Utility of MALDI-TOF MS as a new tool for Streptococcus pneumoniae serotyping

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.

MALDI-TOF mass spectrometry for sub-typing of Streptococcus pneumoniae

“…This latter point was highlighted as a major roadblock to progress in a recent systematic review [ 14 ]. Despite these limitations, our findings and conclusions are similar to those of Ercibengoa et al [ 11 ]. This carefully conducted study of 60 isolates of four common pneumococcal serotypes failed to confirm presence of either novel or previously established discriminatory MALDI-TOF peaks.…”

“…Encouragingly, in two of these, MALDI-TOF mass spectra clustering identified common pneumococcal serotypes fairly well [ 9 , 10 ]. However, the most recently published study yielded considerably less optimistic results [ 11 ].…”

À la carte, Streptococcus pneumoniae capsular typing: using MALDI-TOF mass spectrometry and machine-learning algorithms as complementary tools for the determination of PCV13 serotypes and the most prevalent NON PCV13 serotypes according to Argentina’s epidemiology

“…Subsequently, Ikryannikova (52) published an article referring to the di culty of discriminating pneumococcus from Streptococcus mitis by mass spectrometry; for which the authors proposed to use, in addition to biomarker peaks, arti cial intelligence classi er algorithms. However, other authors (53)(54)(55) tried to replicate this methodology but were unable to nd the peaks described.…”

Episode I. Exploring Streptococcus pneumoniae capsular typing through MALDI-TOF mass spectrometry and machine-learning algorithms in Argentina: Identifying prevalent NON PCV13 serotypes alongside PCV13 serotypes.

“…Subsequently, Ikryannikova (52) published an article referring to the di culty of discriminating pneumococcus from Streptococcus mitis by mass spectrometry; for which the authors proposed to use, in addition to biomarker peaks, arti cial intelligence classi er algorithms. However, other authors (53)(54)(55) tried to replicate this methodology but were unable to nd the peaks described. It is important to note that this limitation occasionally arose during the creation of the spectral database and during the classi cation of the unknown isolates performed in this manuscript.…”