Molecular characterisation of class I integrons in clinical multidrug-resistant Enterococcus spp.

Abstract

Enterococci have caused health problems and infections in recent years around the world, especially E. faecalis and E. faecium, due to antibiotic resistance. This study examined clinical Enterococcus isolates collected from patients at the Maternity and Children Hospital in Al-Samawah, Al-Muthanna Province, Iraq, focusing on class 1 integrons and their role in resistance. Enterococci isolated from different clinical samples were initially identified using selective medium, then confirmed using Taqman real-time PCR. A Kirby–Bauer disc diffusion test was used to determine the antibiotic susceptibility of isolates. The variable region of class 1 integrons was amplified using Polymerase Chain Reaction (PCR), and the resulting ∼2000 bp amplicons were sequenced. Sequencing analysis of VR amplification products showed the presence of three gene cassettes encoding antibiotic resistance (dhfrXII, dfrA12, aadA2). Three hundred and fifty different clinical samples were isolated between July and November 2024. The current study obtained 125 (35.7 %) enterococcal isolates divided into 35 (28 %) E. faecium and 90 (72 %) E. faecalis. Among the 125 enterococcal isolates, the int1 gene was detected in 67.2 %, and sequencing analysis of CS amplification products showed the presence of three resistance genes in this cassette (dhfrXII, dfrA12, aadA2) within clinical Enterococci, and the phylogenetic tree showed the genetic closeness with the international isolates registered in NCBI. Moreover, the antibiotic resistance and biofilm formation rates within int1-positive enterococci were noticeably higher than those lacking the int1 gene.