Isolation of Pathogens from Peripheral Pulmonary Blood in Rabbit Pneumonia
The low isolation rate of the etiologic pathogens of human pneumonia has been attributed in part to the use of sputum as the culture specimen. We, therefore, considered that pulmonary arterial blood (PA) might be a more telling specimen for bacteriological isolation and experimented with rabbit pneumonia in order to study its accuracy. Bacterial pneumonia was induced by inoculation of 109 cfu/ml of S. aureus (strains 2548 and 5091) through intratracheal tube inserted into the subsegmental bronchi. With this method, the pneumonia was most severe macroscopically, histologically, and bacteriologically at 72 hours after inoculation. At that time, blood samples from the posterior auricular vein (PB) were drawn and, immediately after a thoracotomy, pulmonary arterial blood (PAB) was drawn from the peripheral pulmonary artery. Bronchoalveolar lavage fluid (BALF) was collected with an inserted intratracheal tube and lung homogenates (LH) were sampled from the most severe pneumonic lesions. All these samples were cultured and S. aureus was isolated from 23 out of 35 samples (65%) of LH, 12 out of 37 (32%) of BALF, 5 out of 37 (14%) of PAB and 3 out of 37 (8%) of PB. Contrary to our expectations, the isolation rate of pathogens from PA was low and no diagnostic value in the culturing PA as a culture material in experimental pneumonia.