MIRU-VNTR Typing reveals high heterogeneity in a supposedly clonal group of Mycobacterium bovis
Poster communication in 34th Annual Congress of the European Society of Mycobacteriology
March 1st, 2013
Rodriguez-Campos S., Navarro Y., Romero B., Bezos J., de Juan L., Casal C., Dominguez L., Gutierrez A., Garcia de Viedma D. and Aranaz A.
Spoligotyping is often complemented by MIRu-vNTR typing in order to increase discrimination. In Spain, SB0121 (SIT481) is the most prevalent spoligotype (28%) involved in bovine tuberculosis. In this study we applied MIRu-vNTR typing to a panel of randomly selected Spanish M. bovis SB0121 isolates to assess allelic diversity and overall discriminatory power. Furthermore, MIRu-vNTR was applied to all TB positive animals from selected farms infected by M. bovis SB0121 to evaluate the degree of heterogeneity in supposedly epidemiologically linked isolates. The samples were obtained between 1997 and 2010 from all over Spain and originated from cattle (n = 244), goat (n = 2), wild boar (n = 7), red deer (n = 2), fallow deer (n = 2), badger (n = 2) and domestic pig (n = 2). MIRu-vNTR typing was carried out in a two step approach: 1) Assessing a random selection of isolates (n=115) using 9 vNTR loci: ETR-A, ETR-B, ETR-D, ETR-E, MIRu26, quB11a, quB11b, quB26 and quB3232. 2) Screening of 176 TB-positive animals from 15 farms for heterogeneity applying the 6 most discriminatory MIRu-vNTR markers; in case of encountering differences in the genotypes, the 9-loci MIRu-vNTR type was completed to determine the degree of variation. The first panel of isolates was divided into 65 different MIRu-vNTR (Mv) types achieving a discriminatory power D=0.9856. The most discriminatory loci were in descending order: quB3232, ETR-A, ETR-B, quB11a, quB26, MIRu26, ETR-D, ETR-E and quB11b. To determine a more cost-effective typing format we compared the effect of reducing the number of markers for the analysis: six-loci approach D=0.9826, four-loci D=0.9689. Regarding the second panel screened for heterogeneity in assumedly homogeneous farms, we found 5 out of the 15 farms to be truly homogeneous. In the remaining farms we observed: i) 1 farm with Mv types differing in only 1 locus, ii) 6 farms with Mv types differing in 2-6 loci and iii) 3 farms in which Mv types differing in only 1 locus were found along with Mv types with variation at more than 1 locus. The characterization of the random panel of M. bovis SB0121 isolates revealed high diversity. This finding along with the heterogeneity detected in ten out of the 15 farms under study suggests considering spoligotyping as limited for source tracking. Heterogeneity reveals the potential existence of continuous risk of infection and the involvement of microevolution events in the analyzed farms
 | Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM). |
| Servicio de Micobacterias (MYC). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
Link to 34th Annual Congress of the European Society of Mycobacteriology
