Contagious equine metritis--use of gas liquid chromatography in identifying the causal agent

Cellular fatty acid compositions of contagious equine metritis isolates and three reference Haemophilus equigenitalis cultures were determined by gas chromatography. The chromatographic data were standardised and normalised fatty acid methyl ester (FAME) profiles were produced. The profiles were compared visually and similarity indices were determined using a computer peak matching method. There was little difference between the profiles of the three reference strains, each strain being characterised by three major fatty acids; C 18:1, C 16:0 and 30H-C 14:0. Variations in cultural conditions had no significant effect on the FAME profiles. The identification of laboratory isolates using the technique was in agreement with the presumptive identification based on the currently recommended tests and an improvement on the confirmatory serological identification. The FAME profiles provided confirmation of identity where it was not possible to use the presently recommended serological procedures. The authors recommend the gas chromatography technique for use in the diagnostic laboratory as an adjunct to the presently accepted identification methods.