Farkhondeh Poursina - Isfahan University of Medical Sciences, Department of Microbiology, Faculty of Medicine,
Majid Torabi - Student Research Committee, Isfahan University of Medical Sciences, Isfahan, Iran

Background and Aim : Enterococci can acquire linezolid resistance through chromosomalmutation or the uptake of mobile genetic elements containing particular linezolid resistance genesincluding cfr, optrA, and poxtA. The study aims were to analyze the antibiotic susceptibilitypatterns of Enterococcus isolates, including phenotypic resistance identification, followed bydetection of cfr, optrA, and poxtA genes in MDR isolates.Methods : In this descriptive study (cross-sectional), ۱۷۵ non-duplicate enterococcal isolates wereobtained from different clinical specimens at the Al-Zahra, Amin, and Khorshid hospitals inIsfahan. After the biochemical confirmation of the strains, the PCR amplification of genes (ddl)was performed to determine the enterococci species. The antibiotic resistance profile ofEnterococcus isolates was investigated based on CLSI ۲۰۲۲'s instructions and analyzed usingWhonet ۲۰۲۱ software. then used a multiplex-PCR method to detect optrA, cfr, and poxtA fromwhole genomic bacterial DNA. The confirmation of the gene detection process was done bygenome sequencing. Statistical analyses were performed using SPSS version ۲۶ software. Asignificance level of P < ۰.۰۵ was used to define significant results.Results : Among our isolates, E. faecalis predominated ۷۳.۷%. As well, vancomycin and linezolidresistantenterococci constitute ۲۹.۷% and ۴.۰%, respectively. Nevertheless, MDR prevalenceamong E. faecium was ۹۱.۱%, ۶۸.۹% among E. faecalis, and ۶۶.۶% among other species ofEnterococcus. Our results showed that the prevalence of optrA was ۷۱.۴% and that of poxtA andcfr was ۴۲.۸% among linezolid-resistant enterococci and there is a significant relationship (P <۰.۰۵) between resistance to linezolid and the presence of each of these three genes.Conclusion : This is the first study to describe the linezolid resistance genes cfr, optrA, and poxtAin Iran, and to investigate their prevalence in clinical Enterococcus spp. isolates at IsfahanUniversity of Medical Sciences hospitals. It should be considered alarming if even one specimenis found expressing optrA, poxtA, or cfr, where genes for resistance can spread between clinicalsettings and non-clinical settings, as well as between different species.

Enterococcus spp., linezolid-resistance, poxtA, cfr, optrA