A six year study carried out at Addenbrooke’s has found that infections caused by antibiotic-resistant bacteria can easily spread among patients but are simple to detect by early screening.
Infections caused by bacteria that are resistant to last-line antibiotics can spread easily among patients, are more difficult to treat, and are often associated with higher mortality than infections caused by antibiotic-sensitive bacteria.
Early detection of these types of bacteria is therefore essential in healthcare settings.
To understand in more detail about how these bug spread, researchers at the University of Cambridge and the European Bioinformatics Institute looked at all bacteria resistant to last-line antibiotics (known as carbapenems) collected at Cambridge University Hospitals NHS Foundation Trust over a six-year period.
They found that most of the samples were detected by screening.
This involves collecting samples from patients without symptoms or clinical evidence of infection.
Most of these patients were either hospital inpatients or those who had had contact with healthcare facilities.
This study emphasises the importance of screening patients for carbapenem-resistant organisms in healthcare settings to prevent their spread to other patients.
Dr David Enoch, consultant microbiologist and infection prevention & control doctor for CUH
Tracking bacteria
The researchers used whole genome sequencing (DNA fingerprinting) to identify the bacterial species, antibiotic resistance genes and plasmids (pieces of DNA carrying antibiotic resistance genes).
During the study, they detected an unsuspected outbreak caused by a highly antibiotic-resistant strain - klebsiella pneumoniae sequence type 78, which carried the blaNDM-1 gene on a specific plasmid.
This strain and plasmid appeared to be highly specific for Addenbrooke’s hospital, and had rarely been previously detected in global databases.
They also found carbapenemase genes on plasmids in 86% of samples and evidence of transmission of these genes between different bacterial strains (horizontal transmission).
This study highlights the benefits of using bacterial genome sequencing to help us to understand the transmission of antibiotic resistance genes between bacteria and between patients.
Dr Estée Török, Senior Visiting Research Fellow, University of Cambridge
Dr Leah Roberts, Postdoctoral Fellow, EMBL-EBI added:
“Integration of whole genome sequencing into routine clinical surveillance is important for understanding the spread of pathogens at local and national levels.
"More work is still needed to understand cryptic transmission pathways, like plasmid-mediated AMR dissemination.”
Click here to link to the published paper:
https://www.microbiologyresearch.org/content/journal/mgen/10.1099/mgen.0.001048 (opens in a new tab)
This study was funded by the Academy of Medical Sciences, The Health Foundation, the Wellcome Trust and the NIHR Cambridge Biomedical Research Centre.