DISTRIBUTION OF MIP-RELATED SEQUENCES IN 39 SPECIES (48 SEROGROUPS) OF LEGIONELLACEAE

The macrophage infectivity potentiator gene (mip) from Legionella pneu mophila is a major virulence factor of the species. Thus, mip-detectio n by amplification has been proposed to assess the presence of L. pneu mophila in clinical and environmental samples. The distribution of mip -related sequences within the Legionellaceae was studied by DNA amplif ication using mip-specific primers followed by Southern blot hybridiza tion with an internal probe. Thirty-nine species (48 serogroups) of Le gionellaceae were screened in this attempt. Using this approach, seque nces related to mip were observed in 89% of the tested species includi ng the most recently described L. fairfieldensis, L. lansingensis and L. shakespearei. In several cases, cloning and sequencing of the ampli fied products confirmed the high levels of similarity between the sequ ence found in non-pneumophila species with that of the L. pneumophila mip gene. This confirms previous reports that mip related genes are wi despread among Legionellaceae and therefore specific detection of the species L. pneumophila cannot be based on mip-targeted amplification.