Background
The GNRCS monitors invasive streptococcal disease in Germany. This includes important human pathogens like Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae and Streptococcus dysgalactiae, but also all other streptococci. This report provides an overview of the 123 validly published streptococcal (sub)species, using routine diagnostic techniques.
Methods
Official type-strains of all species and subspecies of the genus streptococcus mentioned in the list of prokaryotic names with standing in nomenclature in 2021 have been analysed using haemolysis- and colony-size-assessment, catalase-, leucine-aminopeptidase- (LAP) and pyrrolidonyl-arylamidase-test (PYR), optochine-susceptibility-test, Lancefield-typing and MALDI-Biotyper®-analysis.
Results
All type-strains showed a negative catalase-test and a positive LAP-reaction. The PYR-test, to discriminate S. pyogenes showed positive reactions by nine other streptococcal species. All type-strains were optochine-resistant except S. pneumoniae. 66 of the type-strains showed α-haemolysis, 19 β-haemolysis and 34 γ-haemolysis with 15% of the α-haemolytic (3×A, 2×C, 4×G, 1×F), 63% of the β-haemolytic (2×A, 7×C, 2×G, 1×F) and 24% of the γ-haemolytic strains (2×A, 3×B, 1×C, 1×G, 1×F) positive for a Lancefield-antigen. The MALDI-Biotyper® was able to correctly assign the species for 68 (57%) type-strains, while 33 (28%) were wrongly identified and 18 (15%) received no species assignment.
Conclusions
The combination of catalase- and LAP-test reliably identifies all streptococci, including recently described species. Optochine susceptibility is still a good marker to exclude pneumococci, but S. pyogenes isolates identified by PYR-test need further confirmation. The widely used MALDI-Biotyper® is able to identify most streptococcal species associated with human infections. However, exceptions should be expected, as the presented study is limited to one type-strain per species.