Abstract
BackgroundWhole-cell matrix–assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has been successfully applied for bacterial identification and typing of many pathogens. The fast and reliable qualities of MALDI-TOF MS make it suitable for clinical diagnostics. MALDI-TOF MS for the identification and cluster analysis of Streptococcus pyogenes, however, has not been reported. The goal of our study was to evaluate this approach for the rapid identification and typing of S. pyogenes.Methods65 S. pyogenes isolates were obtained from the hospital. The samples were prepared and MALDI-TOF MS measurements were conducted as previously reported. Identification of unknown spectra was performed via a pattern recognition algorithm with a reference spectra and a dendrogram was constructed using the statistical toolbox in Matlab 7.1 integrated in the MALDI Biotyper 2.0 software.ResultsFor identification, 61 of 65 S. pyogenes isolates could be identified correctly by MALDI-TOF MS with BioType 2.0 when compared to biochemical identification (API Strep), with an accuracy of 93.85%. In clustering analysis, 44 of 65 isolates were in accordance with those established by M typing, with a matching rate of 67.69%. When only the M type prevalence in China was considered, 41 of 45 isolates were in agreement with M typing, with a matching rate of 91.1%.ConclusionsIt was here shown that MALDI-TOF MS with Soft Biotype 2.0 and its database could facilitate rapid identification of S. pyogenes. It may present an attractive alternative to traditional biochemical methods of identification. However, for classification, more isolates and advances in the MALDI-TOF MS technology are needed to improve accuracy.
Highlights
Streptococcus pyogenes (GAS) is an important gram-positive pathogen
Characterization of GAS is necessary for the prevention and control of the disease, but conventional methods based on serology are often low in specificity, have a high failure rate, are time and labor consuming and are sometimes costly [2]
The 7 GAS isolates were correctly differentiated from 3 suis type 2 (SS2) isolates, and one conserved species characteristic peak was observed (Figure 1)
Summary
Streptococcus pyogenes (GAS) is an important gram-positive pathogen. It can cause a broad spectrum of diseases, including acute pharyngitis, impetigo, rheumatic fever, bacteremia and toxic shock syndrome [1]. A rapid and simple diagnostic tool is of utmost importance for GAS identification. Effective GAS vaccine research is focusing on the M protei [3] and it has been reported that strains of certain M types are epidemiologically associated with particular clinical syndrome [4]. MALDI-TOF MS for the identification and cluster analysis of Streptococcus pyogenes, has not been reported. The goal of our study was to evaluate this approach for the rapid identification and typing of S. pyogenes
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