Antimicrobial resistance (AMR) is a global concern within the One Health framework, affecting humans, animals, plants, and the environment. Addressing this challenge is a priority, and understanding the spread, transmission, and risk of antimicrobial resistance in the environment is essential.
In this context, an innovative pilot study by the UK’s Environmental Agency has explored the potential of marine shellfish as sentinels to assess the presence and identity of antimicrobials and resistant microorganisms, all while minimizing costs by using samples already collected for other purposes.
The Filtering Feeding Advantage
Shellfish, with their unique filter-feeding habit, have piqued the interest of researchers as potential bioindicators to report on water quality concerning antimicrobial resistance. They possess a remarkable ability to concentrate microbial contamination from their surroundings. Moreover, these creatures are already subject to routine examination in Europe, particularly for detecting bacterial faecal indicator organisms like Escherichia coli (E. coli) as part of various monitoring programs.
A Multifaceted Approach
The study leveraged existing practices of monitoring shellfish waters for various substances and the microbiological quality of shellfish flesh. It capitalized on the samples collected during routine monitoring, optimizing resources.
From July 2022 to January 2023, researchers collected shellfish samples from five different sites and subjected them to a comprehensive assessment. The approach included chemical analysis, molecular techniques (AMR gene and metagenomic analysis), and microbiological methods such as E. coli isolation and susceptibility testing.
Key Findings and Future Prospects
One of the primary achievements of this research was the development of sample processing and DNA extraction methods that could be applied to a wide range of bivalve shellfish species, including oysters and mussels. This innovation opens doors to more extensive environmental monitoring using these creatures.
Through the analysis of shellfish samples collected during routine monitoring, the research identified a variety of E. coli strains and generated essential baseline data regarding the prevalence of resistance genes in these indicator organisms.
Furthermore, intriguing trends were observed, such as a potential seasonal variation in the presence of AMR genes and certain antimicrobials. For example, there was a higher abundance of beta-lactamase genes during the summer, conferring resistance to penicillin and similar antibiotics.
Another breakthrough involved the implementation of a targeted mass spectrometric method for antibiotics, antifungals, and their metabolites. This enabled the identification of antibiotics like clarithromycin and trimethoprim, as well as the antifungal clotrimazole in the bivalve shellfish samples.
In conclusion, this study presents compelling evidence that shellfish can serve as sentinel species for monitoring antimicrobial resistance in coastal environments. With further development, they hold the potential to become indispensable tools for environmental monitoring purposes.
Reference (Open Access)
Environment Agency (2023) Shellfish as bioindicator for coastal Antimicrobial Resistance. Environment Agency, Bristol.