Gas chromatography of mycobacterial fatty acids and alcohols: diagnostic applications

Abstract

Capillary gas chromatography of cellular fatty acids and alcohols has been used as a routine method for a period of two years in the mycobacterial diagnostic laboratory of Statens institutt for folkehelse, Oslo, Norway. All mycobacteria (165 isolates) other than Mycobacterium tuberculosis (MOTT) and 24 randomly selected M. tuberculosis isolates were studied. Twelve characteristic lipid constituents allowed the construction of a diagnostic scheme. Without exceptions, all 36 examined isolates belonging to the M. tuberculosis-complex were characterized by a relatively high concentration level of hexacosanoic acid (mean: 4%, range: 1-13%), low level of tetracosanoic acid (mean: 1%, range: 0.1-3%), lack of methylbranched acids other than tuberculostearic acid, and lack of fatty alcohols. Members of the MAIS-complex (73 isolates) were all characterized by the general presence of the fatty alcohols 2-octadecanol (mean: 2%, range: 0.1-5%) and 2-eicosanol (mean: 7%, range: 2-21%), relatively high levels of tetracosanoic acid (mean: 5%, range: 1-15%) and lack (or trace) of hexacosanoic acid and methylbranched acids other than tuberculostearic acid. All 16 isolates of M. gordonae were easily recognized by their unique lack of tuberculostearic acid and their content of 2-methyl-tetradecanoic acid (mean: 5%, range: 2-12%), and the M. xenopi isolates were the only examined strains containing the fatty alcohol 2-docosanol (mean: 9%, range: 2-13%). The six M. malmoense strains contained the two unique constituents 2-methyl eicosanoic acid (mean: 3%, range: 1-4%) and 2,4,6-trimethyl tetracosanoic acid (mean: 3%, range: 2-4%). The ten strains of M. kansasii were characterized by 2,4-dimethyl tetradecanoic acid (mean: 5%, range: 1-11%), whereas the seven strains of M. marinum shared 2,4-dimethyl hexadecanoic acid (mean: 4%, range 0.2-12%) as a specific marker.