Development and use of single "polytropic" diagnostic tubes for the approximate taxonomic grouping of bacteria isolated from foods, water and medicinal preparations

Abstract

Single tubes, containing in all instances a bottom layer of a solid medium for detecting mode of attack on glucose, lactose, mannitol or starch and top layers of solid, semi-solid or liquid media allowing assessment of motility, formation of catalase, oxidase, coagulase, indole, hydrogen sulphide, acetyl methyl carbinol or pigments, as required ("polytropic" diagnostic tubes) were developed for the approximate taxonomic grouping of bacteria commonly encountered in foods, water and medicinal preparations. They are designated as: Gram negative diagnostic tubes (GNT), tubes allowing identification of E. coli, following the principle set out by MCKENZIE, TAYLOR and GILBERT (MTGT), diagnostic tubes for Vibrio parahaemolyticus (VPT), open tubes to assess oxidative attack on glucose (OGT), Gram positive diagnostic tubes (GPT), and mannitol plasma tubes (MPT) for the identification of Staph. aureus. In addition a CP tube for the identification of Cl. perfringens is described, the basis of which is the production of H2S from sulphite in the presence of cycloserine, absence of mitality and failure to produce indole at 46 degrees C. All tubes contain intermediate layers to avoid interactions between changes occurring in top and bottom layers. Upon examination of about 600 pure cultures from collections or freshly isolated from foods etc. such tubes have given results which were in agreement with those of classical testing; in a few instances (testing for indole formation) even better results were obtained. The use of such polytropic tubes in identification routes saving much time and effort is outlines.