Environment Research Laboratory, Faculty of Science, Nepal Academy of Science and Technology, Lalitpur, Nepal.
Department of Microbiology, St. Xavier's College, Kathmandu, Nepal.
Water Environ Res. 2024 Aug;96(8):e11096. doi: 10.1002/wer.11096.
Biofilm development in gram negative bacterial contaminants in water supply systems is linked to persistence as well as antibiotic resistance, which threatens water quality and hence the public health. This study aimed to investigate phenotypic and genetic capacity of biofilm formation by Escherichia coli isolated from supply water with their antibiotic susceptibility pattern. Altogether fifty water samples collected from a city supply water distribution scheme in Kathmandu were analyzed to assess the physicochemical and microbiological quality. Comparing Nepal's national drinking water quality standards 2022, conductivity (4%), turbidity (18%), iron (28%), and residual chlorine (8%) were found exceeding the values above the standards. Among total, 40% of water samples were contaminated with total coliform bacteria. E. coli and Citrobacter species were dominant and isolated from 20 (64.52%) and 11 (35.48%) water samples, respectively. Antibiotic susceptibility testing revealed that E. coli isolates were resistant to ampicillin (20%), nitrofurantoin (10%), and cefotaxime (10%). Citrobacter spp. (54.54%) were found multidrug resistant (MDR) while none of the isolates of E. coli were MDR. Of total, 45% of the isolates developed biofilm while testing with the Microtiter plate method. Biofilm-forming genes bcsA and csgD in E. coli isolates were detected with polymerase chain reaction (PCR) employing specific primers. bcsA and csgD genes were detected in 55% and 45% of the isolates, respectively. This study confirms the occurrences of biofilm forming and antibiotic resistant bacteria like E. coli in the drinking water supply system in Kathmandu alarming its environmental circulation and possible public health threat. Although further study is warranted, this study suggests public health and drinking water treatment interventions to mitigate the biofilm forming antibiotic resistant potential pathogens from supply water in Kathmandu, Nepal. PRACTITIONER POINTS: Forty percent of tested drinking water samples in Kathmandu were contaminated with total coliform bacteria. E. coli and half of Citrobacter spp. isolates were resistant to multiple antibiotics. bcsA and csgD genes were detected in biofilm producing E.coli isolates.
供水系统中革兰氏阴性细菌污染物的生物膜发展与持久性和抗生素耐药性有关，这威胁着水质，进而威胁公共健康。本研究旨在调查从供水系统中分离的大肠杆菌的表型和遗传形成生物膜的能力及其抗生素药敏模式。总共分析了来自加德满都市供水分配系统的 50 个水样，以评估理化和微生物质量。与尼泊尔 2022 年国家饮用水质量标准相比，电导率（4%）、浊度（18%）、铁（28%）和余氯（8%）超过了标准值。总共，40%的水样受到总大肠菌群的污染。大肠杆菌和柠檬酸杆菌是优势菌，分别从 20 个（64.52%）和 11 个（35.48%）水样中分离出来。抗生素药敏试验显示，大肠杆菌分离株对氨苄西林（20%）、呋喃妥因（10%）和头孢噻肟（10%）耐药。柠檬酸杆菌属（54.54%）被发现为多药耐药（MDR），而没有分离出的大肠杆菌分离株为 MDR。在总共的试验中，有 45%的分离株在微量滴定板法试验中形成生物膜。采用聚合酶链反应（PCR）和特定引物检测大肠杆菌分离株的生物膜形成基因 bcsA 和 csgD。bcsA 和 csgD 基因分别在 55%和 45%的分离株中被检测到。本研究证实了生物膜形成和抗生素耐药菌如大肠杆菌在加德满都饮用水供应系统中的存在，这令人警惕其环境循环和可能的公共卫生威胁。尽管需要进一步的研究，但本研究建议采取公共卫生和饮用水处理干预措施，以减轻尼泊尔加德满都供水系统中生物膜形成和抗生素耐药潜在病原体的威胁。
