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Updated: Jan 29, 2026
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Utility of MALDI-TOF MS as a new tool for Streptococcus pneumoniae serotyping
María Ercibengoa1,2,3, Marta Alonso1,2, Diego Vicente1,2,3
1Hospital Universitario Donostia-Instituto de Investigación Sanitaria Biodonostia, San Sebastián, Spain.
Abstract:
Nowadays, more than 95 different Streptococcus pneumoniae serotypes are known, being less than one third responsible for the majority of severe pneumococcal infections. After the introduction of conjugate vaccines, a change in the epidemiology of the serotypes causing invasive pneumococcal disease has been observed making the surveillance of circulating serotypes especially relevant. Some recent studies have used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) technology to identify the most frequent pneumococcal serotypes that cause invasive disease. The objectives of this study were to evaluate the efficacy of previously described discriminatory peaks determined by MALDI-TOF MS for the identification of serotypes 6B, 19F, 19A and 35B using reference and clinical isolates and to try to identify other discriminatory peaks for serotypes 11A, 19F and 19A using transformed pneumococcal strains. Most of the proposed peaks defined in the literature for the identification of serotypes 6B, 19F, 19A, 35B were not found in the spectra of the 10 reference isolates nor in those of the 60 clinical isolates tested corresponding to these four serotypes. The analysis and comparison of the mass spectra of genetically modified pneumococci (transformed strains) did not allow the establishment of new discriminatory peaks for serotypes 11A, 19F, and 19A. MALDI-TOF MS in the usual range of 2,000 to 20,000 m/z did not prove to be a valid technique for direct S. pneumoniae serotyping.
Insights
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is not effective for direct Streptococcus pneumoniae serotyping. Previously identified discriminatory peaks failed to identify common serotypes in reference and clinical isolates.
Area of Science:
- Microbiology
- Immunology
- Mass Spectrometry
Background:
- Over 95 Streptococcus pneumoniae serotypes exist, with a subset causing most severe infections.
- Vaccine introduction has altered pneumococcal disease epidemiology, necessitating serotype surveillance.
- Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been explored for serotype identification.
Purpose of the Study:
- To assess previously identified MALDI-TOF MS discriminatory peaks for Streptococcus pneumoniae serotypes 6B, 19F, 19A, and 35B.
- To identify new discriminatory peaks for serotypes 11A, 19F, and 19A using genetically modified strains.
Main Methods:
- Evaluation of MALDI-TOF MS spectra from 10 reference and 60 clinical Streptococcus pneumoniae isolates.
- Analysis of mass spectra from genetically modified (transformed) pneumococcal strains.
- Focus on the 2,000 to 20,000 m/z range for discriminatory peaks.
Main Results:
- Previously proposed discriminatory peaks for serotypes 6B, 19F, 19A, and 35B were not detected in reference or clinical isolates.
- Genetically modified strains did not yield new discriminatory peaks for serotypes 11A, 19F, or 19A.
- MALDI-TOF MS proved invalid for direct Streptococcus pneumoniae serotyping within the tested mass range.
Conclusions:
- MALDI-TOF MS, as applied, is not a reliable method for direct Streptococcus pneumoniae serotyping.
- Further research is needed to develop accurate and rapid serotyping techniques.
- Accurate serotyping remains crucial for monitoring pneumococcal disease epidemiology post-vaccination.
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