Optimal data processing procedure for automatic bacterial identification by gas-liquid chromatography of cellular...

Gas-liquid chromatography of cellular fatty acids was used in automatic identification of clinical bacterial isolates. The intraspecies variation in the occurrence of fatty acids and the variation in the relative gas-liquid chromatography peak areas of different fatty acids were evaluated and compared with the relative peak areas of these acids. A new chromatogram comparison method involving the use of an exponential function was developed to adjust to data variation optimally. This method was compared with several previously published methods of correlation analysis with data from representative clinical bacteriological isolates. The efficacies of the methods in separating different bacterial species into distinct clusters were compared. The new exponential function method was superior to the others both in its ability to separate species into different clusters and in giving a greater degree of identity to strains within a proper cluster. The results indicate that the gas-liquid chromatography of bacterial cellular fatty acids can be used effectively in the identification of clinically isolated bacteria. However, the usefulness of the analysis depends on the comparison method used and on its ability to cope with data variations.