x Abu Dhabi, UAEThursday 18 January 2018

MRSA: a killer moves from the hospital to the street

While cases of MRSA infection date to the 1960s and were once largely confined to hospitals, the bacteria is increasingly appearing in gymnasiums, dormitories and even on public transportation systems.

Hospital staff in Oregon put on protective gowns, gloves and masks upon entering the room of a patient who has tested positive for MRSA.
Hospital staff in Oregon put on protective gowns, gloves and masks upon entering the room of a patient who has tested positive for MRSA.

MRSA is a superbug that has wreaked such havoc in British hospitals that the government ordered a £50 million (Dh341m) "deep clean" of the hospitals to reduce the number of MRSA infections acquired by patients. The move followed the deaths of thousands of people from infections picked up while in hospital, often after coming in with relatively minor ailments. MRSA or methicillin-resistant Staphylococcus aureus is a form of bacterium that, as its name suggests, is resistant to a group of antibiotics, including penicillin.

While cases of MRSA infection date to the 1960s and were once largely confined to hospitals, the bacteria is increasingly appearing in gymnasiums, dormitories and even on public transportation systems. In Britain last year, 1,593 people died after falling ill from MRSA in hospitals but while there are tentative signs that hospital-acquired MRSA infections might have peaked - last year's death toll in Britain was 3.5 per cent down on the 2006 figure - the same cannot be said of infections picked up outside medical institutions. Such community-acquired infections are a particular problem in the United States.

Mark Enright, professor of molecular epidemiology at Imperial College London, said community-acquired MRSA infections, which can spread through simple skin-to-skin contact, have "really taken off" in the US. "Community-acquired MRSA is the most common cause for people to go to casualty due to an infectious disease throughout the major cities," he said. Typically in large American cities, he said, infections have begun with people who live on the streets or inject drugs. MRSA infections are "almost ubiquitous" among prisoners, he said.

"If you go to any major city in the United States, they tend to have problems with homeless people and drug users. That's maybe why [European countries] are catching up more slowly because they don't have the same vulnerable groups that start it off," he said. Children are also at risk when they get into scrapes that leave them with grazed elbows and knees, wounds that can become infected. While the bacteria involved in community-acquired MRSA infections tend to be more sensitive to some antibiotics, they are usually more aggressive. Staphylococcus aureus is anything but rare. Doctors estimate about a third of us have it in our nasal passages or on our skin without knowing it.

While people can carry it for years without realising it, if the skin is broken and the wound infected with MRSA, a serious infection can occur. The early signs are small red bumps that grow and turn into large boils. If the MRSA remains as a skin infection, the consequences are not likely to be severe. When the bacteria enter the bloodstream, however, they can cause a variety of problems, including blood poisoning, internal abscesses, lung infections and meningitis. Heavy use of antibiotics to counter infections over the years have made the bacteria resistant to them, leaving doctors powerless to prevent deaths.

Known as Panton-Valentine leukocidin (PVL) strains after the toxin they produce, they can cause flesh-eating lesions. A particularly prevalent - and deadly form - of MRSA often picked up outside hospitals is known as USA300. First isolated in 2001, it is now the most common cause of Staphylococcus infections in the US. Such strains that originated in communities are becoming more common in medical settings.

"In the United States, they've found that community strains are being transmitted within hospitals as well," said Dr Katie Hardy, a clinical scientist at the division of immunity and infection at the University of Birmingham, in England. Originally, the community-acquired and hospital-acquired strains "were fairly distinct, but because community-acquired MRSA patients are being admitted to hospital, these strains are being found in hospital", she said. "That's a challenge."

Improved diagnosis of community-acquired MRSA is important, said Dr Christopher Penfold, a lecturer in the school of molecular medical sciences at the University of Nottingham, in England. Specialists say this can be achieved through improving awareness among doctors, who may diagnose the early signs of community-acquired MRSA as something else. There have also been calls for the development of new laboratory tests for the strains associated with community-acquired MRSA, since these could allow rapid treatment with those antibiotics to which it is susceptible.

Dr Penfold said basic hygiene can also reduce infection rates: "Wash your hands - there's nothing else practically you could do to stop yourself getting it." New antibiotics would also be a significant help, although Prof Enright said there is little likelihood of help from them any time soon. Discovering new antibiotics has proved harder than expected, he said, and the financial incentives for pharmaceutical giants to invest in developing them are modest, since patients typically will only take the drugs for a few days.

"It's not like a lot of medicines that elderly people take for the rest of their lives. There aren't the returns," he said. In the absence of new antibiotics, Dr Penfold said, there could be alternative treatment breakthroughs, possibly through the use of antimicrobial peptides, components of the immune system that appear not to cause bacteria to evolve resistance. There is research to isolate those molecules, which are formed from amino acids, and find out better how they work and what uses they could have against bacteria.

Other researchers are interested in bacteriophages, viruses that infect bacteria and reproduce inside them. "There was a lot of interest in the early 20th century, but with the advent of antibiotics, this was reduced. Now that we have a problem with very few antibiotics to treat infections, its potentially becoming more interesting," Dr Penfold said. While there are several research avenues, with only the current battery of defences at their disposal clinicians are concerned about the potential growth of community-acquired MRSA infections.

Prof Enright said they could become more common in Europe - MRSA infections in developing countries are difficult to track because there are other larger problems such as sepsis - and could increase very significantly. "It's going to increase, but how bad it gets is anybody's guess to be honest. In the early 1990s MRSA in hospitals was extremely rare, but now it's common," he said. "It's the nightmare scenario. If you have MRSA in the community - as it makes treating people more difficult.

"We have to be more careful and not let it get out of hand. I am not sure whether we could deal with it." dbardsley@thenational.ae