Phenotypic and molecular characterization of carbapenem resistance among clinical isolates of Pseudomonas aeruginosa and Acinetobacter baumannii.

BACKGROUND

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) and Acinetobacter baumannii (CRAB) were listed on the WHO bacterial priority pathogens list in 2017. These gram-negative bacteria often cause healthcare-associated infections (HAIs), which pose an increasing threat to public health. This study aimed to isolate and identify CRPAs and CRABs from a tertiary care hospital in central Nepal and characterize carbapenem resistance genes at the molecular level.

MATERIALS AND

METHODS

A total of 59 isolates, including 27 Pseudomonas aeruginosa and 32 Acinetobacter baumannii, were collected from different clinical samples from April 2021 to December 2022. Antibiotic susceptibility was determined via the Kirby disc diffusion method. The modified carbapenem inactivation method (mCIM) was used for phenotypic confirmation of carbapenem resistance. Conventional polymerase chain reaction (PCR) was used to detect carbapenem resistance genes.

RESULTS

Among the 59 isolates, 76.3% were multidrug resistant (MDR), 63.0% were extended-spectrum beta-lactamase (ESBL), and 62.7% were carbapenem resistant. Among the carbapenem-resistant isolates (n = 37), 75.7% of metallo-beta-lactamase (MBL) producers and 70.3% carried at least one carbapenem resistance gene. The blaCTX-M gene was predominant among the ESBL-positive isolates, present in 58.8% of the P. aeruginosa isolates and 87.5% of the A. baumannii isolates, whereas 29% of both isolates harbored the blaTEM gene. Among the CR-PA isolates, 58.3% carried blaVIM-2, 16.7% carried blaNDM-1, and 8.33% carried blaOXA-23. Among the CR-AB isolates, 56% harbored blaOXA-23, 32% carried blaNDM-1, 16% had both blaNDM-1 and blaOXA-23, and 8% contained both blaOXA-58 and blaOXA-23.

CONCLUSION

This study highlights a significant burden of MDR and carbapenem-resistant P. aeruginosa and A. baumannii, with the co-occurrence of carbapenem resistance genes, in a clinical setting in Nepal. Our findings suggest that active surveillance of antibiotic resistance in pathogens could inform clinicians and healthcare providers about the treatment of infections.