The ancient killer is fast becoming resistant to antibiotics, scientists warn

The ancient killer is fast becoming resistant to antibiotics, scientists warn

Salmonella Typhi. (Credits: Microbewriter / Wikimedia Commons / CC BY SA 4.0)

Translated by Julio Batista
Original Carly Cassell for ScienceAlert

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

According to new research, the bacteria that cause typhoid fever develop extensive drug resistance and quickly replace strains that are not resistant.

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Currently, antibiotics are the only way to effectively treat typhoid fever, which is caused by bacteria. Salmonella enterica serovar Typhi (S Typhi). However, in the last three decades, the resistance of bacteria to oral antibiotics has been growing and spreading.

By sequencing the genomes of 3,489 strains of S Typhia contracted from 2014 to 2019 in Nepal, Bangladesh, Pakistan and India, the researchers found a recent increase in extensive drug-resistant (XDR) Typhi.

XDR Typhi is not only resistant to first-line antibiotics such as ampicillin, chloramphenicol and trimethoprim / sulfamethoxazole, but also becomes more resistant to newer antibiotics such as fluoroquinolones and third-generation cephalosporins.

What is worse, these strains are spreading globally at a high rate.

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

Most strains have been exported to Southeast Asia as well as East and South Africa, but typhus superbacteria have also been found in the UK, US and Canada.

“The speed with which highly resistant S. Typhi strains have emerged and spread in recent years is a real cause for concern and underscores the need to urgently expand prevention measures, especially in the most vulnerable countries,” the disease expert said. infectious diseases Jason Andrews of Stanford University.

Scientists have been warning about drug-resistant typhoid fever for years, but new research is the largest analysis of the bacterium’s genome to date.

In 2016, the first strain of XDR typhoid fever was identified in Pakistan. In 2019, it became the dominant genotype in the country.

Historically, most strains of typhoid fever have fought third-generation antimicrobials such as quinolones, cephalosporins, and macrolides.

But in the early 2000s, mutations that gave resistance to quinolones accounted for more than 85% of all cases in Bangladesh, India, Pakistan, Nepal and Singapore. At the same time, resistance to cephalosporins prevailed.

Today, only one oral antibiotic remains: macrolide, azithromycin. And this drug may not work for a long time.

A new study has found that mutations that confer resistance to azithromycin are also spreading, “compromising the effectiveness of all oral antimicrobial agents for treating typhoid fever.” Although S Typhi XDR has not yet adopted these mutations, if they are, we are in serious trouble.

If left untreated, up to 20% of typhoid fever cases can be fatal, and today there are 11 million cases of typhoid fever per year.

Future epidemics can be somewhat avoided with conjugate typhus vaccines, but if access to these vaccines does not spread globally, the world could soon have another health crisis.

“The recent emergence of azithromycin and S Typhi-resistant XDRs creates greater urgency for the rapid spread of prevention measures, including the use of typhoid conjugate vaccines in countries endemic to typhus,” the authors wrote.

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

South Asia may be the main center for typhoid fever, accounting for 70% of all cases, but if COVID-19 has taught us anything, it is that disease variants are easily spreading in our modern, globalized world.

To prevent this, health experts say countries need to expand access to typhoid vaccines and invest in new antibiotic research. A recent study in India, for example, estimates that if children are vaccinated against typhus in urban areas, it could prevent up to 36% of typhus cases and deaths.

Pakistan is currently leading the way in this regard. It is the first nation in the world to offer routine immunization against typhoid fever. Millions of children received the vaccine last year, and health experts say more nations should follow suit.

Antibiotic resistance is one of the leading causes of death in the world, taking the lives of more people than HIV / AIDS or malaria. When available, vaccines are one of the best tools we have to prevent future disasters.

We have no time to lose.

The study was published in Lancet microbe.

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