No abstract

SUMMARY. The pathogenicity of 40 strains of Mycobacterium avium, M . paratuberculosis, M . intracellulare and M . lepraemurium was * investigated in chickens, rabbits, guinea-pigs, mice and calves. Mycobactin dependence and serological type were also determined. There was no evidence that mycobactin dependence was related to pathogenicity. Antigenic similarities were demonstrated between M . avium and M . paratuberculosis, and one isolate had the pathogenic characteristics of both species.

Samples of sewage, sewage sludge and sewage effluent from one or more of four sewage treatment plants were examined for the presence of Leptospira, Mycobacterium, Escherichia coli, Brucella abortus and Bacillus anthracis. Brucella abortus and Bacillus anthracis were not isolated. Eleven strains of E. coli potentially enteropathogenic for calves or piglets, eight pathogenic strains of Mycobacterium and one patho;genic Leptospira strain were isolated from 101, 189 and 189 samples respectively. Sewage sludge is no;t considered to play a major part in the epidemiology of disease caused by these organisms.

A modification to Schaefer's agglutination method for serotyping mycobacteria within the Mycobacterium avium‐M. intracellulare‐M. scrofulaceum complex is described. The antigens are screened against polyvalent sera and subsequently a reduced range of absorbed antisera. This expedites the serotyping procedure and conserves expensive antiserum stocks.