Superbugs act like bouncers, find scientists

SCOTTISH scientists have made a breakthrough in discovering how superbugs such as MRSA become resistant to treatment with antibiotics.

University of Edinburgh researchers have mapped the complex molecular structure of an enzyme found in many bacteria.

Dr David Dryden, of the university’s school of chemistry, who led an international study into superbugs, said the molecules – known as restriction enzymes – act like “bouncers” in a nightclub controlling the speed at which bacteria can acquire resistance to drugs and eventually become superbugs.

The study focused on E coli, but researchers said the results would apply to many other infectious bacteria.

After prolonged treatment with antibiotics, bacteria may evolve to become resistant to many drugs, as is the case with superbugs such as MRSA.

Bacteria become resistant by absorbing DNA – usually from other bugs or viruses – which contains genetic information enabling the bacteria to block the action of drugs.

Restriction enzymes can slow or halt this absorption process. Enzymes that work in this way are believed to have evolved as a defence mechanism for bacteria.

Dr Dryden, whose findings were published this month in the journal Genes & Development, said: “We have known for some time that these enzymes are very effective in protecting bacteria from attack by other species. Now we have painted a picture of how this occurs, which should prove to be a valuable insight in tackling the spread of antibiotic-resistant superbugs.

“The restriction enzymes are fascinating machines, it is one protein but has multiple activities.”

Hugh Pennington, emeritus professor of bacteriology at the University of Aberdeen, said the research would add to the overall knowledge of how bugs continue to evolve.

“It could be helpful in terms of finding better ways of analysing DNA and how the bugs evolved in the first place,” he said. “This is not something which would be used for patient treatment, but would be helpful for follow-up investigations tracking how something such as MRSA was spreading throughout a hospital.”

MRSA rates have been falling across the UK. Infection rates are estimated to be approximately 25 per cent of what they were four years ago.

Oliver Blatchford, consultant in public health medicine at NHS Health Protection Scotland, said: “The NHS in Scotland has seen a steady reduction in the numbers of MRSA bloodstream infections.

“In the last reported quarter, July to September 2011, Scotland had 48 of these infections, which was the lowest number we have had since the start of the surveillance programme in 2005, when it was 221 MRSA bloodstream infections in a quarter.

“This reduction in MRSA bacteraemias [blood stream infections] has been the result of several different programmes aimed at improving the quality of healthcare services in Scotland.”

The research was carried out in collaboration with the universities of Leeds and Ports-mouth with partners in Poland and France.