Diarrhoeal infections are in the top ten greatest causes of death globally. Until recently in Vietnam, it was the cause of 12% of deaths among children under five.
The situation has been improving, but the bacteria that cause diarrhoea have been fighting back in the face of cleaner environments – adapting to be less vulnerable to antibiotics, traditionally one of the most effective ways of combating the condition. To find out how to stop this, Oxford University researchers are mapping the spread of drug-resistant strains of the bacteria. They've sequenced the genomes of bacteria that cause diarrhoeal disease to find out more about them, and they're working with a global network to find new ways to save more young lives from this potentially-fatal disease.
Vietnam has an increasing and urbanising population. The population has tripled in 60 years, from 32 million in 1960 to nearly 100 million today, with 40% living in urban environments. Although there have been significant improvements in sanitation, the risk of infectious disease is still high, with food- and water-borne diseases a major cause of illness. This high infectious disease burden and uncontrolled antibiotic usage makes Vietnam a dynamic setting for the study of emerging enteric (intestinal) pathogens.
Researchers from the Oxford University Clinical Research Unit (OUCRU) team in Ho Chi Minh City work with three major hospitals that admit more than 200,000 children a year between them. More than a tenth of these are for diarrhoea.
Historically, a bacterium called Shigella flexneri has been responsible for the majority of diarrhoeal disease in developing countries, while Shigella sonnei has dominated in developed countries. This pattern, however, is changing, with S. sonnei emerging as a significant pathogen in industrialising countries, including Vietnam. Some strains are developing resistance to ciprofloxacin, the main antibiotic used against Shigella.
In response, teams in Oxford’s labs have mapped the genomes of S. sonnei from numerous samples gathered from patients with diarrhoea. Data scientists have mapped the movement of these strains through time and space – to track where and how the new drug-resistant strain has evolved.
They have been able to show, by tracking mutations through the genome, that the resistant strain now prevalent in Vietnam emerged in South Asia around 2007.
This information is critical in helping the team, in collaboration with other research groups around the world, to develop better treatments that will help children’s immune responses to the specific pathogens causing disease.