Virulence Factors and Stability of Coliphages Specific to Escherichia coli O157:H7 and to Various E. coli Infection.

Characteristics of E. coli O157:H7-specific infection bacteriophages (O157 coliphages) and broad-host-range bacteriophages for other E. coli serotypes (broad-host coliphages) were compared. The burst sizes of the two groups ranged from 40 to 176 PFU/infected cell. Distributions of the virulence factors stx1, stx2, ehxA, and saa between the two groups were not differentiated. Broad-host-range coliphages showed lower stability at 70°C, in relation to O157 coliphages. However, O157 coliphages showed high acid and ethanol tolerance by reduction of only 22% and 11% phages, respectively, under pH 3 and 70% ethanol for 1 h exposure. Therefore, these results revealed that the O157 coliphages might be more stable under harsh environments, which might explain their effective infection of the acid-tolerant E. coli O157:H7.