Identification of species of viridans group streptococci in clinical blood culture isolates by sequence analysis of the RNase P RNA gene, rnpB.
OBJECTIVE
Viridans group streptococci (VGS) cause severe diseases such as infective endocarditis and septicaemia. Genetically, VGS species are very close to each other and it is difficult to identify them to species level with conventional methods. The aims of the present study were to use sequence analysis of the RNase P RNA gene (rnpB) to identify VGS species in clinical blood culture isolates, and to compare the results with the API 20 Strep system that is based on phenotypical characteristics.


METHODS
Strains from patients with septicaemia or endocarditis were analysed with PCR amplification and sequence analysis of the rnpB gene. Clinical data were registered as well.


RESULTS
One hundred and thirty two VGS clinical blood culture isolates from patients with septicaemia (n=95) or infective endocarditis (n=36) were analysed; all but one were identified by rnpB. Streptococcus oralis, Streptococcus sanguinis and Streptococcus gordonii strains were most common in the patients with infective endocarditis. In the isolates from patients with haematological diseases, Streptococcus mitis and S. oralis dominated. In addition in 76 of the isolates it was possible to compare the results from rnpB analysis and the API 20 Strep system. In 39/76 (51%) of the isolates the results were concordant to species level; in 55 isolates there were no results from API 20 Strep.


CONCLUSIONS
Sequence analysis of the RNase P RNA gene (rnpB) showed that almost all isolates could be identified. This could be of importance for evaluation of the portal of entry in patients with septicaemia or infective endocarditis.
Westling
Katarina
K
Department of Medicine, Division of Infectious Diseases, I 73, Karolinska Institutet, Karolinska University Hospital/Huddinge, SE 141 86 Stockholm, Sweden. Katarina.Westling@ki.se
Julander
Inger
I
Ljungman
Per
P
Vondracek
Martin
M
Wretlind
Bengt
B
Jalal
Shah
S
D015373:Bacterial Typing Techniques; D001769:Blood / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics*; D004696:Endocarditis / Q000382:microbiology; D005838:Genotype; D006801:Humans; D010641:Phenotype; D016133:Polymerase Chain Reaction; D043262:Ribonuclease P / Q000235:genetics*; D018805:Sepsis / Q000382:microbiology; D017421:Sequence Analysis; D013290:Streptococcal Infections / Q000382:microbiology*; D034363:Viridans Streptococci / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism
D004269:DNA, Bacterial; D043262:Ribonuclease P