Scientists warn: An ancient killer is quickly becoming resistant to antibiotics


Scientists warn: An ancient killer is quickly becoming resistant to antibiotics

Typhoid may be rare in developed countries, but this ancient threat, believed to have existed for millennia, is still a major threat in our modern world.

According to new research, the bacterium that causes typhoid is developing widespread drug resistance and is rapidly replacing strains that are not resistant.

Currently, antibiotics are the only way to effectively treat typhoid, which is caused by the bacterium Salmonella enterica Serovar Typhi (S Typhi). But over the past three decades, the bacterium’s resistance to oral antibiotics has increased and spread.

Sequencing the genomes of 3,489 S typhi strains contracted in Nepal, Bangladesh, Pakistan and India from 2014 to 2019, researchers noted a recent surge in extensively drug resistant (XDR) typhi.

In addition to being resistant to front-line antibiotics such as ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole, XDR Typhi is also becoming increasingly resistant to newer antibiotics such as fluoroquinolones and third-generation cephalosporins.

Worse, these strains are spreading around the world at a rapid pace.

While most XDR typhi cases originate in South Asia, researchers have identified nearly 200 cases of international spread since 1990.

Most strains have been exported to Southeast Asia and East and South Africa, but superbugs have also been found in Britain, the United States and Canada.

“The speed at which highly resistant strains of S. Typhi have emerged and spread in recent years is a real concern and underscores the urgent need to scale up prevention efforts, particularly in the most vulnerable countries,” says Jason , infectious disease specialist Andrews from Stanford University.

Scientists have been warning about drug-resistant typhoid for years, but the new research is the largest genome analysis of the bacterium yet.

In 2016, the first XDR typhoid strain was identified in Pakistan. By 2019, it was the dominant genotype in the nation.

Historically, most XDR typhoid strains have been treated with third-generation antibiotics such as quinolones, cephalosporins, and macrolides.

But by the early 2000s, mutations that confer resistance to quinolones accounted for more than 85 percent of all cases in Bangladesh, India, Pakistan, Nepal and Singapore. At the same time, cephalosporin resistance also prevailed.

Today there is only one oral antibiotic left: the macrolide azithromycin. And this drug may not last much longer.

The new study found that mutations that confer resistance to azithromycin are now also spreading and “threatening the effectiveness of all oral antimicrobials used to treat typhoid.” Although these mutations have not yet been inherited by XDR S Typhi, we’re in serious trouble if they are.

Left untreated, up to 20 percent of typhoid cases can be fatal, and today there are 11 million typhoid cases a year.

Future outbreaks can be prevented to some extent with typhoid conjugate vaccines, but unless access to these vaccines is expanded globally, the world could soon face another health crisis.

“The recent emergence of XDR and azithromycin-resistant S Typhi creates greater urgency for a rapid expansion of preventive measures, including the use of typhoid conjugate vaccines in typhoid-endemic countries,” the authors write.

“Such measures are required in countries where the prevalence of antimicrobial resistance among S Typhi isolates is currently high, but should not be limited to such environments given the propensity for international spread.”

South Asia may be the main hub for typhoid with 70 percent of all cases, but if COVID-19 has taught us anything it’s that disease variants spread easily in our modern, globalized world.

To prevent this, health experts argue that nations need to expand access to typhoid vaccines and invest in new antibiotic research. A recent study in India, for example, estimated that vaccinating children against typhoid in urban areas could prevent up to 36 percent of typhoid cases and deaths.

Pakistan is currently leading on this front. It is the first country in the world to offer routine vaccination against typhoid. Last year millions of children were given the vaccine and health experts argue more nations need to follow suit.

Antibiotic resistance is one of the leading causes of death worldwide, claiming more lives than HIV/AIDS or malaria. Where available, vaccines are among the best tools we have to prevent future disasters.

We have no time to lose.

The study was published in The Lancet Microbe.

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