MRSA superbug spreading from hospitals across UK
First comprehensive study discovers large number of small outbreaks
MRSA, the antibiotic-resistant superbug usually associated with hospital infections, is widespread in the general UK community, according to the first comprehensive study of the transmission of the bacteria.
Researchers at the Wellcome Trust Sanger Institute and London School of Hygiene and Tropical Medicine used new “genomic surveillance” technology to trace the spreading of MRSA (methicillin-resistant Staphyloccus aureus) in the east of England for a year. MRSA bacteria are resistant to many antibiotics and cause a wide range of diseases, from skin inflammation to fatal sepsis.
But contrary to the common idea that most MRSA transmission results from large outbreaks in hospitals, the study published in Science Translational Medicine on Wednesday showed many relatively small outbreaks “in hospitals, in the community, GP surgeries, homes and in between these places”.
“I was surprised by how many outbreaks we detected,” said Sharon Peacock, the project leader. “But the good news is that we can learn from the results to improve infection control.”
The researchers tracked everyone who tested positive for MRSA in samples submitted to the Clinical Microbiology and Public Health Laboratory in Cambridge — 1,465 people altogether. The lab serves three hospitals and 75 GP practices in the east of England.
The researchers said that sequencing of the patients’ MRSA genomes showed that the region had 173 separate infection clusters during the course of 12 months, which is “indicative of repeated lapses in infection control”. The study found that, while most of the MRSA strains were already known to circulate in the UK, some originated in other countries, such as Taiwan and the US.
“We identified a critical role for some persistent carriers who spread MRSA in multiple [hospital] wards during complex healthcare pathways,” the researchers said. “This frequently involved indirect transmission, in which apparent acquisition by a new case occurred after the index case had left the ward, which is suggestive of environmental contamination or health workers colonised [by MRSA].”
About one healthy individual in 30 in Britain and other industrialised countries is “colonised” by MRSA living harmlessly on the skin or in the nose. These “carriers” may pass the bacteria on to hospital patients who are more vulnerable, both because their immune system is weaker and because they often have a pathway for MRSA to get through the skin, such as a surgical wound, feeding tube, drip or catheter. Once MRSA is inside the body, it can quickly lead to a life-threatening infection.
Starting next year, the researchers at the Sanger Institute and London School of Hygiene and Tropical Medicine will pass on all MRSA tracking information in real time to infection control workers, who will then be able to intervene more quickly and effectively to fight outbreaks.
“Our study has shown that sequencing all MRSA samples as soon as they are isolated can rapidly pinpoint where MRSA transmission is occurring,” said Prof Peacock. “If implemented in clinical practice this would provide numerous opportunities to catch outbreaks early and target these to bring them to a close, for example by ‘decolonising’ carriers and implementing barrier nursing.
“We have the technology in place to do this and it could have a really positive impact on public health and patient outcomes,” she added.