Global response' needed as typhoid evades antibiotics

The bacteria that causes typhoid fever is becoming increasingly resistant to common antibiotics used to treat the disease, with resistant strains spreading to hundreds of countries in the past three decades, new analysis shows.

The study published in The Lancet Microbe shows how resistant strains originally from South Asia, where the disease burden is highest, have spread to other countries 200 times since 1990. To isolate the drug-resistant typhoid strains, the researchers performed genome sequencing on 3,489 S.Typhi candidates obtained from blood samples collected between 2014 and 2019 from people in Bangladesh, India, Nepal and Pakistan with confirmed cases of typhoid fever. For comparison, they sequenced another 4,169 S.Typhi samples collected from 70 countries between 1905 and 2018.

The findings show that resistant S. Typhi strains have spread between countries at least 197 times since 1990, with strains that often occurred in South Asia and South-East Asia, East and Southern Africa spreading to countries including the United States, the UK and Canada.

Researchers also compared strains showing resistance to macrolides and quinolones, which are considered the most critically important human antibiotics. Typhoid strains resistant to quinolones, a class of antibiotics that act against a wide range of disease causing bacteria have risen and spread at least 94 times since 1990, with most (97 per cent) originating from South Asia, according to the study.

As a result, we need not think of typhoid as a problem in certain countries or regions but rather a global problem that requires a global response. That includes funding for surveillance and typhoid vaccines. One of the challenges with addressing typhoid is lack of reliable diagnostics.

Blood cultures require sophisticated laboratory infrastructure, are expensive, take two to five days for results, and miss 40 per cent of cases. As a consequence, many people with fever are treated with antibiotics for suspected typhoid, when they do not actually have the disease, fueling drug resistance ended the authors.

Reference: This piece was produced by SciDev.Net's Global desk. https://www.scidev.net/global/news/global-response-needed-as-typhoid-evades-antibiotics/