: “Biological and Molecular Characteristics of Salmonella Typhimurium Isolates in Poultry”

Abstract

Salmonella is considered to be one of the most important causative agents which infect animal causing great mortalities and various morbidity changes. Avian salmonellosis is a large group of diseases of poultry caused by the genus Salmonella. Twelve strains of Salmonella (10 chickens and 2 ducks) isolated from poultry flocks in different geographical areas and these isolates were serotyped as Typhimurium. All strains in this study were characterized by phenotypic and genotypic methods to compare the usefulness of the methods in epidemiological studies. The obtained results, the twelve local isolates of S.Typhimurium were sensitive to ten different antibiotics by percentage 91.7%, 83.3%, 75% and 50% .While 100%, 83.3% and 66.7% of the isolates were resistant to this antibiotics. All isolates could be classified as either invasive or cytotoxic according different assays. The results showed that, all isolates of S.T. were able to invade the Vero cells by different percentage (33.3% have high invasion capability, 41.7% have moderate capability and 25% have low capability) and the isolates with high invasiveness capability exhibited high epithelial cell cytotoxicity (ranged from 49% to 80%). Also, all strains were able to adhere to Vero cells by different degrees (75% of strains have high adherence capability while 25% of them have moderate capability). The molecular characterization of Egyptian isolates were performed using sequence analysis of invA whole gene of most invasive strain that amplified by PCR technique by specific synthetized primers and all of S.T. strains have invA gene at specific molecular size (2058 bp). Sequencing of invA gene of the local isolate has been done for characterization and to detect the similarity and differences between it and the reference strains (isolates) all over the world. The nucleotide sequence of the highly virulence Egyptian isolate collected in 2014 was determined and encoding a 685 amino acid polypeptide then compared with invA gene of S.T. published sequences on Genbank. The results of the homology percentage of nucleotide and amino acid sequence leading us to say that the Egyptian S.Typhimurium strain has high similarity with other published S.Typhimurium strains (~99%) which use in antigen or vaccine production, so this local strain can be used in vaccine production in the future instead of other international strains.