Community Medicine, Microbiology, Pharmacology

Typhoid: S. Typhi is more resistant to drugs.

A study published in The Lancet Microbe found that the bacteria that cause typhoid are becoming increasingly resistant to some of the most important antibiotics for human health.
Even the largest analysis of the Salmonella Typhi (S. Typhi) genome shows that resistant strains (almost all of them from South Asia) have spread to other countries nearly 200 times since 1990.


Researchers note that typhoid is a global public health problem that infects 11 million people and kills more than 100,000 people each year. Although it is most prevalent in South Asia, which accounts for 70% of the global burden of disease, it is also affecting sub-Saharan Africa, Southeast Asia, and Oceania, emphasizing the need for a global response.


Antibiotics can be used to successfully treat typhoid, but their effectiveness is threatened by the emergence of resistant strains of S. typhi. Analysis of the growth and spread of resistant S. Typhi has so far been limited and most studies are based on small samples. The study’s lead author said “The rate at which highly resistant S. Typhi strains have emerged and spread in recent years is a real cause of concern and underscores the urgent need to expand preventive measures, especially in the countries most at risk.” Jason Andrews of Stanford University, USA.


“At the same time, the fact that resistant strains of typhoid have spread worldwide multiple times also underscores the need to consider typhoid control and antibiotic resistance as a global issue rather than a regional one,” said Mr. Mr. Andrews…


In the new study, scientists performed whole-genome sequencing of 3489 S. Typhoid isolates derived from blood samples from people with confirmed typhoid cases in Bangladesh, India, Nepal and Pakistan between 2014 and 2019. A collection of 4169 S. Typhi specimens isolated from more than 70 countries between 1905 and 2018 was also sequenced and included for analysis.


Genes conferring resistance were identified in 7658 sequenced genomes using a gene database.
If the strain contained genes conferring resistance to the classic first-line antibiotics ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole, the strain was classified as multidrug resistant (MDR). The authors traced the existence of genes that confer resistance to macrolides and quinolones, two of the most important antibiotics for human health. Analysis shows that resistant strains of S. Typhi have spread between countries at least 197 times since 1990. This strain was most common from South and South Asia to Southeast Asia, East and South Africa, but has also been reported in the UK. In the US and Canada, researchers say.


A study published in The Lancet Microbe found that the bacteria that cause typhoid are becoming increasingly resistant to some of the most important antibiotics for human health. Even in the largest analysis of the S. Typhi genome, resistant strains (mostly from South Asia) have spread to other countries nearly 200 times since 1990. Antibiotics can be used to successfully treat typhoid, but they are is very high risk of emergence of resistant strains S. typhi.