N-formylkansosaminyl-(1----3)-2-O-methyl-D-rhamnopyranose: the type-specific determinant of serovariant 14 of the Mycobacterium avium complex.

Significant occurrences of pulmonary and disseminated infections due to "atypical" mycobacteria have again focused attention on the Mycobacterium avium serocomplex. An examination of the major surface glycopeptidolipid antigen of one of the more prominent and one of the first described serovariants, the Boone strain (serovariant 14), has shown that it is characterized by a unique terminal disaccharide unit, N-formylkansosaminyl-(1----3)-2-O-methyl-D-rhamnopyranose. The structure of the entire oligoglycosyl hapten is N-formylkansosaminyl-(1----3)-2-O-methyl-alpha-D-rhamnopyranosyl-( 1----3)-2-O- methyl-alpha-L-fucopyranosyl-(1----3)-alpha-L-rhamnopyranosyl-(1----2)-6 -deoxy- L-talose. We had previously described a 4,6-dideoxy-2-O-methyl-3-C-methyl-4-(2-methoxy propanamido)-L-mannopyranose (an N-acylkansosamine) as the characteristic sugar of the trehalose-containing lipo-oligosaccharide antigens of strains of Mycobacterium kansasii. Thus, a derivative of this sugar is now found to occur in other mycobacteria as part of other antigens. The other distinguishing feature of the structure is the presence of D-rhamnopyranose, which occurs only sparingly in Nature.