Prevalence and Characteristics of Metallo-beta-Lactamase-positive and High-risk Clone ST235 Pseudomonas aeruginosa at Ardabil Hospitals

Carbapenems are the most commonly administered drugs for the treatment of multidrug-resistant Pseudomonas aeruginosa (MDR P. aeruginosa) infections. However, carbapenem-resistant P. aeruginosa is spreading rapidly and has led to a new threat to human health worldwide.

The current study aimed to determine the prevalence of imipenem-resistant P. aeruginosa, detect metallo-β-lactamase (MBL)-producer isolates, and evaluate their clonal relationships in strains isolated from patients referring to the hospitals of Ardabil city, Iran.

The resistance rate to imipenem was evaluated using the disk diffusion method. Double-disk synergy test and PCR technique were used for phenotypic and genotypic screening of MBL-positive P. aeruginosa, respectively. Ultimately, enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and multilocus sequence typing (MLST) methods were used for assessing clonal relatedness among the isolates.

The prevalence of imipenem-resistant P. aeruginosa strains was estimated at 57.1% (48 out of 84 isolates). In addition, 45 (93.7%) out of 48 imipenem-resistant P. aeruginosa isolates were phenotypically screened as MBL-positive, among which 16 (35.5%) and three (6.6%) isolates harbored blaIMP and blaVIM-1 genes, respectively. However, blaNDM, blaSIM-2, blaSPM, and blaGIM-1 genes were not detected in this study. MBL-producing P. aeruginosa strains were divided into 42 ERIC-PCR types. Based on the results of MLST, P. aeruginosa ST235 was the only identified sequence type.

Our results revealed a high and alarming prevalence of imipenem-resistant and blaIMP-positive P. aeruginosa ST235 at Ardabil hospitals. Continuous monitoring is essential to control the further spread of this highly virulent and drug-resistant clone.