It is commonplace for the term lobar pneumonia to be used when there is clinical and radiographic evidence of confluent consolidation occupying the greater part of one or more lobes of one or both lungs. The term segmental pneumonia is used when such consolidation is not extensive enough to occupy most of a lobe but corresponds more closely to the anatomy of a bronchopulmonary segment in one or more lobes. Where the area of radiographic shadowing is even more confined, then subsegmental pneumonia is an appropriate descriptive term, although this still implies a confluent and localized process. Where subsegmental shadowing is patchy (non-confluent) and poorly localized, being scattered throughout part or the whole of one or both lungs, the term bronchopneumonia remains entirely acceptable.
This anatomical classification is complementary but subservient to causal classification, being of only limited value in establishing the likely infective agent, for although lobar pneumonia is usually caused by Streptococcus pneumoniae it can be caused by many other microorganisms besides, as indeed can all other anatomical types. Every reasonable effort should therefore be made to establish the identity of the pathogenic organism responsible for pneumonia in each patient, in order that specific antimicrobial therapy can be directed against it, for without this information some patients will not recover who otherwise would have done so.
The causal organism can only be guessed at when the patient is first seen and it is useful in this respect to classify the patient as having either community-acquired pneumonia or nosocomial pneumonia, as the spectrum of infecting organisms is different in each case. Nosocomial pneumonia is a particular problem in post-operative patients and in those treated in intensive care units, the latter group being highly susceptible to lower respiratory tract infection. The differing types of causal organisms found in the hospital situation are due in part to the altered immunocompetency of patients who are afflicted with other serious disease, in part to the alteration of bacterial flora that results from treatment with antibiotics and in part to the instrumentation or intubation of the upper airways of patients. Such hospital-acquired infections are more frequently due to aerobic gram-negative bacilli and Staphylococcus aureus than are those acquired in the community.
confluent ['kɔnfluənt] a. 融合的，连合的
subservient [səb:sə:viənt] a.从属的，次要的
streptococcus [,streptəu'kɔkəs] n. 链球菌属
streptococcus pneumoniae 肺炎链球菌
intubation [,intju:'beiʃən] n. 插管法(尤指喉管插入法)
aerobic [,eə'rəubik] a. 有氧的，需氧的
gram negative 革兰氏阴性
bacillus [bə'siləs] ([复] bacilli [bə'silai]) n. 杆菌,杆菌属,芽胞杆菌属
staphylococcus [,stæfiləu'kɔkəs] n. 葡萄球菌属
staphylococcus aureus ['ɔ:riəs] 金黄色葡萄球菌
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