Evaluation of β-lactamases and Molecular Typing of Pseudomonas aeruginosa Clinical Strains Isolated from Hospitalized Children in Tehran

 The opportunistic human pathogen, Pseudomonas aeruginosa, is a critical cause of nosocomial infection with high morbidity and mortality rate. Eradication of P. aeruginosa has been troublesome due to its high capacity to develop strong multidrug resistance (MDR).

 The purposes of this study were to define the pattern of antimicrobial sensitivity, typing, and prevalence of metallo-β-lactamase (MBL) and detect the oprD, blaCTX-M, blaSHV, blaTEM, blaIMP, blaNDM, and blaVIM among clinical isolates of P. aeruginosa collected from Tehran hospitals.

 Clinical isolates were collected from hospitalized children in selected hospitals in Tehran from March 2019 to February 2020. The antimicrobial susceptibility test (AST) was performed by the Kirby-Bauer disk diffusion method. Composed disc diffusion tests were performed to screen MBL production. MBLs and extended-spectrum β-lactamases (ESBL) encoding genes were amplified by polymerase chain reaction (PCR). Amplification of the oprD gene were performed for carbapenem-resistant P. aeruginosa. Random amplified polymorphic DNA (RAPD-PCR) Fingerprinting was used for genotyping the isolates.

 A total of 80 P. aeruginosa isolates were collected. Isolates were resistant to cefepime 35%, ceftazidime 20%, ciprofloxacin 22%, tazobactam 16%. Out of 80 isolates, 16 were carbapenems-resistant. Gentamicin, tobramycin, and amikacin had the highest susceptibilities of 85%,90%, and 90%, respectively. OprD, blaCTX-M, blaSHV, and blaTEM were detected in 80(100%), 36(45%),22 (27.5%), 17 (21.25%), and 1 (1.25%) blaIMP and blaNDM, respectively. In this study, the blaVIM gene was not detected in the isolates, and no mutation was observed regarding the presence of an insertion element in the OprD gene. Isolates were divided into 13 and 14 common and single types, respectively.

 P. aeruginosa isolates showed a high rate of β- lactamases production, and the prevalence of carbapenem-resistant, which can be related to different mechanisms, was alarming. On the other hand, the results demonstrated that there was beta-lactam antibiotic resistance and clonal spread among the hospital population. This shows the necessity of molecular surveillance in tracking beta-lactamase-producing strains.