title: Utility of new 24-locus variable-number tandem-repeat typing for discriminating Mycobacterium tuberculosis clinical isolates collected in Bulgaria.
abstract: The present study evaluated new markers for molecular typing of Mycobacterium tuberculosis with a collection of strains circulating in Bulgaria. A study sample included 133 strains from epidemiologically unlinked patients from different regions of the country. Spoligotyping was used as a primary typing tool; it subdivided these strains into 37 types, including 15 clusters and 22 singletons. Traditional IS6110-restriction fragment length polymorphism (RFLP) typing and novel 24-locus variable number tandem-repeat (VNTR) typing methods were applied to the selection of 73 strains. Discriminatory power (Hunter-Gaston index [HGI]) of these methods was found to be 0.983 and 0.997, respectively. The 73 strains were subdivided into 66 types by a 24-locus mycobacterial interspersed repetitive unit (MIRU)-VNTR scheme, 62 types by a classical 12-locus MIRU-VNTR scheme, 51 types by IS6110-RFLP typing, and 31 types by spoligotyping. A combination of the five most polymorphic loci (MIRU40, Mtub04, Mtub21, QUB-11b, and QUB-26) was shown to achieve a high discrimination (HGI = 0.984). To conclude, a complete 24-locus scheme excellently differentiated strains in our study, whereas a reduced 5-locus set provided a sufficiently high differentiation and may be preliminarily suggested for the first-line typing of M. tuberculosis isolates in Bulgaria.
authors.affiliation: Department of Pathogenic Bacteria, Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors.forename: Violeta
authors.initials: V
authors.lastname: Valcheva
authors.forename: Igor
authors.initials: I
authors.lastname: Mokrousov
authors.forename: Olga
authors.initials: O
authors.lastname: Narvskaya
authors.forename: Nalin
authors.initials: N
authors.lastname: Rastogi
authors.forename: Nadya
authors.initials: N
authors.lastname: Markova
mesh_terms: D000328:Adult; D015373:Bacterial Typing Techniques; D002031:Bulgaria / Q000453:epidemiology; D005838:Genotype; D006801:Humans; D018598:Minisatellite Repeats / Q000235:genetics*; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000235:genetics; D016133:Polymerase Chain Reaction; D014397:Tuberculosis, Pulmonary / Q000453:epidemiology / Q000382:microbiology