Investigation of integron gene cassettes in trimethoprim-sulfamethoxazole-resistant Acinetobacter baumannii isolates

Abstract

Background: The spread of antibiotic-resistance genes among healthcare-associated infections (HAIs) poses serious problems in the treatment of these infections. Recently, these resistance genes have also been shown to be present in integrons.

Objectives: By focusing on integron-mediated mechanisms of antibiotic resistance, we sought to elucidate the genetic determinants underpinning the development of multidrug resistance in clinical isolates of Acinetobacter baumannii.

Material and methods: In this study, 27 TMP-SXT-resistant A. baumannii isolates were obtained from various clinical samples. Class I and class II integrons were determined using polymerase chain reaction (PCR). Samples were sent for DNA sequence analysis of the integron to a private firm (BMLabosis, Ankara, Turkey). The similarities of the DNA sequences with the associated integron were determined using National Center for Biotechnology Information (NCBI) GenBank.

Results: While all isolates were resistant to TMT-SXT and gentamicin, amikacin and tobramycin resistance rates were detected as 70% and 26%, respectively. Class I and class II integrons were found in 1 strain and 2 isolates, respectively. It was also determined that the dfrA12 gene and the aadA2 gene were found in the class I integrons. It was determined that 2 isolates carrying class II integron had dfrA1 and sat2 genes. Both class I and class II integrons were detected in 1 of these isolates.

Conclusions: Despite the low integron detection in the resistant isolates, with the detection of class I and class II integrons among A. baumannii isolates, it was determined that HAIs could spread very rapidly within the hospital and cause multidrug resistance. This study reveals the need for comprehensive surveillance and molecular characterization of integron-mediated resistance mechanisms to inform effective strategies to combat infections caused by multidrug-resistant (MDR) A. baumannii.

Keywords: Acinetobacter baumannii; antibiotic resistance; integron gene cassettes.