[Experimental study on development and lung injury in pneumonia under neutropenic condition]

This study was performed to demonstrate the characteristic findings in pneumonia under neutropenic condition. The results were as follows. 1) After nebulizing Klebsiella pneumonia DT-S strains, the survival rate in the neutropenic mouse group rapidly decreased compared with that of the control group. 2) In the neutropenic state, a rapid decline of survival rate was demonstrated during the initial stage of infection. Bacteremia and endotoxemia developed earlier than in the healthy control group. 3) In neutropenic pneumonia, the neutrophil cell count in BALF was significantly lower than that in usual pneumonia. Consequently, a large number of bacteria grew in the alveolar spaces during the early period after inhalation. Neither inflammatory cell infiltration nor thickening of the alveolar wall was present; however, structural destruction of alveolar and vascular walls was found. 4) These pathological changes were also seen following intratracheal inoculation of some extracellular enzymes of Klebsiella pneumoniae DT-S into rabbit lung. However, no destruction of alveolar walls was observed after nebulizing the killed Klebsiella pneumoniae DT-S. It was suggested that the significant amount of enzymes produced by the bacteria growing in the alveoli caused tissue damage, especially in the neutropenic state. 5) Thus the typical inflammatory changes that occurred in the usual state, were not seen in neutropenic pneumonia, and a large number of bacteria grew in the alveoli. Marked tissue damage was caused by extracellular enzymes produced by bacteria. Consequently, bacteria entered the blood stream and bacteremia and endotoxemia developed. These processes observed in neutropenic pneumonia readily progressed to bacteremia of endotoxemia, which are more severe in this state.