Researchers have detected multidrug-resistant typhoid in a number of developing countries, highlighting the need for global surveillance of antimicrobial resistant pathogens.

The findings were based on a "landmark" genomic study involving contributors from more than two dozen countries. The study showed antibiotic-resistant typhoid is linked to a single clade (family of typhoid bacteria) dubbed H58, and that that clade has now spread across the globe, the Wellcome Trust Sanger Institute reported.

"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," said Vanessa Wong, first author from the Wellcome Trust Sanger Institute. 

The concerning findings reveal H58 is replacing other less-resistant typhoid strains that have been developing around the world for centuries. Multidrug resistant H58 has spread across Asia and Africa over the past three decades, leading to an epidemic in southern Africa.

"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," says 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."

The study aims to provide guidelines for future multidrug-resistant typhoid surveillance efforts. The researchers hope to gain more insight into how antimicrobial resistance comes about and spreads across continents.

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

The findings were published in a recent edition of the journal Nature Genetics.