Abstract
Although multilocus sequence typing (MLST) has been used to study molecular epidemiology and to explore the population structure of Enterococcus faecium, vancomycin-resistant E. faecium (VREF) strains lacking the pstS gene that were non-typable using conventional MLST methods were reported recently. We found nationwide emergence of VREF isolates lacking pstS in Korea and hereby report the molecular characteristics of these isolates. Forty-six VREF isolates lacking the pstS gene were identified among 300 VREF rectal isolates collected from hospitalized patients between 2014 and 2015. MLST was performed and clonal relatedness was determined by pulsed-field gel electrophoresis (PFGE). Four VREF ST1421 isolates were whole-genome sequenced. Among the VREF rectal isolates lacking pstS, 98% were classified as ST1421, which has identical allelic profiles to ST17 for all housekeeping genes except pstS. PFGE pattern analyses revealed 32 pulsotypes. All isolates harbored Tn1546 components with various transposase and insertion sequences. The whole-genome sequencing of four VREF ST1421 isolates showed that the pstS gene region was deleted at various locations with considerable inversion. The pstS gene was also depleted in 12.1% of 33 VREF clinical isolates in 2006–2007 and in 11.8% of 59 clinical isolates in 2012–2013. VREF ST1421 strains lacking the pstS gene have emerged in Korea. The emergence and spread of pstS-deleted VREF strains pose a serious challenge for epidemiological investigation. Alternative molecular typing methods to MLST will be increasingly necessary.
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Funding
This research was supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (Government-wide R&D Fund Project for infectious disease research, HG18C0062) and the Bio & Medical Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science & ICT (NRF-2016M3A9B6919187).
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Rectal swab surveillance for VREF and collection of bacterial isolates were approved by the Infection Control Committee of the Samsung Medical Center. Collection of VREF blood isolates was approved by the Institutional Review Board of the Samsung Medical Center.
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Kim, H.M., Chung, D.R., Cho, S.Y. et al. Emergence of vancomycin-resistant Enterococcus faecium ST1421 lacking the pstS gene in Korea. Eur J Clin Microbiol Infect Dis 39, 1349–1356 (2020). https://doi.org/10.1007/s10096-020-03853-4
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DOI: https://doi.org/10.1007/s10096-020-03853-4