RESEARCHERS from St Andrews and Dundee universities have made a breakthrough which could prove crucial in tackling MRSA (methicillin-resistant S aureus) and resistant infections.

In conjunction with the Wellcome Trust Sanger Institute, Scottish university scientists have discovered that MRSA emerged long before the introduction of the antibiotic methicillin into clinical practice.

The findings, published in Genome Biology, found that S aureus acquired the gene that confers methicillin resistance as early as the mid-nineteen-forties, 15 years before methicillin was first introduced.

The widespread use of earlier antibiotics, such as penicillin, is now believed to have allowed the MRSA to take hold.

Professor Matthew Holden, molecular microbiologist at the University of St Andrews, said: “Our study provides important lessons for future efforts to combat antibiotic resistance.

“It shows that new drugs which are introduced to circumvent known resistance mechanisms, as methicillin was in 1959, can be rendered ineffective by unrecognized, pre-existing adaptations in the bacterial population. These adaptations happen because, in response to exposure to earlier antibiotics, resistant bacterial strains are selected instead of non-resistant ones as bacteria evolve.”

Bacteria can become resistant to antibiotic treatment and the NHS has consistently warned of the dangers that the overuse of antibiotics can incur, warning patients to seek antibiotic treatment only when absolutely necessary.

Figures on Scottish antibiotic use were published last year, and marked an overall decline.

Dr Michael Lockhart, consultant medical microbiologist for Health Protection Scotland was “encouraged” by the results but cautioned that “overuse and inappropriate use of antibiotics has led to a rise in resistant infections around the world”.

A worldwide study, conducted between 2009 and 2014, found that two-thirds of countries examined reported drug resistant strains of “last resort” extended-spectrum cephalosporin antibiotics, used to treat post-operative infections and pelvic inflammatory disease. Holden added: “S aureus has proven to be particularly adept at developing resistance in the face of new antibiotic challenges, rendering many antibiotics ineffective.

“This remains one of the many challenges in tackling the growing problem of antimicrobial resistance.

“In order to ensure that future antibiotics retain their effectiveness for as long as possible, it is essential that effective surveillance mechanisms are combined with the use of genome sequencing to scan for the emergence and spread of resistance.”