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J Glob Antimicrob Resist. 2019 Jan 11. pii: S2213-7165(19)30008-6. doi: 10.1016/j.jgar.2019.01.001. [Epub ahead of print]

Distribution of the optrA gene in Enterococcus isolates at a tertiary care hospital in China.

Author information

1
Department of Laboratory Medicine, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, 321# Zhongshan Road, Gulou District, Nanjing, Jiangsu Province 210008, PR China. Electronic address: zwq_096@163.com.
2
Department of Laboratory Medicine, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, 321# Zhongshan Road, Gulou District, Nanjing, Jiangsu Province 210008, PR China. Electronic address: shuoshuo65@163.com.
3
Department of Laboratory Medicine, Jiangning District Hospital of Traditional Chinese Medicine, 657# Tianyin Avenue, Jiangning District, Nanjing, Jiangsu Province 211100, PR China. Electronic address: 32548026@qq.com.
4
Department of Laboratory Medicine, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, 321# Zhongshan Road, Gulou District, Nanjing, Jiangsu Province 210008, PR China. Electronic address: njzhangzf@hotmail.com.
5
Department of Laboratory Medicine, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, 321# Zhongshan Road, Gulou District, Nanjing, Jiangsu Province 210008, PR China. Electronic address: 1070299160@qq.com.
6
Department of Laboratory Medicine, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, 321# Zhongshan Road, Gulou District, Nanjing, Jiangsu Province 210008, PR China. Electronic address: shenhan10366@sina.com.
7
Department of Clinical Laboratory, Jinling Hospital, Nanjing University School of Medicine, Nanjing University, 305# East Zhongshan Road, Qinhuai District, Nanjing, Jiangsu Province 210008, PR China. Electronic address: zchunni27@hotmail.com.

Abstract

BACKGROUND:

Linezolid-resistant Enterococcus spp. and Staphylococcus spp. have spread all over the world. The present study aims to investigate the prevalence of linezolid-nonsusceptible Enterococcus (LNSE) and the potential mechanism and molecular epidemiology of LNSE isolates collected from Nanjing Drum Tower Hospital, 2014-2017.

METHODS:

The susceptibilities to linezolid of 2 555 Enterococcus isolates recovered from April 2014 to November 2017 were retrospectively determined by the linezolid E-test. The minimum inhibitory concentrations (MICs) of vancomycin and teicoplanin were determined for the linezolid-nonsusceptible isolates by the E-test. Polymerase chain reactions (PCRs) and DNA sequencing were used to investigate the potential molecular mechanism. Clonal relatedness between these LNSE strains was analyzed by multilocus sequence typing. Whole genome sequencing was performed for LNSE isolates.

RESULTS:

Twenty-seven Enterococcus isolates (1.1%, 27/2555), including 24 Enterococcus faecalis and 3 Enterococcus faecium isolates with linezolid MICs of 4∼48μg/mL, were identified. Among these isolates, 20 E. faecalis and 3 E. faecium isolates were positive for the optrA gene. We failed to find any mutations in domain V of the 23S rRNA and the genes encoding ribosomal proteins L3 and L4 and the cfr gene. The 24 LNSE E. faecalis isolates can be classified into 8 STs, with the greatest number identified as ST16 (eight isolates), followed by ST480 (four isolates), ST476 (four isolates), ST631 (three isolates), ST585 (two isolates), and 3 others belonging to ST428, ST25 and ST689, respectively. Three E. faecium isolates were classified into ST17, ST400 and ST195, respectively. Comparison of the deduced OptrA amino acid sequences of the 23 isolates obtained by PCR-based sequencing and WGS with that of the original OptrA from E. faecalis E349 revealed 7 variants, including KD (EF438, EF5152, EF1765, EF5505, EF2469, EF3157 and EF2389), EDP (EF437 and EM2369), EDM (EM333 and EM429), D (EF5473 and EF4106), EDD (EF5141), RDK (EF2597) and DP (EF353) in 16 isolates, with no mutations in the other 7 isolates (EF294, EF2916, EF346, EF349, EF439, EF4946 and EF6735). The optrA gene was found at the downstream of the fexA gene by searching pE349 sequence based on WGS data.

CONCLUSIONS:

The emergence of linezolid-nonsusceptible enterococcus isolates with optrA-mediated resistance mechanisms and ST16 E. faecalis clonal dissemination in our hospital may pose a potential challenge to public health.

KEYWORDS:

23S rRNA gene; cfr gene; enterococcus; linezolid; optrA; resistance

PMID:
30641287
DOI:
10.1016/j.jgar.2019.01.001

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