Summary auto-generated
This study reclassified Proteus vulgaris biogroup 3, a historically heterogeneous bacterial group, using DNA-DNA hybridization analysis. Researchers examined 52 strains, including 36 from biogroup 3, and identified four distinct genomospecies within this biogroup. Following a 1999 Judicial Commission decision to designate P. vulgaris biogroup 2 strains as the true P. vulgaris species, the authors formally named biogroup 3 strains as Proteus hauseri sp. nov., with type strain ATCC 700826T. Three additional genomospecies (4, 5, and 6) containing 5, 18, and 11 strains respectively were identified but remain unnamed due to insufficient biochemical differentiation. P. hauseri is distinguished by positive indole production and negative salicin fermentation and aesculin hydrolysis. All four groups showed similar antimicrobial susceptibility patterns, with resistance to ampicillin and cefazolin. Most isolates originated from human urine samples, with smaller numbers from other clinical sources. The study clarifies the taxonomy of an important urinary pathogen and highlights ongoing challenges in phenotypic differentiation of closely related species.
Key findings
- Proteus vulgaris biogroup 3 contains four genetically distinct species identifiable by DNA-DNA hybridization at 74-99% relatedness within groups
- Proteus genomospecies 3 was formally named P. hauseri sp. nov., with ATCC 700826T designated as the type strain
- Three unnamed genomospecies (4, 5, and 6) were identified but could not be reliably separated by biochemical tests or protein patterns
- P. hauseri and genomospecies 4, 5, and 6 show similar antimicrobial susceptibility patterns with resistance to ampicillin and cefazolin but susceptibility to fluoroquinolones and aminoglycosides
- L-rhamnose fermentation is the primary biochemical test distinguishing P. genomospecies 4 from most other groups
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Abstract
Strains traditionally identified as Proteus vulgaris formed three biogroups. Biogroup 1, characterized by negative reactions for indole production, salicin fermentation and aesculin hydrolysis, is now known as Proteus penneri. Biogroup 2, characterized by positive reactions for indole, salicin and aesculin, was shown by DNA hybridization (hydroxyapatite method) to be a genetic species separate from biogroup 1 and from biogroup 3 which is positive for indole production and negative for salicin and aesculin. In this study, 52 strains were examined, of which 36 strains were Proteus vulgaris biogroup 3, which included the current type strain of the species P. vulgaris (ATCC 29905(T)), and compared to seven strains of Proteus vulgaris biogroup 2 and nine type strains of other species in the genera Proteus, Providencia and Morganella. By DNA hybridization, these 36 strains were separated into four distinct groups, designated as Proteus genomospecies 3, 4, 5 and 6. DNAs within each separate Proteus genomospecies were 74--99% related to each other in 60 degrees C hybridization reactions with =< 4.5% divergence between related sequences. Proteus genomospecies 3 contained the former P. vulgaris type strain and one other strain and was negative in reactions for salicin fermentation, aesculin hydrolysis and deoxyribonuclease, unlike the reactions associated with strains considered as typical P. vulgaris which are positive in reactions for salicin, aesculin and DNase. Genomospecies 3 can be distinguished from Proteus genomospecies 4, 5 and 6 because it is negative for Jordan's tartrate. Proteus genomospecies 4, containing five strains, was differentiated from Proteus penneri, genomospecies 3 and 6 and most, but not all, strains of genomospecies 5, by its ability to ferment L-rhamnose. Proteus genomospecies 5 and 6, containing 18 and 11 strains, respectively, could not be separated from each other by traditional biochemical tests, by carbon source utilization tests or SDS-PAGE of whole-cell proteins. In an earlier publication, a request was made to the Judicial Commission that the former type strain of P. vulgaris (ATCC 13315) be replaced by P. vulgaris biogroup 2 strain ATCC 29905(T), a strain considered more biochemically typical of P. vulgaris strains. This would have the effect of assigning the name P. vulgaris to P. vulgaris biogroup 2. Since this request has been acceded to, the name Proteus hauseri is herein proposed for Proteus vulgaris genomospecies 3. Its type strain is ATCC 700826(T). Proteus genomospecies 4, 5 and 6 will remain unnamed until better phenotypic differentiation can be accomplished. All Proteus genomospecies were similar in their antimicrobial susceptibility patterns. Nineteen strains were isolated from urine, four from faeces, two from wounds, nine from other human sources and two from animals.