Molecular Detection of Metallo-β-Lactamase-Encoding Genes in the Clinical Isolates of Acinetobacter baumannii: A...

The rise of multidrug-resistant Acinetobacter baumannii, particularly in healthcare settings, poses significant treatment challenges. Detecting metallo-β-lactamase (MBL)-encoding genes in these isolates is crucial for understanding resistance mechanisms and guiding effective infection control strategies.

The study aims (i) to evaluate the antibiotic susceptibility and resistance profiles of Acinetobacter baumannii and (ii) to detect MBL-encoding genes in multidrug-resistant isolates using multiplex polymerase chain reaction (PCR).

A prospective cross-sectional study was conducted over 18 months (January 2023 to June 2024) at a tertiary care center. Ninety-four nonduplicate Acinetobacter baumannii isolates from various clinical samples collected from wards and ICUs were identified and tested for antimicrobial susceptibility using the VITEK 2 system (bioMérieux, Marcy-l'Étoile, France). PCR was used to identify the blaOXA-51-like gene, and all 94 nonduplicate isolates were screened for MBL genes (blaVIM, blaIMP, blaNDM, and blaGIM) using multiplex PCR.

Of the 94 clinical Acinetobacter baumannii isolates, 41.48% were from ICU and emergency units. High resistance rates were observed for cephalosporins (92.56%) and carbapenems (imipenem 78.72%; meropenem 84.04%). A total of 79 (84.04%) isolates were identified phenotypically as carbapenem-resistant Acinetobacter baumannii (CRAB), all of which were positive for the blaOXA-51 gene. PCR screening of all 94 isolates revealed the presence of MBL-encoding genes in 68 isolates (72.34%), with blaNDM detected in 61 (64.89%), blaIMP in 11 (11.70%), blaVIM in six (6.38%), and blaGIM in four (4.25%) isolates. Coexistence of multiple MBL genes was observed in 11 (11.70%) isolates, predominantly the blaNDM + blaIMP combination in four (4.25%) isolates. A rare combination of blaNDM + blaVIM + blaIMP was identified in three isolates.  Conclusion: 72.34% of the total 94 Acinetobacter baumannii isolates harbored MBL genes, primarily blaNDM (61/94, 64.89%). The coexistence of multiple MBL genes in device-associated infections underscores the need for early detection to prevent transmission and reduce mortality. Prudent antibiotic use, continuous surveillance, and robust stewardship are essential for controlling MBL resistance. Given that this study was conducted at a single tertiary care facility, further research is needed to validate these findings in diverse healthcare settings.