PubMedCrossRef 41. Sainte-Marie G: A paraffin embedding technique for studies employing immunofluorescence. J Histochem Cytochem 1961, (10):250–256. Competing interests The authors declare that they have no competing interests. Authors’ contributions NAC carried out the microbiological work and the animal studies. GP and AdMdL conceived of the study. NAC,

AdMdL and GP designed the experiments. NAC performed the statistical analyses and prepared the figures. NAC and AdMdL wrote the draft of the manuscript. GP revised it for significant intellectual content. All authors read and approved the final version of the manuscript.”
“Background Brucella is a genus of bacteria causing brucellosis, a zoonosis that affects a large variety of mammals and that is readily transmitted to humans. The VX-770 cost genus includes several classical species that can be distinguished by their preferential host range, surface structure, biochemical and physiological features, and genetic markers. This classification is reflected in some degree of genetic polymorphism,

one of the main sources of which is the copy number and distribution of IS711 (IS6501) [1, 2]. B. melitensis and B. suis contain seven complete IS711 copies [3]. B. abortus carries six complete and one truncated IS711 copies [4], B. ceti and B. pinnipedialis more than 20 copies [5, 6] and B. ovis 38 copies [7]. IS711 is very stable: its mobility has been demonstrated only by using a “”transposon trap”" in vitro in B. ovis and B. pinnipedialis, SRT2104 chemical structure but not in B. melitensis nearly and B. abortus [3]. Based on this stability, polymorphism at the alkB locus [8] is used to differentiate B. abortus from B. melitensis, B. ovis and B. suis in the AMOS multiplex PCR assay [9]. IS711 stability is not only relevant for Brucella typification: its mobility is implicated in the generation of genetic diversity and speciation, as shown by the distribution of IS711 among the extant Brucella species. Here we report that IS711 transposition and the generation of the associated polymorphism takes place in B. abortus under natural conditions, when genetic drift should be limited by the selective pressure imposed by the host. Results and discussion In a previous

work with 46 B. abortus strains, it was found that two find more isolates (B12 and B16) displayed IS711 profiles that were different from that typical of B. abortus field strains [10]. This is confirmed here by the genetic profiling summarized in Table 1, and by the IS711 Southern blot presented in Figure 1. The latter shows that, while the reference strain B. abortus 544 presented seven IS711-carrying fragments, isolates B12 (x-B12), and B16, B49 and B50 (x-B16) displayed an additional one. It is known that RB51, a lipopolysaccharide rough strain obtained from B. abortus 2308 by multiple in vitro passages on antibiotic containing media, harbors eight copies plus an additional one that transposed into the lipopolysaccharide wboA gene [11]. Similarly, B.