The Fermentation of Propylene Glycol by Members of the Escherichia-Aerobacter-Intermediate Groups

The possibility has been suggested of differentiating the "in-termediates " from Escherichia and Aerobacter by the use of propylene glycol (Dozois et al., 1936). It was observed, in the limited number of cultures'studied, that Escherichia and Aero-bacter formed acid from propylene glycol, while the "intermedi-ates " did not. In order to determine whether the utilization of this glycol might serve as a convenient additional taxonomic characteristic of this group, extensive observations were deemed advisable. Therefore, the propylene-glycol broth medium was used, in the study of a number of stock cultures, and in the routine examination of strains isolated from water, milk, crabmeat, oys-ters and feces. In an attempt to differentiate between the various strains of the "intermediates " observations on the fermentation of propy-lene glycol, ethylene glycol, adonitol and inositol were made. Those coli-form microorganisms which were found to be methyl-red positive and Voges-Proskauer negative, and which also grew in citrate broth (Koser's) were classed as members of the "inter-mediate " group. METHODS AND MATERIALS One per cent of the specific sugar alcohol was added to sugar-free broth of a pH of 7.0. The indicator used was chlorpheno