A genetic study of typhoid has shown that nearly half of infections are now caused by a single antibiotic-resistant strain. Typhoid infects more than 20 million people per year around the world, and kills around 200,000. Although vaccines are available, their use is not widespread in Asia and Africa where instead the disease is treated with antibiotics. With drug resistance an increasing problem, fighting typhoid is becoming more difficult and antibiotics are often wasted.
The study by a consortium of 74 researchers from around the world analysed the DNA of almost 2000 typhoid pathogens. Their results provide convincing evidence that a single strain, H58, of the bacterium Salmonella Typhi is becoming the dominant strain, displacing previously well-established strains that were treatable with antibiotics. H58 emerged around 25 – 30 years ago in South Asia and spread from there across the continent before crossing into Africa.
Typhoid causes a high fever, headaches, weakness and constipation. The bacteria are present in the urine and faeces of carriers and the disease is spread through contaminated food and water. H58 is known to exist in Kathmandu, and there are fears that resistant infections will increase following the damage caused by the recent earthquakes in Nepal.
The dominance of multiple-drug-resistant typhoid raises concerns about our ongoing ability to treat typhoid effectively. “These results reinforce the message that bacteria do not obey international borders,” says Dr Stephen Baker. “Any efforts to contain the spread of antimicrobial resistance must be globally coordinated.”