Multilocus sequence analysis for the taxonomic updating and identification of the genus Proteus and reclassification of Proteus genospecies 5 O'Hara et al. 2000, Proteus cibarius Hyun et al. 2016 as later heterotypic synonyms of Proteus terrae Behrendt et al. 2015

Background Members of the genusProteusare mostly opportunistic pathogens that cause a variety of infections in humans. The molecular evolutionary characteristics and genetic relationships amongProteusspecies have not been elucidated to date. In this study, we developed a multilocus sequence analysis (MLSA) approach based on five housekeeping genes (HKGs) to delineate phylogenetic relationships of species within the genusProteus. Results Of all 223Proteusstrains collected in the current study, the phylogenetic tree of five concatenated HKGs (dnaJ, mdh, pyrC, recAandrpoD) divided 223 strains into eleven clusters, which were representative of 11 species ofProteus. Meanwhile, the phylogenetic trees of the five individual HKGs also corresponded to that of the concatenated tree, except forrecA, which clustered four strains at an independent cluster. The evaluation of inter- and intraspecies distances of HKG concatenation indicated that all interspecies distances were significantly different from intraspecies distances, which revealed that these HKG concatenations can be used as gene markers to distinguish differentProteusspecies. Further web-based DNA-DNA hybridization estimated by genome of type strains confirmed the validity of the MLSA, and each of eleven clusters was congruent with the most abundantProteusspecies. In addition, we used the established MLSA method to identify the randomly collectedProteusand found thatP. mirabilisis the most abundant species. However, the second most abundant species isP. terraebut notP. vulgaris. Combined with the genetic, genomic and phenotypic characteristics, these findings indicate that three species,P. terrae,P. cibariusandProteusgenospecies 5, should be regarded as heterotypic synonyms, and the species should be renamedP. terrae, whileProteusgenospecies 5 has not been named to date. Conclusions This study suggested that MLSA is a powerful method for the discrimination and classification ofProteusat the species level. The MLSA scheme provides a rapid and inexpensive means of identifyingProteusstrains. The identification ofProteusspecies determined by the MLSA approach plays an important role in the clinical diagnosis and treatment ofProteusinfection.