Evidence for increased horizontal gene transfers among streptococci from group A streptococcal endemic regions

Streptococcus dysgalactiae subsp. equisimilis (group G streptococcus, GGS) is generally regarded as a commensal organism but can cause a similar spectrum of diseases as Streptococcus pyogenes (group A streptococcus, GAS). While the lateral acquisition of genes between these two phylogenetically closely related species is well documented, the extent and mechanisms of lateral transfers are yet to be elucidated. We have recently demonstrated that cross-species genetic transfers are common between GGS and two closely related human pathogens, group A streptococcus and the group B streptococcus. Furthermore, we suggested that phage mediated lateral gene transfers may occur more frequently in populations with a high burden of GAS infection. To further substantiate this, we examined the dissemination of a functional prophage in selected GGS and GAS isolates belonging to distinct genotypes from GAS-endemic and non-endemic regions. Our results confirm that phage mediated lateral transfers between GAS and GGS are common in GAS endemic regions. This observation further impacts on the epidemiology of GAS diseases in endemic regions and future vaccine stratagies.