Experience of gas-liquid chromatography in clinical microbiology

In clinical microbiology, gas-liquid chromatography (GLC) is used mainly for the following applications: (1) demonstration of microbial metabolites in cultures: studies of short-chain fatty acids (chain length 2 to 6 carbon atoms) and of the non-volatile lactic and succinic acids are the basis of taxonomy of obligate anaerobes on the genus level. Demonstration of these compounds in spent culture media is also used for identification of anaerobic bacteria in the clinical laboratory. (2) Investigation of long-chain fatty acids of cell membranes and the cell wall: analysis of fatty acids with chain lengths of 9 to 20 carbon atoms are used primarily for taxonomic purposes. A practical application for use in clinical bacteriology is the Microbial Identification System (MIS) based on equipment built by Hewlett-Packard. Although this system is excellently suited for quantitative analysis of long chain fatty acids and gives valuable preliminary or confirmative information, it often requires additional testing for identification of bacteria to species level. (3) Direct rapid diagnosis of infection: demonstration of metabolic products in body fluids can be of value in infections with anaerobes (demonstration of fatty acids) and yeasts (sugars). GLC combined with mass spectrometry or frequency-pulsed electron capture GLC techniques have been applied to studies of sera, fecal specimens, and cerebrospinal fluids. These latter applications are still in an experimental stage. However, the rapid diagnosis of tuberculosis directly from cerebrospinal fluid and sputum is well advanced. The potential of direct diagnosis without the resort to cultures warrants continued research with these techniques.