Metallo-beta-lactamase mediated resistance in clinical isolates of Acinetobacter spp

Abstract

Introduction: Acinetobacter spp. is one of the most common opportunistic bacterial pathogen causing hospital acquired infections. Its extensive resistance spectrum has earned it a “red alert” label among human pathogens. The emergence of MBL production among Acinetobacter spp has proved a global threat due to its broad spectrum of activity and limited treatment options. Aims: To determine the prevalence of MBL among clinical isolates of Acinetobacter spp in a tertiary care hospital and to determine their antibiotic susceptibility pattern. Materials and Methods: 57 clinical isolates of Acinetobacter spp obtained over a period of 1 year was subjected to antibiotic susceptibility testing by Kirby Bauer disc diffusion method as per CLSI guidelines. The carbapenem resistant strains were screened for MBL production by Imipenem-EDTA Combined disc test and Double disc synergy test. MBL E-test was used for confirmation of MBL production. Results: Of the 57 isolates, carbapenem resistance was recorded in 39 isolates. Screening tests for MBL showed 24 to be positive by CDT and 16 to be positive by DDST. All 24 of the Acinetobacter spp isolates that tested MBL positive by the screening test showed positive result by E-test. The prevalence of confirmed MBL by E-test among Acinetobacter spp was found to be 42.2%. The MBL isolates, in addition to resistance to cephalosporins and carbapenems, showed statistically significant resistance to fluoroquinolones and aminoglycosides. Colistin was found to be 100% sensitive and hence may prove a possible therapeutic option. Keywords: Metallo -beta-lactamase, Acinetobacter, Combined dist test, Double disc synergy test, E-test.