title: Potential of MALDI-TOF MS as an alternative approach for capsular typing Streptococcus pneumoniae isolates.
abstract: Streptococcus pneumoniae can be classified in more than 90 capsular types, as traditionally determined by serological methods and more recently by PCR-based techniques. Such methods, however, can be expensive, laborious or unable to accurately discriminate among certain serotypes. Therefore, determination of capsular types, although extremely important for epidemiological purposes and for estimating the impact of pneumococcal conjugate vaccines, is mainly restricted to research laboratories, being rarely performed in the clinical setting. In the present study, MALDI-TOF MS was evaluated as an alternative tool to characterize 416 pneumococcal isolates belonging to serotypes 6A, 6B, 6C, 9N, 9V or 14. For MALDI-TOF MS analysis, each isolate was submitted to an extraction protocol using formic acid and acetonitrile. Measurements were performed with a Bruker Microflex LT mass spectrometer using default parameters and generating spectra in the range of 2,000-20,000 m/z. Spectra were analyzed with the BioNumerics software v7.6. Isolates were mainly distributed according to the capsular type in a Neighbor Joining tree and serotypes investigated were successfully discriminated by the presence/absence of 14 selected biomarkers. The results suggest that MALDI-TOF MS is a promising alternative for typing pneumococcal strains, highlighting its usefulness for rapid and cost-effective routine application in clinical laboratories.
authors.affiliation: Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Tatiana C A
authors.initials: TC
authors.lastname: Pinto
authors.affiliation: Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Natalia S
authors.initials: NS
authors.lastname: Costa
authors.affiliation: Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Luciana F S
authors.initials: LF
authors.lastname: Castro
authors.affiliation: Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Ribeiro
authors.affiliation: Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Ana Caroline N
authors.initials: AC
authors.lastname: Botelho
authors.affiliation: Universidade Federal Fluminense, Niterói, RJ, Brazil.
authors.forename: Felipe P G
authors.initials: FP
authors.lastname: Neves
authors.affiliation: Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Jose Mauro
authors.initials: JM
authors.lastname: Peralta
authors.affiliation: Instituto de Microbiologia Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Lucia M
authors.initials: LM
authors.lastname: Teixeira
mesh_terms: D015373:Bacterial Typing Techniques / Q000379:methods*; D016000:Cluster Analysis; D011008:Pneumococcal Infections / Q000382:microbiology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013296:Streptococcus pneumoniae / Q000737:chemistry* / Q000145:classification*