Resistant typhoid pathogens are spreading – new mutations making bacteria more resistant to modern antibiotics


Cause for concern: In recent years, typhoid bacteria have rapidly developed new antibiotic resistance, as shown by genetic analysis. The mutations make the pathogens resistant to modern emergency antibiotics and are now spreading from India. This development is worrying, emphasize the researchers in The Lancet Microbe journal. In extreme cases, this can mean that no oral treatment for typhoid fever works.

More than eleven million people contract typhoid fever every year and about 100,000 die from it, mainly in South Asia and Africa. The causative agent of this bacterial infection, Salmonella enterica serovar typhi, is usually transmitted through contaminated water or food. Although the infection can be easily treated with antibiotics, strains resistant to antibiotics are spreading rapidly.

From South Asia to the world

Cassia Esther da Silva of Stanford University and her colleagues have now investigated how widespread and where such resistant and multi-resistant typhoid bacteria are now widespread. For their study, they analyzed bacterial DNA from 3,489 pathogen samples taken from South Asia between 2014 and 2019. In addition, they evaluated another 4,169 samples that came from more than 70 countries and were collected over the past 100 years.

Analyzes have shown that multidrug-resistant strains of a type of pathogen immunized from older classes of antibiotics have been circulating in South Asia for decades. As the team reports, they mostly originated in India and have been introduced from there to other countries and territories more than 197 times since 1990. The most common transmissions were within South Asia or Southeast Asia, but resistant typhoid strains also reached Africa, North America and Europe.

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New Resistances Are Growing

However: in the meantime, new resistant forms are spreading in addition to these “classic” multi-resistant typhoid bacteria. They have developed mechanisms that also immunize them to modern classes of antibiotics such as cephalosporins, quinolones and macrolides. In the early 1990s, there were strains of bacteria resistant to fluoroquinolones. In 2010, these already accounted for 95 percent of the type samples from India, Pakistan and Nepal, as reported by da Silva and colleagues.

Variation of variants (FQ-NS: Resistant to fluoquinolones; MDR: Multi-resistant; XDR: Extremely multi-resistant) © Da Silva et al. / lancet microbe, 4.0. CC BY

Over the past 20 years, at least seven lines of bacteria have developed resistance to azithromycin, a commonly used macrolide antibiotic. The research team also identified several strains of cephalosporins with associated resistance genes. Like the early multidrug-resistant typhoid bacteria, most of these new strains evolved in India.

“A real cause for concern”

“The development and spread of highly resistant strains of Salmonella typhi has been a real concern in recent years,” said senior author Jason Andrews from Stanford University. “This underscores the urgent need to expand and intensify preventive measures, particularly in the most vulnerable countries.”

Researchers see a particular danger in the fact that the types of pathogens can exchange newly acquired resistance genes with each other. This can then result in bacterial strains that are insensitive to both the older active ingredients and the newer quinolone and macrolide antibiotics. “Such organisms would survive any treatment with established oral antimicrobial agents,” da Silva and colleagues wrote. “This will lead to an increase in hospital admissions and an increase in morbidity and mortality.”

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a global problem

According to the research team, their results are also a clear indicator that India remains an important hotspot for the emergence of antibiotic resistance – more urgently needs to be done. Andrews says, “The fact that resistant strains of typhoid bacteria have often spread internationally also underscores that controlling typhoid fever and resistance should be viewed as a global problem, not a local problem.” in the form of.” (The Lancet Microbe, 2022; doi: 10.1016/s2666-5247(22)00093-3,

Source: The Lancet

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