Virulence Genes and Pathogenicity Assessment of Salmonella Isolated From Diseased Chickens

This study emphasizes Salmonella infections in broiler farms to monitor and notify the growing threat of antimicrobial resistance and its impact on public health. During the first half of 2024, 14% (14/100) of broiler farms were positive for Salmonella. Five serotypes were identified; the most prevalent were S. enteritidis (35%) and S. typhimurium (28%), followed by S. Kentucky (21%), and less commonly S. Infantis and S. virchow (7% each). Antibiotic susceptibility testing revealed multidrug resistance (MDR) across isolates, showing high resistance to lincomycin (85.7%) and significant resistance to β-lactams (Ampicillin: 42.8%, Ceftriaxone: 28.5%). Colistin sulfate demonstrated the highest efficacy with sensitivity percent 85.7%.The pathogenicity index (PI) evaluated for different serotyped found that there are four serotypes (S. enteritidis, S. typhimurium, S. kentucky, and S. virchow) which classified as intermediately pathogenic, while S. Infantis exhibited as low pathogenicity index. PCR analysis detected three virulence genes (invA, spvC, avrA) in all isolates, with percentage 100%. This study reinforces the critical function of virulence factors and MDR in Salmonella-associated pathogenicity and underscores the importance of robust biosecurity measures, prudent antibiotic use, and continued surveillance to mitigate risks in poultry production and public health.