Horizontal gene transfer (HGT) plays an important role in the dissemination of antibiotic resistance genes. In sewer systems, human-associated and environmental bacteria are mixed together and exposed to many substances known to increase HGT, including various antibacterial compounds. In wastewaters, those substances are most often detected below concentrations known to induce HGT individually. Still, it is possible that such wastewaters induce HGT, for example via mixture effects. Here, a panel of antibiotics, biocides and other pharmaceuticals was measured in filter-sterilized municipal and hospital wastewater samples from Gothenburg, Sweden. The effects on HGT of the chemical mixtures in these samples were investigated by exposing a complex bacterial donor community together with a GFP-tagged E. coli recipient strain. Recipients that captured sulfonamide resistance-conferring mobile genetic elements (MGEs) from the bacterial community were enumerated and characterized by replicon typing, antibiotic susceptibility testing and long read sequencing. While exposure to municipal wastewater did not result in any detectable change in HGT rates, exposure to hospital wastewater was associated with an increase in the proportion of recipients that acquired sulfonamide resistance but also a drastic decrease in the total number of recipients. Although, concentrations were generally higher in hospital than municipal wastewater, none of the measured substances could individually explain the observed effects of hospital wastewater. The great majority of the MGEs captured were IncN plasmids, and resistance to several antibiotics was co-transferred in most cases. Taken together, the data show no evidence that chemicals present in the studied municipal wastewater induce HGT. Still, the increased relative abundance of transconjugants after exposure to hospital wastewater could have implications for the risks of both emergence and transmission of resistant bacteria.

水平基因转移（HGT）在抗生素抗性基因的传播中起重要作用。在下水道系统中，人类相关细菌与环境细菌混合在一起，并暴露于许多已知会增加HGT的物质中，包括各种抗菌化合物。在废水中，最常检测到的这些物质的浓度低于已知可单独诱导HGT的浓度。尽管如此，这种废水还是有可能例如通过混合效应而诱发HGT。在这里，从瑞典哥德堡对经过过滤灭菌的市政和医院废水样品中的一组抗生素，杀菌剂和其他药物进行了测量。通过暴露复杂的细菌供体群落和带有GFP标签的大肠杆菌，研究了这些样品中化学混合物对HGT的影响。受体菌株。列举了从细菌群落中捕获具有磺酰胺耐药性的移动遗传元件（MGE）的收件人，并通过复制子分型，抗生素敏感性测试和长时间阅读测序对其进行了表征。尽管暴露于城市废水不会导致HGT率发生任何可检测的变化，但暴露于医院废水却与获得磺胺耐药性的接受者比例增加有关，但接受者总数却急剧减少。尽管医院中的浓度通常高于市政废水，但没有一种被测物质可以单独解释医院废水的观察效果。捕获的大部分MGE是IncN质粒，在大多数情况下，对几种抗生素的耐药性是共转移的。两者合计，数据显示没有证据表明所研究的城市废水中存在的化学物质会诱发HGT。尽管如此，在暴露于医院废水后，转导结合剂的相对丰度增加可能会对耐药菌的出现和传播风险产生影响。