Typhoid fever may be rare in developed countries, but this ancient threat, believed to have been around for thousands of years, remains a major threat in our modern world.
According to new research, the bacteria that cause typhoid fever are developing widespread drug resistance, and they are rapidly replacing non-resistant strains.
Currently, antibiotics are the only way to effectively treat typhoid caused by bacteria Intestinal salmonella S Typhi. However, over the past three decades, bacterial resistance to oral antibiotics has been growing and spreading.
Researchers found a recent spike in drug-resistant (XDR) typhimurium, by sequencing the genomes of 3,489 strains of contracted typhimurium from 2014 to 2019 in Nepal, Bangladesh, Pakistan and India.
XDR Typhi is not only impervious to frontline antibiotics, such as ampicillin, chloramphenicol and trimethoprim/sulfamethoxazole, but it is also increasing resistance to newer antibiotics, such as fluoroquinolones and third generation cephalosporins.
Even worse, these strains are spreading globally at a rapid rate.
While most cases of XDR typhi originate in South Asia, researchers have identified nearly 200 cases of international spread since 1990.
Most strains have been exported to Southeast Asia, as well as eastern and southern Africa, but super typhoid bacteria have also been found in the United Kingdom, the United States and Canada.
Says Jason, an infectious disease specialist at Stanford University.
Scientists have been warning about drug-resistant typhoid for years, but the new research is the largest genome analysis on the bacteria to date.
In 2016, the first strain of typhoid XDR was identified in Pakistan. By 2019, it has become the dominant genotype in the country.
Historically, most strains of typhoid XDR were fought with third-generation antimicrobials, such as quinolones, cephalosporins, and macrolides.
But by the early 2000s, mutations conferring resistance to quinolones accounted for more than 85 percent of all cases in Bangladesh, India, Pakistan, Nepal and Singapore. At the same time, resistance to cephalosporins was also dominant.
Today, there is only one oral antibiotic left: macrolide, azithromycin. This medicine may not work for longer.
The new study found that mutations that confer resistance to azithromycin are now also spreading, “threatening the efficacy of all oral antimicrobials for treating typhoid.” While these mutations have not been embraced by XDR S Typhi, if they are, we are in serious trouble.
If left untreated, up to 20 percent of typhoid cases can be fatal, and today, there are 11 million cases of typhoid annually.
Future outbreaks can be prevented to some extent with conjugate typhoid vaccines, but if access to these shots is not expanded globally, the world may soon face another health crisis.
“The recent emergence of azithromycin-resistant XDR and S Typhi creates greater urgency for the rapid expansion of prevention measures, including the use of conjugate typhoid vaccines in typhoid endemic countries,” the authors wrote.
“Such measures are required in countries where the prevalence of antimicrobial resistance among S Typhi isolates is currently high, but given the tendency to international spread, it should not be restricted to such conditions.”
South Asia may be the main epicenter of typhoid fever, accounting for 70 percent of all cases, but if COVID-19 teaches us anything, it is that in our modern, globalized world, disease variants spread easily.
To prevent this from happening, health experts argue that states should expand access to typhoid vaccines and invest in new antibiotic research. One recent study in India, for example, suggests that if children were vaccinated against typhoid in urban areas, it could prevent up to 36 percent of typhoid cases and deaths.
Pakistan is currently leading the way on this front. It is the first country in the world to introduce routine immunization against typhoid. Last year, millions of children were given the vaccine, and health experts say more countries need to follow suit.
Antibiotic resistance is one of the leading causes of death worldwide, killing more people than HIV/AIDS or malaria. Vaccines, where they are available, are among the best tools we have for preventing future catastrophe.
We don’t have time to waste.
The study was published in Lancet microbe.
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