The world is facing an epidemic of multidrug-resistant typhoid. This is the conclusion of the largest study to date of the genomes of the bacteria that causes the disease, Salmonella enterica Typhi. According to researchers, a clone of the bacterium that is often multiresistant, called H58, rolls across Asia and Africa. Its spread is likely to increase the cost of treatment and lead to more complications, they warn.
"There is a sense of urgency now," said Gordon Dougan, a geneticist at the Wellcome Trust Sanger Institute in Hinxton, UK, and an author of the paper.
typhoid spread by contaminated water or food, causing fever, headaches and other symptoms. If untreated, the disease can lead to complications such as gastrointestinal perforation and kill up to 20% of patients. estimates range from 10 million to 30 million cases per year. About 0,000 people die. S. enterica Typhi that are resistant to multiple antibiotics appeared in the 1970s but H58 was of particular concern to scientists because it is cropping up in more and more countries.
for an overview of its spread, the scientists analyzed the genomes of 1,832 samples from 21 countries Asia, Africa and Oceania. The clone probably emerged in South Asia around 1985 and then picked up the resistance genes in subsequent years, before spreading to Southeast Asia and Africa, Dougan said.
In Africa, the clone was probably introduced repeatedly in Kenya and was broadcast from there to the south, the authors report online today in Nature Genetics . In an article last month in PLOS Neglected Tropical Diseases , Dougan and other scientists followed the emergence of H58 in one hospital in Malawi. From 1998 to 2010, there were an average of 14 typhoid fever diagnoses a year in hospital. Approximately 7% of isolates were resistant to multiple drugs. In 2014, there were 782 diagnoses, 97% with multidrug resistance. "As soon as it arrives in your country, you have to turn to more expensive antimicrobial," said Dougan.
It is not known why H58 is so successful. One possible explanation: The clone may have mutated to survive better in the fabric carriers that spread the disease without becoming ill themselves. There are some genetic changes in H58 that can point to that says Dougan. "But that's speculation," he warns. Why some bacterial clones become dominant is still a mystery, says Mark Achtman, a microbiologist at the University of Warwick in the UK. "It is a phenomenon that we see again and even in different bacteria and it has never been heard. "
The document is one of the largest samples of bacterial genome that whoever published Achtman said. Much was already known about H58 spread, he said. "But this is the first time we had such a comprehensive list of Salmonella typhi and the H58 group in typhi." Said Dougan he and his colleagues have sequenced more typhoid isolates to identify the origins of H58.
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