Differences in Chlamydia trachomatis cryptic plasmid loads in two types of female commercial sex workers in Korea

Female sex workers in Korea can generally be divided into one of two categories, namely, historically rooted brothel-based prostitutes (BBPs) and a newly developed category of freelance prostitutes (FLPs). Though some social differences are known, there have been few reports of distinguishing biological characteristics between the two groups. We examined the chlamydial plasmid loads (CPLs) and the numbers of detached host cells (NDCs) from these two groups with different approaches to selling sex. Chlamydial plasmid and human genomic DNA were extracted from endocervical swabs of the subjects, and we determined the CPLs and the NDCs using real-time PCR analysis. Forty-six women in the FLP group and 21 women in the BBP group had a chlamydial infection. The CPL and NDC values were higher in the FLP than in the BBP group (P=0.000, P=0.0001 respectively). In the FLP group, younger-aged women had higher CPLs and more detached cells than did older women (P=0.02, P=0.01 respectively). However, the BBP group did not show any such age-related differences in CPL and NDC values. There was a statistically significant positive correlation between the NDC and the CPL values in the BBPs (P<0.001) as well as in the FLPs (P<0.001). In conclusion, different biological characteristics were observed between FLPs and BBPs, as based on different CPL and the NDC values. The high plasmid loads among the sex workers were isolated from large numbers of scraped cells within a cotton swab. Thus, minor injury may render the endocervical epithel of FLPs more easily detachable than that of BBPs.