A UK company claims to have discovered a compound that renders the MRSA superbug vulnerable to the antibiotic it normally resists.MRSA – methicillin-resistant Staphylococcus aureus – is defined by its ability to resist the antibiotic methicillin. Like penicillin, methicillin works by blocking bacterial enzymes called PBPs, which normally strengthen cell walls by forming cross links. The first MRSA strains appeared in 1961, just two years after methicillin was launched. These bacteria got their resistance by picking up the gene for another PBP enzyme, PBP2a, to which methicillin cannot bind. MRSA strains now cause up to 60% of all “staph” infections in some hospitals. Some MRSA strains are also becoming resistant to other antibiotics – including vancomycin, the antibiotic doctors resort to when nothing else works. But Michael Levey’s team at Pharmaceutica in Worcestershire, UK, may have discovered a way to restore methicillin’s killing power. Following on from work done in the 1990s, his team found that certain compounds containing the amino acid glycine greatly increased 20 different MRSA strains’ susceptibility to methicillin. The dose needed to kill them dropped from 256 milligrams per litre to just 4 mg/l.
