Undetectable superbug strain of Strep A discovered which is immune to some antibiotics

A superbug strain of Strep A has been discovered which is undetectable and immune to some antibiotics, scientists have found.

Strep A is a common infection which causes strep throat, or tonsillitis, scarlet fever and, in extreme cases, invasive Group A Strep (iGAS), which can be fatal.

Researchers from Australia found Strep A has evolved a new way to nullify some antibiotics and this type of antimicrobial resistance (AMR) is undetectable with current methods .

Some antibiotics work by starving the bacteria of a key food source called folates and this kills the infection.

Normally, the Strep A bacteria makes this chemical itself and once the supply is cut off, it dies. However, the Australian researchers found, for the first time, that the bacteria has developed a way to use folates made by the human host.

“This makes the antibiotic ineffective and the infection would likely worsen when the patient should be getting better,” Dr Timothy Barnett, study author and head of the Strep A Pathogenesis and Diagnostics team at Wesfarmers, said.

“This new form of resistance is undetectable under conditions routinely used in pathology laboratories, making it very hard for clinicians to prescribe antibiotics that will effectively treat the infection, potentially leading to very poor outcomes and even premature death.

Treated with penicillin

“Unfortunately, we suspect this is just the tip of the iceberg – we have identified this mechanism in Group A Strep but it’s likely it will be a broader issue across other bacterial pathogens.”

In Britain, Strep A is most commonly treated with penicillin which is not affected by this new form of resistance. Trimethoprim and Sulfamethoxazole are the antibiotics which are circumnavigated by this new form of AMR.

A primary school child in Surrey sadly died of Strep A last week after developing a case of iGAS. There is an ongoing outbreak at their school, Ashford Church of England School, as well as at a nearby school, and powerful antibiotics have been prescribed.

Health authorities in the UK say they regularly check whether cases of bacterial infections are resistant to any treatments and there is no reason to believe the current outbreak in Surrey is the new superbug strain of Strep A.

Official statistics from the UK Health Security Agency show that for every 100,000 cases of scarlet fever, 3.1 people will develop iGAS.

However, the rate is around nine per 100,000 for children under one and eight for children aged one to four.

Data show the rate of iGAS is higher this year than it was pre-pandemic for children aged between one and nine years old.

Dr Asha Bowen, a study co-author, said: “We’ve previously known how to detect antimicrobial resistance in a laboratory and are able to use that information to predict what treatments would work.

“These new mechanisms are ones that are really slipping under our radar and more scientific research is needed because a future without antibiotics is a really scary one to contemplate.”

This form of AMR goes undetected because the bacteria appears to be killed by antibiotics in a laboratory because there is no alternative source of folate as fuel.

Microbe uses human folate as energy

But the same microbe, if in a person, would be unaffected by the drug as it could use human folate as energy.

AMR kills around 1.27 million people globally a year, with Dr Barnett calling it a “silent pandemic” which poses a greater threat to humanity than Covid-19.

“In addition to 10 million deaths per year by 2050, the World Health Organization estimates AMR will cost the global economy $100 trillion if we can’t find a way to combat antibiotic failure,” he said.

“Without antibiotics, we face a world where there will be no way to stop deadly infections, cancer patients won’t be able to have chemotherapy and people won’t have access to life-saving surgeries.

“In order to preserve the long-term efficacy of antibiotics, we need to further identify and understand new mechanisms of antibiotic resistance, which will aid in the discovery of new antibiotics and allow us to monitor AMR as it arises.”

The team is now working on creating a testing method for this form of antibiotic resistance, but getting diagnostic tools into primary care settings is notoriously difficult as often the tests are more expensive than the pills.

The new findings are published in Nature Communications.