七ヶ宿ダムの大腸菌群汚染について

概要

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Fecal contamination occurred in ichigashuku Dam during summer months were investigatedto develop effective control strategies. The phenotypic and genotypic methods were applied to identify sources of fecal indicator organism, Escherichia coli isolated from the dam. The phenotypic characterization of E. coli isolates was based on the biochemical API 20E test system, whereas the genetic relationship of strains was assessed by using rep-PCR DNA fingerprinting. Total coliforms counts in the dam varied seasonally and increased significantly from July to October. The number of totalcoliforms in summer was higher than 1000MPN/100mL,which was Japanese standard value for a A-typelake. Most of E.coli strains isolated from the dam showed the similar phenotypic and genotypic profiles to those isolated from the upper reaches of the dam. Although it became unclear where the fecal pollution was derived from, E.coli isolates from Yokogawa and Kumazawa Bridge closely related to those from the dam according to the combined API and DNA based similarity coefficients.