Summary auto-generated
This study examined the genetic and phenotypic diversity of 22 Aerococcus urinae strains isolated from human infections. A. urinae is a gram-positive coccus recently recognized as a urinary tract pathogen. The researchers discovered two biotypes: an esculin-negative group (predominantly from Denmark) and a previously unrecognized esculin-positive group (non-Danish isolates). DNA relatedness studies using the hydroxyapatite method showed that 14 of 15 esculin-negative strains exhibited very high DNA similarity (>90% at optimal and stringent temperatures with <1.5% sequence divergence). The esculin-positive strains showed greater genetic heterogeneity, forming at least two DNA hybridization subgroups. 16S rRNA sequence analysis confirmed that all A. urinae strains are closely related (98.2–99.3% similarity over 1,320 bases) and distinct from the closely related species A. viridans (92.6–93.5% similarity). The authors conclude that both biotypes belong to a single species, A. urinae, which likely contains two or more genetic subspecies. However, formal subspecies designation was deferred because the groups cannot be definitively differentiated phenotypically. The placement of A. urinae in the genus Aerococcus is supported by both genetic and phenotypic evidence.
Key findings
- A previously unrecognized esculin-positive biotype of A. urinae was identified among non-Danish clinical isolates, distinct from the well-characterized esculin-negative Danish strains
- DNA relatedness studies confirm that both biotypes belong to a single species, A. urinae, with genetic evidence supporting the existence of at least two or more subspecific genetic groups
- 16S rRNA sequence analysis demonstrates 98.2–99.3% similarity among A. urinae strains and 92.6–93.5% similarity to the related species A. viridans, confirming the taxonomic classification of A. urinae within the genus Aerococcus
- A. urinae is clinically significant as a human pathogen causing urinary tract infections, bacteremia, and endocarditis, with pathogenic potential comparable to established urinary tract pathogens
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Abstract
A number of Aerococcus-like organisms were recently recognized as human pathogens. Five Aerococcus-like strains were proposed as members of the new species Aerococcus urinae (with type strain E2 [= NCTC 12142]) on the basis of the results of a 16S rRNA sequence analysis. The intraspecies phenotypic and genetic relatedness of 22 selected A. urinae strains was investigated, and a hitherto unrecognized esculin hydrolysis-positive biotype was identified. A total of 14 of the 15 more common esculin-negative strains exhibited very high DNA relatedness as determined by the hydroxyapatite method (the levels of relatedness were greater than 90% in 55 and 70 degrees C reactions, with 1.5% or less divergence in related sequences). The DNA relatedness among the six esculin-positive strains was more heterogeneous, and two DNA hybridization subgroups were formed. Our results are compatible with the hypothesis that both biotypes are members of the single species A. urinae, which contains two or more genetic subspecies. The putative subspecies have not been formally proposed since they cannot be definitively differentiated. The inclusion of A. urinae in the genus Aerococcus is supported by the results of 16S rRNA sequencing. The rRNA sequence data also is compatible with placing both biotypes in a single species.