OBJECTIVES: Acinetobacter baumannii emerged as a major nosocomial pathogen responsible for infections. In this study, we report the molecular characterization, association of insertion sequences and sequence types of clinical isolates of carbapenem resistant A. baumannii. MATERIALS AND METHODS: A total of 763 non-duplicate isolates of A. baumannii received from 8 centres across India during January 2014 to December 2017 were studied. Susceptibility testing was done by Kirby-Bauer method. PCR was performed for detection of extended spectrum β-lactamases, metallo β-lactamases, oxacillinases and ISAba1. Mapping PCR was performed to identify the position of ISAba1 with respect to blaOXA-23 like and blaOXA-51 like gene. MLST was performed to identify the sequence type. Whole genome sequencing was done to decipher the genetic arrangement of ISAba1 with blaOXA-23 like and with blaOXA-51 like. RESULTS: All the isolates were resistant to imipenem and meropenem. blaOXA-23 like was the predominant carbapenemase. All isolates were positive for ISAba1. The common sequence types were ST848, ST451 and ST1305 which belongs to International clone II. Whole genome sequencing showed considerable variation in the insertion site location. CONCLUSIONS: In conclusion, high prevalence of blaOXA-23 like in A. baumannii and its association with ISAba1 and sequence types belonging to IC-II facilitates the successful dissemination of these extremely drug resistant strains.
OBJECTIVES:Acinetobacter baumannii emerged as a major nosocomial pathogen responsible for infections. In this study, we report the molecular characterization, association of insertion sequences and sequence types of clinical isolates of carbapenem resistant A. baumannii. MATERIALS AND METHODS: A total of 763 non-duplicate isolates of A. baumannii received from 8 centres across India during January 2014 to December 2017 were studied. Susceptibility testing was done by Kirby-Bauer method. PCR was performed for detection of extended spectrum β-lactamases, metallo β-lactamases, oxacillinases and ISAba1. Mapping PCR was performed to identify the position of ISAba1 with respect to blaOXA-23 like and blaOXA-51 like gene. MLST was performed to identify the sequence type. Whole genome sequencing was done to decipher the genetic arrangement of ISAba1 with blaOXA-23 like and with blaOXA-51 like. RESULTS: All the isolates were resistant to imipenem and meropenem. blaOXA-23 like was the predominant carbapenemase. All isolates were positive for ISAba1. The common sequence types were ST848, ST451 and ST1305 which belongs to International clone II. Whole genome sequencing showed considerable variation in the insertion site location. CONCLUSIONS: In conclusion, high prevalence of blaOXA-23 like in A. baumannii and its association with ISAba1 and sequence types belonging to IC-II facilitates the successful dissemination of these extremely drug resistant strains.