Identification of Achromobacter species by cellular fatty acids and by production of keto acids.

The cellular fatty acid composition and metabolic products of 12 reference strains of Achromobacter sp. and A. xylosoxidans were determined by gas-liquid chromatography (GLC). Results showed that the two Achromobacter groups are strikingly different and can be readily distinguished on the basis of cellular fatty acids and the short-chain acids produced by Achromobacter sp. The major cellular fatty acids of Achromobacter sp. were octadecenoic (18:1) and a 19-carbon cyclopropanoic (19:0 delta) acid, whereas hexadecanoic (16:0) and a 17-carbon cyclopropanoic (17:0 delta) acid were principal components of the lipids of A. xylosoxidans. Hydroxy acids were not found in strains of Achromobacter sp. but comprised approximately 20% of the cellular fatty acids of A. xylosoxidans. In addition, Achromobacter sp. produced relatively large amounts of 2-ketoisocaproic acid, which was detected in only trace amounts from strains of A. xylosoxidans. The data show that GLC tests provide additional criteria for differentiating groups which are very closely related when evaluated with conventional tests. The GLC tests can be readily adapted in the clinical laboratory because they are rapid, highly reproducible, relatively inexpensive, and simple to perform.