LAUSR

OBJECTIVE Linezolid-resistant Enterococcus faecalis F102 was recovered from surface water in Switzerland and subjected to comprehensive genotypic characterization and analysis of the genetic environment of the oxazolidinone/phenicol resistance gene optrA. METHODS Whole Genome Sequencing (WGS) was performed to detect linezolid resistance mechanisms including mutations within 23S rRNA and in genes for ribosomal proteins, and acquired resistance genes. The isolate was further characterized by multilocus sequence typing (MLST) and identification of virulence genes. RESULTS WGS detected the presence of optrA identical to the original optrA gene from E. faecalis E349. Analysis of the genetic environment revealed the association of optrA with fexA and a Tn6674-like transposon in co-existence with spc and ermA resistance genes. Sequence alignment indicated that the genetic environment of optrA was identical to a Tn6674-like variant from E. faecalis isolated previously from diseased and healthy humans and from food producing animals in the Asia-Pacific region. E. faecalis F102 did not contain any mutations in the 23S rRNA, nor in the genes for the ribosomal proteins L3, L4 and L22. A total of 12 other resistance genes and 16 virulence genes were detected. E. faecalis F102 was assigned in silico to sequence type (ST)16. CONCLUSIONS The spread of optrA-carrying E. faecalis ST16 with a high pathogenic potential in surface water is a worrisome aspect from a public health perspective.