Bhikhoo Raeesa, Bezuidenhout Krisdan, Molale-Tom Lesego, Mienie Charlotte, Bezuidenhout Carlos
Unit for Environmental Sciences and Management: Microbiology, North-West Univrersity, Potchefstroom, South Africa.
South African Research Chair: Cities, Law and Environmental Sustainability (CLES), North-West University, Potchefstroom, South Africa.
PLoS One. 2025 Aug 19;20(8):e0329599. doi: 10.1371/journal.pone.0329599. eCollection 2025.
Microplastics are widespread in marine environments, with significant contributions from land-based wastewater treatment plants (WWTPs). A desktop study was conducted on regulatory framework for marine outfalls in South African coastal cities. The South African regional policy permits proper disposal of wastewater in a marine outfall provided raw wastewater is treated and will not have an adverse effect on the receiving body. The experimental study investigated the capacity of microplastics to serve as reservoirs for multidrug-resistant (MDR) bacteria originating from WWTP effluent. Experiments challenging the regulations were based on microbiology of the effluent that is discharged through an outfall. Microcosms were set up by spiking seawater with WWTP effluent and adding the collected plastic pieces. Scanning electron microscopy (SEM) was used to determine colonization on the microplastics. After 30 days of microcosm exposure, selective media and incubation conditions were used to isolate Enterobacteriaceae. Pure isolates were tested against 16 antibiotics normally used in human clinical settings. In the initial biofilms directly from microplastics from the WWTPs, several genera generally associated with wastewater treatment were isolated. Dominant species isolated and identified were Citrobacter sp., Escherichia sp., Enterobacter sp., Serratia sp., Klebsiella sp. and Pseudomonas sp.. Several isolates were resistant to the last resort of antibiotics, (doripenem and imipenem; 9% to 27%) and some of these isolates were resistant to up to ten of the antibiotics. These findings highlight that clinically relevant Enterobacteriaceae colonize microplastics and survive in biofilms on these microplastics surfaces. Bacterial infections caused by Carbapenem-resistant Enterobacteriaceae have become a global concern in the fight against bacterial infections. Our findings highlight the need for more data to challenge existing marine outfall policies and the outdated notion stating that dilution alone can solve pollution problems.
微塑料在海洋环境中广泛存在，其中很大一部分来自陆基污水处理厂（WWTPs）。针对南非沿海城市海洋排污口的监管框架进行了一项桌面研究。南非的区域政策允许在经过处理且原污水不会对受纳水体产生不利影响的情况下，将污水妥善排放至海洋排污口。该实验研究调查了微塑料作为源自污水处理厂废水的多重耐药（MDR）细菌储存库的能力。基于通过排污口排放的废水微生物学进行了挑战相关规定的实验。通过向海水中添加污水处理厂废水并加入收集的塑料碎片来建立微观世界。使用扫描电子显微镜（SEM）来确定微塑料上的定殖情况。在微观世界暴露30天后，使用选择性培养基和培养条件分离肠杆菌科细菌。对纯分离株进行了针对通常用于人类临床环境的16种抗生素的测试。在直接来自污水处理厂微塑料的初始生物膜中，分离出了几个通常与废水处理相关的属。分离并鉴定出的优势菌种为柠檬酸杆菌属、大肠杆菌属、肠杆菌属、沙雷氏菌属、克雷伯氏菌属和假单胞菌属。一些分离株对最后手段的抗生素（多利培南和美罗培南；9%至27%）具有抗性，其中一些分离株对多达十种抗生素具有抗性。这些发现突出表明，具有临床相关性的肠杆菌科细菌定殖在微塑料上，并在这些微塑料表面的生物膜中存活。耐碳青霉烯类肠杆菌科细菌引起的细菌感染已成为抗击细菌感染中的一个全球关注点。我们的发现突出表明需要更多数据来挑战现有的海洋排污口政策以及那种认为仅靠稀释就能解决污染问题的过时观念。
