Animal role in Salmonella 'overstated'
Stuart Reid, co-author of the Salmonella research paper
A new study has shown that Salmonella populations in humans and animals are more different than previously thought, meaning domestic animals are "unlikely" to be a major source of antibiotic resistant Salmonella in humans.
In the largest study of its kind, scientists have studied the numbers of human-to-human and animal-to-human transmissions of Salmonella typhimurium DT104. Findings suggest that the spillover from local animals to humans is less than previously thought.
The research team studied DNA from more than 373 human and animal samples, which were collected over a 22-year period, mainly from Scotland.
By studying the genetic variation in both the bacteria and the drug-resistant genes, researchers found distinctions between bacterial populations in humans and animals living side-by-side.
Scientists found more variation in drug resistance in the human-infecting Salmonella bacteria. They also found that the estimated number of times that the bacteria moved from animals to humans was surprisingly low.
Dr Alison Mather, first author on the study from the Wellcome Trust Sangar Institute, explained: "We found that people have a more diverse source of infection and antibiotic resistance than just the local animals, pointing towards alternative sources."
Senior author at the Institute, Professor Nicholas Thompson, says these data "challenge the established view that local animals are the predominant source of Salmonella infections in Scotland."
Around 94 million people all over the world develop gastroenteritis or food poisoning due to Salmonella each year, at a cost of more than £4 billion to the US and European Union. This presents a global public health issue, made worse by antibiotic resistance.
Co-author Professor Stuart Reid, from the Royal Veterinary College (RVC), said: "This finding in no way undermines the importance of prudent antimicrobial use in all species.
"But our study does demonstrate that greater effort needs to be focused on understanding the natural history of the pathogens and on identifying the major sources of resistance in our global ecosystems."
Veterinary practices are being urged to help owners safely dispose of any unused and expired pet medicines - not just antibiotics - during November's Animal Medicines Amnesty. 
