[Molecular typing of Legionella for determining the source of infection]

The ubiquitous occurrence of Legionellae requires an exact typing of isolated strains in order to demonstrate the source of infection. Monoclonal antibodies, analysis of genomic and plasmid DNAs, and the typing of alloenzymes are suitable for this purpose. Typing of Legionella pneumophila serogroup 1 strains by using monoclonal antibodies was found to be a rapid and adequate method. Other serogroups of L. pneumophila and non-pneumophila species are of considerably less antigenic diversity, so that the use of monoclonal antibodies is not particular profitable. In such cases, genotypic methods are needed to discriminate between unrelated strains. There are no changes in the genome structure, defined as restriction patterns, during passages on artificial media and cultured Acanthamoeba. The possibility that different species, serogroups and monoclonal or genomic subtypes can be isolated in a given water supply points to necessity to test a sufficiently large number of colonies grown from the water samples. A clonal distribution of some Legionella strains has been observed.