Rapid differentiation of the major causative agents of bacterial meningitis by use of frequency-pulsed electron capture gas-liquid chromatography: analysis of amines

The major causative agents of bacterial meningitis (Haemophilus influenzae serogroup B, Neisseria meningitidis serogroups B and C, Klebsiella pneumoniae, Steptococcus pneumoniae, and two types of Escherichia coli) were cultured in a chemically defined medium, and selected strains were further studied in Todd-Hewitt medium. After acidic extraction of the spent media with chloroform, a basic extraction was made with chloroform to obtain amines. A third extraction was performed on re-acidified Todd-Hewitt medium with ethyl ether to obtain hydroxyacids. The extracts were derivatized with heptafluorobutyric anhydride-ethanol to form electron-capturing derivatives, and the derivatives were analyzed on a frequency-pulsed electron capture gas-liquid chromatograph (FPEC-GLC) equipped with a PEP-2 computer. The data obtained from the study showed that amines were produced by these organisms that formed characteristic patterns. Different serotypes of K. pneumoniae and the two serogroups of N. meningitidis produced different types of FPEC-GLC profiles within serotypes. E. coli produced several hydroxy acids on Todd-Hewitt medium that made it unique among the organisms studied. The methods used are practical and the techniques have potential for use in clinical laboratories and hospitals as a valuable aid for the rapid identification of the major causative agents of bacterial meningitis.