Abstract
The current study aimed to survey the prevalence, antimicrobial resistance, and virulence-associated genes of Salmonella enterica recovered from broiler chickens farms located in North coast, Egypt. A total of 200 broiler chickens’ cloacal swabs and farm environmental samples were randomly collected from four small scale broiler chicken farms at 5 weeks of production cycle. It was recorded that out of 200 samples, Salmonella species were identified in 26 (13%) samples. Salmonella strains were observed in 16% (16/100) of cloacal swabs, 10% (10/100) of environmental samples. S. Enteritidis (6%) was the most common identified serotypes followed by S. Kentucky (4%), S. Shangani (2.5%) and S. Virchow (0.5%). The antimicrobial susceptibility testing revealed absolute resistance to SXT (88.5%) followed by AMC and AMP (65.4% and 61.5%, respectively). On the other hand, lower rates of resistance were observed for DO (50%), CTX (42.3%), CEC (30.8%) and CIP (19.2%). Interestingly, only one isolate was resistant to IMP (3.8%). PCR targeting 5 virulence genes (invA, ompA, ompF, stn and pefA) were performed to detect the virulence of identified Salmonella serovars. Generally, all Salmonella isolates showed at least two virulence-associated genes. Of note, invA gene (genus specific gene) was detected in 100% (26/26) of the isolates. On the contrary, pefA gene was completely absent in all isolates. Finally, it was concluded that S. Enteritidis was the most common identified serotypes in the examined sources. Circulation of such strains in broiler farms required introducing special biosecurity measures for control of Salmonella. Such measures might limit the adverse effects of antibiotics and ensure the safety of the environment and animal-derived food.

Key words: Salmonella, broilers, Prevalence, antibiotic resistance, Virulence