High genetic relatedness among Mycobacterium avium strains isolated from pigs and humans revealed by comparative IS1245 RFLP analysis

Members of the Mycobacterium avium complex cause pig mycobacteriosis and opportunistic human infections. Infections due to environmental mycobacteria are increasing in both industrial and developing countries. Mycobacterium-infected pig carcasses can pass for human consumption due to the poor specificity of meat control by visual detection at the slaughter houses.The genetic relatedness of porcine and human MAC isolates in Finland has been unknown. M. avium isolates isolated from pig organs (n = 16) and clinical samples (n = 13) were compared by IS1245 RFLP analysis to evaluate the similarity of the isolates obtained from human and porcine samples.Nearly identical multicopy M. avium subsp. hominissuis IS1245 RFLP fingerprints were obtained for isolates of porcine and human origin. IS1245 RFLP patterns of 38% of the porcine and human M. a. hominissuis isolates were >90% similar. The RFLP patterns of two porcine and two human isolates showed >95% similarity. The high similarity of the IS1245 RFLP patterns of the human and porcine M. a. hominissuis isolates indicates close genetic relatedness, suggesting that M. a. hominissuis is transmitted between pigs and humans, or that pigs and humans share common environmental sources of infection. Porcine and human isolates with RFLP patterns differing by only one or two bands were found, which shows that the same M. a. hominissuis strains may infect both humans and pigs.