operation. We evaluated van quantitative PCR (qPCR) on one enrichment broth as a VRE-screening approach. We obtained 255 sets of five rectal specimens from 243 patients. The specimens were cultured using an amoxicillin-containing enrichment broth. Subsequently , a chromogenic agar was incubated and suspect colonies were inoculated on a blood agar plate and characterized by matrix-assisted laser desorption ioniza-tion-time of flight (MALDI-TOF), followed by a vancomycin Etest in cases in which Enterococcus spp. were detected. The culturing results were compared with the outcome of van qPCR on all enrichment broths of the first rectal swab. The van qPCR was positive for 43% of the sample sets (vanA, n 5; vanB, n 101; vanA and vanB, n 3). Based on culture data, 20 (7.8%) of the sets were VRE positive in at least one of five samples. The negative predictive value of van qPCR on the first enrichment broth was 99.3%. With a cutoff quantification cycle (C q) value of 35 to discriminate negative and positive samples, 87% of the negative patients can be identified within a day after obtaining the sample, compared to 7 days in the cultur-ing approach. VRE screening using qPCR on one enrichment broth can quickly identify non-VRE-colonized patients and therefore decrease costs and limit unnecessary isolation restrictions.