Moulder J W
Infect Immun. 1983 Feb;39(2):898-907. doi: 10.1128/iai.39.2.898-907.1983.
When monolayers of mouse fibroblasts (L cells) persistently infected with Chlamydia psittaci (strain 6BC) were dispersed in medium 199 and plated out in new flasks, the monolayers that grew out consisted almost exclusively of inclusion-free host cells that retained full resistance to superinfection with C. psittaci (covert infection). After a delay that was inversely proportional to the initial density of the newly transferred L cell population, the percentage of host cells containing visible chlamydial inclusions increased rapidly (overt infection), and most of the L cells were destroyed by extensive chlamydial multiplication (wipeout), leaving only a few survivors to start new persistently infected monolayers. When persistently infected L cell populations grown in medium 199 were transferred to Eagle minimal essential medium, the onset of overt multiplication was strongly suppressed although covert multiplication of C. psittaci continued unabated, as shown by host cell retention of resistance to superinfection and the prompt resumption of overt multiplication after transfer back into medium 199. The difference(s) between the two media responsible for the different expression of the persistently infected state was not determined. A single dose of 100 U of penicillin G per ml of medium 199 given at the time persistently infected monolayers were divided almost completely suppressed the appearance of visible signs of chlamydial infection for several weeks, although resistance to superinfection was retained at all times. The same amount of penicillin given 7 days after replating did not prevent the occurrence of the first expected wipeout, but there was a long period of inclusion-free L cell growth between the first wipeout and the second. It was concluded that covert multiplication of C. psittaci in persistently infected L cells may continue indefinitely without the appearance of visible signs of infection. The transition between covert and overt chlamydial multiplication appears to be a penicillin-sensitive, multistep process that is regulated, at least in part, by the host cell density and the composition of the growth medium.
当用鹦鹉热衣原体（菌株6BC）持续感染的小鼠成纤维细胞（L细胞）单层在199培养基中分散，并接种到新的培养瓶中时，生长出来的单层几乎完全由无包涵体的宿主细胞组成，这些细胞对鹦鹉热衣原体的再次感染保持完全抗性（隐性感染）。在与新转移的L细胞群体的初始密度成反比的延迟之后，含有可见衣原体包涵体的宿主细胞百分比迅速增加（显性感染），并且大多数L细胞因衣原体大量繁殖而被破坏（清除），仅留下少数幸存者开始新的持续感染单层。当在199培养基中生长的持续感染的L细胞群体转移到伊格尔最低必需培养基中时，显性繁殖的开始受到强烈抑制，尽管鹦鹉热衣原体的隐性繁殖仍未减弱，这表现为宿主细胞对再次感染的抗性保留以及转移回199培养基后显性繁殖迅速恢复。导致持续感染状态不同表达的两种培养基之间的差异尚未确定。在持续感染的单层被分割时，每毫升199培养基中加入单剂量100 U青霉素G，几乎完全抑制了衣原体感染可见迹象的出现达数周之久，尽管对再次感染的抗性始终保留。重新接种7天后给予相同量的青霉素并不能阻止首次预期的清除发生，但在第一次清除和第二次清除之间有一段无包涵体的L细胞长时间生长。得出的结论是，鹦鹉热衣原体在持续感染的L细胞中的隐性繁殖可能无限期持续而不出现可见的感染迹象。衣原体隐性和显性繁殖之间的转变似乎是一个对青霉素敏感的多步骤过程至少部分受宿主细胞密度和生长培养基组成的调节。
