Investigating the distribution of integrons among clinical isolates of acinetobacter baumannii and their association to carbapenem resistance

Abstract

Background: Background: To determine the dissemination of classes of integrons and their roles in carbapenem resistant strains of Acinetobacter baumannii. Integron1, 2 and 3 have been reported in various microrognisms and are implicated in conferment of multi drug resistance. Carriage of carbapenem resistance genes on these integrons has not been consistent. Multidrug drug resistance is being increasingly reported in A.baumannii. Though integron 1 and 2 have been detected, there is no report from India correlating carbapenem resistance to the presence of integrons in A.baumannii. Methods & Materials: Materials and methods: One hundred fifteen (n=115) clinical isolates of A.baumannii were collected from different clinical specimens of clinical microbiology laboratories two different tertiary care hospitals. Cultures were identified by routine microbiology methods and also by VITEK-2 system. Antimicrobial susceptibility testing and minimum inhibitory concentration for panel of 20 antibiotics were examined. To investigate classes of integrons, multiplex PCR for integrase intI1 and intI2 was performed along with A.baumannii species specific marker (Ab-ITS). ClassA, B and D carbapenemases were identified in these isolates and the distribution of carbapenemases with specific reference to type of integron has been determined by PCR. Results: Results: A total of 115 isolates were included in this study. Genotypic and phenotypic results showed 93(80%) as carbapenem resistant and 22(20%) as carbapenem sensitive isolates. Out of the 93 carbapenem resistant isolates, 76 (81%) isolates possessed integrons. 58(62%) isolates carried class 1 integron and 18(19%) isolates carried class 2 integron. Surprisingly, 11 carbapenem resistant isolates and two carbapenem sensitive isolates harboured both classes of integrons. One carbapenem sensitive isolate had only class 2 integron. Conclusion: Conclusion: Multiplex PCR for the detection and identification of integron classes along with species specific marker (Ab-ITS) will be a useful method for the epidemiological studies. This rapid, reliable determination of the genetic relatedness of clinical isolates in this antibiotic era is essential when investigating cases of nosocomial outbreak.