Genomic analysis reveals diverse, drug-resistant E. coli in diabetic foot infections

New research led by King's College London, in collaboration with the University of Westminster, has shed light on the diversity and characteristics of E. coli strains that drive diabetic foot infections.

Published in Microbiology Spectrum, the research provides the first comprehensive genomic characterization of E. coli strains isolated directly from diabetic foot ulcers across multiple continents. The findings could help to explain why some infections become particularly difficult to treat and why they can lead to severe, sometimes life-threatening, outcomes.

Diabetic foot infections remain one of the most serious complications of diabetes and are a leading cause of lower-limb amputation worldwide. Although clinicians have recognised that these chronic wound infections are often complex, little is known about the specific pathogens involved, particularly E. coli, despite its frequent detection in clinical samples.

Researchers analyzed whole-genome sequences from 42 E. coli strains isolated from infected diabetic foot ulcers in patients across Nigeria, the UK, Ghana, Sweden, Malaysia, China, South Korea, Brazil, India and the USA. By sequencing the complete DNA of each bacterial strain, the team was able to examine global patterns in the biology of E. coli associated with diabetic foot disease. This approach enabled the researchers to compare genetic differences between strains, identify genes linked to antibiotic resistance, and pinpoint factors that contribute to disease severity.

The genomic analysis showed that the E. coli strains were highly diverse. The bacteria belonged to many different genetic groups and carried a wide range of genes linked to antibiotic resistance and disease. This demonstrates that there is no single type of E. coli responsible for diabetic foot infections, and distinct lineages were independently capable of adapting to the diabetic foot environment.

By analyzing how the strains are related and identifying the resistance mechanisms and virulence traits (the features or tools that make a microbe more harmful) they carry, the research helps explain why some diabetic foot infections are particularly difficult to treat or can progress rapidly to severe illness.

Notably, around 8 per cent of the strains were classified as multidrug-resistant or extensively drug-resistant, meaning they are resistant to multiple or nearly all available antibiotics.

Understanding these bacteria at a genomic level is a crucial step towards improving diagnosis and enabling more targeted treatments for people with diabetes. By identifying which E. coli strains are most common and which antibiotics they are likely to resist, clinicians can choose therapies that are more likely to work, helping to reduce prolonged infection, hospitalisation, and the risk of amputation."

Dr. Vincenzo Torraca, Lecturer in Infectious Disease at King's College London and senior author of the paper

Victor Ajumobi, a second-year PhD student at King's College London and the University of Westminster, and first author of the paper, added: "This information will be particularly valuable in low-resource settings, where E. coli infections of diabetic foot ulcers are more common and where rapid diagnostic tools for antimicrobial resistance are not always readily available."

Future research will focus on understanding how specific virulence factors identified in the study contribute to disease progression. Many of the isolates carry genes that enable E. coli to attach to host tissues or evade the immune system. Investigating how these traits operate within the diabetic foot environment could reveal new therapeutic targets and support the development of improved treatment strategies.