Detection of Different Types of Metallo-β-Lactamases among Pseudomonas aeruginosa Isolates Obtained from Intensive Care Unit Patients

Introduction: Pseudomonas aeruginosa is a serious challenge for antimicrobial therapy, due to chromosomal mutations or intrinsic resistance to various antimicrobial agents, such as Metallo-β-Lactams (MBL). This study aimed to investigate the prevalence of β-lactamases encoding genes among P. aeruginosa strains isolated from intensive care unit (ICU) patients by phenotypic and multiplex PCR methods. Methods: A total of 48 non-duplicate strains of P. aeruginosa were collected from different clinical specimens of patients hospitalized in ICU wards of a teaching hospital in Isfahan, Iran. Susceptibility test was performed by disk diffusion method. All meropenem resistant strains were subjected to modified Hodge test (MHT) for detection of carbapenemases. Multiplex PCRs were performed to detect β-lactam-resistant P. aeruginosa isolates. Results: In disk diffusion method, P. aeruginosa strains showed the most (97.9%) resistance against imipenem and meropenem and the least (45.8%) against colistin. Thirty-six (75%) out of the 48 isolates were multidrug resistant. PCR amplification of β-lactamase genes showed the presence of blaVIM genes in 7 (14.6%) and blaIMP in 15 (31.3%) strains. Also, blaSME, SPM, GIM, AIM and NDM genes were not observed in any of the strains. We only found a statistically significance difference between the presence of blaIMP gene and multidrug-resistant (MDR) positivity and source of specimen (p=0.009 and 0.002, respectively). Conclusion: Rapid and reliable identification of MBLs appears to be necessary for effective treatment of related infections. Besides, our results may provide useful perception to make a more appropriate choice of antibiotics, which may put a stop to carbapenem-resistant infections.