Molecular analysis and epidemiological typing of Vancomycin-resistant Enterococcus outbreak strains

Anbjørg Rangberg,Jetmund Ringstad,Oliver Kacelnik,Astri Lervik Larsen,Marthe Bjørland,Christine Monceyron Jonassen,Hanne Skarpodde Sæther

doi:10.1038/s41598-019-48436-2

Abstract

Outbreaks of multidrug resistant bacteria including vancomycin-resistant enterococci (VRE) in healthcare institutions are increasing in Norway, despite a low level of resistance compared to other European countries. In this study, we describe epidemiological relatedness of vancomycin-resistant Enterococcus faecium isolated during an outbreak at a Norwegian hospital in 2012–2013. During the outbreak, 9454 fecal samples were screened for VRE by culture and/or PCR. Isolates from 86 patients carrying the vanA resistance gene were characterized using pulsed-field gel electrophoresis (PFGE), MALDI-TOF mass spectrometry and single nucleotide polymorphism typing. PFGE revealed two main clusters, the first comprised 56 isolates related to an initial outbreak strain, and the second comprised 21 isolates originating from a later introduced strain, together causing two partly overlapping outbreaks. Nine isolates, including the index case were not related to the two outbreak clusters. In conclusion, the epidemiological analyses show that the outbreak was discovered by coincidence, and that infection control measures were successful. All typing methods identified the two outbreak clusters, and the experiment congruence between the MALDI-TOF and the PFGE clustering was 63.2%, with a strong correlation (r = 72.4%). Despite lower resolution compared to PFGE, MALDI-TOF may provide an efficient mean for real-time monitoring spread of infection.

Highlights

Enterococci are commensals of the gastrointestinal tract of humans and other mammals but are a leading cause of healthcare associated infections[1]
A total of 86 vanA VREfm isolates were identified as part of the SØ12 outbreak at our hospital, through screening of a total of 9454 samples (Fig. 1)
Rapid and sensitive microbial detection is important to limit the spread of infection, and determination of epidemiological relatedness is necessary for investigation of contamination patterns of resistant bacteria, and for outbreak management

Summary

Introduction

Enterococci are commensals of the gastrointestinal tract of humans and other mammals but are a leading cause of healthcare associated infections[1]. Vancomycin-resistant enterococci (VRE) were discovered in 19803,4, and have become one of the most problematic multiresistant hospital associated pathogens[5]. Apart from individual outbreaks[13], vancomycin resistance in enterococci is still rare in Norway compared to countries in eastern and southern Europe[14,15] and the USA, where a high percentage of resistance is reported[16]. Www.nature.com/scientificreports reported VRE cases was low, with an average of only four cases each year[17]. In 2010, a major VRE outbreak was discovered at Haukeland University Hospital on the west coast of Norway, leading to 289 reported cases of VRE infection or colonization. This outbreak was caused by E. faecium with the vanB resistance gene[18]. During the five year-period prior to outbreak, only two VRE isolates were reported from the county of Østfold, both of those in 2011

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