Comparison of species identification of endocarditis associated viridans streptococci using rnpB genotyping and 2 MALDI-TOF systems

Jenny Isaksson; Magnus Rasmussen; Bo Nilson; Liselott Svensson Stadler; Siri Kurland; Lars Olaison; Elisabeth Ek; Björn Herrmann

doi:10.1016/j.diagmicrobio.2014.12.007

Comparison of species identification of endocarditis associated viridans streptococci using rnpB genotyping and 2 MALDI-TOF systems

Diagn Microbiol Infect Dis. 2015 Apr;81(4):240-5. doi: 10.1016/j.diagmicrobio.2014.12.007. Epub 2014 Dec 27.

Authors

Jenny Isaksson¹, Magnus Rasmussen², Bo Nilson³, Liselott Svensson Stadler⁴, Siri Kurland⁵, Lars Olaison⁶, Elisabeth Ek⁷, Björn Herrmann⁸

Affiliations

¹ Section of Clinical Bacteriology, Department of Medical Sciences, Uppsala University, SE-751 85 Uppsala, Sweden.
² Division for Infection Medicine, Department of Clinical Sciences, Lund University, BMC B14, SE-22184 Lund, Sweden.
³ Clinical Microbiology, Labmedicin, Region Skåne, SE-221 85 Lund, Sweden; Department of Laboratory Medicine Lund, Section of Medical Microbiology, Lund University, SE-22362 Lund, Sweden.
⁴ Department of Infectious Diseases, Sahlgrenska Academy, University of Gothenburg, SE-413 46 Gothenburg, Sweden.
⁵ Section of Infectious Diseases, Department of Medical Sciences, Uppsala University, SE-751 85 Uppsala, Sweden.
⁶ Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg, SE-416 85 Gothenburg, Sweden.
⁷ Section of Infectious Diseases, Department of Medical Sciences, University of Gothenburg, SE-413 46 Gothenburg, Sweden.
⁸ Section of Clinical Bacteriology, Department of Medical Sciences, Uppsala University, SE-751 85 Uppsala, Sweden. Electronic address: bjorn.herrmann@medsci.uu.se.

PMID: 25616316
DOI: 10.1016/j.diagmicrobio.2014.12.007

Abstract

Streptococcus spp. are important causes of infective endocarditis but challenging in species identification. This study compared identification based on sequence determination of the rnpB gene with 2 systems of matrix-assisted laser desorption ionization-time of flight mass spectrometry, MALDI Biotyper (Bruker) and VITEK MS IVD (bioMérieux). Blood culture isolates of viridans streptococci from 63 patients with infective endocarditis were tested. The 3 methods showed full agreement for all 36 isolates identified in the Anginosus, Bovis, and Mutans groups or identified as Streptococcus cristatus, Streptococcus gordonii, or Streptococcus sanguinis. None of the methods could reliably identify the 23 isolates to the species level when designated as Streptococcus mitis, Streptococcus oralis, or Streptococcus tigurinus. In 7 isolates classified to the Mitis group, the rnpB sequences deviated strikingly from all reference sequences, and additional analysis of sodA and groEL genes indicated the occurrence of yet unidentified Streptococcus spp.

Keywords: Infective endocarditis; MALDI-TOF; Streptococcus spp; rnpB.

Publication types

Comparative Study
Evaluation Study
Research Support, Non-U.S. Gov't

MeSH terms

Endocarditis, Bacterial / diagnosis*
Endocarditis, Bacterial / microbiology
Genotyping Techniques / methods*
Humans
Sensitivity and Specificity
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*
Streptococcal Infections / diagnosis*
Streptococcal Infections / microbiology
Viridans Streptococci / chemistry
Viridans Streptococci / genetics
Viridans Streptococci / isolation & purification*