Escherichia phage sp.
This study aimed to characterize eight newly isolated phages for the control of E. coli mastitis, a major production disease in dairy cattle, and to investigate the specificity of phage interactions with their bacterial hosts. Physico-chemical characterization of phages was performed, followed by in vitro stability and lytic activity assays in raw and heat-treated milk. Genome sequencing of phages and bacteria was performed to determine the proteins involved in the phage attachment. The host range specificity was linked to the diversity of the bacterial collection and to the presence of two receptor-binding proteins (RBP) among Tevenvirinae. Indeed, several bacterial serogroups and sequence types were identified, and the structural similarity of the RBPs revealed a variable region in the long tail fiber and a more conserved short tail fiber. Phage stability was maintained across physiological pH and temperature ranges, as well as in raw and heat-treated milk. Phage lytic activity demonstrated bacterial decreases below detection level, but regrowth occurred in raw milk after 5h of incubation for 4/8 phages, suggesting resistances. In conclusion, phage specificity was mainly associated with the long tail fiber and milk components didn't hinder the effectiveness of phages to control bovine mastitis, although resistances should be investigated.