Spread of resistant typhus pathogens – wissenschaft.de

Bacterial infectious disease causes around 100,000 lives each year, mainly in South Asia and Africa. Genetic analyzes of more than 7,000 pathogen samples from around the world now reveal that typhus bacteria are increasingly developing new antibiotic resistance. In the last 30 years alone, resistant variants of these pathogens have been transmitted across national borders 197 times, with the starting point being mostly India. The research team finds it particularly worrying that several strains of bacteria have developed in recent years that, if combined, could make all common oral typhoid drugs ineffective.

Typhoid fever is an infectious disease that occurs mainly in poorer countries or in poor hygiene conditions. Its causative agent, Salmonella enterica serovar Typhi, is usually transmitted by contaminated water or food. The infection causes persistent high fever, headache and abdominal pain and blurred consciousness and can lead to intestinal bleeding and death in severe cases. Every year, around 11 million people become ill with typhus and around 100,000 people die of it. Typhoid fever occurs most in South Asia, Southeast Asia and sub-Saharan Africa. So far, the infection can be easily treated with antibiotics, but the first strains resistant to older antibiotics have been spreading since the 1970s. However, they can usually still be fought with newer classes of active ingredients, such as cephalosporins, fluoroquinolones and macrolide antibiotics.

Several new resistances

Kesia Esther da Silva of Stanford University and her colleagues have now studied the state of the spread of resistance among typhoid pathogens around the world. For their study, they analyzed bacterial DNA from 3,489 samples of pathogens from South Asia taken between 2014 and 2019 and another 4,169 other samples from the last hundred years and from more than 70 countries around the world. Analyzes showed that a good quarter of isolates showed resistance genes to “classical” antibiotics. The focus of these multi-resistant pathogens was predominantly in India. From there, these bacteria have been introduced to other countries and regions more than 197 times since 1990 alone. “The most common international transit routes have been in South Asia and from South Asia to Southeast Asia, East Africa and South Africa,” the team said. However, their data also show that the share of these classic resistances in South Asian countries has now fallen slightly.

On the other hand, several new resistance to the typhoid pathogen has emerged in recent years and has spread rapidly since then. As early as the 1990s, bacteria developed defense mechanisms against modern fluoroquinolones. In 2010, these resistances accounted for 95 percent of typhus samples from India, Pakistan and Nepal, according to da Silva and colleagues. Since 2010, samples have increasingly included triple mutation variants, making bacteria even less sensitive to quinolone antibiotics. In the last 20 years, at least seven bacterial lines have developed resistance to azithromycin, a commonly used macrolide antibiotic. The research team also identified several cephalosporin-resistant strains. As with early multidrug-resistant typhoid bacteria, most of these new strains have developed in India.

“A real cause for concern”

“The speed with which highly resistant Salmonella Typhi strains have evolved and spread in recent years is a real problem,” said lead author Jason Andrews of Stanford University. “This underlines the urgent need to expand and intensify preventive measures, especially in the most vulnerable countries.” “The fact that resistant strains of typhus have so often been able to spread internationally also underscores that typhoid control and resistance should be seen as a global problem, not a local problem,” says Andrews.

The researchers consider the risk of typhoid pathogens to exchange newly acquired resistance genes as particularly serious, resulting in strains that are not sensitive to both common active ingredients and new quinolone and macrolide antibiotics. “Such organisms would avoid any treatment with established oral antimicrobials,” writes da Silva and colleagues. “This would lead to an increase in hospitalizations and increased morbidity and mortality.”

Source: Kesia Esther da Silva (Stanford University) et al., The Lancet Microbe; doi: 10.1016 / S2666-5247 (22) 00093-3

Leave a Reply

Your email address will not be published.