EFFECT OF ANTIMICROBIAL AGENTS, ESPECIALLY FOSFOMYCIN, ON THE PRODUCTION AND RELEASE OF VERO TOXIN BY ENTEROHEMORRHAGIC ESCHERICHIA-COLI O157-H7

In 1996, Japan had several large outbreaks of enterohaemorrhagic Esche richia coli (EHEC) O157:H7 infection. We surveyed physicians who exami ned and treated these patients, and found that most of the patients (9 5.9%) received antimicrobial agents as treatments, in particular, fosf omycin comprised 84.0% of the prescribed treatment. Since the administ ration of antimicrobial agents for EHEC infection is under discussion, we also analyzed the effects of 7 antimicrobial agents including fosf omycin on the production and release of Vero toxins (VTs) by EHEC. The addition of fosfomycin into EHEC culture in CAYE broth at 5 h after t he start of incubation caused a marked increase of VT1 release and pro duction, as revealed by an immunological toxin assay (RPLA). However, a cytotoxicity assay of Vero cells showed a small increase of biologic al activity in the specimens treated with fosfomycin because the Vero cell assay reflects total cytotoxicity of VT1 and VT2. These results i ndicate that further study is necessary before concluding whether anti microbial agents actually worsen an EHEC infection.