Urban wastewater treatment plants (UWTPs) are reservoirs of antibiotic resistance. Wastewater treatment changes the bacterial community and inevitably impacts the fate of antibiotic resistant bacteria and antibiotic resistance genes (ARGs). Some bacterial groups are major carriers of ARGs and hence, their elimination during wastewater treatment may contribute to increasing resistance removal efficiency. This study, conducted at a full-scale UWTP, evaluated variations in the bacterial community and ARGs loads and explored possible associations among them. With that aim, the bacterial community composition (16S rRNA gene Illumina sequencing) and ARGs abundance (real-time PCR) were characterized in samples of raw wastewater (RWW), secondary effluent (sTWW), after UV disinfection (tTWW), and after a period of 3 days storage to monitoring possible bacterial regrowth (tTWW-RE). Culturable enterobacteria were also enumerated.

Secondary treatment was associated with the most dramatic bacterial community variations and coincided with reductions of ~2 log-units in the ARGs abundance. In contrast, no significant changes in the bacterial community composition and ARGs abundance were observed after UV disinfection of sTWW. Nevertheless, after UV treatment, viability losses were indicated ~2 log-units reductions of culturable enterobacteria. The analysed ARGs (qnrS, bla_CTX-M, bla_OXA-A, bla_TEM, bla_SHV, sul1, sul2, and intI1) were strongly correlated with taxa more abundant in RWW than in the other types of water, and which associated with humans and animals, such as members of the families Campylobacteraceae, Comamonadaceae, Aeromonadaceae, Moraxellaceae, and Bacteroidaceae.

Further knowledge of the dynamics of the bacterial community during wastewater treatment and its relationship with ARGs variations may contribute with information useful for wastewater treatment optimization, aiming at a more effective resistance control.

城市污水处理厂（UWTP）是抗生素耐药性的储存库。废水处理改变了细菌群落，不可避免地影响了抗生素抗性细菌和抗生素抗性基因（ARG）的命运。一些细菌是ARGs的主要载体，因此，在废水处理过程中将其消除可能有助于提高抗药性。这项研究在全面的UWTP上进行，评估了细菌群落和ARGs负载的变化，并探讨了它们之间的可能联系。为了这个目标，细菌群落组成（16S rRNA基因Illumina测序）和ARGs丰度（实时PCR）在原废水（RWW），次要废水（sTWW），UV消毒（tTWW），以及经过3天的储存监测之后进行了表征可能的细菌再生（tTWW-RE）。还列举了可培养的肠细菌。

二级处理与细菌群落变化最为显着有关，并且与ARGs丰度的〜2 log-units降低相吻合。相反，在sTWW进行紫外线消毒后，未观察到细菌群落组成和ARGs丰度的显着变化。然而，经过紫外线处理后，活力损失显示可培养肠杆菌减少了约2个对数单位。分析的ARGs （qnrS，bla _CTX-M，bla _OXA-A，bla _TEM，bla _SHV，sul1，sul2和intI1）与RWW中比其他类型的水中含量更高的分类单元密切相关，并且与人和动物相关，例如弯曲杆菌科，Comamonadaceae，Aeromonadaceae，Moraxellaceae和Bacteroidaceaceae。

进一步了解废水处理过程中细菌群落的动态及其与ARGs变化的关系，可能有助于优化废水处理，从而更有效地控制阻力。