Historical changes in pig farming led to the global spread of salmonella, resistant to antibiotics, a new international study led by UK researchers suggests.
The research provides evidence that intensive farming practices over the last century has enabled the salmonella bacteria to spread internationally.
The overreliance on antibiotics also led to the bacteria evolving to be resistant to antibiotics, according to the study, which was led by the University of Warwick.
Salmonella enterica is a type of bacteria responsible for millions of illnesses annually, that can contaminate food, water, and food processing facilities.
It can enter the food supply chain, with pork being a major source of infections. The pathogen can ‘jump’ from pigs to humans, causing severe, potentially fatal, illnesses.
Until now, the impact of intensive farming practices and global trade on salmonella prevalence around the world and the spread of antibiotic resistance remained unclear.
In the study, DNA was analysed from 362,931 strains of bacteria, leading to the detection of nine salmonella populations that are abundant in pigs.
The scientists linked the expansion of the bacteria with two historical events in the 20th Century: the first was the development of intensive pig farming in the early 20th Century.
The second was due to the overuse of antibiotics after the 1960s, with Europe and the United States contributing the most to international transmissions of the bacteria.
Professor Sascha Ott, of University of Warwick, said the study showed how the global trade of pork played a key role in the evolution of salmonella – "posing direct threats to food safety worldwide".
Dr Zhemin Zhou, honorary research fellow at the university added that the majority of salmonella genomes included were from developed countries, with limited data from developing countries, especially those in South America and Africa.
“As the majority of salmonella genomes included were from developed countries, with limited data from developing countries, especially those in South America and Africa, further research should look at these understudied regions.
"This should improve knowledge of salmonella evolution and aid efforts to prevent illnesses caused by this pathogen."
