Serotypes Diversity, Virulence, and Antimicrobial Resistance of Non-Typhoidal Salmonella Isolates in Commercial and Backyard Egg Production Systems in Egypt

Multi -drug resistant (MDR) non -typhoidal Salmonella in poultry food chain are emerging worldwide. This study aimed to estimate the serotypes diversity, virulence and antimicrobial resistance traits of nontyphoidal Salmonella in commercial and backyard egg production systems in Kafrelsheikh Governorate, Egypt. A total of 610 samples (200 egg shells, 200 egg contents, and 210 environmental samples) were collected from 10 commercial layers farms and 170 samples (50 egg shells, 50 egg contents, and 70 environmental samples) were collected from 10 backyard layers flocks. The overall prevalence of Salmonella was 4.1% for each production system. Six commercial flocks (60%) and three backyard layers flocks (30%) harbored at least one Salmonella isolate. The prevalence rates of Salmonella spp. in eggs and environmental samples from commercial layers flocks were 2.5% (10/400) and 7.1% (15/210), respectively. The prevalence rates of the same samples in backyard production were 6% (6/100) and 1.4% (1/70), respectively. The egg shell contamination positively associated with Salmonella detection in egg cartoon trays in commercial layers farms (Pearson's R= 0.8, P = 0.004). The serotype distribution was as follows: S. Typhimurium 1.3%, S. Enteritidis 1.03%, S. Kentucky 0.8%, S. Infantis 0.3%, S. Molade 0.3%, S. Tamale 0.3%, S. Labadi 0.1%, and S. Papuana 0.1%. The fimH, hilA, stn, and sopA virulence genes were detected in 46.8%, 37.5%, 31.3%, and 40.6% of isolates, respectively. Around two thirds (59.4%) of Salmonella strains were resistant to at least one antibiotic and 12 isolates (37.5%) were MDR. The study highlighted the wide -spread of MDR Salmonella in egg production systems in study region. Extended surveillance and veterinary monitoring of antibiotics use in this sector are mandatory for public safety.