Phylogenetic analysis of Salmonella species isolated from cows, buffaloes, and humans based on gyrB gene sequences

This study aimed to investigate the role of dairy cows and buffaloes as reservoirs of nontyphoidal salmonelloses (NTS), to reveal the occurrence of NTS among dairy workers and children with acute diarrhea and to study the gyrB gene phylogenetic relations of the obtained Salmonella strains, 300 samples were chosen randomly from clinically infected animals, including 100 feces and 50 raw milk from buffaloes and cows. Five hundred samples were chosen randomly from healthy animals, including 150 feces and 100 raw milk from buffaloes and cows. A total of 160 stool samples were randomly chosen from healthy workers (60) and children with acute diarrhea (100). Salmonella species were isolated from the examined samples and identified by polymerase chain reaction. Sequencing and phylogenetic analyses of gyrB gene were also performed. S. enteritidis and S.typhimurium were isolated from 0.5% (2/400) of the cows and buffaloes, respectively. Dairy workers were found to be at greater risk of exposure to Salmonella infection (5%) than children (1%). S. enteritidis was isolated from 1.7% (1/60) of dairy workers. S. typhimurium was isolated from 3.33% (2/60) and 1% (1/100) of dairy workers and children, respectively. Phylogenetic analysis of Salmonella species gyrB gene sequences from both animals and humans falls inside one clade, and all of them were closely related to each other with less significant genetic distance (99.9:100). In conclusion, cows and buffaloes act as reservoirs of Salmonella infection in dairy farms in Egypt and contribute a risk of zoonotic transmission to human.