CERVICAL LYMPHADENITIS CAUSED BY A FASTIDIOUS MYCOBACTERIUM CLOSELY-RELATED TO MYCOBACTERIUM GENAVENSE IN AN APPARENTLY IMMUNOCOMPETENT WOMAN - DIAGNOSIS BY CULTURE-FREE MICROBIOLOGICAL METHODS

Fastidious mycobacteria usually infect immunocompromised hosts (human immunodeficiency virus-infected or otherwise immunosuppressed patients ). We here describe severe lymphadenitis, caused by a fastidious mycob acterium closely related to Mycobacterium genavense, in an apparently immunocompetent woman, whose brother had died from an unidentified myc obacterial infection in 1969. A variety of techniques, including inocu lation of nude mice, histopathology, electron microscopy, lipid analys is, ATP measurements, and molecular biology, were used to characterize this mycobacterium. AII attempts to culture the etiological agent on many different media failed. The organism multiplied only in congenita lly athymic nude mice. Although phenotypically similar to M. genavense , the mycobacterium differs from M. genavense by three nucleotides of the 16S rRNA gene Sequence. Various antimycobacterial drugs were admin istered, including gamma interferon, but multiple relapses occurred. F inally, therapy with a combined regimen of clarithromycin, clofazimine , rifabutin, and ethambutol was curative. To our knowledge, this is th e first report of lymphadenitis in an apparently immunocompetent patie nt, caused by a noncultivable Mycobacterium sp. closely related to M. genavense. This study emphasizes the importance of employing a variety of diagnostic approaches such as the inoculation of laboratory animal s, histopathology, electron microscopy, lipid analysis, ATP measuremen ts, ind molecular biology to characterize novel microorganisms that ca nnot be cultured in vitro.