title: Infectivity of penicillin-induced Chlamydia psittaci forms for cell cultures from the chorioallantoic membrane of chick embryos.
abstract: L-cells were infected at high multiplicity with meningopneumonitis organsims (MP) and incubated in medium with penicillin (200 units/ml) and without the drug. At intervals up to 36 hours cells were removed and L-cell associated chlamydial infectivity was determined for cell cultures from the chorioallantoic membrane (CAM) of chick embryos which were treated before inoculation with Diethylaminoethyl (DEAE)-Dextran. In control L-cells, the infectivity decreased at 8 hours and reached it lowest level 16 hours after infection. In penicillin-treated L-cells in contrast, infectivity remained at low levels from 2 and up to 36 hours after infection. At 16 hours after infection about 90% of both penicillin-treated and nontreated L-cells contained single or multiple Giemsa-stained intracytoplasmic inclusions which in both series contained almost exclusively reticulate bodies (RB) by electron microscopy. RB from 16 hour infected penicillin-treated and non-treated L-cells were partially freed from cell debris and their infectivity (ID50) for CAM-culture cells (TC) was assayed 3 times. Penicillin-induced RB had TCID50 of 10(4.0)/ml compared to control RB of 10(4.5)/ml. The TCID50 of the original MP strain for CAM-culture cells was 10(8.0)/ml. Penicillin-induced RB and control RB from 16 hour L-cell samples were frozen and thawed 3 times and titrated in CAM cells; the TCID50 of both series dropped to 10(1.0)/ml while the TCID50 of the original MP inoculum after freezing and thawing 3 times was 10(7.0)/ml.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D002691:Chlamydophila psittaci / Q000187:drug effects / Q000472:pathogenicity*; D002823:Chorion; D003637:DEAE-Dextran; D005455:Fluorescent Antibody Technique; D007739:L Cells; D010406:Penicillins / Q000494:pharmacology
chemical_list: D010406:Penicillins; D003637:DEAE-Dextran