A genomic study of the leproma-derived and cultivable mycobacterium HI- 75. The direct DNA sequencing of PCR product of 16S ribosomal RNA

Abstract

The sequence of the polymerase chain reaction (PCR) product of 16S ribosomal RNA (16S rRNA) of the leproma-derived and cultivable Mycobacterium HI-75 (M. HI-75) was examined to obtain the knowledge of its taxonomic characteristics directly by dideoxy method. The sequence was most similar to that reported for Mycobacterium scrofulaceum (MS) with 0.5% differences in the sequenced 973 bases of 16S rRNA. The mycobacterium examined in this study was originally isolated as M. leprae (ML) by Skinsnes, et al. in 1975 from leproma of a lepromatous type Hansen's disease patient and therefore named as Mycobacterium leprae HI-75 (M. HI-75) by them. The claim was denied by Stanford, et al. in 1976 who reported the identity of HI-75 as MS. The bacillus was maintained in the second author's laboratory from 1984 using either Ogawa's or Sauton's media in the beginning and Ogawa's medium enriched with glucuronic acid and N-acetyl-D-glucosamine recently. During that period of time Sasaki reported the nerve invasion and the growth of the inoculated bacilli either to the nude mice or the I131 immunocompromized Swiss mice. This episode provoked a doubt that there should be a missing link of knowledge between leprosy and M. scrofulaceum since the nerve invasion of the bacilli has been regarded rather as a characteristics of ML and not that of MS. In addition to that the other genomic study about HI-75 performed by Williams by PCR and restriction flagment length polymorphism (RFLP) suggested the resemblance of the bacilli as either M. smegmatis or M. fortuition and not MS (1994, pers. comm.). Those raised the question whether M. HI-75 has changed during the cultivation for 21 years. The 16SrRNA obtained from the strain by the present study indicated that M. HI-75 still preserve some characters of MS. The result should be consonant with that by Stanford et al. 19 years ago and thereby suggesting the maintenance of the original characteristics at that time. Therefore the present study indicated the missing link of the knowledge between ML, its nerve invasion and MS which should be brought into elucidation in future by the analytical study awaring the possibility that ML might transform genomically in vivo or MS beside ML might invade and grow in the nerve.