Mechanisms of Linezolid Resistance Among Enterococci of Clinical Origin in Spain—Detection of optrA- and cfr(D)-Carrying E.faecalis

摘要

The mechanisms of linezolid resistance among 13 and 6 isolates, recovered from six Spanish hospitals during 2017–2018, were investigated. The presence of acquired linezolid resistance genes and mutations in 23S rDNA and in genes encoding for ribosomal proteins was analyzed by PCR and amplicon sequencing. Moreover, the susceptibility to 18 antimicrobial agents was investigated, and the respective molecular background was elucidated by PCR-amplicon sequencing and whole genome sequencing. The transferability of the linezolid resistance genes was evaluated by filter-mating experiments. The gene was detected in all 13 isolates; and one -positive isolate also carried the recently described (D) gene. Moreover, one isolate displayed the nucleotide mutation G2576T in the 23S rDNA. This mutation was also present in all six isolates. All linezolid-resistant enterococci showed a multiresistance phenotype and harbored several antimicrobial resistance genes, as well as many virulence determinants. The gene was located upstream of the gene in 12 of the isolates. Moreover, an (A)-like gene was located downstream of in two isolates recovered from the same hospital. The gene was transferable in all but one isolates, in all cases along with the gene. The (D) gene was not transferable. The presence of and mutations in the 23S rDNA are the main mechanisms of linezolid resistance among and , respectively. We report the first description of the (D) gene in . The presence of the and (D) genes in Spanish hospitals is a public health concern.