Typhoid warning: ‘Global response needed’ as highly contagious disease evades antibiotics | Science | News

Typhoid fever is a life-threatening illness that results from infection with the bacteria Salmonella typhi, a relative of the microbe that causes salmonella food poisoning. The highly contagious infection is spread through contaminated water and poor sanitation and results in symptoms such as a rising temperature, headache, fatigue, cough, constipation and general aches and pains. According to the World Health Organization (WHO), there are about 11-20 million cases of typhoid fever every year, resulting in some 128,000-161,000 deaths.

In their study, infectious disease specialist Professor Jason Andrews of Stanford University and his colleagues report that drug-resistant typhoid strains originating in South Asia have spread 197 times since 1990 to other countries, including the UK.

He told SciDev.net: “The repeated acquisition of antimicrobial resistance among S. typhi and spread across borders is worrying.

“We have very few antibiotics that are effective against typhoid.”

Their findings, the team said, highlight the need to treat drug-resistant typhoid as a global problem.

During their study, the researchers sequenced the genomes of 3,489 S. typhi candidates obtained from blood samples collected from patients with confirmed cases of typhoid fever from Bangladesh, India, Nepal and Pakistan between 2014-2019.

They then compared it with another 4,169 S. typhi samples collected from 70 different countries between 1905 and 2018.

This, they said, makes their study the largest ever conducted on the S. typhi bacterium.

Analysis showed that acquired resistance genes were present in 26.8 percent of the 7,657 samples analyzed.

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According to Prof. Andrews, multidrug resistant typhoid has been found in Pakistan, while strains resistant to the widely used antibiotic azithromycin have been observed in Bangladesh, India and Nepal.

He added: “If multidrug resistant strains gain resistance to azithromycin, we will run out of effective oral antibiotics for the treatment of typhoid fever.”

Mutations that promote resistance to azithromycin have emerged seven times over the past two decades, the researchers reported — with the resulting strains also conferring resistance to another class of important antibiotics, the cephalosporins.

The team also found strains resistant to the quinolones, an important group of broad-spectrum antibiotics, responsible for more than 85 percent of S. typhi cases in Bangladesh, rising to more than 95 percent of all cases in India, Nepal and Pakistan in 2010.

Quinolones developed into the primary treatment for suspected cases of typhoid fever in the 1990s, as they had been shown to be highly effective against the disease by then.

According to the researchers, strains resistant to quinolones have spread around the world at least 94 times since 1990, mostly from South Asia.

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Prof. dr. Andrews added: “A worrying finding from our study is that resistant strains often spread and outcompete more” [antibiotic] sensitive strains.

“As a result, we don’t need to see typhoid as a problem in certain countries or regions, but rather as a global problem that requires a global response.

“That also includes funding for surveillance and typhoid vaccines.”

The full findings of the study are published in the journal The Lancet Microbe.

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