Prevalence of Antimicrobials and Virulence-Related Genes in Salmonellae Detected in Local Hatcheries in Northern Upper Egypt

Salmonellosis represents a critical problem not only to the poultry producers owing to it is economic impact, but also for poultry consumers due to it is zoonotic health problems. In the present study avian Salmonellae were isolated from local hatcheries in 2 Egyptian governorates, Beni Suef and El Fayoum, during the period from May, 2018 until November, 2019. Samples were collected from 16 local chicken hatcheries in Beni Suef (N=12) and El Fayoum (N=4) governorates. Specimens were collected from liver of dead in shell embryos. Salmonella isolation was successful in 31.25% of the samples. Serotyping revealed detection of S. kentucky, S. sinchew, S. infantis S. larochelle, and S. colindale . Salmonellae examination for antimicrobial susceptibility by disc diffusion method showed resistance to several antimicrobial drugs including [penicillin, amoxicillin, cefradine and streptomycine (no sensitivity at all) followed by apramycin and tetracyclines (25% sensitivity for each)]. On the other hand, Salmonellae were sensitive to enrofloxacin (100%) fosfomycin (75%) and sulphamethoxazole-trimethoprime (75%). Molecular screening of both virulence and drug resistance genes revealed the harboring of invA, stn, avrA virulence genes by all isolates. Phenotypic and genotypic variation in drug resistance was observed for different serovars and different classes of antimicrobial agents; S. infantis and S. larochelle were positive for PCR targeting qnrA gene although phenotypically they were sensitive to enrofloxacin. All of the tested serovars (except S. colindale ) showed sensitivity to sulphamethoxazole-trimethoprime although they harbored sul1 gene. At the same time S. colindale harbored tetA gene and it was sensitive to oxytetracycline by disc diffusion. Similar discrepancy was observed for florfenicol and some aminoglycosides.