Application of gas-liquid chromatographic analysis of cellular fatty acids for species identification and typing of coagulase-negative staphylococci

Abstract

Gas-liquid chromatography (GLC) of bacterial cellular fatty acids was used to analyze 264 isolates of coagulase-negative staphylococci, of which 178 were Staphylococcus epidermidis. The presence and amounts of individual fatty acids were determined to generate fatty acid profiles for each of the seven coagulase-negative species tested. The fatty acid profiles were then analyzed by computerized correlation and cluster analysis to calculate mean correlation values between isolates belonging to the same or different species, as well as to establish cluster analysis dendrograms. These data ultimately allowed the clustering of individual samples into species-specific clusters. Species identification by the GLC clustering was highly consistent with species identification by biochemical assays; the results were similar in 92.4% of the cases. The GLC profile correlation analysis was further used to analyze multiple blood isolates from 60 patients in order to determine the usefulness of this methodology in establishing identity, as well as differences between consecutive patient isolates. The correlation between those multiple S. epidermidis isolates determined to be identical by standard techniques (such as the antibiogram, biotype, and plasmid profile) was significantly (P < 0.001) higher than that between random isolates of the same species. The correlation coefficient was >97 for 40 (97.6%) of the 41 patients with multiple identical blood isolates, compared with <95 in all 19 (100.0%) patients with multiple nonidentical isolates. The successful use of the computerized GLC analysis in this study demonstrated its appropriate application for species identification and typing of coagulase-negative staphylococci.