Study on the pathogenesis of normal flora in respiratory tract infection and on the diagnostic methods for the flora

经胸针吸法从急性肺炎、肺脓肿和胸胸脓肿患者的口腔中分离出正常菌群——milleri链球菌群和厌氧菌群，可防止病原菌与正常菌群的污染。提示米勒梭菌群和厌氧菌是肺部感染的重要致病菌。对其在肺炎小鼠模型中的致病性机制的研究表明，米勒梭菌组和厌氧菌混合感染分别比单一感染时死亡率更高，肺内存活时间更长，病理组织学改变更严重。这表明米勒梭菌群与厌氧菌群之间可能存在协同作用。体外研究表明，从感染性病变中分离的米勒氏菌群菌株对人白细胞的吞噬和杀伤功能的抑制能力强于正常菌群。抑菌效果与菌囊的存在程度有关。添加以粘多糖为主要成分的荚膜物质也能抑制嗜中性粒细胞对粟粒葡萄球菌组的吞噬杀伤功能。荚膜物质的存在可能是米勒氏葡萄球菌群菌株的致病性。另一方面，厌氧菌的代谢物质短链脂肪酸抑制了嗜中性粒细胞对细菌的吞噬和杀伤功能，而能促进米勒氏菌群的生长。从临床微生物学的角度来看，存在的问题是米勒氏菌群的分离和鉴定。结果表明，这取决于所使用的血琼脂平板和鉴定试剂盒。

Streptococcus milleri group and anaerobes, recognized as normal flora in the mouth, were proved to be isolated from the patients of acute pneumonia, lung abscess and thoracic empyema by the methods of transthoracic needle aspiration, which could prevented the causative organisms from contamination with normal flora. This suggested that S. milleri group and anaerobes were important causative organisms in pulmonary infections.Studies on the mechanisms of their pathogenicity in the mice model of pneumonia showed that the higher mortality, longer survival in the lungs and more severe pathohistological changes in the mixed infection of S. milleri group and anaerobes than in the single infection, respectively. This suggested that there may be a synergistic effect between S. milleri group and anaerobes.In vitro studies demonstrated that S. milleri group strains isolated from the infectious lesions had stronger ability to inhibit the function of phagocytosis and phagocytic killing of human leukocytes against S. milleri group than that from normal flora. The degree of the inhibition depended on the presence of capsule of the bacteria. The addition of capsular material, mainly composed of mucopolysaccharide, could also inhibited the neutrophil function of phagocytic killing against S. milleri group. The presence of capsular material might be a pathogenicity of S. milleri group strains. On the other hand, the metabolic substances of anaerobes, short-chain fatty acids, inhibited the neutrophil function of phagocytosis and phagocytic killing against bacteria, while they could promoted the growth of S. milleri group.The problems from the view of clinical microbiology was the isolation and identification of S. milleri group. It was elucidated that it depended on what kind of blood agar plate and identification kit used.