Kasper D L, Onderdonk A B, Polk B F, Bartlett J G
Rev Infect Dis. 1979 Mar-Apr;1(2):278-90. doi: 10.1093/clinids/1.2.278.
Organisms of the genus Bacteroides represent the major group of obligate anaerobes involved in human infections. Bacteroides usually cause either bacteremia or localized abscesses. Of the numerous species of Bacteroides, Bacteroides fragilis is the single most frequent clinical isolate. B. fragilis and Bacteroides melaninogenicus have chemically incomplete lipopolysaccharides as compared with the lipopolysaccharides (endotoxins) of aerobic bacteria, and the lipopolysaccharides of Bacteroides lack the biologic potency characteristic of endotoxin. This inactivity may account for the very infrequent occurrence of disseminated intravascular coagulation or purpura that can accompany sepsis due to these organisms. Furthermore, strains of B. fragilis have an immunologically common capsular polysaccharide. In an animal model of intraabdominal sepsis, the encapsulated strains caused abscesses when given without other organisms, but abscess formation from unencapsulated strains of Bacteroides generally required the administration of a synergistic aerobe. The abscesses caused by encapsulated strains were shown to be directly attributable to the capsular polysaccharide, which is an important virulence factor of this organism. Patients or experimental animals infected with B. fragilis develop antibodies to the capsular polysaccharide, and these antibodies can be detected in a radioactive antigen-binding assay.
拟杆菌属的微生物是参与人类感染的主要专性厌氧菌。拟杆菌通常引起菌血症或局部脓肿。在众多拟杆菌物种中，脆弱拟杆菌是最常从临床分离出的单一菌种。与需氧菌的脂多糖（内毒素）相比，脆弱拟杆菌和产黑色素拟杆菌的脂多糖在化学组成上不完整，且拟杆菌的脂多糖缺乏内毒素的生物学活性特征。这种无活性可能解释了由这些微生物引起的败血症很少伴有弥散性血管内凝血或紫癜的原因。此外，脆弱拟杆菌菌株具有免疫上常见的荚膜多糖。在腹腔内脓毒症的动物模型中，有荚膜的菌株在不与其他微生物一起给予时会引起脓肿，但无荚膜的拟杆菌菌株形成脓肿通常需要给予协同需氧菌。有荚膜菌株引起的脓肿被证明直接归因于荚膜多糖，这是该微生物的一种重要毒力因子。感染脆弱拟杆菌的患者或实验动物会产生针对荚膜多糖的抗体，并且这些抗体可以在放射性抗原结合试验中检测到。
