Abstract:

Objective To detect the changes of heat shock protein 60 （HSP60） during the subcultures of standard and clinical strains of Chlamydia trachomatis （Ct）, and to determine if the absence of chlamydial inclusions is associated with the persistent infection of Ct. Methods A total of 40 Ct strains isolated by cell culture from patients were included in this study and classified into 2 groups according to whether inclusions appeared after initial culture. Reverse transcription PCR was conducted to quantify the levels of HSP60 in specimens containing Ct after 1－4 subcultures. Chi-squared test was performed to analyze the relationship between the levels of HSP60 and treatment outcomes of patients. Results The levels of HSP60 in clinical specimens containing Ct serovar E were significantly higher in subcultures prior to the appearance of inclusions than in subcultures with the appearance of inclusions （P < 0.05）. The ratio of HSP60:16S rRNA mRNA expression after the first, second, third, fourth passage was 0.38 ± 0.06, 0.39 ± 0.03, 0.38 ± 0.04 and 0.39 ± 0.03 respectively in 18 specimens with inclusions appearing after the initial culture, 1.18 ± 0.10, 0.28 ± 0.06, 0.30 ± 0.03 and 0.29 ± 0.05 respectively in 12 specimens with inclusions appearing after the second culture, 1.20 ± 0.04, 1.20 ± 0.04, 0.28 ± 0.04 and 0.28 ± 0.05 in 10 specimens with inclusions appearing after the third culture. Whether inclusions appeared after the initial culture was associated with the treatment outcome of patients. Inclusions were undetected after the initial culture in 16 of 20 specimens from patients with poor response to treatment, but observed in 14 of 20 specimens from patients who tested negative for Ct after one course of treatment. Conclusions It is implicated that no inclusions form after the initial culture in 80% of specimens from patients experiencing treatment failure. The Ct strains whose inclusions do not form after passages may be in a persistent state, and the expression of HSP60 is high in these strains. Specimens should be subjected to at least 3 blind passages to avoid missed diagnosis of Ct infection.

Key words: persistent infection