Seroreactive species-specific lipooligosaccharides of Mycobacterium mucogenicum sp. nov. (formerly Mycobacterium chelonae-like organisms): identification and chemical characterization

Abstract

Summary: Strains of the new species Mycobacterium mucogenicum exhibit physiological and biochemical features very similar to those of the other species of the Mycobacterium fortuitum complex. To define taxonomic criteria for easy identification of M. mucogenicum, the glycolipid patterns of the reference strains and of 32 environmental and clinical isolates were examined by TLC. It was concluded that all M. mucogenicum strains of smooth colony morphology contained species-specific alkali-labile glycoconjugates. Three different patterns were observed among the strains of the smooth colony type. Fractionation followed by conventional chemical analyses of the purified glycolipids showed the specific glycolipids to be lipooligosaccharides (LOS). The three LOS showed a similar fatty acid composition consisting of straight chain (dodeca-, tetradeca-, hexadecanoyl and hexadecenoyl) and methyl-branched (2,4-dimethyleicosanoyl and 2,4-dimethyleicosenoyl) fatty acyl substituents. The most commonly encountered LOS (present in 76% of the smooth strains) contained a tetraacylated pentasaccharide composed of four moles of glucose and one mole of a 2,4-di-O-methylhexose. A LOS composed of arabinose, glucose and mannose was present in 20% of the smooth strains, whereas the newly proposed type strain of M. mucogenicum (ATCC 49650) was the only strain that contained a LOS composed of glucose and galactose. Serological studies clearly differentiated most of the strains of M. mucogenicum from those of the other members of the M. fortuitum complex, and demonstrated the existence of serovars within the former species. Altogether, these data confirm the validity of the new species but show ATCC 49651 to be the most representative strain.