Exposure of Enchytraeus crypticus to ciprofloxacin - A multi- and transgenerational study

The increased consumption of antibiotics and their partial metabolism by the human and animal body have led to the frequent identification of such compounds in various environmental matrices. Ciprofloxacin (CIP) is one of the most widely used antibiotics worldwide and it has low mobility and high sorption to soil, leading to the potential to accumulate and persist on organic fertilizers (manure and sewage sludge) and agricultural soils. Therefore, the presence of CIP in the agricultural environment has become an emerging concern as it may negatively affect soil organisms and soil quality, and contribute to the spread of antibiotic-resistant bacteria, thus threatening food security and public health. In this study, we aimed to evaluate the multigenerational and transgenerational effects of CIP on the reproduction of Enchytraeus crypticus to properly assess the long-term impacts of such exposure. Our results for the multigenerational test showed that the reproduction of the organisms was affected from the third to the last (sixth) generation, highlighting the importance of long-term evaluation. There was also evidence of tolerance to reproduction of E. crypticus, as there was no statistical difference between concentrations for all generations, including for among the last three generations themselves. For the transgenerational tests, almost all results showed no statistical difference from the controls, indicating that the effects of CIP may be reversible when the organisms are transferred to clean media. However, since the last generations in the transgenerational tests showed significant differences from the first of the multigenerational tests, the adverse effects may still persist to some extent in the subsequent generations. Thus, when evaluating the effects of CIP on soil media, its persistence and behavior in this matrix must be considered. We strongly recommend that further long-term exposure studies be conducted and considered in regulatory decision-making, especially for persistent compounds.