[Study on the inhibitory effects of minocycline on genital Chlamydia trachomatis in McCoy cell culture].

In this study of Chlamydia trachomatis (C. trachomatis) from genital origin in McCoy cells, minocycline (MINO) was added to infected cell cultures at specific stages of their growth cycle. Sequential observations were made at each stage by electron microscope with the following results: 1) The minimal inhibitory concentration of MINO against C. trachomatis in McCoy cells was 0.025 micrograms/ml. 2) When MINO and chlamydial inoculation were simultaneously added (inoculum containing 1 microgram of MINO per ml), MINO did not inhibit attachment and invasion of elementary bodies (EBs) to McCoy cells in both cases of inoculation, with and without centrifugation. As 48 hours after inoculation 74% of the infectious EBs in McCoy cells were converted to early intermediate forms (IFs). This suggests that MINO did not inhibit the transformation of EBs to early IFs. Under the influence of MINO, even after 48 hours, reticulate bodies (RBs) and chlamydial inclusions were not recognized. At the stages of transformation of infectious EBs to early IFs, duplication of the cell wall and electron lucent areas in the cytoplasm were observed. 3) Meanwhile, in the case of replacing the media with one containing MINO (1 microgram/ml) at 12 hours after inoculation, the conversion of RBs to late IFs was blocked. 4) Electron microscopically, the average numbers of late IFs and EBs per cross section of the inclusion at 24 hours after inoculation, were 0.64 and 0.17, respectively. At 48 hours after inoculation without MINO (control), the average numbers of late IFs and EBs were 10.5 and 65.6, respectively. When MINO (1 microgram/ml) was added at 24 hours after inoculation and observed at 48 hours, the average numbers of late IFs and EBs numbered 0.10 and 0.67, respectively. This indicates A) statistically, a significant decrease (0.64----0.10) for late IFs and a significant increase (0.17----0.67) for EBs compared with the average number of those at 24 hours after inoculation, B) when compared with the average number of those at 24 hours after inoculation, the sum of late IFs and EBs were nearly the same (0.64 + 0.17 not equal to 0.10 + 0.67), C) somewhat similar ratios of late IFs to EBs (10.5:65.6 = 1:6.2 not equal to 0.10:0.67 = 1:6.7) compared to the average number of those at 48 hours after inoculation without MINO (control). B) suggests that the conversion of RBs to late IFs was blocked by MINO. A), B) and C) suggest that the conversion of late IFs to EBs was not inhibited by MINO.(ABSTRACT TRUNCATED AT 400 WORDS)