Prevalence of Carbapenem-resistance and Molecular Detection of Carbapenemase Genes of blaIMP-1 and blaVIM-2 in Pseudomonas aeruginosa isolated from Ventilated Intensive Care Unit Patients

Pseudomonas aeruginosa (P. aeruginosa) is a life-threatening pathogen in intensive care unit (ICU). The rise of bacterial resistance to carbapenem is a major global health concern due to dwindling treatment options. This study investigated the prevalence of carbapenem-resistant P. aeruginosa (CRPA) and its imipenemase-1 metallo-β-lactamase (blaIMP-1) and verona-integron encoded metallo-beta-lactamase 2 (blaVIM-2) genes in ventilated ICU patients. From November 2024 to March 2025, 150 respiratory samples (sputum and bronchial wash) were collected from ICU patients in Sulaymaniyah, Iraq. The isolates were identified using standard microbiological examinations, the BD Phoenix™ M50 system and 16S rRNA sequencing for CRPA isolates only. Carbapenemase activity was phenotypically assessed via the modified carbapenem inactivation method (mCIM), while polymerase chain reaction was used to target the carbapenemase-encoding genes. The prevalence rate of P. aeruginosa was 33.3% (50/150), including 6.6% (10/150) CRPA among all patients and 20% (10/50) CRPA in P. aeruginosa positive cases. Clinically significant antimicrobial resistance patterns of 5 (10%) MDR and 8 (16%) XDR were observed in P. aeruginosa, predominately including CRPA in both categories. Genotypic analysis revealed that none of the CRPA isolates carried the blaVIM-2 gene, whereas 20% (2/10) isolates harbored the blaIMP-1 gene in chromosomal DNA and plasmid-enriched DNA, suggesting potential plasmid association and horizontal gene transfer risk. The mCIM assay also confirmed carbapenemase activity only in blaIMP-1 gene positive isolates, suggesting that other resistance mechanisms may play a role in evading carbapenems. This study underscores an urgent need for intensive molecular surveillance in ICU, as the plasmid-mediated blaIMP-1 gene could lead to hardly controllable nosocomial infections.