Abstract

BackgroundMembers of the genus Proteus are mostly opportunistic pathogens that cause a variety of infections in humans. The molecular evolutionary characteristics and genetic relationships among Proteus species 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 genus Proteus.ResultsOf all 223 Proteus strains collected in the current study, the phylogenetic tree of five concatenated HKGs (dnaJ, mdh, pyrC, recA and rpoD) divided 223 strains into eleven clusters, which were representative of 11 species of Proteus. Meanwhile, the phylogenetic trees of the five individual HKGs also corresponded to that of the concatenated tree, except for recA, 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 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 was congruent with the most abundant Proteus species. In addition, we used the established MLSA method to identify the randomly collected Proteus and found that P. mirabilis is the most abundant species. However, the second most abundant species is P. terrae but not P. vulgaris. Combined with the genetic, genomic and phenotypic characteristics, these findings indicate that three species, P. terrae, P. cibarius and Proteus genospecies 5, should be regarded as heterotypic synonyms, and the species should be renamed P. terrae, while Proteus genospecies 5 has not been named to date.ConclusionsThis study suggested that MLSA is a powerful method for the discrimination and classification of Proteus at the species level. The MLSA scheme provides a rapid and inexpensive means of identifying Proteus strains. The identification of Proteus species determined by the MLSA approach plays an important role in the clinical diagnosis and treatment of Proteus infection.

Highlights

  • Members of the genus Proteus are mostly opportunistic pathogens that cause a variety of infections in humans

  • Dai et al BMC Microbiology (2020) 20:152 (Continued from previous page) genomic and phenotypic characteristics, these findings indicate that three species, P. terrae, P. cibarius and Proteus genospecies 5, should be regarded as heterotypic synonyms, and the species should be renamed P. terrae, while Proteus genospecies 5 has not been named to date

  • This study suggested that multilocus sequence analysis (MLSA) is a powerful method for the discrimination and classification of Proteus at the species level

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Summary

Introduction

Members of the genus Proteus are mostly opportunistic pathogens that cause a variety of infections in humans. Most members of the genus Proteus are opportunistic pathogens that cause a variety of infections in humans, including urinary tract infections [1], wounds, and respiratory tract, skin, eye, ear, nose, and throat infections [2]. Strains of P. vulgaris comprised three biogroups based on three biochemical reactions, namely, indole production, salicin fermentation and aesculin hydrolysis. Biogroup 3 was positive for indole production but negative for salicin fermentation and aesculin hydrolysis [4] and further separated into four groups by DNA-DNA hybridization, which were designated Proteus genospecies 3, 4, 5 and 6 [4]. The genus Proteus comprises ten validly published species and three unnamed genospecies to date (4, 5 and 6)

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