For SAG7, a second PCR targeting a larger flanking region was required for 14% of the strains, which did not have a 16 kb genomic island encompassing the VNTR. The repeat sizes of the six VNTRs were sufficiently large for
evaluation of the number of repeats on agarose gels. Moreover, the conversion of results into allelic profiles should make it possible to construct databases for exchange between laboratories. The MLVA-6 scheme includes a set of markers with different diversity indices, making it suitable for epidemiological studies. Markers with selleck inhibitor a moderate diversity and small number of alleles (presumably reflecting their slow rate of evolution) define clusters, whereas markers displaying more rapid evolution reflect variability within clusters. The MLVA-6 method described here is a rapid, selleck reproducible and epidemiologically meaningful typing tool. Three loci studied in the present MLVA scheme are in common with the MLVA scheme proposed by Radtke et al. . The 3 additional loci studied here provide more weight to clusters while maintaining a high discrimination power.
Moreover, in the MLVA scheme proposed here, only one locus (SAG7) was missing in some strains (14%), and another primer pair targeting larger consensual flanking region confirmed the absence of this locus with a specific amplification. Unlike Radtke et al., we sought to develop a MLVA scheme in which a PCR product was amplified in all strains whether the
VNTR was present or absent. In fact, negative amplification may result from the lack of a VNTR locus or modification of the flanking regions, especially as some VNTRs are close to transposases or insertion sequences such as SAG4 (alias SATR1) which is close to IS1381. Thus, the possibility of negative amplification for 3 out of 5 VNTR loci in the Radtke et al. MLVA analysis could be a real problem in terms of resolution and reproducibility of the genotyping method. Nevertheless, cumulative works allow to define the best set of VNTR loci, as has already been Anidulafungin (LY303366) done for other bacterial species such as Mycobacterium tuberculosis [22, 42–46] and Staphylococcus aureus [30, 47–49]. YH25448 Finally, the study of 34 isolates of bovine origin provided information about their distribution, especially those belonging to MLST CC17. Population analysis by MLVA revealed a clonal distribution of the strains similar to that obtained by MLST. The greater discriminatory index of MLVA (0.96) made it possible to distinguish between strains within the clonal complexes defined by MLST. Thus, MLVA divided CC23 into two groups: one associated with serotype III and the other associated with serotype Ia. Moreover, MLVA also separated CC17 into two groups: one corresponding to strains of human origin and the other, containing several related STs (ST-61, ST-64, ST-301 etc.), corresponding to strains of animal origin only. A previous study analyzing 75 strains of S.