Scientists from the International Livestock Research Institute (ILRI), the University of Liverpool, the University of Edinburgh and elsewhere have traced how livestock systems act as a reservoir for antimicrobial-resistant (AMR) bacteria and AMR genetic determinants that may infect or colonize people.
This sheds light on the factors influencing AMR at the intersection of multiple species and the One-Health sector. The study, undertaken in Nairobi, Kenya, appears in this week's BMC Medicine, and helps detail how to avoid and manage the development of drug resistance in bacteria.
Alexander Fleming, who discovered the world's first antibiotic, penicillin, warned that misusing antibiotics could lead to AMR. He showed that bacteria, viruses, fungi and parasites evolve when exposed to antibiotic drugs and eventually no longer respond to those medicines. As a result of drug resistance, antibiotics and other antimicrobial medicines become ineffective and infections become increasingly difficult or impossible to treat.
Today AMR can be found worldwide and is a serious problem. It has been estimated that unless the issue is tackled now, by 2050 one person will die every three seconds because of AMR.
"High-income countries can apply resources and large investments against AMR in ways which low-income countries can't," explained study lead scientist Dishon Muloi, a Research Fellow at the International Livestock Research Institute (ILRI) and former Ph.D. student at the University of Edinburgh.
"But AMR isn't just a high-income problem or a low-income country problem. With the ease at which it can spread around the world, it's everybody's problem. So resistance in a community in Nairobi could actually mean clinical failures in a clinic in Hong Kong in two days or three days. We are not yet treating the problem with the urgency it needs, considering our connected world."
One path by which AMR is hypothesized to develop is through the large amount of antibiotics used in the livestock industry, where bacteria develop resistance and then spread to people. Quantifiable information addressing this has thus far been insufficient. Today's study used genomics, epidemiology, and ecology to look into the patterns of AMR gene carriage in an exemplar organism, E. coli.
As part of a controlled epidemiological assessment of 99 households in Nairobi, Kenya, scientists sequenced the whole genomes of bacteria isolated from 311 human, 606 cattle, and 399 wildlife excrement samples. Using statistical models, they looked at the prevalence of AMR carriage and described the diversity and structure of the AMR genes in distinct host populations around the city. They also investigated conditions that could lead to the spread of AMR genes from humans to sympatric animals at the household level.