Variable and novel mycobacterial insterpersed repetitive units (MIRU) in the genome of the Mycobacterium avium complex

ROMANO MI; PAOLICCHI F; CARDOSO LS; PAVLIK I; MORSELLA C; BIGI F; KLEPP L; CATALDI A; AMADIO A

Florianopolis, Brasil

Workshop; Second General Meeting INCO-DEV Concerted Action. “Improved Diagnosis, Drug Resistance Detection and Control of Tuberculosis in Latin America”; 2003

Organisms of the Mycobacterium avium complex (MAC) are almost universally distributed in the environment and are present in birds, animals and humans. M. avium subspecies paratuberculosis (MAP) causes paratuberculosis, a chronic granulomatous enteritis in herds. MAP is also implicated as a cause of the Crohn’s disease in humans. MAP is present in retail pasteurized milk and maybe transmitted to humans by this route. M. avium subspecies avium causes tuberculosis in HIV+ patients and animals of economic interest as pigs. Repetitive sequences are common in the genome of prokaryotic organism. The length, sequence and position of these sequences in the genome are highly variable and often unique for a single strain. Using in silico analysis we found 28 novel variable number of tandem repeat structures (VNTR), called mycobacterial interspersed repetitive units (MIRU) in the genome of Mycobacterium avium complex. At the loci the motif configuration in a consensus sequence contains stop codons, initiation codons and the bacterial ribosome-binding site that overlaps the flanking genes. Seventy-nine MAP isolates from cattle and deer from Buenos Aires, Argentina, and twenty-six MAA isolates from humans and animals from Brazil were analyzed with four of these tandem repeat loci from M. avium genome and the results compared to those obtained by using restriction fragment length polymorphisms (RFLP) analysis with the IS900 probe, IS1245 and PRA. The analysis identified 8 different allele profiles with the combination of four VNTR-MIRU loci in the 26 MAA with 17 different RFLP and 5 different PRA profiles. However, MAP with different RFLP profiles had a unique allele profile with these four VNTR-MIRU loci. VNTR typing may be generally useful for strain differentiation and evolutionary studies in bacteria. In the present study we can not differentiate MAP isolates. Their typing is therefore problematic and requires the analysis with the remaining VNTR-MIRU loci and the use of the previously described MIRU 2 (Bull et al, Cellular Probes 17 (2003) 157-164) could be an alternative for typing of this mycobacteria.