First Report Cfr and Optr A Co-harboring Linezolid-Resistant Enterococcus faecalis in China

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• Enterococcus faecalis is a significant opportunistic pathogen.
• Emergence of resistance to last-resort antibiotics like linezolid is a growing global health concern.
• The cfr and optrA genes are known mechanisms conferring resistance to phenicol and oxazolidinone antibiotics.

Purpose of the Study:

• To characterize a clinical isolate of Enterococcus faecalis resistant to linezolid.
• To investigate the genetic basis and transferability of the optrA and cfr resistance genes.
• To report the first co-occurrence of optrA and cfr in a clinical E. faecalis strain in China.

Main Methods:

• Isolation and identification of the E. faecalis strain.
• Antimicrobial susceptibility testing (MIC determination).
• Plasmid analysis, gene sequencing, and bacterial conjugation experiments.

Main Results:

• A linezolid-resistant E. faecalis strain was isolated, lacking mutations in common resistance loci.
• The optrA and cfr genes were identified and found to be located on two distinct, transferable plasmids.
• Transfer of these plasmids to a recipient strain conferred resistance to linezolid and chloramphenicol.

Conclusions:

• The co-harboring of optrA and cfr on separate plasmids in E. faecalis represents a novel mechanism for multidrug resistance.
• The transferability of these plasmids highlights the potential for rapid dissemination of antibiotic resistance.
• This finding underscores the need for enhanced surveillance of antibiotic resistance in clinical settings in China.