The molecular characterization of colistin-resistant isolates of Acinetobacter baumannii from patients at intensive care units

Safar Farajnia; Fariba lotfi; Alireza Dehnad; Maryam Shojaie; Roya Raisi; Leila Rahbarnia; Ahad Bazmani; Behrooz Naghili; Samaneh Shiry

doi:10.18502/ijm.v14i3.9768

Safar Farajnia Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
Fariba lotfi Department of Biological Sciences, Faculty of Basic Sciences, Higher Education Institute of Rab-Rashid, Tabriz, Iran
Alireza Dehnad Department of Biotechnology, East Azerbaijan Research and Education Center Agricultural and Natural Resources, Razi Vaccine and Serum Research Institute, AREEO, Tabriz, Iran
Maryam Shojaie Department of Biological Sciences, Faculty of Basic Sciences, Higher Education Institute of Rab-Rashid, Tabriz, Iran
Roya Raisi Department of Biological Sciences, Faculty of Basic Sciences, Higher Education Institute of Rab-Rashid, Tabriz, Iran
Leila Rahbarnia Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
Ahad Bazmani Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
Behrooz Naghili Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
Samaneh Shiry Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran

DOI: https://doi.org/10.18502/ijm.v14i3.9768

Keywords: Acinetobacter baumannii; Beta-lactamase OXA-23, Beta-lactamase OXA-143, OXA-72 carbapenemase, Be- ta-lactamase OXA-58, Colistin

Abstract

Background and Objectives: The objective of this study was to determine molecular characterization and genetic diversity of colistin-resistant A. baumannii clinical isolates in Intensive Care Unit hospitalized patients.

Materials and Methods: A total of 127 A. baumannii clinical isolates were evaluated for antimicrobial susceptibility. PCR reaction and sequencing were performed for the detection of mutations in pmrAB and lpx ACD genes.

Results: Based on antimicrobial susceptibility testing, 40.94% and 33.85% of the isolates were MDR and XDR respec- tively whereas 3.93% of them were found to be PDR. Results of agar dilution MIC and E-test indicated that 76% of the isolates were sensitive to colistin. All of the isolates were positive for bla OXA-51 and 50% of them were positive for both blaOXA-23-like and bla OXA-143-like genes while only 25% of the isolates were positive for bla OXA-72 . None of them were positive for the bla OXA-58-like gene. There is no mutation in pmrA. The V162A substitution for pmrB gene was repeated in two isolates, and E394D and Y292H substitutions in lpxA were observed in two isolates; also, C120R and F165L substitutions in lpxC gene was repeated in two isolates. Analysis of phylogenetic tree based on alterations in lpxACD and pmrB genes indicated the appearance of new isolates compared to the reference strain ATCC17978 A. baumannii isolates.

Conclusion: The present study indicated the prevalence of MDR and XDR A. baumannii isolates and the emergence of PDR isolates in the northwest portion of Iran. The appearance of colistin-resistant isolates with new mutations in pmrB, lpxACD genes indicates new resistance mechanisms.