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The increasing number of nosocomial pathogens with resistances against last resort antibiotics like linezolid leads to a pressing need for the reliable detection of these drug-resistant bacteria. National guidelines on infection prevention, e.g., in Germany, have already recommend screening for linezolid-resistant bacteria, although a corresponding screening agar medium has not been provided. In this study we analyzed the performance and reliability of a commercial, chromogenic linezolid screening agar. The medium was capable to predict more than a hundred linezolid-resistant isolates of E. faecium, E. faecalis, S. aureus, S. epidermidis, and S. hominis with excellent sensitivity and specificity. All isolates were collected at the National Reference Centre between 2010 and 2020., Competing Interests: Declaration of competing interest All authors have nothing to declare., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Objectives: To investigate an outbreak of linezolid-resistant Staphylococcus epidermidis (LRSE) in an interdisciplinary ICU, linezolid consumption and infection control measures taken., Methods: Routine surveillance of nosocomial infections revealed colonization and infection with LRSE affecting 14 patients during a 15 month period. LRSE isolates were analysed with respect to their clonal relatedness, antimicrobial susceptibility, the presence of cfr and/or mutations in the 23S rRNA, rplC, rplD and rplV genes. cfr plasmids were characterized by Illumina sequencing. Medical records were reviewed and antibiotic consumption was determined., Results: Molecular typing identified the presence of three different LRSE clusters: PFGE type I/ST168 (n = 5), PFGE type II/ST5 (n = 10) and PFGE type III/ST2 (n = 1). Ten strains harboured the cfr gene; we also detected mutations in the respective ribosomal protein genes. WGS revealed an almost identical 39 kb cfr plasmid obtained from strains of different genetic background (ST2, ST5, ST168) that shows high similarity to the recently published LRSE plasmid p12-02300. Due to an increase in the number of patients treated for infections with MRSA, a significant increase in linezolid usage was noted from January to July 2014 (from 5.55 to 20.41 DDDs/100 patient-days)., Conclusions: Here, we report the molecular epidemiology of LRSE in an ICU. Our results suggest the selection of resistant mutants under linezolid treatment as well as the spread of cfr-carrying plasmids. The reduction of linezolid usage and the strengthening of contact precautions proved to be effective infection control measures.

Objectives: Linezolid-resistant Staphylococcus epidermidis (LRSE) and linezolid-dependent ST22 strains have been shown to predominate in tertiary care facilities all over Greece. We report herein the dissemination of ST22 but also ST2, ST5 and ST168 linezolid-dependent LRSE clones in four unrelated German hospitals., Methods: Fourteen LRSE clinical isolates recovered during 2012-14 from five distantly located German hospitals were tested by for MIC determination broth microdilution and Etest, PCR/sequencing for cfr and for mutations in 23S rRNA, rplC, rplD and rplV genes, MLST, PFGE and growth curves without and with linezolid at 16 and 32 mg/L., Results: Most (11, 78.6%) isolates had linezolid MICs >256 mg/L. Five isolates carried the cfr gene. Eight isolates belonged to ST22, two isolates each to ST168 and ST2 and one isolate each to ST5 and ST23. Ten isolates [seven belonging to ST22 and one to each of ST2, ST5 and ST168; all these STs belong to clonal complex (CC) 5] exhibited linezolid-dependent growth, growing significantly faster in linezolid-containing broth. Four isolates were non-dependent (one belonging to each of ST22, ST2, ST23 and ST168). Four isolates came from three different hospitals, whereas four and six isolates were recovered during outbreaks of LRSE in two distinct hospitals., Conclusions: The multi-clonal dissemination of CC5 linezolid-dependent LRSE throughout German hospitals along with the clonal expansion of ST22 linezolid-dependent LRSE in Greek hospitals is of particular concern. It is plausible that this characteristic is inherent and provides a selective advantage to CC5 LRSE under linezolid pressure, contributing to their dissemination throughout hospitals in these countries.

Objectives: This study was a detailed investigation of Staphylococcus epidermidis clinical isolates exhibiting linezolid resistance., Methods: Thirty-six linezolid-resistant S. epidermidis from eight German hospitals, including isolates from suspected hospital-associated outbreaks between January 2012 and April 2013, were analysed with respect to their antimicrobial susceptibility and the presence of cfr and/or mutations in the 23S rRNA, rplC, rplD and rplV genes. Relatedness of isolates was estimated by MLST and SmaI macrorestriction analysis. Characterization of cfr plasmids was carried out by means of Illumina sequencing., Results: The MICs of linezolid varied substantially between the isolates. No apparent correlation was detected between the level of resistance, the presence of cfr and ribosomal target site mutations. S. epidermidis isolates from two hospitals were confirmed as clonally related, indicating the spread of the respective clone over a period of 1 year. Next-generation sequencing revealed two different categories of cfr-expressing plasmids, both of them varying in genetic arrangement and composition from previously published cfr plasmids: p12-00322-like plasmids showed incorporation of cfr into a pGO1-like backbone and displayed capabilities for intra- and inter-species conjugational transfer., Conclusions: To date, linezolid-resistant S. epidermidis have rarely been isolated from human clinical sources in Germany. Here, we describe the emergence and outbreaks of these strains. We detected previously described and novel point mutations in the 23S ribosomal genes. The cfr gene was only present in six isolates. However, this is the first known description of cfr incorporation into conjugative vectors; under selective pressure, these vectors could give reasonable cause for concern., (© The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)