Phenotypic and Molecular Detection of Metallo-Beta-Lactamase Genes Among Imipenem Resistant Pseudomonas aeruginosa and Acinetobacter baumannii Strains Isolated From Patients with Burn Injuries

Background: Pseudomonas aeruginosa and Acinetobacter baumannii are the common causes of nosocomial infections especially among patients with burn injuries. Objectives: The current study aimed to determine the frequency of blaIMP, blaVIM, blaDIM, blaAIM, blaGIM and blaNDM genes among P. aeruginosa and A. baumannii strains isolated from patients with burn injuries hospitalized in Shahid Motahari hospital, Tehran, Iran. Methods: The current cross-sectional study evaluated a total of 309 nonduplicate isolates of P. aeruginosa and 189 isolates of A. baumannii collected from different clinical samples of patients with burn injuries in Shahid Motahari hospital in Tehran, Iran, from 2012 to 2015. Antibiotic susceptibility tests were conducted by Kirby-Bauer disc diffusion and broth microdilution methods according to the clinical and laboratory standards institute (CLSI) guidelines. The frequency of metallo-beta-lactamase (MBL) producers was evaluated by the combination disk diffusion test (CDDT). The blaIMP, blaVIM, blaDIM, blaAIM, blaGIM and blaNDM genes were detected by polymerase chain reaction (PCR) and sequencing techniques. Results: The most effective agent against the studied isolates was colistin. By CDDT, it was found that among 278 imipenem resistant P. aeruginosa strains, 178(64.02%) were MBL producers. The blaIMP-1 and blaVIM-1 genes were detected in 30(16.8%) and 52(29.2%) of P. aeruginosa isolates, respectively. Result of 187 imipenem resistance A. baumannii strains showed that 85(45.4%) were MBL producers. The blaOXA-51, blaIMP-1 and blaVIM-1 genes were detected in 187(100%), 10(5.3%) and 34(18.18%) of A. baumannii isolates, respectively. Conclusions: The high prevalence of MBLs-producing P. aeruginosa and A. baumannii strains in the study were one of the major concerns.