The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei‑MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan, 430079, People's Republic of China.
World J Microbiol Biotechnol. 2020 Mar 14;36(4):54. doi: 10.1007/s11274-020-02830-5.
Enterococcus faecalis (E. faecalis) is a Gram-positive bacterium closely related to many refractory infections of human and shows the resistant ability against the antibacterial effects of silver. Simvastatin is a semisynthetic compound derived from lovastatin and a hydroxymethyl glutaryl coenzyme A(HMG-COA) reductase inhibitor showing certain inhibitive effects on bacteria. The main purpose of this study was to establish and characterize the Ag/silver nanoparticles (AgNPs)-resistant E. faecalis, and further evaluate the function of extracellular polymeric substances (EPS) in the silver resistance and the effect of simvastatin on the silver-resistance of E. faecalis. The results showed that the established silver-resistant E. faecalis had strong resistance against both Ag and AgNPs and simvastatin could decrease the silver-resistance of both original and Ag/AgNPs-resistant E. faecalis. The Transmission electron microscopy (TEM), High-angle annular dark-field (HAADF) and mapping images showed that the silver ions or particles aggregated and confined in the EPS on surface areas of the cell membrane when the silver-resistant E. faecalis were incubated with Ag or AgNPs. When the simvastatin was added, the silver element was not confined in the EPS and entered the bacteria. These findings may indicate that the silver resistance of E. faecalis was derived from the entrapping function of EPS, but simvastatin could compromise the function of EPS to decrease the silver resistant ability of E. faecalis.
粪肠球菌（E. faecalis）是一种革兰氏阳性细菌，与许多人类难治性感染密切相关，表现出对银的抗菌作用的耐药能力。辛伐他汀是一种半合成化合物，来源于洛伐他汀，是羟甲基戊二酰辅酶 A（HMG-COA）还原酶抑制剂，对细菌具有一定的抑制作用。本研究的主要目的是建立和表征对银/银纳米颗粒（AgNPs）具有耐药性的粪肠球菌，并进一步评估细胞外聚合物质（EPS）在银耐药性中的作用以及辛伐他汀对粪肠球菌银耐药性的影响。结果表明，所建立的耐银粪肠球菌对银和 AgNPs 均具有很强的耐药性，辛伐他汀可以降低原始和耐 Ag/AgNPs 的粪肠球菌的耐药性。透射电子显微镜（TEM）、高角度环形暗场（HAADF）和映射图像显示，当耐银粪肠球菌与 Ag 或 AgNPs 孵育时，银离子或颗粒聚集并局限在细胞膜表面的 EPS 中。当加入辛伐他汀时，银元素没有被局限在 EPS 中，而是进入了细菌。这些发现可能表明，粪肠球菌的银耐药性源于 EPS 的捕获功能，但辛伐他汀可以破坏 EPS 的功能，降低粪肠球菌的银耐药能力。
