Comparative Study of Screening Methods for Detection of Metallo-β-lactamase Production in Pseudomonas aeruginosa

A BSTRACT Introduction: Pseudomonas aeruginosa is a leading cause of nosocomial infections, particularly among hospitalized and critically ill patients. The emergence of metallo-β-lactamase (MBL)-producing P. aeruginosa has become a major therapeutic and infection control challenge due to resistance to carbapenem antibiotics. Early detection of MBL-producing isolates is essential for appropriate antimicrobial therapy and to prevent the spread of antimicrobial resistance. This study aimed to detect MBL production in imipenem-resistant clinical isolates of P. aeruginosa using the combined disk test (CDT), E -test, and modified carbapenem inactivation method (mCIM). Materials and Methods: Clinical specimens received in the microbiology laboratory between July 2022 and December 2023 were processed for the isolation and identification of P. aeruginosa using standard phenotypic methods. Antimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute 2022 guidelines. Imipenem-resistant isolates were screened for MBL production using the CDT, E -test, and mCIM. Results: Atotal of 105 imipenem-resistant P. aeruginosa isolates were evaluated. Twenty (19.04%) isolates were positive for MBL production by all three phenotypic methods. Individually, the E -test detected MBL production in 52 (49.52%) isolates, the CDT in 50 (47.61%), and the mCIM in 45 (42.85%) isolates. Conclusion: The CDT, E -test, and mCIM are useful phenotypic methods for detecting MBL production in P. aeruginosa . Although each method differs in sensitivity and detection rate, their use can facilitate early identification of MBL-producing isolates, support appropriate antimicrobial therapy, and strengthen infection control measures to limit the spread of carbapenem-resistant P. aeruginosa .