Mycobacterial interspersed repetitive units typing reveals high genetic diversity of Mycobacterium tuberculosis isolates in Austria
Abstract number: P1679
Pietzka A., Stöger A., Pietzka D., Hasenberger P., Indra A., Ruppitsch W., Allerberger F.
Objectives: The aim of the study was to determine the suitability of Mycobacterial interspersed repetitive units (MIRU) typing for recognising biodiversity of Mycobacterium tuberculosis isolates in Austria. Austria has a total population of 8 million and a yearly incidence of tuberculosis of 11/100,000.
Methods: Mycobacterial interspersed repetitive units (MIRU) typing is a PCR-based typing method which assigns the number of tandem repeats in 12, 15, or 24 independent loci (MIRUs). MIRU-analysis was performed with the 24 MIRU primer system as described  on 1294 isolates collected from 2003 to 2005 in Austria. Amplified products were analysed on an automated sequencer. User defined filtering and grouping was performed with an own software tool.
Results: Two of the 24 MIRU-VNTR primers did not generate analysable results. The remaining 22 primer allowed the classification of the 1294 isolates into 1085 different MIRU types. The eight most frequently found MIRU profiles contained 14, 13, 11, eight, and six isolates. All other types were comprised of five or less isolates. The MIRU type comprising 14 isolates was assigned to the Haarlem lineage, the MIRU type comprising 11 isolates was assigned to the Beijing lineage, and one MIRU type comprising six isolates was assigned to the URAL lineage. All of the other frequently found MIRU profiles could not be assigned to known lineages .
Eighty-eight of the 1294 isolates were of the Beijing spoligotype; they yielded 71 different MIRU types. One MIRU type was found in 11 Beijing isolates, seven types were found in two isolates each, and 63 types were shown by a single isolate only.
Clonal variants within the same host were detected in 27 out of 44 cases.
Conclusion: Our results highlight the diversity of M. tuberculosis isolates in Austria. MIRU is more discriminative than spoligotyping or IS6110 RFLP . MIRU even allows the differentiation of the Beijing family in 71 separate MIRU types. We consider MIRU typing to be a valuable typing method suitable to allow for differentiation between reactivation and reinfection in individual cases, and to provide the discriminatory power necessary to recognize clusters of tuberculosis in Austria.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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