Development and evaluation of a coculture technique for identification of anaerobic organisms

We investigated a method to reduce oxygen tension and produce anaerobic conditions conveniently by coculture with a nonfermentative organism. The biochemical reactions of 94 strains representing 41 different species were determined using prereduced media and gas chromatography according to standard methods. The standard reactions were compared with those obtained by preparing similar media, modified by containing no cysteine or resazurin, under aerobic conditions. Preincubation of the modified biochemical media with a standard suspension of a culture of Acinetobacter lwoffi provided reducing conditions. In 1,449 individual tests using 22 different biochemicals, 1,349 (93%) of the reactions agreed. Only two misidentifications resulted when using the modified media, one each at the species and genus levels. Two strains of Actinomyces odontolyticus failed to grow in coculture.