Assessment of 16srRNA Methylase Genes Among Non-ESBL and ESBL-Producing Klebsiella pneumoniae Isolates

Abstract

The aim of our study was to investigate mechanisms of aminoglycoside resistance in extended-spectrum beta-lactamases (ESBL)producing Klebsiella pneumoniae (K. pneumoniae) isolates from Iran. To this end, 154 clinical isolates of K. pneumoniae were collected from two hospitals in Ilam city, Iran. The Kirby-Bauer (agar diffusion) antibiotic testing method was used to determine the susceptibility pattern of the isolates against kanamycin, gentamicin, tobramycin, netilmicin and amikacin. Aminoglycoside acetyltransferases (aac(3)-IIa, aac(6')-Ib, and aac(3)-Ia), 16SrRNA methylase genes (armA and rmtB) and ESBL genes (blaTEM, blaSHV , and blaCTX-M) were detected by PCR amplification. 59.1% (n = 91) of K. pneumoniae isolates were detected ESBL producers with the phenotypic test. Moreover, blaTEM, blaSHV and blaCTX-M were detected in 83.5% (n=76), 52.7% (n=48) and 26.4% (n=24) of the ESBL-producing isolates, respectively. Among 52 resistant or intermediate isolates against aminoglycosides, the aac(3)-IIa, aac(6')-Ib and rmtB genes were detected in 55.8% (n = 29), 80.8% (n = 42) and 1.9% (n = 1) of the isolates, respectively; none of the isolates, however, had the aac(3)-Ia and armA genes. Therefore, the results showed the high prevalence of aminoglycosides resistance in the K. pneumoniae isolates. As observed, the acetyltransferase modifying enzymes (aac genes) played major roles in determining this resistance. However, the rate of 16srRNA methylase genes was extremely low in K. pneumoniae.

The Molecular Epidemiology of Resistance to Antibiotics among Klebsiella pneumoniae Isolates in Azerbaijan, Iran

“…In the study of Iraj et al, the aac (3) IIa, aac (6) Ib, and rmtB genes were identified in 55.8%, 80.8%, and 1.9% of the isolates, respectively. e aac (3) Ia and armA were not found in any of the isolates [68]. In the previous studies from Spain by Elisenda et al, the most frequent AME genes in Enterobacteriaceae were aph (3) Ib (65.4%) and ant (3) Ia (37.5%) [69], whereas in the recent study, the most frequent AME genes in K. pneumoniae were ant (3) Ia (44%) followed by aac (6) Ib (32%) and aph (3) Ib (32%).…”