Drug-Resistant Typhoid: A Growing Global Health Risk

Typhoid fever, a bacterial infection once easily treated with antibiotics, is making a dangerous comeback. New research reveals that drug-resistant strains of Salmonella enterica serovar Typhi (S Typhi) are not only emerging rapidly but are also spreading across countries and continents (1^✔ ✔Trusted Source
The international and intercontinental spread and expansion of antimicrobial-resistant Salmonella Typhi

Go to source). Health experts warn that without urgent action, the world may soon face a typhoid crisis where even modern medicines fall short.

Typhoid and Drug Resistance: A Growing Threat

In a massive genomic study, scientists analyzed 3489 S Typhi strains collected between 2014 and 2019 from Nepal, Bangladesh, Pakistan, and India. These were combined with a global collection of 4169 S Typhi genomes dating back to 1905.

Here’s what they found:

• 94 independent occurrences of mutations causing fluoroquinolone resistance were detected, almost all originating from South Asia.
• 138 international and 59 intercontinental transfers of drug-resistant S Typhi strains were documented.
• In Pakistan, extensively drug-resistant (XDR) typhoid strains emerged in 2016 and rapidly replaced older, less-resistant types.
• Bangladesh saw a steady rise in azithromycin-resistant strains beginning around 2013.

These numbers paint a clear and concerning picture: drug-resistant typhoid is no longer a localized problem — it’s a global one.

Tracing the Resistance: How Did It Begin?

The Story of Multidrug Resistance

In the 1970s, S Typhi strains resistant to multiple drugs like ampicillin, chloramphenicol, and trimethoprim–sulfamethoxazole first appeared. One specific lineage, genotype 4.3.1 (haplotype H58), became globally dominant, especially across South Asia.

When fluoroquinolones came into use in the 1990s, they offered hope. But that didn’t last long. By the 2010s, most typhoid cases in South Asia had developed mutations making them resistant to these drugs too.

XDR Typhoid: A New, More Dangerous Strain

In 2016, a new form of S Typhi was detected in Pakistan. Termed extensively drug-resistant (XDR) typhoid, these bacteria carried genes on both plasmids and chromosomes, making them resistant to nearly all oral antibiotics — including third-generation cephalosporins and fluoroquinolones.

Shockingly, within just a few years, this XDR strain completely replaced less resistant strains in the region.

Azithromycin Resistance on the Rise

Adding to the concern, azithromycin resistance — a last-line oral therapy — began emerging independently across multiple typhoid lineages. This resistance was tied to mutations in the AcrB efflux pump, first noticed in Bangladesh around 2013. Since then, these resistant strains have steadily increased in number.

How Drug-Resistant Typhoid Is Spreading Globally

The study found frequent international and intercontinental spread of resistant S Typhi strains. This means a resistant strain emerging in South Asia can quickly surface in distant countries, leading to local outbreaks and making global control harder.

The patterns show that once these strains arrive in a new area, they tend to expand locally, often replacing previously circulating, drug-sensitive typhoid strains.

What This Means for the Future

Vaccination and Surveillance Are Key

Given how fast resistance is evolving, relying only on antibiotics is no longer enough. Vaccination campaigns — especially with typhoid conjugate vaccines — are now critical to prevent infections before they happen.

Meanwhile, genomic surveillance will play a major role in tracking the spread of resistant strains and informing public health strategies.

Responsible Antibiotic Use Matters

One important takeaway from this study is the urgent need for responsible antibiotic use. Overuse and misuse of antibiotics fuel the emergence of resistance. Public awareness campaigns and stricter antibiotic stewardship policies are needed more than ever.

Typhoid may be an ancient disease, but the threat it poses today is alarmingly modern. Understanding and responding to the emergence of drug-resistant S Typhi is crucial if we are to avoid a global health disaster. It also highlights the urgent need for investment in new antimicrobial treatments and rapid diagnostics. Without collective global action, the progress made against typhoid fever over decades could quickly unravel, placing millions more at risk.

Behind every statistic is a life at risk — let’s choose prevention, champion research, and protect the generations to come.

Reference:

1. The international and intercontinental spread and expansion of antimicrobial-resistant Salmonella Typhi - (https://www.medrxiv.org/content/10.1101/2021.09.03.21262852v1.full)

Source-Medindia