Typhoid fever is an acute intestinal infectious disease caused by Salmonella typhi. The route of infection is fecal-oral transmission . The main symptoms after infection are high fever, accompanied by abdominal pain, severe diarrhea, headache, rose spots on the body, etc. It is often called "typhoid fever". Intestinal bleeding or perforation is its most serious complication .
Typhoid fever is relatively rare in my country and developed countries, but this ancient bacteria, which is thought to have existed for thousands of years, still poses a threat to the world today. Because, over the past three decades, resistance to oral antibiotics in Salmonella typhi serovar (Salmonella typhi) has been growing and spreading.
In a new study published in "The Lancet Microbe" on June 21, 2022, an international research team led by University of Cambridge and Stanford University found that antibiotics are still effective in treating typhoid fever. The only method, but S typhi has developed widespread drug resistance and is rapidly replacing non-resistant strains. Health experts call for greater efforts to develop a new generation of antibiotics.
In the new study, researchers examined the genomes of 3,489 S.typhi strains isolated during prospective enteric fever surveillance studies in Nepal, Bangladesh, , and India between 2014 and 2019. In the largest sequencing effort to date, found that extensively drug-resistant (XDR) typhoid bacteria have increased significantly in recent years.
Extensively drug-resistant typhoid fever is not only insensitive to first-line antibiotics such as ampicillin , chloramphenicol and trimethoprim / sulfamethoxazole , but also to fluoroquinolones and third-generation cephalosporins New antibiotics such as are also becoming more and more resistant. To make matters worse, these strains are spreading rapidly around the world.
While most cases of extensively drug-resistant typhoid fever originate from South Asia, researchers determined that nearly 200 internationally transmitted cases have been identified since 1990.
Most strains have spread to Southeast Asia, East Africa and South Africa; the superbug has also been found in the United Kingdom, the United States and Canada.
Jason Andrews, an infectious disease expert at Stanford University and lead author of the study, said: "The emergence and rate of spread of highly drug-resistant typhoid strains in recent years is indeed concerning, highlighting the need to expand prevention measures, especially in the Countries most at risk."
Scientists have been warning about drug-resistant typhoid for years, but the new study is the largest genome analysis of Salmonella typhi to date.
In 2016, researchers first discovered an extensively drug-resistant typhoid strain in Pakistan. By 2019, this strain had become the dominant genotype in Pakistan.
Historically, most extensively drug-resistant typhoid strains have been treated with third-generation antibiotics, such as quinolones, cephalosporins, and macrolide antibiotics.
But by the early 2000s, mutations causing quinolone resistance accounted for more than 85% of all cases in Bangladesh, India, Pakistan, Nepal and Singapore. At the same time, cephalosporin resistance is also taking hold.
Today, there is only one oral antibiotic left: the macrolide antibiotic azithromycin, but researchers say it may not be effective for long.
The new study also found that mutations that confer resistance to azithromycin are also spreading and are threatening the effectiveness of all oral antibiotics used to treat typhoid fever.
Researchers say that although these mutations have not yet entered the genome of the extensively drug-resistant S Typhi strain, it would be a bigger problem if mutations occurred.
Up to 20% of typhoid cases can be fatal if left untreated, and today there are 11 million cases of typhoid fever worldwide each year. The authors of
write: "The recent emergence of extensively drug-resistant and azithromycin-resistant Salmonella enterica serovar Typhimurium strains adds urgency to the rapid expansion of preventive measures, including the use of typhoid conjugate vaccines in typhoid-endemic countries."
Antibiotic resistance is now one of the world's leading causes of death, claiming more lives than AIDS or malaria. Health experts have called on countries to expand the use of typhoid vaccines and provide Investing in research on new antibiotics.
Researchers say we have no time to waste
Paper link:
https://doi.org/10.1016/S2666-5247(22)00093-3
