Source: CDC/Janice Haney Carr
Emerging Health Threats: Disinfecting hospital patients can stop further spread, but community strains could slip under the radar.
By tracing the strains of multidrug-resistant Staphylococcus aureus (MRSA) that turned up in 450 hospitals across Europe over six months, scientists have discovered that patients transport the bug between healthcare centres. The research, published this week in PLoS Medicine, suggests that identifying and treating patients harbouring the ‘superbug’ could help to control infection rates.
“[C]ontrol efforts aimed at interrupting the spread [of MRSA] within and between health care institutions may not only be feasible but ultimately successful and should therefore be strongly encouraged,” write Hajo Grundmann, from the Dutch National Institute for Public Health and the Environment in Bilthoven, and colleagues.
This type of control strategy is likely to be effective, say experts. The UK already has policies in place which were designed to tackle spread of the bacteria between patients. But some scientists fear the picture is more complicated, suggesting that strains of MRSA emerging in the community may alter the dynamics of the disease in the future.
For their study, Grundmann and colleagues recruited 450 hospitals in 26 European countries and asked them to collect bacterial samples from patients with invasive S. aureus infections picked up while in hospital. Regional laboratories analysed more than 3000 isolates of the bacteria, and assessed how they related to each other by looking at one region of a specific gene, known as spa. The researchers then mapped these results geographically to get a better idea of the genetically diversity of MRSA strains on the continent.
Different spa MRSA types appeared in different countries, and the dominant ones clustered together in distinct geographical areas. The clustering suggests that the bacteria are spreading within networks of healthcare facilities, say the authors, and this shows that MRSA is spread by patients who are repeatedly admitted to different hospitals.
According to Barry Farr, from the University of Virginia Health System, USA, many other studies have reported the spread of MRSA clones within an individual hospital or a group of local healthcare facilities. This research helps to confirm that specific MRSA strains spread through healthcare facilities and suggests that better infection control in these locations could be “very beneficial”, he says.
“More than 120 epidemiological studies have reported that screening to detect MRSA colonisation coupled with contact isolation can control healthcare related spread,” adds Farr.
Screening patients to stop transmission
Despite these findings, there is no policy in place for MRSA screening in US hospitals. UK health authorities have taken a different tack. In England, since early 2009 patients admitted to hospital for non-emergency surgery have been screened for MRSA, says Richard James, from the University of Nottingham. By 2011, all patients — including those admitted for medical emergencies — will be screened, he adds.
This policy can potentially break the chain of MRSA transmission between healthcare facilities, says James. But for now, the tests used to identify MRSA in hospital patients take three days to complete. By the time healthcare staff receive the results any infected patients admitted for a short period may have left the hospital, and could have potentially spread the bug to others.
There are quicker testing alternatives, but these cost more, according to James. Some might say the testing is done simply to tick a box, he adds.
Nevertheless, screening policies still allow health authorities to intervene. The spread of MRSA could be reduced if patients released from hospital and known to be carrying the bug are given follow-up treatment with antiseptic shower gels and nasal creams to eliminate the bacteria. “If we use this information it will help us stay ahead of the game,” says James.
Community strains in the mix
Strains of the bacteria arising outside hospitals, known as community-acquired MRSA, are becoming an increasing problem in the UK and elsewhere in the world. In the USA, more than half of all MRSA infections are now picked up in the community. Scientists predict that once inside hospitals, community strains will take over from their healthcare counterparts as a source of infection.
James says that MRSA prevention policies focused on hospitals could miss this growing problem. “It would be a great surprise if community-acquired MRSA rates in England don’t follow what is seen in the USA,” says James. Health authorities in the UK are not actively looking for community MRSA.
Unlike strains circulating in hospitals, which typically affect vulnerable and older patients, community strains generally affect young, healthy people, causing skin and soft tissue infections. Most patients are treated outside the hospital by general practitioners, but studies in the USA have suggested these strains of the bacteria can still find their way into healthcare facilities.
Michael Millar, from Barts and The London National Health Service Trust, believes community MRSA strains can play a role in altering infection dynamics. “The past does not allow us to predict the future,” he says.
The paper gives us a snapshot in time of the MRSA situation in Europe, explains Millar, where so far MRSA has been mainly a hospital problem. “Unfortunately this data does not tell us what will happen next.”