Table_1_Effect of chemical modifications of tannins on their antimicrobial and antibiofilm effect against Gram-negative and Gram-positive bacteria.DOCX

BackgroundTannins have demonstrated antibacterial and antibiofilm activity, but there are still unknown aspects on how the chemical properties of tannins affect their biological properties. We are interested in understanding how to modulate the antibiofilm activity of tannins and in delineating the relationship between chemical determinants and antibiofilm activity.
Materials and methodsThe effect of five different naturally acquired tannins and their chemical derivatives on biofilm formation and planktonic growth of Salmonella Typhimurium, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus was determined in the Calgary biofilm device.
ResultsMost of the unmodified tannins exhibited specific antibiofilm activity against the assayed bacteria. The chemical modifications were found to alter the antibiofilm activity level and spectrum of the tannins. A positive charge introduced by derivatization with higher amounts of ammonium groups shifted the anti-biofilm spectrum toward Gram-negative bacteria, and derivatization with lower amounts of ammonium groups and acidifying derivatization shifted the spectrum toward Gram-positive bacteria. Furthermore, the quantity of phenolic OH-groups per molecule was found to have a weak impact on the anti-biofilm activity of the tannins.
ConclusionWe were able to modulate the antibiofilm activity of several tannins by specific chemical modifications, providing a first approach for fine tuning of their activity and antibacterial spectrum.

背景 单宁已被证实兼具抗菌与抗生物膜活性，但单宁的化学性质如何影响其生物学活性，仍存在诸多未明确的研究空白。本研究旨在探索调控单宁抗生物膜活性的可行路径，并厘清其化学决定因素与抗生物膜活性之间的内在关联。
材料与方法 本研究采用卡尔加里生物膜装置（Calgary biofilm device），测定了5种天然来源单宁及其化学衍生物对鼠伤寒沙门氏菌（Salmonella Typhimurium）、铜绿假单胞菌（Pseudomonas aeruginosa）、大肠埃希氏菌（Escherichia coli）及金黄色葡萄球菌（Staphylococcus aureus）的生物膜形成与浮游菌生长的影响。
结果 多数未修饰单宁对受试菌株展现出特异性抗生物膜活性。实验结果表明，化学修饰可改变单宁的抗生物膜活性水平与活性谱。通过引入大量铵基进行衍生化所引入的正电荷，可将抗生物膜活性谱转向革兰氏阴性菌；而引入少量铵基的衍生化及酸化衍生化，则将活性谱转向革兰氏阳性菌。此外，每分子单宁所含的酚羟基（phenolic OH-groups）数量，对其抗生物膜活性仅存在微弱影响。
结论 本研究通过特定化学修饰实现了多种单宁抗生物膜活性的精细化调控，为精准调节其抗菌活性与抗菌谱提供了初步研究思路。