Genomic research reveals new Strep A variant in Australia

27 February 2023

IMB researchers have discovered a new variant of the Strep A bacterium in Australia, by conducting genomic surveillance to track its spread.

IMB’s Professor Mark Walker, together with co-lead Dr Mark Davies from The Peter Doherty Institute for Immunity and Infection, has detected a strain of Strep A called M1uk in Australia and determined the mutation that makes it produce more toxin compared with the original bacterium.

Strep A can lead to deadly infections

Group A Streptococcus (Strep A) is a bacterial pathogen commonly found in the throat and on the skin and causes common infections such as sore throat, scarlet fever and impetigo, but in some rare cases, the bacteria can also lead to severe, life-threatening infections known as invasive group A Streptococcus diseases (iGAS), like sepsis or toxic-shock syndrome.

The new variant has been associated with a surge in cases of scarlet fever and invasive Strep A infections  around the world, with a similar trend observed in Australia.

A recent surge of Strep A cases

“The surge of cases in the UK has been associated with the new variant M1uk, and now we need to monitor its spread around Australia to find out if it is directly linked with the clinical increase of cases or not – we can do this using enhanced genomic surveillance,” Dr Mark Davies said.

“This work is the result of extensive collaboration across Victoria and Queensland that has involved research labs and clinical public health labs.”

The mechanism of how the new variant has changed was also characterised through the collaboration.

New variant produces more virulence toxin

Professor Mark Walker
Professor Mark Walker

“In the UK, the new variant quickly took over from the original strain and this may be because it produces more of a virulence toxin which undermines the immune system, which is caused by a single mutation in a bacterial gene near the toxin,” Professor Walker said.

“This mutation results in ineffective termination of gene transcription leading to elevated levels of the neighbouring toxin gene.”  

Professor Walker is leading a research effort to develop an mRNA vaccine against Strep A and recently was part of a team securing almost $8 million in philanthropic funding from the Leducq Foundation.

This research was published in Nature Communications.