Qualitative Analysis To Ascertain Genotypic Identity of or Differences between Mycobacterium tuberculosis Isolates in Laboratories with Limited Resources.

Mycobacterium tuberculosis is currently genotyped using mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) typing, although the high cost of this technique restricts its implementation in resource-limited settings. We designed a MIRU-VNTR format, MLP3 (MIRU-VNTR length polymorphism triplex), that is based on the qualitative comparison of 5 nonfluorescent 3-band fingerprints in conventional electrophoresis and minimizes costs and technical demands. MLP3 successfully resolved cross-contamination alerts, discriminated reinfections from reactivations, clarified suspected microepidemics, and tracked transmission events of high epidemiological interest.