Occurrence, antimicrobial susceptibility and genomic characterization of Salmonella enterica isolated from milk and related sources

Salmonellosis is a common foodborne bacterial disease of major public health concern in the world, especially in developing countries. The study sought to identify and characterize the genetics and antimicrobial resistance attributes of Salmonella enterica isolated from milk and related sources, totally 250 samples. Bacteria identification was done using a modified procedure of BAM of US-FDA and antimicrobial resistance was evaluated using the Kirby-Bauer disk diffusion method whereas a partial fragment of the invA gene was amplified and sequenced for molecular characterization. Salmonella enterica was recovered from 14.8% of the studied samples of raw milk, faecal matter from cows, milk collection utensils and hand of milkers. Averagely, antimicrobial susceptibility and resistance were 68.86% and 18.86%, respectively. Meanwhile, Imipenem recorded 100% susceptibility, Teicoplanin recorded 100% resistance with MAR Index being 0.11–0.77. Five sequences were identified as Salmonella enterica subsp. enterica with 99.04–100% identity to serovars like Typhimurium, Enteritidis, Kentucky, Agona and Anatum. Polymorphism within the DNA sequences revealed four haplotypes having 10 segregating sites and neutrality indices indicating an increasing S. enterica population demographics in the study area. Evolutionary studies revealed monophyletic relation among isolates of the present study and paraphyletic relation to isolates of other studies in Africa.