Emerging Impact of Little-Known Strep Bacteria on Severe Infections in Australia

Recent research from the Peter Doherty Institute for Infection and Immunity highlights an under-recognized strep bacterium, Streptococcus dysgalactiae subspecies equisimilis (SDSE), as a growing cause of severe infections in Australia. Unlike the well-known group A strep, SDSE has been largely overlooked despite its increasing role in invasive diseases, particularly affecting First Nations Australian communities. The study, which analyzed over a decade of clinical and genomic data, reveals that SDSE is responsible for an expanding burden of serious infections, with rising incidence rates across both urban southeast Australia and remote northern regions. Notably, the research identified a bacterial clone, stG62647, spreading rapidly in Australia, Europe, and North America.

The investigation, published in The Lancet Microbe, underscores significant regional disparities. In metropolitan areas, infection rates are comparable to those of group A strep, with cases rising from 2011 to early 2023. Remote regions report fewer cases overall, but the number surpasses that in urban settings by 25%. The direct impact on First Nations populations is profound, with these communities experiencing over three times the risk of invasive SDSE compared to non-Indigenous Australians.

Genomic analysis revealed that SDSE behaves differently from its cousin, group A strep, in terms of transmission and recurrence, suggesting that current control strategies, such as antibiotics for close contacts, may not be as effective. Experts emphasize the urgent need for improved surveillance, targeted prevention measures, and vaccine development, with industry players like Moderna exploring genomic data to create broad-spectrum vaccines. These findings highlight critical health disparities and emphasize the importance of addressing social determinants and health inequities to combat the rising threat of SDSE infections in Australia.