Application of MIRU–VNTR on smear slides: a shortcut for detection of polyclonal infections in tuberculosis patients


Mixed (polyclonal) infections are one of the main problems in tuberculosis (TB) management. The best available method for detecting polyclonal infections in TB is mycobacterial interspersed repetitive unit–variable number tandem repeat (MIRU–VNTR). According to multiple studies, MIRU–VNTR method can be applied to detect TB-related polyclonal infections in sputum samples or cultures. Setup of MIRU–VNTR on smear slides can be an efficient approach, regardless of the limitations of cultures and sputum samples in many laboratories. The present study aimed at investigating the diagnostic potential of MIRU–VNTR on smear slides in detecting mixed infections. Ziehl–Neelsen-stained microscopic slides were prepared from 14 clinical specimens. For amplifying 24 MIRU–VNTR loci, PCR assay was performed on the smear slides, clinical specimens, and cultures. Based on the 24-locus MIRU–VNTR analysis, polyclonal infections were reported in 42.85% of smear slides, while the corresponding rate was estimated at 57.1% (8/14) in the clinical samples. In the corresponding cultures, the rate of mixed infection was 7.14% (1/14). Use of smear slides can be a safe option for transferring clinical specimens between environmental and reference laboratories. Considering their significant impact on TB treatment, it is essential to diagnose mixed infections in low-resource countries with a high prevalence of mixed infections. The present findings show that direct MIRU–VNTR on smear slides can be conveniently used for the detection of mixed infections.

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We express our gratitude to the Mycobacteriology and Pulmonary Research Department, Pasteur Institute of Iran. Pasteur Institute of Iran (No: 927) funded this study.

Author information

MKK was responsible for writing the manuscript, FV was responsible for supervising the study, and FV, SDS, and AF contributed to the study design. MKK, HG, and SK performed the laboratory work, and MM, GF, and MKK were responsible for isolating the strains and laboratory work. All authors read and approved the final manuscript.

Correspondence to Farzam Vaziri.

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The authors declare that there is no conflict of interests.

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Research ethics committee of Pasteur Institute of Iran approved the study protocol (No: 927), and informed consents were collected from all the patients.

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Kargarpour Kamakoli, M., Khanipour, S., Masoumi, M. et al. Application of MIRU–VNTR on smear slides: a shortcut for detection of polyclonal infections in tuberculosis patients. Mol Biol Rep (2020).

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  • Tuberculosis
  • Mixed infections
  • Smear slide
  • Low-resource countries