Differentiation of selected Enterobacteriaceae by pyrolysis-gas-liquid chromatography

Pyrolysis-gas-liquid chromatography was used to differentiate selected species of Enterobacteriaceae. Individual cultures of Salmonella typhi, Hafnia alvei, and Proteus vulgaris, and 12 strains of Yersinia enterocolitica were grown in nutrient broth. After harvest and lyophilization, the bacterial samples were pyrolyzed at 900 degrees C, and their volatile fractions were separated on a 50-m capillary column coated with Carbowax 20M. The resulting pyrolysis elution patterns (pyrograms) of the four species were monitored on an integrating console, which was coupled with the chromatographic detector. The pyrograms were divided into 312 30-s time interval areas, and each interval area was normalized in relation to the area of the entire curve. The normalized areas were evaluated by stepwise linear discriminant analysis, and the discriminating component coordinates were used to generate a plot of the canonical variables. Distinct clustering patterns allowed discrimination among the four genera of Enterobacteriaceae studied. The tight clustering of the 12 Y. enterocolitica strains suggests the advantage of pyrolysis-gas-liquid chromatography over traditional approaches for species identification.