Chuck Bednar for redOrbit.com – @BednarChuck
A clone of the bacteria that causes typhoid fever is currently sweeping across Asia and Africa. This could very well lead to an epidemic of a drug-resistant form of the disease, according to a new study published online Monday in the journal Nature Genetics.
According to Science, the largest study ever of the Salmonella enterica Typhi genome was conducted, and researchers found that the multidrug-resistant form H58 is becoming widespread. This could lead to more complications and increase the cost of treating typhoid fever.
Gordon Dougan, a geneticist at the UK’s Wellcome Trust Sanger Institute and study author, told the website that there is “a sense of urgency” about the spread of H58. He also said that this microbe might have mutated to better survive in the tissue of carriers, but that while there are some genetic changes to support that theory, at this point it remains “speculation.”
Tracking the rise of the drug-resistant H58 lineage
In their study, Dougan and his colleagues call the emergence of multidrug-resistant typhoid “a major global health threat affecting many countries where the disease is endemic.” According to Science, the disease affects up to 30 million people per year and is believed to be responsible for 200,000 deaths annually as it is spread through contaminated food and water.
The disease can cause symptoms such as headache and fever, and can lead to complications like gastrointestinal perforation if not treated, the publication added. Antibiotic-resistant forms of the S. enterica Typhi bacteria first emerged in the 1970s, but experts are most concerned about H58, as this clone of the disease-causing pathogen has started appearing in more countries.
Dougan and his fellow researchers conducted whole-genome sequence analysis of 1,832 samples of the bacteria from 21 different countries and identified the single, dominant H58 lineage that they believe has emerged and spread throughout Asia and Africa over the last three decades. The clone likely surfaced in South Asia in 1985 and became more resistant in the years following, the study authors explained to Science.
Mark Achtman, a microbiologist at the University of Warwick, told Science that the new study is one of the largest bacterial genome samples published to date. He added that while scientists had already known a lot about how H58 spreads, that this paper marked “the first time that we’ve had such an exhaustive overview of Salmonella typhi and the H58 group within typhi.”
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