Serotyping of pneumococci: evaluation of the genetic approach and performance with clinical samples

Analysis of Streptococcus pneumoniae using Fourier-transformed infrared spectroscopy allows prediction of capsular serotype

Determination of the capsule type of clinical isolates of Streptococcus pneumoniae is a prerequisite for epidemiological studies and further vaccine development. The Quellung reaction for serotyping is expensive and mostly done in reference centres. We wanted to evaluate whether Fourier-transformed infrared (FT-IR) spectroscopy is suitable for capsular type analysis and prediction of pneumococcal serotypes. We used the IR-Biotyper™ (Bruker) to create a database containing the spectra of 120 strains from invasive disease. The strains covered the 24 vaccine serotypes contained in the 13-valent conjugate vaccine (PCV13) and the 23-valent polysaccharide vaccine (PSV23). Hierarchical clustering analysis was performed. Finally, two different classification sets were created (PCV13 and PSV23). They were used to predict the serotype of 168 different challenge strains (invasive and non-invasive disease) covering 48 different serotypes (vaccine and non-vaccine types). FT-IR spectra from pneumococci (1300–800 cm⁻¹) clustered along their serotype as determined by the Quellung reaction (120 strains, 24 different serotypes). Strains with unknown serotype fell within the cluster of the correct serotype, as long as the latter was represented in the database (168 strains, 48 different serotypes). Concordance between the Quellung reaction and FT-IR spectroscopy was excellent (kappa ≥ 0.75). FT-IR spectroscopy is a fast and cost-effective method to predict the capsular serotype of pneumococci.

Streptococcus pneumoniae as an agent of urinary tract infections - a laboratory experience from 2010 to 2014 and further characterization of strains

Streptococcus pneumoniae is a rare cause of urinary tract infection. Between January 2010 and December 2014, 26 urine samples from 18 different patients contained S. pneumoniae at the Department for Infectious Diseases, University Hospital of Heidelberg. Patient age varied between three and 72 years. 13 patients were male and five were female. Past medical histories of 16 patients were available. Eight patients had a past medical history of renal transplant and four patients had other renal dysfunctions. Further analyses of the isolates revealed that the aspect of colonies is more resembling S. mitis than invasive isolates of S. pneumoniae. Optochin disk diameters tend to be 14 mm or smaller. Identification using MALDI-TOF or VITEK2 identification cards was accurate. Only 2 isolates showed a decreased susceptibility towards penicillin (MIC = 0.5 mg/L). Eight different serotypes were identified using a PCR approach as well Neufeld-Quellungs reaction.

Single-Step Multiplex PCR Assay for Determining 92 Pneumococcal Serotypes

For pneumococcal disease surveillance, simple and cost-effective methods capable of determining all serotypes are needed. Combining a single-tube multiplex PCR with fluorescently labeled primers followed by amplicon analysis using automated fluorescent capillary electrophoresis, each serotype of 92 reference isolates and 297 recently collected clinical isolates was successfully determined.

Capsular typing of Streptococcus pneumoniae isolated in an Algerian hospital using a new multiplex PCR-based scheme

We developed a new sequential multiplex-PCR-based typing scheme (MPBTS) for pneumococcal capsular classification. The serogroup/type of 37 control isolates obtained by the Quellung reaction, MPBTS, and nucleotide sequencing, were fully concordant. The serogroups/types of 75 invasive isolates determined by MPBTS, presented 100% specificity and 96% sensitivity, when compared with the Quellung reaction.