RIBOSOMAL INTERNAL TRANSCRIBED SPACER SEQUENCES ARE IDENTICAL AMONG MYCOBACTERIUM-AVIUM-INTRACELLULARE COMPLEX ISOLATES FROM AIDS PATIENTS,BUT VARY AMONG ISOLATES FROM ELDERLY PULMONARY-DISEASE PATIENTS

Sequencing 280 bp of the internal transcribed spacer (ITS) between the 16S and 23S rRNA genes in a collection of 46 clinical isolates of the Mycobacterium avium-intracellulare complex (MAI complex) identified n ine different sequences, grouping these isolates in nine 'ITS sequevar s'. This analysis extends the subdivision within the MAI complex to 18 ITS sequevars and also improves discrimination from other mycobacteri al species. Evaluation of the sequevar grouping among different clinic al sources revealed strong association of the M. avium sequevar Mav-B with AIDS and with lymphadenitis in children (18 out of 20 and 3 out o f 3 respectively). Isolates from elderly patients with pulmonary disea se and not suspected of being HIV infected belonged predominantly to M . intracellulare ITS sequevars and sequevars not assigned to either M. avium or M. intracellulare. On the other hand, animal isolates were o f both the Mav-A and Mav-B sequevars. We conclude that ITS sequevar ty ping is an accurate way of identifying distinct MAI complex strains. T he observed differences between clinical sources suggest that ITS sequ evars reflect possibly important, biologically and clinically relevant polymorphisms between MAI complex organisms.