Identification of viridans streptococci by pyrolysis-gas chromatography

An isothermal method of pyrolysis-gas chromatography (Py-GC) was used for the identification of viridans streptococci. Pyrograms from 104 reference strains were subjected to a discriminant analysis to produce classification coefficients for the identification of 74 test organisms. Five groups representing recognised species were discriminated but Streptococcus milleri strains could not be distinguished from S. sanguis. If S. milleri and S. sanguis are regarded as a single pyrogroup, only three strains out of 74 were incorrectly identified by Py-GC. A multidimensional scaling analysis of the Py-GC data produced a similar species grouping, but this statistical method was less satisfactory for pyrogram data than discriminant analysis. While Py-GC was moderately successful for the identification of viridans streptococci, this study indicated that the technique has limited use in diagnostic medical microbiology because it is time-consuming and lacks flexibility.