Isolation and Characterization of a Coliphage Specific for Escherichia coli 0157:H7.

Enterohemorrhagic Escherichia coli serogroup 0157:H7 is harbored by cattle and causes bloody diarrhea and hemolytic uremic syndrome in persons who consume raw milk and under-cooked beef. Samples of manure from Wisconsin dairy farms were tested for the presence of E. coli 0157:H7 as well as for bacteriophages (coliphages) specific for this microorganism. No E. coli 0157:H7 bacteria were isolated from any of the 21 manure samples taken from 12 farms. Nineteen of 20 samples yielded "nonspecific" coliphages that produced plaques both on 0157:H7 and on other E. coli . Only one sample yielded a coliphage that plaqued on 14 strains of 0157:H7 but not on other E. coli . This coliphage, designated "AR1," is tailed and ca. 187 nm long; it produces distinct plaques ca. 0.5 mm in diameter; single-step growth experiments showed a latent period of 20 to 25 min and a burst size of 34 progeny plaque-forming units (PFU). AR1 was also tested against other enterobacteria, including: Escherichia hermanii , four species of Salmonella , four types of Yersinia enterocolitica , and a strain of Shigella dysenteriae which produces an enteric toxin similar to that produced by E. coli 0157:H7. Of these enteric bacteria, only S. dysenteriae yielded plaques, which suggests that there is a relationship between production of this toxin and susceptibility to coliphage AR1. Coliphage AR1 may be useful in detecting or identifying E. coli 0157:H7 and possibly other bacteria producing the same toxin, from human stool, animal manure, and food samples.