An experiment was carried out using microcosms to evaluate the impact of the fluoroquinolone antibiotic on nematode trophic groups structure and bacterial abundance. Sediment samples were experimentally enriched with four increasing doses of ciprofloxacin [D1 (50 ppm), D2 (100 ppm), D3 (200 ppm) and D4 (500 ppm)] and compared to non-enriched sediments (used as control). Ciprofloxacin changed the trophic composition of nematodes taxa where the relative abundance of microvores (M), epigrowth feeders (EF) and ciliate consumers (CF), raised in a control microcosm, was highly affected and significantly decreased in response to the increasing doses. Nevertheless, the abundance of deposit feeders (DF), optional predators (FP) and exclusive predators (Pr) showed a significant increase. Results from the multivariate analysis showed a clear impact of this antibiotic on nematode trophic assemblages. Microcosms treated with the three highest doses [D2, D3 and D4] were different from the control. The exceptions were those treated with the lowest dose, D1, and which were grouped with the control. The SIMPER analysis results showed that the average dissimilarity continuously increased in the treated microcosms compared to the control. Furthermore, our results have shown that ciprofloxacin also leads to a significant decrease in bacterial density with the highest dose, which could explain the results obtained for nematode trophic groups distribution. Thus, the bacteriophages nematodes only use bacteria as a nutrition source and the lack or presence in small quantity of this food could induce a decrease in their abundance as well as changing of nematodes groups repartition.

Our work demonstrates that the nematode responses were dependent on sediment enrichment with ciprofloxacin and opens new perspectives on the potential impact of antibiotics on functional nematode diversity.

使用缩影进行了一项实验，以评估氟喹诺酮类抗生素对线虫营养基团结构和细菌丰度的影响。沉积物样品在实验中富含四种递增剂量的环丙沙星[D1（50 ppm），D2（100 ppm），D3（200 ppm）和D4（500 ppm）]，并与未富集的沉积物（用作对照）进行了比较。环丙沙星改变了线虫类群的营养组成，其中在对照微观世界中饲养的微食虫（M），外生食虫（EF）和纤毛虫（CF）的相对丰度受到严重影响，并随着剂量的增加而显着降低。尽管如此，沉积物饲养者（DF），可选捕食者（FP）和排他捕食者（Pr）的数量仍显着增加。多元分析的结果表明，这种抗生素对线虫的营养组合有明显的影响。用三个最高剂量[D2，D3和D4]处理的缩影与对照不同。例外的是用最低剂量D1治疗的那些，并与对照分组。SIMPER分析结果表明，与对照相比，处理过的微观世界中的平均相异性持续增加。此外，我们的结果表明，环丙沙星在最高剂量下也会导致细菌密度显着降低，这可以解释线虫营养族分布的结果。从而，

我们的工作表明，线虫的反应取决于环丙沙星对沉积物的富集，并为抗生素对功能性线虫多样性的潜在影响开辟了新的视角。