A multilocus sequence analysis for the taxonomic update and identification of the genus Proteus

Abstract Background: The members of the genus Proteus are commonly opportunistic pathogens that cause a variety of infections in humans. The molecular evolutionary characteristics and genetic relationships among Proteus species are remain unelucidated. In this study, we developed a multilocus sequence analysis (MLSA) approach based on five housekeeping genes (HKGs) to delineate phylogenetic relationships of species within genus of Proteus. Results: Of all 223 Proteus strains collected in current study, phylogenetic tree of concatenated five HKGs (dnaJ, mdh, pyrC, recA and rpoD) divided into eleven clusters, which representative of their counterpart species. Meanwhile, phylogenetic trees of the five individual HKGs were also corresponded to that of the concatenated tree, except for recA, which clustered four strains at an independent cluster. The evaluation of inter- and intra-species distance of HKGs concatenation, all inter-species indicated more significant different distances than those of intra-species, which revealed these HKGs concatenation can be used as gene marker to distinguish different Proteus species. Further web-based DNA-DNA hybridization estimated by genome of type strains confirmed the validity of the MLSA and each of eleven clusters were congruent with eleven different Proteus species. In addition, we used the established MLSA method to identify the randomly collected Proteus, and found that P. mirabilis is the most species of Proteus. However, the top second is P. terrae, but not P. vulgaris. Combined with the genetic, genomic and phenotypic characteristics, three species, P. terrae, P. cibarius and Proteus genospecies 5 should be regarded as the heterotypic synonyms.Conclusions: Our data suggested the MLSA was a powerful method for the discrimination and classification of the Proteus at species level. The MLSA scheme provides a rapid, economical and precise identification of Proteus strains. The identification of Proteus species determined by the MLSA approach plays an important role in clinical diagnosis and treatment of Proteus infection.