Usefulness of fatty acid composition for differentiation of Legionella species

Numerical analysis of fatty acid methyl ester (FAME) profiles of 199 isolat es and 76 reference strains, belonging to all validly described species of the genus Legionella that can be cultured in laboratory media, was used to differentiate between the species of this genus. With the exception of the strains that autofluoresced red, it was possible to differentiate all the o ther Legionella species. The strains of the species L. bozemanii, L. dumoff ii, L. feeleii, L. gormanii, L. maceachernii, L. micdadei, and L. quinlivan ii did not farm single clusters, showing some degree of variability in the fatty acid compositions. The strains of the blue-white autofluorescent spec ies had very similar fatty acid compositions and were difficult to distingu ish from each other. Nine isolates had fatty acid profiles unlike those of any of the validly described species and may represent different FAME group s of known species or undescribed Legionella species. The method used in th is study was useful for screening and discriminating large number of isolat es of Legionella species. Moreover, the results obtained can be included in a database of fatty acid profiles, leading to a more accurate automatic id entification of Legionella isolates.