Tracking Resistance: Phenotypic and Genomic Insights into Antimicrobial Resistance in Aquatic Bacterial Pathogens in Vietnam
Margaret Crumlish1*, Kathryn Grace1, Emily Parry1, Kim M. Ahn2, Vo H. Phuong3, Le H. Phuoc3 and Christopher J. Payne1
1Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK; 2Vietnam National university of Agriculture, Hanoi, Vietnam; 3Southern Monitoring Center for Aquaculture Environment and Epidemic, Research Institute for Aquaculture No. 2, Ho Chi Minh City, Vietnam
Vietnam is the top producer of striped catfish (Pangasianodon hypophthalmus). However, the sector is increasingly challenged by bacterial diseases caused by Edwardsiella ictaluri and motile Aeromonas species, which lead to high mortality and economic losses. The widespread use of antibiotics to manage disease outbreaks in Vietnam raises the risk of antimicrobial resistance (AMR) emerging within the striped catfish sector. Despite this risk, little is known about the current levels and patterns of AMR in these pathogens circulating catfish farms, underscoring the need for targeted surveillance.
In this study, we aimed to investigate the phenotypic and genotypic resistance profiles of these pathogens within the striped catfish sector.We performed antimicrobial susceptibility testing (n = 15 antibiotics) and PCR screening (n = 21 genes) on 84 bacterial isolates (n = 18 A. dhakensis, n = 24 A. hydrophila, n = 42 E. ictaluri), representing natural disease outbreaks in the Mekong Delta region between 2017 and 2021.
Findings from this study revealed an overall trend of increased antimicrobial resistance levels, with average multiple antibiotic resistance values increasing from 0.33 to 0.75 between 2017 and 2021, respectively. More than 50% of isolates were resistant against antibiotic compounds used within the Vietnamese aquaculture sector. Further, multidrug resistance was evident in more than 70% of E. ictaluri, with isolates resistant to more than five antibiotic classes. All 21 genes screened were detected in at least one genome investigated, with isolates carrying an average of seven genes in their genome. However, species-specific resistance genotypes were detected, primarily in genes encoding resistance to aminoglycosides, beta-lactams and potentiated sulfonamides.
Understanding the prevalence and mechanisms of AMR in these pathogens is essential for developing effective, sustainable disease control strategies in Vietnamese catfish farming. Continued surveillance and promoting responsible antibiotic use will be critical to safeguarding food security and rural livelihoods in Vietnam.
