Frequency of Metallo-β-Lactamases and Carbapenemase Enzymes in Clinical Isolates of Pseudomonas aeruginosa

Due to the increased prevalence of antibiotic resistance to beta-lactam and carbapenem compounds, the identification of beta-lactamase-producing enzymes is essential for the timely treatment of such isolates. The study aimed to determine the prevalence of Metallo-β-Lactamases (MBL) and Klebsiella Pneumoniae Carbapenemase    (KPC) genes among Pseudomonas aeruginosa clinical isolates.

In this cross sectional- descriptive study a total of 97 clinical isolates were collected from hospitalized patients of Hamadan hospitals from November 2017 to May 2018. After confirmation of the isolated strains, antibiotic susceptibility of the isolates was determined by disk agar diffusion, Minimum Inhibitory Concentration (MIC) was performed for imipenem using Etest method, Combined Double-Disk Test (CDDT) and Modified Hodge test (MHT) and identification of carbapenemase genes was performed by Polymerase Chain Reaction (PCR).

The results of statistical analysis showed that the highest antibiotic resistance was to cefoxitin, 92 (94.8%), and the lowest antibiotic resistance was to piperacillin-tazobactam, 38 (39.2%). Among the carbapenem antibiotics, the highest antibiotic resistance was to imipenem 48 (49.4%). Among of 49 (50.51%) carbapenem-resistant isolates, 42 (85.71%) had positive results for MIC, 26 (53.06%) and 25 (51.02%) isolates had positive results for IMP / EDTA (CDDT) and MHT test respectively. PCR results also showed that the highest and lowest gene presence among resistant isolates was related to IMP, 20 (40.8%) and GIM gene, 6 (12.24%), respectively.

Results showed that a high percentage of P. aeruginosa isolates 49 (50.51%) were resistant to carbapenem antibiotics, and a high percentage of carbapenem-resistant isolates produced beta-lactamase genes.