The pathogenic potential and genetic attributes of Escherichia coli in milk from dairy cows with subclinical mastitis

The centrality of milk and dairy products to the human diet allows potential pathogens to pose a threat to human health. Pathogenic Escherichia coli is a zoonotic foodborne pathogen with many virulence genes which cause variations in its pathogenicity. The current study aimed to investigate the pathogenic potential of E. coli from milk of dairy cows with subclinical mastitis and evaluate the genetic relatedness to E. coli from human sources. The majority of the E. coli isolates belonged to the A (55.0%) and B2 (22.5%) phylogenetic groups and the most prevalent virulence genes were colV (90.0%), fyuA (75.0%) and vat (42.5%). Mice injected with G4-BD23 (P < 0.05) and G5-BD3 had lower survival rates than controls and visible pathological changes to lung and kidney. Nineteen MLST types were identified in 40 dairy E. coli isolates and three STs (ST10, ST48 and ST942) were shared with those from human sources. Some dairy E. coli isolates were phylogenetically related to human E. coli isolates indicating pathogenic potential.