Phenotypic and Molecular Detection of Metallo-β-Lactamase Genes and Antimicrobial Resistance Profiles among Clinical Pseudomonas aeruginosa Isolates from Intensive Care Unit Patients in Misurata, Libya

Abstract

Pseudomonas aeruginosa is an important cause of healthcare-associated infections in intensive care units (ICUs), where invasive devices and antimicrobial exposure promote multidrug resistance. This prospective cross-sectional study assessed antimicrobial resistance, phenotypic metallo-β-lactamase (MBL) production, and MBL-encoding genes among 83 non-duplicate clinical P. aeruginosa isolates recovered from ICU patients at Misurata Medical Centre, Libya, from September 2025 to March 2026. Antimicrobial susceptibility testing was performed by disk diffusion. Carbapenem-resistant isolates were screened using the imipenem–EDTA combined-disk method, while all isolates were tested by PCR for blaVIM, blaIMP, blaNDM, and blaSPM. Carbapenem resistance and multidrug resistance were detected in 50.6% and 59.0% of isolates, respectively. Respiratory specimens were the predominant source (56.6%). Phenotypic MBL production was detected in 71.4% of carbapenem-resistant isolates, whereas targeted MBL genes were identified in 32.5% of all isolates. blaVIM was the predominant gene (19.3%), followed by blaIMP (10.8%), blaNDM (8.4%), and blaSPM (1.2%). MBL gene-positive isolates showed significantly greater resistance to carbapenems and other tested antimicrobial agents. Previous carbapenem exposure and mechanical ventilation were independently associated with MBL gene carriage. The phenotypic test showed 92.6% sensitivity and 66.7% specificity compared with PCR. These findings highlight a substantial burden of MBL-associated resistance among ICU-derived P. aeruginosa in Misurata and support enhanced carbapenem stewardship, molecular surveillance, and infection-prevention measures.