Fate and transport modelling for evaluating antibiotic resistance in aquatic environments: Current knowledge and research priorities.

Antibiotics have revolutionised medicine in the last century and enabled the prevention of bacterial infections that were previously deemed untreatable. However, in parallel, bacteria have increasingly developed resistance to antibiotics through various mechanisms. When resistant bacteria find their way into terrestrial and aquatic environments, animal and human exposures increase, e.g., via polluted soil, food, and water, and health risks multiply. Understanding the fate and transport of antibiotic resistant bacteria (ARB) and the transfer mechanisms of antibiotic resistance genes (ARGs) in aquatic environments is critical for evaluating and mitigating the risks of resistant-induced infections. The conceptual understanding of sources and pathways of antibiotics, ARB, and ARGs from society to the water environments is essential for setting the scene and developing an appropriate framework for modelling. Various factors and processes associated with hydrology, ecology, and climate change can significantly affect the fate and transport of ARB and ARGs in natural environments. This article reviews current knowledge, research gaps, and priorities for developing water quality models to assess the fate and transport of ARB and ARGs. The paper also provides inputs on future research needs, especially the need for new predictive models to guide risk assessment on AR transmission and spread in aquatic environments.

Antibiotics usage practices in aquaculture in Bangladesh and their associated factors.

Background: Irrational and inappropriate use of antibiotics in aquaculture can contribute to the development of antibiotic resistance. Objectives: In this study, we aimed to assess antibiotic usage in inland and coastal fish farms in Bangladesh and identify factors associated with this practice. Methods: We conducted a cross-sectional study to collect antibiotic usage information from 672 fish farmers in Bangladesh. The frequency of use, the types of antibiotics, the purpose of usage, and antibiotic prescribing practices were estimated. Adjusted odds ratios (aOR) were calculated to measure the association between antibiotic usage and factors related to the characteristics of the farms and farmers using multivariable logistic regression models. Results: Twenty-two farms reported using antibiotics in the last 24 h preceding the interview (3%, 95% CI: 2-5%); 36 farms (5%, 95% CI: 4-7%) in the last 72 h, 141 farms (21%, 95% CI: 18-24%) in the last 14 days, and 478 farms (71%, 68-75%) reported antibiotic usage at least once since the start of their production cycle. Antibiotics usage in the last 14 days preceding the interviews was higher in freshwater fish farms (98%) than in brackish water farms (2%). Oxytetracycline, ciprofloxacin, and amoxicillin were the most frequently used antibiotics. Most of the antibiotics were reported to be used for both therapeutic and prophylactic purposes (71%, 95% CI: 63-78%). Antibiotics used within the last 14 days were mainly advised by feed dealers or drug sellers (51%, 95% CI: 43-60%), followed by farmers themselves (31%, 95% CI: 23-38%) and local service providers (18%, 95% CI, 12-25%). Fish farms having history of antibiotic use within the last 14 days preceding interviews was significantly associated with illness in fish (aOR 1.98, 95% CI:1.21-3.29) compared to farms with healthy fish and fishes cultured in ponds (aOR 9.34, 95% CI: 3.69-23.62) compared to enclosure cultures. Conclusions: Improvement of fish health through better farming practices and changes in feed dealers' and farmers' attitudes towards self-prescription of antibiotic without veterinarian diagnostics may help to reduce the levels of antibiotic usage and thus contribute to mitigating antimicrobial resistance.