LONDON: Scientists studying a bacterium that causes scarlet fever, severe sore throat and a form of heart disease say they are closer to developing a vaccine that could one day prevent hundreds of thousands of infections a year.

In a study in the journal Nature Genetics, scientists from Britain and Australia found detailed differences between strains of Group A Streptococcus bacteria - known as Strep A - from 22 countries, but also found several molecular targets common across many strains, offering the potential for vaccine development.

Strep A is one of the world's top 10 causes of death from infectious diseases. It is estimated to cause more than half a million deaths every year.

It can cause several different infections, ranging from Strep throat to scarlet fever, which are constant threats in many parts of the world, to an illness called rheumatic heart disease, which can affect certain populations including Aboriginal Australians.

There is no effective vaccine for Strep A, and efforts to develop one have been hampered by the huge number and variety of Strep A strains - meaning it is very tricky to develop a vaccine that could be effective against all of them.

In this work, researchers from Britain's Wellcome Sanger Institute and Cambridge University, and from Australia's Doherty Institute and Queensland University, sequenced the DNA of more than 2,000 Strep A samples from 22 countries, including in Africa and from Australian Aboriginal communities.

"Using all the data we collected, we narrowed down common genes in almost all strains of Strep A globally," said Mark Davies of the Wellcome Sanger and Doherty institutes, who co-led the work.

"This is a tremendous step forward in identifying what may work as a global vaccine candidate."

Mark Walker, director of the Australian Infectious Diseases Research Centre, said the findings should "renew the momentum" and enable a fast-track approach to a global Strep A shot since potential drug developers could use the database to find the molecular targets most likely to lead to an effective vaccine.