Typhoid-causing bacteria have become increasingly resistant to antibiotics – study

Typhoid-causing bacteria have become increasingly resistant to antibiotics – study

The bacteria that cause typhoid fever have become increasingly resistant to antibiotics and have spread widely over the past three decades, a new study suggests.

The largest genome analysis of Salmonella enterica serovar Typhi (S. Typhi) also reveals that resistant strains – nearly all originating in South Asia – have spread to other countries nearly 200 times since 1990.

According to the research, while antibiotic resistance has generally declined in South Asia, strains resistant to macrolides and quinolones – two of the most important antibiotics for human health – have increased sharply and have spread to other countries.

Lead author Jason Andrews of Stanford University said: “The speed with which highly resistant strains of S. Typhi have emerged and spread in recent years is a real cause for concern and highlights the need to urgently expand prevention measures. , especially in high-risk countries.

“At the same time, the fact that resistant strains of S. Typhi have spread internationally so often also underscores the need to view typhoid control and antibiotic resistance more generally as a global rather than a local problem.”

Typhoid fever causes 11 million infections and over 100,000 deaths a year, and is most prevalent in South Asia – which accounts for 70% of the global disease burden.

It is also an issue in Sub-Saharan Africa, Southeast Asia and Oceania, highlighting the need for a global response.

Antibiotics can be used to successfully treat typhoid fever, but their effectiveness is threatened by resistant strains.

The authors of the new study performed complete genome sequencing on 3,489 typhoid strains collected from blood samples collected between 2014 and 2019 from people in Bangladesh, India, Nepal and Pakistan with confirmed cases of typhoid fever.

Another 4,169 samples isolated from more than 70 countries between 1905 and 2018 were also sequenced and included in the analysis.

The study found that resistant strains of S. Typhi had spread between countries at least 197 times since 1990.

Although these strains occur most frequently in South Asia and from South Asia to Southeast Asia, East and South Africa, they have also been reported in the UK, US and Canada.

According to the research, genetic mutations conferring resistance to quinolones have emerged and spread at least 94 times since 1990, with nearly all (97%) originating in South Asia.

Quinolone-resistant strains accounted for more than 85% of S. Typhi in Bangladesh in the early 2000s, increasing to more than 95% in India, Pakistan and Nepal in 2010, the researchers found.

Mutations causing resistance to azithromycin – a widely used macrolide antibiotic – have emerged at least seven times in the last 20 years.

The researchers say their findings add to recent evidence of the rapid increase and spread of strains resistant to third-generation cephalosporins, another class of antibiotics critically important to human health.

The results are published in the journal The Lancet Microbe.

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