DISCUSSION
The goal of this study was to isolate and characterize bacteriophages against O8 E. coli, with special emphasis on those infecting O8:F18 ETEC, which were reported to be the most common in feces. In this study, sewage was collected from waste drainage of entire pig farms, which was considered to be a good source from which to isolate bacteriophages against O8 ETEC, especially since these farms had a record of post-weaning E. coli-related diarrhea. The percentages of bacteriophages isolated from sewage samples and fecal were 13 and 5%, respectively. This difference may be likely due to the pooling of feces from large numbers of animals that occurs in sewage and the use of 100 ml sewage samples versus 5 g feces samples. In this study, the rates of recovery of bacteriophages from sewage samples were 50% from March until June and 16.7% in November and December suggesting a substantial seasonal effect on the isolation of bacteriophages. Furthermore, higher isolation rates in the warmer months have been reported for other bacteriophages (Comeau and Krisch, 2005).