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

MRC Tuberculosis and Related Infections Unit, Clinical Sciences Centre, Hammersmith Hospital, DuCane Road, London W12 ONN, UK Department of Medical Microbiology, St Mary's Hospital Medical School, Norfolk Place, London W2 1PG, UK Public Health Laboratory Service, Regional Tuberculosis Centre, Dulwich Hospital, London SE22 8QF, UK ABSTRACT Summary: 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 nine different sequences, grouping these isolates in nine ‘ITS sequevars’. This analysis extends the subdivision within the MAI 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. avium 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 sequevars and sequevars not assigned to either M. avium or M. intracellulare . On the other hand, animal isolates were of both the Mav-A and Mav-B sequevars. We conclude that ITS sequevar typing is an accurate way of identifying distinct MAI complex strains. The observed differences between clinical sources suggest that ITS sequevars reflect possibly important, biologically and clinically relevant polymorphisms between MAI complex organisms. Tel: +44 171 723 1252 ext. 5746. Fax: +44 171 262 6299. e-mail: k.desmet@ic.ac.uk Keywords: M. avium-intracellulare complex, DNA sequence analysis, 16S ribosomal RNA, AIDS, virulence Present address: Department of Medical Microbiology, St Mary's Hospital Medical School, Norfolk Place, London W2 1PG, UK.