Single Non-Coding Nucleotide Difference Renders African Salmonella Variant Highly Lethal

Scientists at the University of Liverpool have identified a single genetic change in Salmonella that is playing a key role in the devastating epidemic of bloodstream infections currently killing approximately 400,000 people each year in sub-Saharan Africa. Invasive non-typhoidal Salmonellosis (iNTS) occurs when Salmonella bacteria, which normally cause gastrointestinal illness, enter the bloodstream and spread through the human body. The African iNTS epidemic is caused by a variant of Salmonella typhimurium (ST313) that is resistant to antibiotics and generally affects individuals with immune systems weakened by malaria or HIV. In a new study published online on February 27, 2018 in PNAS, a team of researchers led by Professor Jay Hinton at the University of Liverpool have identified a specific genetic change, a single-nucleotide polymorphism (SNP), that helps the African Salmonella to survive in the human bloodstream. The open-access article is titled “Role of a Single Noncoding Nucleotide in the Evolution of an Epidemic African Clade of Salmonella.” Professor Hinton explained: "Pinpointing this single letter of DNA is an exciting breakthrough in our understanding of why African Salmonella causes such a devastating disease, and helps to explain how this dangerous type of Salmonella evolved." SNPs represent a change of just one letter in the DNA sequence and there are thousands of SNP differences between different types of Salmonella. Until now, it has been hard to link an individual SNP to the ability of bacteria to cause disease. Using a type of RNA analysis called transcriptomics, the scientists identified SNPs that affected the level of expression of important Salmonella genes.
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