Abstract
Among 30 strains of leptospires isolated from samples of sewage taken before and during treatment at two sewage plants in England, only one appeared to belong to Leptospira interrogans, the species that comprises the leptospires that are pathogenic to man and animals. That strain, Compton 746, was isolated from settled sewage, before treatment at a treatment plant that deals mainly with human sewage. It was shown serologically to belong to serogroup Tarassovi and appears to represent a new serovar that has been named mogdeni after the name of the sewage plant, Mogden, from which it was isolated.