Existence of Integron I and II Genes from Clinical Isolate Staphylococcus aureus and Their Role in Drug Resistance

Abstract

An integron is a gene capture and dissemination system. They have been identified on both genomic and mobile genetic elements which often contain one or more genes that encode antibiotic resistance. They are commonly associated with bacterial genera in the family of Enterobacteriaceae. Currently, there have been recent reports showing the presence of integrons in Staphylococcus species. The aim of the present study was to assess the existanxe of Class I and II integrons from 60 clinically isolated S. aureus and to evaluate their association with multi-drug resistance. The isolates were screened for antimicrobial susceptibility using the Kirby-Baur disc diffusion test against six different antimicrobial drugs -- Amoxicillin (AMC), Ampicillin (AMP), Chloramphenicol (CAPH), Erythromycin ERY), Tetracycline (TET) and Vancomycin (VAN). Genomic DNA was isolated from resistant isolates by phenol chloroform method. Two sets of specific primer sequences were used to amplify the conserved region of Class I and II integrons and agarose gel electrophoresis was used for analysing the PCR products. Antibiotic resistance pattern of AMC 29 (48.33%), AMP 57 (95%), CAPH 8 (13.33%), ERY 18 (30%), TET 5 (8.33%) and VAN 2 (3.33%) were observed. Among 60 clinical isolates, 41 (68.33%) isolates were resistant to two and more antimicrobial drugs. A total of 11 (26.83%) Class I and 3 (7.32%) Class II integrons were detected. Class I integron was more prevalent than Class II integron in multi-drug resistant S. aureus. In the present study, integrons might have played a role in the multidrug resistance pattern of S. aureus.

Keywords: Staphylococcus aureus, antimicrobial resistance, molecular characterization, integron