Hospital outbreak caused by linezolid resistant Enterococcus faecium in Upper Austria

Heidrun Kerschner,Rainer Hartl,Sigrid Machherndl-Spandl,Franz Allerberger,Adriana Cabal,Petra Apfalter,Werner Ruppitsch

doi:10.1186/s13756-019-0598-z

Abstract

BackgroundEnterococcus faecium is part of the human gastrointestinal flora but may act as opportunistic pathogen. Environmental persistence, high colonization capability and diverse intrinsic and acquired resistance mechanisms make it especially successful in nosocomial high-risk settings. In March 2014, an outbreak of Linezolid resistant Enterococcus faecium (LREfm) was observed at the hematooncology department of a tertiary care center in Upper Austria.MethodsWe report on the outbreak investigation together with the whole genome sequencing (WGS)-based typing results including also non-outbreak LREfm and susceptible isolates.ResultsThe 54 investigated isolates could be divided in six clusters based on cgMLST. Cluster one comprised LREfm isolates of genotype ST117 and CT24, which was identified as the causative clone of the outbreak. In addition, the detection of four other clusters comprising isolates originating from hematooncology patients but also at other hospitals, pointed to LREfm transmission between local healthcare facilities. LREfm patients (n = 36) were typically at risk for acquisition of nosocomial pathogens because of immunosuppression, frequent hospitalization and antibiotic therapies. Seven of these 36 patients developed LREfm infection but were successfully treated. After termination of the initial outbreak, sporadic cases occurred despite a bundle of applied outbreak control interventions.ConclusionsWGS proved to be an effective tool to differentiate several LREfm clusters in an outbreak. Active screening for LREfm is important in a high-risk setting such as hematooncology, where multiple introductions are possible and occur despite intensified infection control measures.

Highlights

Enterococcus faecium is part of the human gastrointestinal flora but may act as opportunistic pathogen
In March 2014, routine surveillance cultures of stool and urine from four patients hospitalized at the department of internal medicine 1 (DIM1) of an Austrian tertiary care center tested positive for Linezolid resistant Enterococcus faecium (LREfm)
ST117, CT24 has been previously identified in outbreaks caused by VAN-resistant E. faecium [26, 27] up to our knowledge, this clone has been never associated to LREfm outbreaks

Summary

Introduction

Enterococcus faecium is part of the human gastrointestinal flora but may act as opportunistic pathogen. Environmental persistence, high colonization capability and diverse intrinsic and acquired resistance mechanisms make it especially successful in nosocomial high-risk settings. Enterococci are gram-positive bacteria found in the environment and as part of the human gastrointestinal flora [1]. They can act as opportunistic pathogens causing a broad range of diseases such as blood stream or wound-associated infections [2]. Hospital-adapted clones such as clonal complex (CC) Enterococcus faecium show persistence in the environment and high colonization capability [3]. LREfm outbreaks tend to be mostly colonizations, clinical outbreaks with invasive LREfm infections have been reported [14]

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