Ribosomal internal transcribed spacer sequences are identical among Mycobacterium aviurn - intraceIIulare complex isolates from AIDS patients , but vary among isolates from elderly pulmonary disease patients

3 Public Health Laboratory Service, Regional Tuberculosis Centre, Dulwich Hospital, London SE22 8QF, UK Sequencing 280 bp of the internal transcribed spacer (ITS) between the 165 and 235 rRNA genes in a collection of 46 clinical isolates of the Mycobacterium awium-intracellulare complex (MA1 complex) identified nine different sequences, grouping these isolates in nine ' ITS sequevars '. This analysis extends the subdivision within the MA1 complex to 18 ITS sequevars and also improves discrimination from other mycobacterial species. Evaluation of the sequevar grouping among different clinical sources revealed strong association of the M. awium sequevar Mav-B with AIDS and with lymphadenitis in children (18 out of 20 and 3 out of 3 respectively). Isolates from elderly patients with pulmonary disease and not suspected of being HIV infected belonged predominantly to M. intracellulare ITS sequevan and sequevars not assigned to either M. awium or M. intracel/u/are. On the other hand, animal isolates were of both the Mav-A and Mav-B sequevan. We conclude that ITS sequevar typing is an accurate way of identifying distinct MA1 complex strains. The observed differences between clinical sources suggest that ITS sequevan reflect possibly important, biologically and clinically relevant polymorphisms between MA1 complex organisms.