抄録
Morphological change of a goat pneumonitis (GP) strain of Chlamydia psittaci in L cell monolayers induced by penicillin were investigated by electron microscopy. When the drug was added simultaneously with GP to the cell culture, its minimal inhibitory dose was estimated to be 1μg (1.6 units) per ml of medium. Penicillin interefered with the growth cycle of the psittacosis organism at a concentration higher than 1μg/ml by producing enlarged initial bodies 3 to 5μ in diameter. The abnormally enlarged initial bodies did multiply as such to some extent, but did not develop in to infective elementary bodies in the presence of an inhibitory dose of penicillin.
In the presence of a small dose of penicillin, ranging from 0.05 to 0.1μg/ml, an excessive cytoplasmic membrane was formed within the enlarged initial bodies 15 hours or more after the onset of infection. At that time were produced a number of irregular-shaped “miniature initial bodies” and small empty vesicles. The miniature initial bodies had been liberated from the initial bodies by a buddinglike process.
Free miniature initial bodies did not develop further. In the presence of a smaller dose of penicillin, ranging from 0.025 to 0.5μg/ml, clusters of electron-dense granules were formed within the maturing intermediate forms of the psittacosis organism. They were never found in the control intermediate forms grown in penicillin-free medium. The biochemical nature of those granules is not known at the moment.
