DILEMMA OF DIRECT MIRU-VNTR GENOTYPING OF CLINICAL SAMPLES OF TUBERCULOSIS

Background and Aim:Twenty-four loci mycobacterial interspersed repetitive unit-variable number tandem repeat analysis (MIRU-VNTR) is extensively used for genotyping and detection of polyclonal infections in tuberculosis (TB). The aim of the present study was to compare the accuracy of direct and indirect MIRU-VNTR genotyping and detection of polyclonal infections between old and fresh clinical samples.Methods:Two series of TB samples were collected for retrospective and prospective comparison. After genomic DNA extraction from clinical samples and their respective cultures, 24 loci MIRU-VNTR was performed.Results:In the 14 old samples, no mixed infections were observed, in clinical samples and their respective cultures. In nine fresh samples, 44.4% of mixed infection was observed in the clinical samples, but no mixed infections were observed in their respective cultures. Surprisingly, in the old samples, 92.86% of samples (13/14) had an allelic change between clinical samples and their respective cultures. On the other hand, in fresh samples, only one sample (1/9) had an allelic change between clinical samples and their respective cultures.Conclusion:We concluded that 24 loci MIRU-VNTR undoubtedly has a high reliability in direct genotyping of clinical samples, especially in the prospective studies. However, selecting starting material, such as clinical specimen or respective culture can be controversial in the retrospective studies. Regarding polyclonal infections the prospective studies gives us a better view to detect these infections, especially in clinical specimen.

کلیدواژه ها:

Tuberculosis ، MIRU-VNTR ، retrospective studies ، prospective studies