Rare or well done?

Professor Stuart Reid CBE BVMS PhD DVM DipECVPH FRSE FRSB FRCVS

Fellowship Day 2019

Report of presentation

Overnight before Fellowship Day, something in the order of 120,000 eggs, 2.25 tonnes of beef and one-third of a million chickens had been delivered into London, all of which could potentially carry pathogenic, possibly drug-resistant, organisms that could affect human health.

So said Professor Stuart Reid, principal of the Royal Veterinary College, setting the scene for his presentation, which examined the challenge of antimicrobial resistance. He commented that there had been a ‘tsunami’ of articles in both the popular press and the scientific press about the risks to human health in a post-antibiotic era if a solution to antimicrobial resistance was not found.

However, when it came to issues such as antimicrobial resistance it was, he said, not only important to be aware of the scale of the problem, but also to understand the context, population structures and processes.

His interest in this area had been stimulated by a research paper published in 2006 (D’Costa VM, et al. Science 311(5759):374–7) which had reported the scale and diversity of resistance in bacteria isolated from the soil. “You could see that there’s an enormous amount of resistance out there, but probably more importantly, that the diversity of that resistance is phenomenal,” Professor Reid said. This had prompted him to ask: if antimicrobial resistance is so diverse in the environment, what is it like if you look at humans and animals?

His research team studied several thousand bacterial isolates from beef cattle and humans in Scotland, which had been collected as part of surveillance over a 15-year period. “What we discovered was that not only was there widespread Salmonella in those populations…but the diversity of the resistance in those Salmonella was markedly different in the two populations, and there was a lot more diversity in the human isolates than there was in the animal isolates,” he said.

“Now, if you’ve got 25 different types of flower in your garden and I have three in mine, the chances are that you didn’t get the other 22 from me.”

This observation caused “quite a stir” in the scientific and medical communities, he said. The question then arose of whether the Salmonella and their resistance determinants were moving from the human population to the animal population – something that was contrary to popular belief.

The team examined the genomic aspects of their finding. Whole genome sequencing indicated that salmonellae did move from humans to animals and from animals to humans, but this did not happen often.

“On the back of the diversity work that we had done, we were also able to show that Salmonella in general circulate within their own host species,” Professor Reid said. “Although they do cross from animals to humans and humans to animals, this is a relatively rare event.”

“That also caused a bit of a stir.”

This finding told them that, while antimicrobial use in both people and animals was important, the issue was not simply about the flow of resistance in one direction or the other – the environment was also potentially having a huge influence. This suggested that medics, vets and lab-based scientists were unlikely to be able to provide answers and that solutions would only be found by considering the animal, human and environmental aspects.

The Food and Agriculture Organization of the United Nations viewed the issue of resistance at three levels – technical (the scientific level), social (how behaviours, such as prescribing behaviours, need to change) and institutional (governmental, regulatory). All needed to come together for a true One Health solution.

“My take home message from this is that the solution to antimicrobial resistance…is going to require many disciplines, not just our own discipline, to come together.”

Science, he said, tended to recognise individuals, but it was actually teams that got things done.

After his presentation, Professor Reid was asked how momentum could be maintained in efforts to reduce antimicrobial use. For example, there had been a huge decrease in antimicrobial use in farm animal practice, and farmers would want to see some sort of result or reward for that. It was hard to explain to them that their efforts were only part of a bigger picture and there was already “a little bit of a backlash” from farmers who felt that they were “doing their bit” but they did not see others doing the same.

“I think, first of all, we need to jointly own the problem,” Professor Reid replied. For example, there was now much better clinical audit of antimicrobial prescribing in GP practices. Also, he noted that companies such as McDonald’s and Tesco were likely to have a much bigger impact on antimicrobial resistance than any government agency because they operated across international trade boundaries. If such companies decided that their producers were not going to use an antimicrobial, then its use would disappear internationally. Market forces and consumer demand would drive this.

However, he concluded: “If we are in a position where we are starting to negotiate new trade deals, then given the efforts that have gone on in this country, at great expense and great effort, we have to make sure that the people we start trading with in new trading relationships are held to the same standards as our farmers and our producers here.”