02:24pm Tuesday 15 October 2019

University of East Anglia researchers contribute to Salmonella gene discovery

They tracked the spread of the rapidly-evolving intestinal disease non-Typhoidal Salmonella in sub-Saharan Africa, where it kills one in four who catch it.

The findings reveal that the emergence and spread of the blood-borne infection have been worsened by Africa’s HIV epidemic.

Medical microbiologist Prof John Wain, from UEA’s Norwich Medical School, was closely involved in early stages of the research, published in the journal Nature Genetics. The full team spanned nine countries.

They found that non-Typhoidal Salmonella is caused by a new form of the bacterial pathogen Salmonella Typhimurium that has spread from two different focal hubs in Southern and Central Africa beginning 52 and 35 years ago, respectively.

They also found that one of the major contributing factors for the spread of the disease was the acquisition of genes that have become resistant to drugs used to treat salmonellosis.

The high mortality rate among sub-Saharan Africans is in stark comparison to the rest of the world, where it is a leading cause of acute inflammatory diarrhoea that is fatal in less than 1 per cent of those infected.

The disease is more severe in sub-Saharan Africa because people there have particularly susceptible immune systems – due to malnutrition at a young age, HIV, and malaria. And the population is large enough for this detrimental pathogen to enter, adapt, circulate and thrive.

Lead by the Wellcome Trust Sanger Institute, researchers used whole genome sequencing to define a novel lineage of Salmonella Typhimurium that is causing a previously unrecognised epidemic across the region. They found that the genetic makeup is evolving into a more typhoid like bacteria, able to efficiently spread around the human body.

From sequenced samples, the team created a phylogenetic or ‘family tree’ depicting the pathogen‟s evolution, dating when each sample first emerged and overlaying this with geographical information about where these samples came from.

This is the first time that the power of whole-genome sequencing has been used to track the spread of non-Typhoidal Salmonellae. The research highlights the power this approach has to monitor the emergence and spread of dangerous pathogens both locally and globally over time.

Prof Wain said: “This research has a message for our interconnected world and should act as a warning to us all. This is almost certainly not the only emerging drug resistant human pathogen nor is sub-Saharan Africa the only region of the world where it can occur.

“The emergence of multi-drug resistant pathogens where surveillance and research infrastructure are poor is a situation which needs addressing. Now the world knows about this new strain of Salmonella it is imperative that we do something about it. Using data from this research we must facilitate local diagnosis and surveillance of this new form of infectious disease.”

University of East Anglia – Communications Office

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