Serological and bacteriological investigation of Mycobacterium ranae (fortuitum).

Twenty strains of a species of fast growing Mycobacterium, some named M. fortuitum and others said to be similar to the strain of M. peregrinum, in the possession of the National Collection of Type Cultures, were examined serologically and bacteriologically. They were all found to be of the same species, but they were divisible into four serotypes (I to IV), on a basis of three variable antigens, which do not exactly correspond to the subspecies described in previous reports. The strains varied in the number of years that they had been kept in culture and were of widely divergent origin. With the exception of serotype II strains, which all came from sputa from Welsh miners, the serotypes were independent of years in culture or site of origin. Based on bacteriological and serological identity and chronological priority, we consider that M. ranae (Kuster) Bergey et al. should be reinstated in place of M. fortuitum Cruz. A modified scheme for identification of the species is proposed, which would not exclude any of the four serotypes.