September 14, 2021
Antibiotic-resistant bacteria are on the rise globally, threatening animal and human health. While trends in antimicrobial resistance (AMR) in bacteria from terrestrial animals are increasingly studied, AMR in aquatic animals destined for human consumption is seldom documented. The aquaculture and fisheries industry is experiencing rapid growth, and aquatic animals are now the fastest-growing food animal sector globally. Asia contributes the largest share of this production—over two-thirds of global output. In a study in Nature Communications, researchers address this blind spot, reviewing current evidence on AMR in farmed and wild-caught aquatic food animals over two decades in Asia, the world’s most productive aquaculture and fisheries region.
What We Found:
Researchers reviewed 749 point prevalence surveys of antimicrobial resistance from aquatic food animals in Asia between 2000 and 2019. The resulting dataset was used to establish a baseline of multi-drug resistance and map resistance in freshwater and marine systems, providing an initial assessment of the geographic distribution of resistance hotspots from aquatic animals entering the human food supply.
The study used the percentage of antimicrobial compounds with resistance exceeding 50% (P50) in each survey as a summary metric of multi-drug resistance. Elevated levels of multi-drug resistance (33%) are already present in farmed aquatic animals intended for human consumption. By contrast, multi-drug resistance from wild-caught animals decreased sharply between 2000 and 2019, from 52% to 22%, although the authors caution that data from capture fisheries were scarce, and additional work is needed to document resistance trends and influencing factors in wild-caught fish.
Concerning levels of resistance to medically important antimicrobials were identified in foodborne pathogens. In these pathogens, a dual-threat profile was identified, marked by high rates of resistance to first-line antimicrobials (penicillins, sulfonamides, tetracyclines) as well as an erosion of last-resort therapeutic options for foodborne Vibrio and Aeromonas spp. infections. Across all surveys from Gram-negative bacteria in the study, the mean colistin resistance was 41.3%.
The study revealed that hotspots of AMR correspond to areas experiencing rapid aquaculture and fisheries growth. Freshwater hotspots of multi-drug resistance were identified along Asia’s major river systems; marine water hotspots were located in northeastern and southern China and coastal India on the Arabian Sea and Bay of Bengal between India and Sri Lanka.
The research further identified central and eastern China; the western and central regions of India, and along the Indo-Gangetic Plain; and Indonesia as areas that would benefit most from increased surveillance efforts.
“This work is, to our knowledge, the largest synthesis of resistance data from cultured and wild-caught aquatic food animals to date in Asia. Our findings could help governments and international organizations set priorities to upscale surveillance across the continent,” said CDDEP co-author and ETH Zürich Professor Thomas Van Boeckel.
Why It Matters:
Antimicrobial resistance has been recognized by the United Nations General Assembly as a major risk because of its harmful consequence for human and animal health, sustainable development, and the long-term viability of food production industries.
To date, limited visibility on antimicrobial resistance in a high-growth aquaculture and fisheries industry in Asia has precluded targeted interventions. The research contributes to the broader picture of resistance in bacteria from aquatic food animals. Taken together, the results suggest that aquatic food animal production may serve as an under-appreciated route for transmission of antimicrobial-resistant bacteria from aquatic animals and their environment to humans.
Amongst the key takeaways from this study is the persistently high rate of multi-drug resistance in cultured fish destined for human plates over the last twenty years in Asia, a region that produces 90% of the world’s farmed fish. Furthermore, the relative scarcity of surveys identified in the review points to a need for systematic AMR surveillance, particularly from the most heavily consumed aquatic animals.
Maps of multi-drug resistance in freshwater and marine environments provide an evidence base for policymakers across Asia to direct interventions, establish measurable, time-bound AMR reduction targets, and inform prioritization of future surveillance efforts.
Antibiotics are amongst the cornerstones of modern medicine. This research provides further evidence that we are dangerously close to losing the precious gift of these medicines.
“Our work highlights the necessity for urgent solutions. The findings underscore a need for increased surveillance to inform targeted risk-reduction strategies, and immediate action to secure healthy aquatic environments and sustainable food production systems without reliance on routine antimicrobial use,” said study author Daniel Schar of the Université Libre de Bruxelles.
The article titled “Twenty-year trends in antimicrobial resistance from aquaculture and ﬁsheries in Asia” can be accessed online at Nature Communications