Transposon Tn5281 is the main distributor of the aminoglycoside modifying enzyme gene among isolates of Enterococcus faecalis in Tehran hospitals

Abstract

Infections with high levels of gentamicin-resistant (HLGR) isolates of Enterococcus faecalis are common in Tehran hospitals. Genes encoding such resistance are transmissible by conjugation at high frequency. The purpose of this study was to determine the existence of Tn5281 and its flanking aminoglycoside modifying enzyme gene aac(6')-aph(2") among 102 HLGR isolates of E. faecalis cultured from patients at three hospitals in Tehran, Iran. These isolates were detected by disks containing 120 microg of gentamicin and made 65% of all E. faecalis during the study period. DNA was extracted from HLGR isolates and subjected to PCR assays targeting aac(6')-aph(2") and conjugative transposon Tn5281. The amplified aac(6')-aph(2") gene was labeled with digoxigenin and probed with Tn5281 amplicons in dot blot hybridization assays. The aac(6')-aph(2") gene was detected in 91%-92% (n = 93) of the HLGR isolates. All isolates containing aac(6')-aph(2") were positive in long-PCR targeting Tn5281 and the probe hybridized with Tn5281 amplicons. The number of HLGR isolates of E. faecalis has increased considerably in Tehran hospitals. Tn5281 is the main cause of transmission of aac(6')-aph(2") to different isolates of E. faecalis in the hospitals studied.

Genetic Diversity, Antimicrobial Resistance, and Virulence Factors of Enterococcus faecalis Isolates Obtained from Stool Samples of Hospitalized Patients

“…However, the prevalence of the ermA gene in the present study was 14%. This finding is in contrast with the findings of former studies, which reported that above 90% of E. faecalis isolates had the ermA gene (44,45). The prevalence rates of the aph(2 )Ia and aac( 6)-Ie genes in the present study were 66% and 40%, respectively.…”

“…Nine types of cluster genes encode vancomycin resistance, among which vanA-vanN. vanA and vanB are the most important and prevalent genes in vancomycin-resistant Enterococcus species (45). Genetic factors such as plasmids, integrons, and transposons contribute to the emergence, transfer and the spread of antimicrobial resistance genes, particularly in Enterococcus species, thereby resulting in treatment failure (47).…”

“…Several studies in Iran and other countries have also reported the genetic diversity of the E. faecalis isolates. For example, a study in Isfahan, Iran, found fourteen ERIC types among 53 E. faecalis isolates (45). Another study in Indonesia showed that all E. faecalis isolates had > 60% similarity and reported five clusters (19).…”

High-level Gentamicin Resistance and Detection of aac (6’)Ie-aph (2”)Ia Gene in Enterococci Isolated from Pediatric Hospital in Northwest of Iran

“…In our study, high-level resistance to gentamicin was observed in 31 % of isolated enterococci. This frequency is lower than the rates reported by Dadfarma (57.4%, 2013) and Feizabadi (65%, 2008) (8,26). In this study, the frequency of HLGR isolates was higher in clinical specimens, which may be due to high consumption of antibiotics in clinics or due to collection of samples from hospitalized patients.…”