Antimicrobial Susceptibility Profile of Salmonella Isolates from Veterinary Specimens in Owerri, Imo State, Nigeria

The antimicrobial susceptibility profile of Salmonella isolates obtained from veterinary specimens in Owerri was investigated. Chicken and pig faecal samples were aseptically collected, cultured, and identified using standard microbiological techniques, including morphological and biochemical characterization. Antimicrobial susceptibility testing against ten antibiotics was performed using the Kirby–Bauer disk diffusion method, while plasmid detection was carried out using the alkaline lysis method. A total of 100 Salmonella isolates were recovered from both sources. Isolates from chicken faeces exhibited higher resistance rates compared to those from pig faeces. Specifically, chicken isolates showed high resistance to Ampicillin (100%), Cefotaxime (96%), Ceftazidime (94%), Imipenem (86%), Meropenem (86%), Ciprofloxacin (74%), Ertapenem (96%), and Levofloxacin (78%), with moderate resistance to Aztreonam (53%) and Gentamycin (54%). In contrast, pig isolates showed high resistance to Ampicillin (98%), Cefotaxime (100%), Aztreonam (90%), Imipenem (96%), Ceftazidime (100%), and Meropenem (76%), moderate resistance to Ciprofloxacin (38%), and low resistance to Gentamycin (22%) and Levofloxacin (28%).Multidrug-resistant (MDR) isolates were subjected to plasmid profiling and curing. Twenty-five non-typhoidal Salmonella isolates were analyzed. Post-curing results indicated incomplete elimination of plasmid-mediated resistance. Notably, chicken isolates gained resistance to three antibiotics after curing, while pig isolates lost resistance to only one antibiotic. These findings suggest partial success in plasmid elimination and highlight the complexity of resistance mechanisms. The increasing antimicrobial resistance observed among Salmonella isolates poses a significant public health threat and underscores the need for continuous surveillance and development of effective antimicrobial strategies.