First Survey of Metallo-β–Lactamase Producers in Clinical Isolates of Pseudomonas aeruginosa From a Referral Burn Center in Kurdistan Province

Background: Treatment of infectious diseases is becoming more challenging with each passing year. This is especially true for infections caused by Pseudomonas aeruginosa, an opportunistic pathogen with the ability to rapidly develop resistance to multiple classes of antibiotics.

Objectives: This study was conducted to determine the prevalence of metallo-β-lactamase (MBL)–producing strains among multidrug-resistant P. aeruginosa strains isolated from burn patients.

Materials and Methods: The isolates were identified, tested for susceptibility to various antimicrobial agents, and screened for the presence of MβLs by using the double-disk synergy test. The minimal inhibitory concentration of imipenem was determined by microplate broth dilution method on Mueller-Hinton agar. To detect VIM, SIM, and GIM MBLs, the isolates were subjected to polymerase chain reaction.

Results: In this study, we identified 100 P. aeruginosa isolates from 176 clinical specimens obtained from burn patients. The isolates showed maximum resistance to ampicillin (100%), ceftazidime (94%), and ceftriaxone (89%). The CLSI-MBL phenotypic test showed that of the 100 P. aeruginosa isolates, 22 (22%) were positive for MBL production in the double-disk synergy test. Of the 22 MBL-positive P. aeruginosa isolates, 8 were resistant to imipenem. PCR analysis showed that 8 isolates were positive for blaVIM1. The other genes blaSIM1 and blaGIM1 were not detected.

Conclusions: The study results demonstrate the serious therapeutic threat of the spread of MBL producers among P. aeruginosa populations. Metallo-β-lactamases were detected in 22% of imipenem-resistant P. aeruginosa isolates. Early detection and infection-control practices are the best antimicrobial strategies for this organism; therefore, systematic surveillance to detect MBL producers is necessary.