How bacteria are developing resistance even to 'last resort' antibiotics

A new study is helping scientists understand how bacteria are building up resistance even to 'last resort' antibiotics – and putting millions at risk of life-threatening infections.

Last week, a World Health Organization (WHO) report warned that high levels (50%) of resistance were in bacteria frequently causing blood infections in hospitals.

The WHO report was based on data reported by 87 countries in 2020.

The researchers examined the whole genome sequences of around 2,000 resistant bacteria, predominantly Escherichia coli collected between 2008 and 2016. The team tracked the spread of genes relating to antimicrobial resistance (AMR).

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For example, some were initially found in North America and spread to Europe, while for others the spread was from Europe to North America.

Professor Alison Mather, group leader at the Quadram Institute and the University of East Anglia, said: "By assembling such a large and diverse collection of genomes, we were able to identify the key genes conferring resistance to these critically important drugs.

"Understanding the mechanisms of transmission is key to the design of interventions to reduce the spread of AMR."

The team focussed on resistance to one particularly important group of antimicrobials, the Extended-Spectrum Cephalosporins (ESCs).

These antimicrobials have been classed as critically important by the WHO because they are a 'last resort' treatment for multi-drug resistant bacteria.

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But their efficacy has declined as bacteria have developed resistance.

Lead author Dr. Roxana Zamudio said: "Antimicrobial resistance is a global problem, and it is only by working collaboratively with partners in multiple countries that we can get a holistic understanding of where and how AMR is spreading."

Understanding the flow of genetic information within and between bacterial populations is key to understanding AMR transmission and the global spread of resistance.

This knowledge will contribute to the design of vitally needed interventions that can halt AMR in the real world where bacteria from diverse hosts and environmental niches interact, and where international travel and trade mean that these interactions are not limited by geography.

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