Pandrug-Resistant Pseudomonas Aeruginosa Isolated from a 4-Year-Old Indigenous Horse with Respiratory Distress: Current AMR Challenges

Abstract

Respiratory diseases in equids are frequently complicated by opportunistic Gram-negative pathogens capable of biofilm formation, which shields them from both host immunity and therapeutics. This report details the isolation of a pandrug-resistant (PDR) Pseudomonas aeruginosa strain from a 4-year-old indigenous Arewa horse presenting with respiratory distress and bilateral nasal discharge in Zaria, Nigeria. Standard microbiological processing of nasal swabs at the AMR Sentinel Laboratory, Department of Veterinary Microbiology, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria yielded non-lactose fermenting, Gram-negative, motile bacilli that were oxidizers and phenotypically identified as P. aeruginosa. In vitro antimicrobial susceptibility testing via the Kirby-Bauer disc diffusion method, interpreted using CLSI (2026) guidelines, revealed total resistance across all tested pharmacological classes of antimicrobials. The isolate demonstrated clinical resistance to Ertapenem, Ampicillin, Nalidixic acid, Ceftizoxime, Tetracycline, and Sulphamethoxazole-trimethoprim, and intermediate resistance to Streptomycin, confirming its PDR classification. With resistant P. aeruginosa already driving fatal healthcare-associated infections in Nigerian hospitals, this interspecies dissemination underscores a critical breakdown in antimicrobial stewardship, demanding urgent epidemiological surveillance and biosecurity interventions.