Occurrence, antimicrobial resistance and molecular characterization of Salmonella spp. from broiler chickens in...

Salmonella spp. are major zoonotic pathogens associated with poultry, representing a significant public health concern due to their role in foodborne infections and the growing emergence of antimicrobial resistance. This study aimed to investigate the prevalence, antimicrobial resistance patterns, and resistance/virulence genes of Salmonella spp. isolated from broiler chickens in the Boumerdès region, Algeria. A total of 110 liver and spleen samples were collected from broilers at a local slaughterhouse between November 2023 and November 2024. Isolation and identification were performed using standard microbiological methods, serotyping, and PCR for resistance and virulence genes. Ten Salmonella strains (9.09%) were recovered, with S. Kentucky (60%) and S. Enteritidis (40%) as the predominant serovars. Antimicrobial susceptibility testing revealed high resistance to nalidixic acid (100%), ciprofloxacin (100%), nitrofuran (80%), and tetracycline (80%), while low resistance was observed against amoxicillin-clavulanic acid (20%), and aminoglycosides (≤ 10%)and sensitivity of 100% for colistin and cefotaxime. All isolates exhibited multidrug resistance (MDR) with sevendistinct resistance profiles (MARI: 0.2-0.6). Phenotypic testing showed no extended-spectrum β-lactamase (ESBL) production. PCR analysis confirmed the universal presence of the virulence gene invA in all isolates, while no blaCTX-M or qnrA genes were detected. In conclusion, Salmonella spp. isolated from poultry in Boumerdès showed worrying resistance to multiple antibiotic classes, including quinolones and tetracyclines, reflecting the impact of uncontrolled antimicrobial use in poultry farming. The detection of MDR strains highlights the urgent need for improved biosecurity, prudent antimicrobial stewardship, and the implementation of a One Health approach to mitigate risks to both animal and human health.