Rapid differentiation of the species of the genus Bacteroides sensu stricto by capillary gas chromatography of cellular carbohydrates

Whole-cell hydrolysates of Bacteroides fragilis , the type species of the genus Bacteroides Castellani and Chalmers 1919, and the genetical closely related species B. vulgatus, B. ovatus, B. eggerthii, B. distasonis, B. uniformis, B. thetaiotaomicron, B. stercoris, B. merdae , and B. caccae were used to determine characteristic carbohydrate patterns by capillary gas chromatography. On the basis of the chemical derivatization of the carbohydrates seven characteristic peaks for peracetylated aldononitriles and nine characteristic peaks for peracetylated o -methyloximes were selected from the carbohydrate fingerprints of the reference strains to prepare a dichotomous identification key. The classification of an unknown strain supposed to belong to the formerly called ' Bacteroides fragilis group'is possible with this key. Some of the advantages of the technique were that the identification of Bacteroides fragilis -like strains requires only 4–5 h after primary isolation and that the bacteria can be exposed to oxygen because viability of the organisms is not necessary. Sophisticated anaerobic techniques can therefore be avoided for identification.