Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.
FEMS Microbiol Rev. 2014 Jul;38(4):660-97. doi: 10.1111/1574-6976.12056. Epub 2014 Jan 27.
The increasing prevalence of antibiotic-resistant bacteria portends an impending postantibiotic age, characterized by diminishing efficacy of common antibiotics and routine application of multifaceted, complementary therapeutic approaches to treat bacterial infections, particularly multidrug-resistant organisms. The first line of defense for most bacterial pathogens consists of a physical and immunologic barrier known as the capsule, commonly composed of a viscous layer of carbohydrates that are covalently bound to the cell wall in Gram-positive bacteria or often to lipids of the outer membrane in many Gram-negative bacteria. Bacterial capsular polysaccharides are a diverse class of high molecular weight polysaccharides contributing to virulence of many human pathogens in the gut, respiratory tree, urinary tract, and other host tissues, by hiding cell surface components that might otherwise elicit host immune response. This review highlights capsular polysaccharides that are structurally identical or similar to polysaccharides found in mammalian tissues, including polysialic acid and glycosaminoglycan capsules hyaluronan, heparosan, and chondroitin. Such nonimmunogenic coatings render pathogens insensitive to certain immune responses, effectively increasing residence time in host tissues and enabling pathologically relevant population densities to be reached. Biosynthetic pathways and capsular involvement in immune system evasion are described, providing a basis for potential therapies aimed at supplementing or replacing antibiotic treatment.
抗生素耐药菌的日益流行预示着即将进入后抗生素时代，其特征是常见抗生素的疗效降低，以及常规应用多方面、互补的治疗方法来治疗细菌感染，特别是多药耐药菌。大多数细菌病原体的第一道防线是一种称为荚膜的物理和免疫屏障，通常由粘多糖层组成，这些多糖通过共价键与革兰氏阳性菌的细胞壁结合，或与许多革兰氏阴性菌的外膜脂质结合。细菌荚膜多糖是一类多样化的高分子多糖，通过掩盖可能引发宿主免疫反应的细胞表面成分，有助于肠道、呼吸道、泌尿道和其他宿主组织中的许多人类病原体的毒力。本文重点介绍了与哺乳动物组织中发现的多糖结构相同或相似的荚膜多糖，包括多糖唾液酸和糖胺聚糖荚膜透明质酸、肝素和软骨素。这种非免疫原性涂层使病原体对某些免疫反应不敏感，有效地增加了在宿主组织中的停留时间，并使达到与病理相关的种群密度成为可能。描述了生物合成途径和荚膜在免疫系统逃避中的作用，为旨在补充或替代抗生素治疗的潜在治疗方法提供了基础。
