ABSTRACT

The present status of antimicrobial-resistant bacteria (AMRB) and antimicrobial-susceptible bacteria (AMSB) in hospital effluent, sewage treatment plant (STP) influent, STP secondary effluent, STP effluent (chlorination), STP effluent (ozonation), and river water were analyzed in an urban river in Japan by a 2-year monitoring survey. The results revealed the existence of multiple AMRB grouped into six classes whose numbers were in the hospital effluent at 19 to 2,800 CFU/mL, in the STP influent at 9 to 3,133 CFU/mL, in the STP secondary effluent at 1 to 148 CFU/mL, in the STP effluent (chlorination) at N.D. to 191 CFU/mL, and in the river water at N.D. to 28 CFU/mL In the case of the STP effluent (ozonation) the level of AMRB was, however, quite low ranging from N.D. to several CFU/mL, roughly 1/10 to 1/100 of the concentrations detected in the STP effluent (chlorination). The bacterial community structure analysis indicates that only ozonation changed the constitution of bacterial phyla. Rates of antimicrobial resistance were high among MDRA (82% in hospital effluent and 79% in STP influent), MDRP (35% and 40%), and MRSA (93% and 87%). MRSA showed resistance against chlorine treatment but could be gradually disinfected by ozonation.

When the hospital effluent and the model STP wastewater prepared by mixing STP influent and STP secondary effluent in a 1:9 ratio were directly treated with ozone, both AMRB and AMSB were inactivated effectively with variance in the time among bacteria, accompanied by a change in the constitution of phyla similar to the observation in the case of the STP effluent (ozonation). Ozonation inactivated almost all target bacteria (>99.9%) after 10 min treatment (CT value: 1.0 mg·min/L). Changing taxonomic diversity of micro-organisms based on 16S rRNA gene sequencing by ozonation showed that ozonation inactivated not only AMRB but also removed antimicrobial resistance genes (AMRGs) in the wastewater.

As a result of the present study, a recommendation was evoked to operate ozonation treatment directly for the hospital effluent immediately after flowing out, leading to desirable contribution to reduce environmental pollution, and the potential hazard to human health caused not only by the AMRB and AMSB but also infectious diseases. Extension of the present results opens a new way to assess environmental risks associated with the spread of AMRB and AMSB in aquatic environments to keep the water environment safe and to maintain human health. To our knowledge, this is the first report to show the inactivation profiles of AMRB and AMSB in real STP wastewater together with hospital effluent by direct ozonation.

摘要

医院出水、污水处理厂（STP）进水、STP二级出水、STP出水（氯化）、STP出水（臭氧化）、河水中抗菌素耐药菌（AMRB）和耐药菌（AMSB）的现状通过为期 2 年的监测调查在日本的一条城市河流中进行了分析。结果显示存在多个 AMRB 分为六类，其数量在医院污水中为 19 至 2,800 CFU/mL，在 STP 进水中为 9 至 3,133 CFU/mL，在 STP 二级出水中为 1 至 148 CFU/mL。 mL，在 ND 到 191 CFU/mL 的 STP 流出物（氯化）中，以及在 ND 到 28 CFU/mL 的河水中，在 STP 流出物（臭氧化）的情况下，AMRB 的水平是相当低的范围从 ND 到几个 CFU/mL，大约是 STP 流出物（氯化）中检测到的浓度的 1/10 到 1/100。细菌群落结构分析表明，只有臭氧作用改变了细菌门的构成。MDRA（医院污水中为 82%，STP 污水中为 79%）、MDRP（35% 和 40%）和 MRSA（93% 和 87%）的抗菌素耐药率很高。MRSA 显示出对氯处理的抵抗力，但可以通过臭氧逐渐消毒。

当医院出水和 STP 进水与 STP 二级出水按 1:9 比例混合制备的模型 STP 废水直接用臭氧处理时，AMRB 和 AMSB 均被有效灭活，但细菌间的时间存在差异，伴随着门的构成类似于在 STP 流出物（臭氧化）的情况下的观察结果。臭氧处理10分钟后几乎可以灭活所有目标细菌（>99.9%）（CT值：1.0 mg·min/L）。基于臭氧化 16S rRNA 基因测序改变微生物的分类多样性表明，臭氧化不仅可以灭活 AMRB，还可以去除废水中的抗菌素耐药基因 (AMRGs)。

作为本研究的结果，提出了对流出后立即对医院废水进行臭氧处理的建议，从而对减少环境污染做出了可取的贡献，并且不仅是 AMRB 和 AMSB 对人类健康造成的潜在危害还有传染病。扩展目前的结果开辟了一种新的方法来评估与 AMRB 和 AMSB 在水生环境中传播相关的环境风险，以保持水环境安全并维护人类健康。据我们所知，这是第一份通过直接臭氧化显示真实 STP 废水中 AMRB 和 AMSB 灭活情况以及医院污水的报告。