Genotypic Characterization of β-Lactam Resistance Genes in Non-fermenting Gram-negative Bacilli Isolated from Canine Infections

Abstract

The growing emergence of multidrug-resistant non-fermenting Gram-negative bacilli in canine infections necessitates the molecular characterisation of key resistance and virulence determinants. This study investigated the genotypic basis of β-lactam resistance in Acinetobacter spp. and Pseudomonas aeruginosa recovered from clinical cases in dogs. The investigation was conducted in the Department of Veterinary Microbiology, College of Veterinary Science and Animal Husbandry, DUVASU, Mathura, Uttar Pradesh, India, between February 2024 and June 2025. Samples were collected aseptically from cases of otitis, wounds, pyoderma, conjunctivitis, abscesses, cysts, pyometra, and urinary tract infections. A total of 72 characterised isolates, including 63 Pseudomonas spp. and 9 Acinetobacter spp., were subjected to PCR assays targeting extended-spectrum β-lactamase genes (blaTEM, blaOXA-1, blaSHV, blaCTX-M, and blaOXA-51). Of the 402 samples, 332 (82.6%) yielded bacterial growth, from which 63 Pseudomonas spp. and 9 Acinetobacter spp. were identified. Molecular detection revealed that blaTEM (52.4%) and blaCTX-M1 (39.7%) predominated among Pseudomonas isolates, whereas Acinetobacter isolates harboured blaCTX-M1 (44.4%), blaTEM (33.3%), and blaOXA-51 (11.1%). The presence of resistance genes underscores the clinical significance of these pathogens in canine infections and highlights the importance of continuous molecular surveillance to guide judicious antimicrobial therapy in veterinary practice.