ISOLATION AND CHARACTERIZATION OF A COLIPHAGE SPECIFIC FOR ESCHERICHIA-COLI-O157-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 undercooked beef. Samples of manure from Wisconsin dairy faillis 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. Copyright © International Association of Milk, Food and Environmental Sanitarians.