Some MRSA infections could be tackled using widely-available antibiotics, suggests new research from an international collaboration.

Since the discovery of penicillin, the introduction of antibiotics to treat infections has revolutionised medicine and healthcare, saving millions of lives. However, widespread use (and misuse) of the drugs has led some bacteria to develop resistance, making the medicines less effective. With few new antibiotics in development, antibiotic resistance is widely considered a serious threat to the future of modern medicine, raising the spectre of untreatable infections.

One of the most widely used and clinically important groups of antibiotics is the family that includes penicillin and penicillin derivatives. The first type of penicillin resistance occurred when bacteria acquired an enzyme, known as a beta-lactamase, which destroys penicillin. To overcome this, drug manufacturers developed new derivatives of penicillin, such as methicillin, which were resistant to beta-lactamase.

In the escalating arms race, one particular type of bacteria known as Methicillin-resistant Staphylococcus aureus — MRSA — has developed widespread resistance to this class of drugs. MRSA has become a serious problem in hospital- and community-acquired infections, forcing doctors to turn to alternative antibiotics, or a cocktail of different drugs which are often less effective, and raises concerns that even these drugs will in time become ineffective.

In previous research, a team of researchers in Cambridge identified an isolate of MRSA (a sample grown in culture from a patient’s infection) that showed susceptibility to penicillin in combination with clavulanic acid. Clavulanic acid is a beta-lactamase inhibitor, which prevents the beta-lactamase enzyme destroying penicillin; it is already used as a medicine to treat kidney infections during pregnancy.

In a study published today in Nature Microbiology, a team of scientists from the UK, Denmark, Germany, Portugal, and USA used genome sequencing technology to identify which genes make MRSA susceptible to this combination of drugs. They identified a number of mutations (changes in the DNA sequence) centred around a protein known as a penicillin-binding protein 2a or PBP2a.

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