Research Roundup: Spillover and spillback, 3D spheres for drug development, drug resistance, and more
In this regular feature on Breakthroughs, we highlight some of the most interesting reads in global health research from the past week.
Nearly three-fourths of new and emerging human diseases are zoonoses, animal diseases that spillover into humans. Now, scientists are reporting “spillback” of human diseases into monkey populations in South America, as Zika virus becomes endemic and as Brazil faces its worst yellow fever outbreak in years. Human strains of Zika have been found in black-striped capuchin monkeys and marmosets, a concerning trend as these species could become a reservoir for the virus. Capuchins are often kept as pets, employed as street entertainers, or hunted as meat, and these routine interactions could lead to future human outbreaks. Meanwhile, Brazil’s yellow fever outbreak has killed nearly 70 people and more than 600 monkeys, threatening rare and endangered species in the Atlantic rainforest.
Researchers at the University of Southampton have designed miniscule 3D spheres that can simulate conditions inside the human body, an exciting development that could help scientists better understand how pathogens interact with human cells. The researchers created one such sphere with a collagen matrix, similar to the makeup of human lungs, to study antibiotics that target and kill the tuberculosis bacterium. The 3D spheres can be used four times longer than existing 2D systems, enabling researchers to monitor the progression of infections over time.
Colistin is often the last line of treatment for multidrug-resistant infections, however, its use as a growth promoter for livestock in China has led to the development of colistin-resistant bacteria on chicken farms. While colistin resistance was first reported in China in 2015, it has now spread to 25 countries across four continents. Scientists have discovered a specific gene (mrc-1) that confers resistance to colistin and that can be easily spread between bacteria. Now, a new study has revealed that mrc-1 is much more prevalent than previously believed. The gene was found in nearly all bacteria collected from chicken farms in China, even though only half of the samples proved resistance to colistin. The findings also suggest that flies may be accelerating the spread of colistin resistance by transporting resistant bacteria from farms to surrounding communities.
A cocktail of three bacteria-killing viruses could provide rapid protection against cholera, filling a critical need during outbreaks, as vaccines do not provide protection until approximately two weeks after administration. The technique is known as phage therapy as it utilizes bacteriophages—viruses that target and kill specific bacteria. While phage therapy has been around for nearly a century, it was largely eclipsed by the advent of antibiotics, but has gained increasing attention in recent years in response to the growing threat of antimicrobial resistance. To develop the regimen, researchers at Tufts University School of Medicine first identified phages that target the cholera bacterium, and then narrowed their focus to those that can survive and function in the human small intestine, where cholera infection takes place. Animal studies suggest that the cocktail could prevent infection when taken just three hours prior to exposure. The research team has established an independent company, PhagePro, and plans to further test and develop the therapy.