Characteristics of stx-Converting Phages of EHEC O157

In this communication, we analyzed primarily an O157 strain isolated during the EHEC outbreak in Tokyo and revealed that all stx-converting phages examined were lambdoid and induced with ultraviolet light or norfloxacin and that an optimal dosage required for induction and patterns of time course in VT-specific DNA synthesis and toxin release were essentially similar to those in an O157 Sakai strain as described in the previous report. But the relationship appears to be rather remote between stx-converting phages lysogenized in O157 strains prevalent in Sakai city, west of Japan and those in O157 strains prevalent in Tokyo and Nagano, east of Japan in 1996, since the immunity is different from each other. Thus, stx-converting phages derived from the same hosts or the same prevalent area are related to each other but lower degree of relatedness is observed for those derived from different years and areas. These results may be accounted for by a hypothesis of the presence of a cassette of lysis genes associated with an stx gene that is mutually exchangeable by recombination between these phages.継続後誌:近畿大学先端技術総合研究所紀要 = Memoirs of Institute of Advanced Technology, Kinki Universit