Typhoid fever may be rare in developed countries, but this ancient threat, believed to have existed for thousands of years, remains a major threat to our modern world.
The bacteria that cause typhoid fever are developing widespread drug resistance and rapidly replacing non -resistant strains, according to new research.
Currently, antibiotics are the only way to effectively treat typhoid caused by the bacteria Salmonella enterica serovar Typhi (S Typhi). However, bacterial resistance to oral antibiotics has been rising and spreading over the past three decades.
The researchers found a recent increase in XDR-XD-XD Typhi by sequencing the genomes of 3,489 Typhi strains contracted from 2014 to 2019 in Nepal, Bangladesh, Pakistan and India.
XDR Typhi is not only resistant to frontline antibiotics such as ampicillin, chloramphenicol and trimethoprim/sulfamethoxazole, but also increases resistance to newer antibiotics such as fluoroquinolones and third generation cephalosporins.
Worse, these strains are rapidly spreading around the world.
While most cases of XDR Typhi originated in South Asia, researchers have identified approximately 200 cases of international spread since 1990.
Most strains are exported to Southeast Asia as well as eastern and southern Africa, but supertyphoid bacteria are also found in England, the United States and Canada.
Jason Andrews, an infectious disease specialist at Stanford University, said: “The rate at which highly resistant strains of S. typhi have emerged and spread in recent years is a real cause for concern and emphasizes the urgent need to expand prevention measures, especially in countries. where many are in danger. ”
Scientists have been warning about drug -resistant typhoid fever for years, but the new research is the largest bacterial genome analysis ever done.
He described the first typhoid XDR strain in Pakistan in 2016. In 2019, the genotype became dominant in the country.
Historically, most XDR typhoid strains have resisted third-generation antimicrobials such as quinolones, cephalosporins, and macrolides.
But in the early 2000s, mutations that confer resistance to quinolones accounted for more than 85% of all cases in Bangladesh, India, Pakistan, Nepal and Singapore. Meanwhile, cephalosporin resistance was also controlled.
Only one oral antibiotic is left now: the macrolide, azithromycin. This medicine may not work for longer.
The new study finds that mutations that confer azithromycin resistance are now widespread and “threaten the effectiveness of all oral antimicrobials for the treatment of typhoid.” Although these mutations are not adopted by XDR S Typhi, if so, we are in serious trouble.
If left untreated, up to 20% of typhoid cases can be fatal, and there are currently 11 million cases of typhoid per year.
Future epidemics could be prevented to some extent by conjugated typhoid vaccines, but the world could soon face another health crisis if access to these doses is not expanded worldwide.
“The recent emergence of azithromycin-resistant XDR and S Typhi creates a more intense need to rapidly expand prevention measures, including the use of conjugated typhoid vaccines in countries where typhoid is endemic, ”Written by the authors. “Such measures are needed in countries where antimicrobials are widespread.” Resistance to S Typhi isolates is currently high, but due to the possibility of spreading around the world, it should not be limited to such conditions. ”
South Asia may be the main center of typhoid fever, which makes up 70% of all cases, but if COVID-19 teaches us anything, it is that various diseases are easily spread in our modern, globalized world.
To prevent this from happening, health experts argue that countries should expand access to typhoid vaccines and invest in new antibiotic research. For example, a recent study in India shows that up to 36% of typhoid cases and deaths would be prevented if children were vaccinated against typhoid in urban areas.
Antibiotic resistance is one of the leading causes of death worldwide and kills more people than HIV/AIDS or malaria. Wherever they are available, vaccines are one of the best tools we have to prevent future disasters.
The study was published in The Lancet Microbe.
Source: Science Alert
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