Background and aim: Salmonellosis is one of the most common foodborne bacterial diseases in the world. The great majority of Salmonella infections in humans are foodborne with Salmonella enterica and Salmonella Typhimurium accounting for a major part of the problem. The objective of this study was to investigate the presence of invA gene in strains of Salmonellae isolated from eggs and diarrheal swabs from human cases. In addition, the relationship between invA gene nucleotide sequences from different sources (human stool and egg samples) have been studied through phylogenetic tree.
Materials and methods: One hundred and seventy eggs (eggshell and its contents) and 160 stool swabs samples were collected from four poultry farms and medical hospital in Giza Governorate.
Results: The study reported the presence of two Salmonella strains in eggshell surface with an overall isolation rate of 1.2 and 0% of the egg content. Salmonella Enteritidis and Salmonella Typhimurium were isolated from eggshell surface with an incidence of 50% for each strain. Six salmonella strains were isolated from human stool with an incidence of 3.75%; the isolated strains are S. Typhimurium, S. Enteritidis, Salmonella Virchow, Salmonella Haifa, and Salmonella Kentucky with an incidence of 33.3%, 16.6%, 16.6%, 16.6%, and 16.6%, respectively. Among eight Salmonella strains, invA gene was detected with percentage of 50%. The phylogenetic analysis of the sequences invA gene, from two isolates included in this study and five isolates retrieved from GenBank showed that sequence from human, layer hens, egg, and water in the same clusters.
Conclusion: Close relation between drinking contaminated water and layer hens and contaminated water is one such source.
Keywords: Salmonella; invA gene; phylogeny.