Why do more people who inject drugs get MRSA infections, and how can we help?

MRSA and people who inject drugs - Matt Hickman

29 May 2019

In Bristol, a small - but significant - number of people who inject drugs (PWID) contribute to increase in hospital admissions in Bristol with community acquired MRSA. Why this might be, and how the number of cases can be reduced, are questions that GP Dr Kate Rush posed to University of Bristol researchers Professor Matt Hickman and Dr Maya Gobin (Public Health England) and collaborators from Bristol Drug Project.

Thanks to an award from the Elizabeth Blackwell Institute Research for Health Scheme, they were able to get to work. MRSA (Meticillin Resistant Staphylococcus aureus) is a strain of bacteria which is resistant to a variety of widely used antibiotics. It usually lives harmlessly on the skin (such people are referred to as having been ‘colonised’ by the bacteria). However, when it does cause infection, MRSA's antibiotic resistance can make it very difficult to treat. Since the 1960s MRSA has become increasingly more prevalent, not just in hospitals but also within the community at large, yet how its prevalence ebbs and flows amongst the population is poorly understood.

To understand the issue, Prof. Hickman and Dr Gobin wanted to enhance public health surveillance of injecting related harms. The team expanded on the annual cross-sectional survey of People Who Inject Drugs (PWID) living in the City of Bristol as part of the national Unlinked Anonymous Monitoring (UAM) survey. The number of participants was increased, more questions were asked about injecting practice, groin and nasal swabs were taken for MRSA testing, and new ethical approval was obtained. MRSA positive swabs were sent to the Public Health England Staphylococcus Reference Unit for whole genome sequencing. The whole project was overseen by a steering committee comprising of the sponsor and members of the University of Bristol, Public Health England, the United Bristol Healthcare Trust, and Bristol Drugs Project.

The results were intriguing: “We found that one in 12 people who inject drugs had MRSA living on their skin - and we identified characteristics that might be associated with MRSA colonisation such as injecting in public places, injecting in groups of three or more, recent healthcare contact and skin and soft tissue infection” explained Prof. Hickman. “And when we looked at the phylogenetic analysis we found specific clusters associated with PWID in Bristol suggesting that there has been ongoing circulation of MRSA within PWID community in Bristol for some time.”

People who are colonised by MRSA are at increased risk of infection, and so the level of colonization observed in Bristol PWID is of concern. The data the team gathered is being used by Public Health England and Bristol Drugs Project to develop and target interventions to prevent the circulation of MRSA and potential future hospitalisations.

The project, which was entirely funded by the EBI Research for Health Scheme, has the scope to reduce the risk of infection for PWID and if early interventions are successful has have the potential to make large savings within the NHS.

The steering group set up for this study has also applied to the Department of Health for a follow up project to design and implement a comprehensive care pathway to reduce the incidence of MRSA colonisation.

Dr Gobin said:"The benefits of this study are potentially enormous; by being able to establish patterns of behaviour associated with MRSA colonization, we can develop interventions to prevent spread of MRSA, which will have implications for limiting spread to the general population. The data we acquired did not previously exist and couldn’t be derived from existing data sources; the EBI funding was therefore invaluable.”

Further information

'Preventing and managing community acquired MRSA in PWID', Eurosurveillance (2019)