Characterization of Legionella species by numerical analysis of whole-cell protein electrophoresis

The results of a computer-assisted whole-cell protein sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of 291 isolates and 74 reference strains belonging to all known species of the genus Legionella revealed that the majority of the species of this genus can be adequately identified by this method. The type strain of Legionella bozemanii did not cluster with the other strains of this species, and the only strain of Legionella geestiana available clustered with the strains of Legionella feeleii. When we performed a numerical analysis by omitting certain portions of the pattern containing dense bands, all of the species could be distinguished. Our results also show that the type strains of Legionella nautarum and Legionella londiniensis deposited in the National Collection of Type Cultures do not correspond to the type strains deposited in the American Type Culture Collection. We used the results of a fatty acid and ubiquinone composition analysis to complement the SDS-PAGE results for several strains whose identities as determined by indirect immunofluorescence were doubtful. Computer-assisted SDS-PAGE of whole-cell proteins can be used in the classification of Legionella species and to identify and screen large numbers of isolates for further, in-depth taxonomic studies of smaller numbers of strains.