Kayser F H
Institute of Medical Microbiology, University of Zurich, Switzerland.
Postgrad Med J. 1992;68 Suppl 3:S17-23.
Over the last decade, the spectrum of organisms causing community-acquired acute lower respiratory tract infections has changed. Streptococcus pneumoniae now causes approximately 30% of outpatient acute pneumonia-less than in former decades-whereas Mycoplasma pneumoniae is found in both young and elderly patients. The Enterobacteriaceae and Staphylococcus aureus are now seen more frequently as respiratory tract pathogens in community-acquired pneumonia patients, and they are the major organisms causing pneumonia in residents of homes for the elderly or nursing homes, and in immuno-compromised patients. Agents that were previously considered non-pathogenic for the respiratory tract include serotypes of Haemophilus influenzae other than type b, H. parainfluenzae and Moraxella (Branhamella) catarrhalis; these organisms affect mainly patients with underlying cardiopulmonary disease. Legionella species can cause sporadic as well as epidemic disease of the lower respiratory tract. Chlamydia pneumoniae is a newly recognized pathogen responsible for mild to severe upper and lower respiratory tract infections. In 60-80% of cases, hospital-acquired pneumonias are caused by Gram-negative bacilli and S. aureus. These organisms colonize the mucosal membranes of the upper respiratory tract and penetrate into the lower tract by aspiration or intubation.
在过去十年中，引起社区获得性急性下呼吸道感染的病原体谱发生了变化。目前，肺炎链球菌所致的门诊急性肺炎约占30%，低于前几十年，而肺炎支原体在年轻和老年患者中均有发现。肠杆菌科细菌和金黄色葡萄球菌现在在社区获得性肺炎患者中更常被视为呼吸道病原体，它们是导致老年之家或疗养院居民以及免疫功能低下患者发生肺炎的主要病原体。以前被认为对呼吸道无致病性的病原体包括b型流感嗜血杆菌以外的其他血清型流感嗜血杆菌、副流感嗜血杆菌和卡他莫拉菌（布兰汉菌）；这些病原体主要感染有潜在心肺疾病的患者。军团菌可引起散发性以及流行性下呼吸道疾病。肺炎衣原体是一种新发现的病原体，可导致轻至重度上、下呼吸道感染。在60% - 80%的病例中，医院获得性肺炎由革兰阴性杆菌和金黄色葡萄球菌引起。这些病原体在上呼吸道黏膜定植，并通过误吸或插管进入下呼吸道。
