Antibiotic resistant typhoid detected in countries around the world

Unappreciated global spread of multiple antimicrobial resistant typhoid mapped by international consortium

Antibiotic resistant typhoid detected in countries around the world

150511-salmonella.pngDOI: 10.1038/ng.3281
Population structure of the S. Typhi H58 lineage.

There is an urgent need to develop global surveillance against the threat to public health caused by antimicrobial resistant pathogens, which can cause serious and untreatable infections in humans. Typhoid is a key example of this, with multidrug resistant strains of the bacterium Salmonella Typhi becoming common in many developing countries. A landmark genomic study, with contributors from over two-dozen countries, shows the current problem of antibiotic resistant typhoid is driven by a single clade, family of bacteria, called H58 that has now spread globally.

"The data was produced by a consortium of 74 collaborators from the leading laboratories working on typhoid and describes one of the most comprehensive sets of genome data on a single human infectious agent. It represents global co-operation in the scientific community at its best. Typhoid affects around 30 million people each year and global surveillance at this scale is critical to address the ever-increasing public health threat caused by multidrug resistant typhoid in many developing countries around the world."

Dr Vanessa Wong, first author from the Wellcome Trust Sanger Institute

The study shows the H58 clade of Typhi is displacing other typhoid fever strains that have been established over decades and centuries throughout the typhoid endemic world, completely transforming the genetic architecture of the disease. Multidrug resistant H58 has spread across Asia and Africa over the last 30 years, and created a previously underappreciated and ongoing epidemic through countries in eastern and southern Africa with important public health consequences.

Vaccination to prevent the disease is not currently in widespread use in these countries; instead the disease is controlled mainly through use of antimicrobial drugs. H58 Typhi is often resistant to the first-line antimicrobials commonly used to treat the disease, and is continuing to evolve as it spreads to new regions and populations, acquiring novel mutations providing resistance to newer antimicrobial agents, such as ciprofloxacin and azithromycin.

"Multidrug resistant typhoid has been coming and going since the 1970s and is caused by the bacteria picking up novel antimicrobial resistance genes, which are usually lost when we switch to a new drug. In H58, these genes are becoming a stable part of the genome, which means multiply antibiotic resistant typhoid is here to stay."

Dr Kathryn Holt, senior author from the University of Melbourne

"H58 is an example of an emerging multiple drug resistant pathogen which is rapidly spreading around the world. In this study we have been able to provide a framework for future surveillance of this bacterium, which will enable us to understand how antimicrobial resistance emerges and spreads intercontinentally, with the aim to facilitate prevention and control of typhoid through the use of effective antimicrobials, introduction of vaccines, and water and sanitation programmes."

Professor Gordon Dougan, senior author from the Sanger Institute

The publication of this research in Nature Genetics coincides with the 9th International Conference on Typhoid and invasive Non-Typhoidal Salmonelloses held by the Coalition against Typhoid (CaT), where these results will be shared with the scientific community. The meeting brings together an international group of healthcare and public health experts, researchers and clinicians to focus on strategies to counteract the spread of typhoid in endemic countries.

"These results reinforce the message that bacteria do not obey international borders and any efforts to contain the spread of antimicrobial resistance must be globally coordinated."

Dr Stephen Baker, an author from The Hospital for Tropical Diseases, an Oxford University Clinical Research Unit in Ho Chi Minh City, Vietnam

Notes to Editors
Publications
  • Phylogeographical analysis of the dominant multidrug-resistant H58 clade of Salmonella Typhi identifies inter- and intracontinental transmission events.

    Wong VK, Baker S, Pickard DJ, Parkhill J, Page AJ et al.

    Nature genetics 2015;47;6;632-9

Funding

A full list of funding agencies can be found in the publication.

Participating Centres

A full list of participating centres can be found in the publication.

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