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Professor Chris Butler, Director of the Primary Care Clinical Trials Unit, writes about the recent PRINCESS trial, which investigated whether probiotics can reduce infections in care home residents.

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Antibiotics can be life-saving, but need to be prescribed only when necessary. Care home residents are prescribed more antibiotics than those of the same age living in their own homes, exposing them to risks of unpleasant side-effects including antibiotic associated diarrhoea. This overprescribing also contributes to the growing problem of anti-microbial resistance.

In this group, acute infections are particularly common because frailer, older people, often have a weakened immune system, and care homes residents live in close proximity so infections can spread more easily.

Since far too many care home residents are getting antibiotics they don’t necessarily need, we need to find ways to improve their health in ways that don’t cause harm and preserve one of the most important weapons in our arsenal against infectious diseases.

Can probiotics be of benefit?

Probiotics are microorganisms that when administered, bring health benefits. As well as their benefits to gut health, many people take probiotics to try to prevent infections, and there have even been calls to investigate their potential in the treatment of COVID-19.

Other than vaccination and good hygiene, there are few proven ways to prevent infections in older care home residents - so probiotics represent an important target in efforts to combat antibiotic resistance.

The market for probiotics is huge with global sales predicted to reach over $64 billion by 2023. What’s interesting, however, is that we’re seeing them used in care homes to prevent infections. In the US, hospital and nursing home market for probiotics was estimated at $92.4 million in 2016 and is growing annually.

There’s evidence to back-up their claimed benefit, yet while clinical studies suggest that probiotics can reduce the length and frequency of infections and reduce antibiotic use in children and adults, there have been very few rigorous clinical trials in care home residents. 

As our population ages, and as concern to improve evidence-based care must increase, it becomes increasingly critical, especially for the frail elderly, that innovations in care is underpinned by the most rigorous research.

So we set-up a collaboration with colleagues in the universities of Cardiff and Southampton to design a placebo-controlled randomised in care homes. We tested whether a daily dose of probiotics would reduce the need for antibiotics and the frequency that care home residents got infections.


This PRINCESS trial (Probiotics to Reduce Infections iN CarE home reSidentS) broke new ground when it comes to research methods: there have not been many rigorous placebo controlled clinical trials done in care homes on any topic in the UK.

We trialled a combination of two common probiotics – a daily dose of Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp. Lactis BB-12. Both are amongst the most widely used probiotics strains, with well documented health benefits including the prevention and treatment of gastro-intestinal infections and diarrhoea.

Working with care homes and their staff right across the UK, we recruited 310 care home residents into our trial, and offered them either a probiotic or a placebo. Our main outcome measure for acute infections was the number of days they were taking antibiotics. After following our group for a year and crunching the numbers we found no significant difference between them – 12.9 days for those taking probiotics compared with 12 days for those on placebo.

In fact, residents who were randomised to the probiotic group were administered significantly more antibiotics for lower respiratory tract infections than the placebo group, and had a small but statistically significant lower self-reported generic wellbeing/capability scores at 3 months.


A worse outcome, you might think?

Our trial was limited, we didn’t test every probiotic so our findings don’t necessarily mean that other probiotic organisms might be beneficial, or that the organisms we studied might be beneficial in other groups of people in other settings.

I hope, however, that the data will change common practice, and help to somewhat re-calibrate the direction of research in this hugely important field of clinical science.

Sometimes showing that something doesn't work can be of huge value!

Read more:

Effect of Probiotic Use on Antibiotic Administration Among Care Home Residents. A Randomized Clinical Trial
Christopher C Butler, Mandy Lau, David Gillespie et al
JAMA doi:10.1001/jama.2020.8556

Opinions expressed are those of the author/s and not of the University of Oxford. Readers' comments will be moderated - see our guidelines for further information.


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