Identification of anaerobic nonsporeforming gram-positive bacilli by biochemical tests and gas-liquid chromatography.

There are many methods to identify anaerobic nonsporeforming bacilli: histological, bacteriological (biochemical test, microsystem API 20 A), serological, cell wall composition analysis, molecular methods and gas-liquid chromatography (GLC). A comparison between biochemical tests and gas-liquid chromatography was made in this study for the identification of this group of microorganisms. GLC conditions were established with the aid of reference strains. These conditions were then applied to ten strains which were previously identified by biochemical tests. Strains were grown in PYG broth and fermentation end products were analyzed, volatile and non volatile fatty acids. Their qualitative determination was made by comparing the retention time of known standards and the chromatographic pattern of reference strains. In addition, a semiquantitative analysis was made. The results of identification by biochemical tests were: five strains belonged to Actinomyces genus; three were Propionibacterium acnes; one Propionibacterium granulosum and one P. propionicum. By the GLC only seven strains were identified: four were Actinomyces and three P. acnes. Only six strains showed identification correlation by both biochemical tests and GLC. GLC is a presumptive identification method that can be used along with other complementary tests for a definitive identification at genus level.