Spatial Patterns and Associated Factors of Intestinal Antibiotic Resistance Genes in Farmed Bullfrogs From Selected...

The proliferation of antibiotic resistance genes (ARGs) in aquaculture ecosystems poses substantial ecological and public health risks. This study conducted a cross-provincial investigation of intestinal ARG profiles in American bullfrogs (Aquarana catesbeiana) from selected farms across 10 major production regions in China. The results showed widespread pollution in the sampled bullfrog aquaculture waters, characterized by high nitrogen and phosphorus levels (total nitrogen: 4.1-7.6 mg/L; total phosphorus: 0.63-5.82 mg/L) and contamination by heavy metals such as copper and zinc. A total of 106 ARG subtypes were detected, dominated by tetracycline (1.71%) and sulfonamide (0.44%) resistance genes. Among the sampled farms, the Sichuan site exhibited the highest overall ARG abundance (10.77%). Eight high-risk ARGs, such as ermB, floR, and qnrA, were identified and were significantly associated with heavy metals, opportunistic pathogens such as Escherichia and Bacteroides, and mobile genetic elements (MGEs). The intestinal microbiota was dominated by Proteobacteria (35.27%) and Firmicutes (27.32%), while reduced microbial diversity was observed in samples from certain sites with relatively high ARG abundance, particularly the sampled farm in Sichuan. ARG community assembly was primarily consistent with stochastic processes, whereas variation in ARG profiles was significantly associated with MGEs, geographic location, heavy metals, environmental factors, and opportunistic pathogens. These results suggest a potential interplay between stochastic ecological dynamics and environmental selection in shaping ARG patterns. Overall, these findings indicate that anthropogenic pollutants and microbial dynamics may jointly contribute to ARG dissemination in bullfrog aquaculture, underscoring the urgency of implementing targeted strategies to mitigate antibiotic resistance risks.