Properties of microorganisms isolated from human leprosy lesions

Diphtheroids, which in addition to Mycobacterium leprae are present in human leprosy lesions, were identified as true corynebacteria by DNA and cell wall analysis. Peptidoglycan (adjuvant) of these leprosy-derived corynebacteria (LDC) consists of N-acetylglycosaminyl-N-acetyl(glycolyl)-muramic acid and L-Ala-D-Glu(NH2)-(L)-meso-A2pm-(L)-D-Ala (A2pm = diaminopimelic acid). (The amino group of the tetrapeptide is attached to the carboxyl group of the muramate). Peripheral polysaccharide (antigen) is arabinogalactomannan with lateral chains of mannofuranose and arabinofuranose. To the latter are linked mycolic acids containing groups of isomers with 24-36 carbon atoms and containing between zero and four double bonds. DNAs of LDC isolates have a guanine + cytosine content of 56% and demonstrate a high degree of homology. LDC ribosomes cross-react with antisera against mycobacteria and with sera from patients with leprosy. Thermostable antigen M of LDC cross-reacts with the main antigens of tuberculin and lepromin. LDC thus represents a homogeneous and unique group of corynebacteria immunologically related to M. leprae. Leprosy might be the result of a pathogenic cooperation between both organisms, as suggested by the enhancement of M. leprae growth rate promoted in mice by living LDC.