Ann Lab Med.  2020 Jul;40(4):321-325. 10.3343/alm.2020.40.4.321.

Emergence of optrA-Mediated Linezolid-Nonsusceptible Enterococcus faecalis in a Tertiary Care Hospital

• Park K
• Jeong YS
• Chang J
• Sung H
• Kim MN

• KMID: 2470329
• DOI: http://doi.org/10.3343/alm.2020.40.4.321

Abstract

This study investigated resistance mechanisms and epidemiology of emerging linezolid-nonsusceptible Enterococcus faecalis (LNSEF) in a tertiary care hospital. LNSEF isolated from clinical samples were collected from November 2017 to June 2019. The isolates were investigated for linezolid resistance and the associated molecular mechanisms, including mutations of 23S rRNA domain V and acquisition of the cfr or optrA resistance gene. We used pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing for the molecular typing of the isolates. Among 4,318 E. faecalis isolates, 10 (0.23%) were linezolid-nonsusceptible. All LNSEF isolates were optrA-positive and cfr-negative. Of these isolates, five were sequence type (ST) 476, two ST585, one ST16, one ST16-like, and one ST480. Six LNSEF isolates obtained in the first year clustered to three types in the PFGE analysis: two ST476 isolates of type A, two ST585 isolates of type B, and two ST16 or ST16-like isolates of type C. Seven cases were of community-onset and three were hospital acquired, but total of eight were healthcare-associated including five community-onset. None of the patients had a history of linezolid treatment, and in one patient, we detected linezolid-susceptible E. faecalis one month before LNSEF detection. In conclusion, heterogenous clones of optrA-positive LNSEF emerged in the hospital mainly via community-onset.

Keyword

Linezolid resistance; Mechanism; Epidemiology; optrA; Enterococcus faecalis; Pulsed-field gel electrophoresis; Multilocus sequence typing

MeSH Terms

Clone Cells
Electrophoresis, Gel, Pulsed-Field
Enterococcus faecalis*
Enterococcus*
Epidemiology
Humans
Linezolid
Molecular Typing
Multilocus Sequence Typing
Tertiary Healthcare*
Linezolid

Figure

• 

  Fig. 1 Pulsed-field gel electrophoresis (PFGE) analysis of linezolid-nonsusceptible Enterococcus faecalis isolates after SmaI-digestion. M denotes Lambda Ladder PFG Marker (New England Biolabs Inc., N0341S, Beverly, MA). Each of lanes from 1 to 6 denoted the pulsotype of isolate number 1, 5, 2, 3, 4, and 6 in order.

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