Evaluation of sclB gene variation in Streptococcus pyogenes (Lancefield group A Streptococcus) and potential for subtyping

Variation of sclB gene sequences in group A Streptococcus (GAS) strains was evaluated for its potential use in subtyping the most common serotypes of Streptococcus pyogenes encountered in the UK. We sequenced a total of 188 strains, including randomly selected invasive GAS and outbreak-related strains. Variability was highest amongst M/emm 89 strains, whereas very little variation was observed amongst M/emm 1 and M/emm 28 GAS strains. Repeat patterns were identified in the collagen structure motif (CSM) of the M/emm 89 GAS strains. The sporadic strains were very diverse and encompassed most of the CSM patterns, whereas the outbreak-related strains were mainly clustered into two CSM groups. sclB gene cluster analysis distinguished outbreak strains from two different healthcare settings in the same geographical area. Sequence variations were assessed by the number of pentameric repeats (CAAAA) present at the 5′ region of the sclB gene. The determination of sclB polymorphisms amongst GAS serotype M/emm 89 strains could be used as an important epidemiological marker to inform clinicians and outbreak control teams during outbreak investigations.