How do antibiotic-resistant bacteria evolve in the intestines of hospitalized patients?

The ability of bacteria to evolve in response to antibiotic treatments has driven the emergence and spread of resistance factors, a development of particular concern in clinical settings. It is increasingly difficult to find effective treatments that can cure patients colonized with drug-resistant bacteria.

A team led by scientists from the Spanish National Research Council (CSIC) has analyzed how antibiotic-resistant bacteria evolve in the intestines of hospitalized patients in real time. The results show the importance of integrating evolutionary concepts, such as genetic diversity, in surveillance and diagnosis programs for antibiotic-resistant strains. Likewise, the study reveals the impact of plasmids, extrachromosomal DNA fragments, on the physiology of these bacteria.

This new work, carried out by teams from the CSIC’s National Center for Biotechnology (CNB), in collaboration with the Center for Biological Research in Epidemiology and Public Health Network (CIBERESP) of the Carlos III Health Institute in Spain, the Ramón y Cajal Institute de Investigación Sanitaria (IRYCIS) in Spain, the University of Zurich in Switzerland and the Pasteur Institute in France, has focused on plasmids, which allow unrelated bacteria to share antibiotic resistance genes.

Álvaro San Millán, a CSIC researcher at the National Center for Biotechnology explains: “In hospital environments, bacteria carrying resistance plasmids are capable of jumping between different hospitalized patients, colonizing their intestinal microbiota. We have seen how plasmids allow bacteria to evolve rapidly within patients”, highlights San Millán.

For Javier de la Fuente, a researcher at the CNB and first author of the work, this collaboration with IRYCIS “has allowed us to see how bacteria behave beyond the test tube, analyzing the bacteria in their real ecosystem: the intestine of patients ”. “Our data shows how they evolve and adapt to the antibiotic treatments administered to patients, in a real clinical situation,” he adds.

Javier de la Fuente, a CNB researcher, observes a Petri dish with bacteria in his laboratory. (Photo: Susana de Lucas)

Rafael Cantón, head of the Microbiology service at the Ramón y Cajal University Hospital and also co-author of the study, highlights: “The study is part of a European surveillance project for the detection of multi-resistant bacteria in hospitals called RGNOSIS, which integrates data from more of 9,000 patients. Projects of this type are essential to help us understand and stop the spread of antibiotic resistance.”

The study is titled “Within-patient evolution of plasmid-mediated antimicrobial resistance”. And it has been published in the journal Nature Ecology and Evolution. (Source: CNB / CSIC)