The current study aimed to investigate the antibacterial activity of different anisotropic structures of silver nanoparticles in the hexagon and spherical shapes against MDR-bacteria isolated from water sources in Egypt. The water samples collected from four different dairy farm-related sites were tested bacteriologically, followed by identification of the antibiotic-resistant profile for the isolates. The result revealed that Enterococcus spp, Proteus spp, and E. coli spp are the most common organisms in all tested water samples, and the antibiotic-resistant profile identified 11/13 waterborne isolates as MDR-bacteria. Herein, spherical and hexagonal silver nanoparticles were prepared with an average size of 26 ± 6 nm and 375 ± 80 nm, respectively, through the chemical reduction method. Further, MDR gram-positive (Enterococcus) and MDR gram-negative (E. coli) were selected for studying the antibacterial property of the synthesized AgNPs using agar well diffusion method. In another experiment, microdilution broth assay coupled with XTT assay is optimized for facilitating the testing of a broad range of AgNPs concentrations efficiently without the need for laborious preparation of the colony counting method. Our results indicated that AgNPs in spherical and hexagonal shapes are potent antibacterial against the MDR-waterborne bacteria in a dose and shape-dependent manner. The hexagonal AgNPs (h-AgNPs) express higher bactericidal activity when compared to spherical AgNPs (AgNSs) against the two tested MDR-bacteria, but the E. coli isolate more sensitive to both tested shapes of AgNPs than the Enterococus isolate. The results recommend that AgNPs can be used as efficient growth inhibitors for water-borne bacterial pathogens, making them applicable to various water filters and antimicrobial applications.

Graphical Abstract

当前的研究旨在研究六边形和球形银纳米颗粒的不同各向异性结构对从埃及水源分离的MDR-细菌的抗菌活性。从四个不同的奶牛场相关地点收集的水样经过细菌学测试，然后鉴定出分离物的抗生素耐药性。结果表明，肠球菌属，变形杆菌，和ē。大肠杆菌是所有测试水样中最常见的生物，其耐药性特征将11/13水性分离株鉴定为MDR细菌。在本文中，通过化学还原法制备了球形和六角形的银纳米颗粒，其平均尺寸分​​别为26±6nm和375±80nm。此外，MDR革兰氏阳性（肠球菌）和MDR革兰氏阴性（É。大肠杆菌选择）以通过琼脂井扩散法研究合成的AgNPs的抗菌性能。在另一个实验中，微稀释肉汤测定法与XTT测定法相结合，可优化有效地测试各种AgNPs浓度，而无需费力地准备菌落计数方法。我们的结果表明，球形和六边形形状的AgNP以剂量和形状依赖的方式有效抵抗MDR水性细菌。相比球形的AgNPs（AGNSS）对两种试验MDR-细菌，但是当所述六边形的AgNPs（H-的AgNPs）表达更高的杀菌活性ë。大肠埃希菌比两种肠球菌对两种测试形状的AgNPs更敏感隔离。结果表明，AgNPs可以用作水性细菌病原体的有效生长抑制剂，使其适用于各种滤水器和抗菌应用。

图形概要