Carbapenemase gene blaOXA-48 detected at six freshwater sites in Northern Ireland discharging onto identified bathing locations.

Faecal contamination of surface waters has the potential to spread not only pathogenic organisms but also antimicrobial resistant organisms. During the bathing season of 2021, weekly water samples, from six selected coastal bathing locations (n = 93) and their freshwater tributaries (n = 93), in Northern Ireland (UK), were examined for concentrations of faecal indicator bacteria Escherichia coli and intestinal enterococci. Microbial source tracking involved detection of genetic markers from the genus Bacteroides using PCR assays for the general AllBac marker, the human HF8 marker and the ruminant BacR marker for the detection of human, and ruminant sources of faecal contamination. The presence of beta-lactamase genes blaOXA-48, blaKPC, and blaNDM-1 was determined using PCR assays for the investigation of antimicrobial resistance genes that are responsible for lack of efficacy in major broad-spectrum antibiotics. The beta-lactamase gene blaOXA-48 was found in freshwater tributary samples at all six locations. blaOXA-48 was detected in 83% of samples that tested positive for the human marker and 69% of samples that tested positive for the ruminant marker over all six locations. This study suggests a risk of human exposure to antimicrobial resistant bacteria where bathing waters receive at least episodically substantial transfers from such tributaries.