Occurrence of multidrug-resistant bacteria and clinically important β-lactamase resistance genes in giant freshwater prawn (Macrobrachium rosenbergii) aquaculture ponds in Thailand.

Abstract

Background and aim: The rapid expansion of giant freshwater prawn (Macrobrachium rosenbergii) aquaculture has raised concerns regarding the emergence and dissemination of antimicrobial resistance (AMR) in aquatic ecosystems. However, information regarding antibiotic-resistant bacteria and resistance genes in freshwater prawn earthen pond systems in Northeastern Thailand remains limited. This study aimed to isolate and characterize antibiotic-resistant bacteria from giant freshwater prawn aquaculture ponds in Kalasin Province, Thailand, and to determine the occurrence of clinically important β-lactamase resistance genes.

Materials and methods: Water samples were collected quarterly from nine earthen ponds located in three districts of Kalasin Province, Thailand, between July 2024 and June 2025. Bacterial isolates were recovered using ampicillin-supplemented selective media and identified through 16S rRNA gene sequencing. Antimicrobial susceptibility was evaluated using agar disk diffusion according to Clinical and Laboratory Standards Institute guidelines. Polymerase chain reaction assays were performed to detect β-lactamase genes, including blaTEM, blaSHV, blaOXA, blaKPC-2, blaNDM-1, and blaIMP.

Results: Twenty antibiotic-resistant isolates representing eight bacterial species belonging to five genera were identified. Aeromonas veronii was the predominant species, accounting for six isolates. Fourteen isolates (70.0%; 95% confidence interval: 45.7-88.1%) exhibited multidrug resistance to at least three antimicrobial classes. Resistance was particularly common against ampicillin, vancomycin, and rifampicin. Molecular analysis revealed the presence of clinically important β-lactamase genes, mainly blaSHV and blaKPC-2. Several isolates carried these genes, and A. veronii isolate MSS1 co-harbored blaSHV and blaKPC-2, indicating the possible clustering of resistance determinants. To the best of our knowledge, this study represents the first report of blaKPC-2-positive bacteria isolated from M. rosenbergii aquaculture ponds in Thailand.

Conclusion: The detection of multidrug-resistant bacteria and clinically relevant β-lactamase genes highlights the role of freshwater prawn aquaculture systems as environmental reservoirs of AMR. These findings provide baseline information for AMR surveillance in Thailand and emphasize the need for improved antimicrobial stewardship, enhanced biosecurity measures, and sustainable disease management strategies within a One Health framework. Further investigations employing metagenomics and whole-genome sequencing are warranted to elucidate resistance dissemination mechanisms.