Drug-resistant typhoid threatens global health

An antibiotic-resistant strain of typhoid bacterium is spreading globally and posing a public health threat, especially in developing countries, a new study has warned.
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," said Dr Vanessa Wong, first author from the Wellcome Trust Sanger Institute.

"It represents global co-operation in the scientific community at its best," said Wong.
"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," Wong said.
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 under-appreciated 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, researchers said.
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.
"Global surveillance at this scale is critical to address the ever-increasing public health threat caused by multidrug resistant typhoid," Wong said.
"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," said Dr Kathryn Holt, senior author from the University of Melbourne.

"In H58, these genes are becoming a stable part of the genome, which means multiply antibiotic resistant typhoid is here to stay," said Holt.
The finding was published in the journal Nature Genetics.