63 ST per isolate); see [37] for a review. This level of STs diversity allowed a wide range of applications from strain characterisation to population GSI-IX purchase structure analysis and to evolutionary studies [37]. A MLST scheme has been recently proposed for Brucella spp., the genus phylogenetically most related to Ochrobactrum [41]. The genes dnaK, gap, omp25 and trpE were analysed for both Brucella spp. and O. anthropi. Considering these 4 loci, genetic diversity in O. anthropi (6.6 polymorphic nucleotides per 100) appeared 5-fold higher than observed in the genus Brucella (1.4%). This difference in genetic diversity could reflect differences in lifestyles, qualifying O. anthropi
as a versatile generalist and Brucella as a narrow niche-specialist. The recA gene displayed the lower genetic diversity in our scheme. It was previously learn more used for studying the phylogenetic interrelationships
among members of the family Brucellaceae and appeared also unable to distinguish between some species in the genus Ochrobactrum [9]. We confirm here the high conservation of this marker and its inefficiency to explore the interrelationships in the species O. anthropi. The rpoB and dnaK sequences were also conserved among strains of O. anthropi. These results justified multi-locus approaches rather than single target-based analyses for sub-typing O. anthropi. However, in our MLST study, two markers reflected the overall diversity determined by the 7 loci. This was the case for trpE and to a lesser extent for the gap gene. Differing from rrs and recA, trpE and gap were less conserved and gave ATM/ATR assay a tree with robust phylogenetic interrelationships at the sub-species level. These two markers could be tested at the intra- and the inter-genus Chlormezanone level in order to solve conflicting taxonomic positions in the family Brucellaceae [9]. The population of 70 strains of O. anthropi appeared structured in 2 major and 3 minor clonal complexes.
The calculation of standardized IA indicated a linkage disequilibrium that also evoked a clonal population structure. However, split decomposition analysis resulted in a network-like graph indicating a significant level of recombination mostly inside clonal complexes. Moreover, phylogenetic conflicts were observed when the trees based on different markers were compared. The persistence of a linkage disequilibrium in populations in which recombination is frequent could be due to an epidemic population structure or to a mix of ecologically separated subpopulations [39]. Our results were compatible with an epidemic population structure composed of a limited number of clones originating from a background of unrelated genotypes recombining frequently. Our results were also compatible with a mix of ecologically separated populations i.e. environmental and clinical strains.