Chlamydia trachomatis : molecular characteristics and epidemiology in Finland

Chlamydia trachomatis is a common cause of sexually transmitted infections (STI), which can lead to pelvic inflammatory disease (PID) and reproductive complications. C. trachomatis genotypes D–K cause urogenital infections and genotypes L1–L3 cause lymphogranuloma venereum (LGV). LGV infection outbreaks were reported in 2003 in Europe after decades among men who have sex with men (MSM). A new variant of C. trachomatis (nvCT) was identified in Sweden in 2006 with a large deletion in the plasmid leading to failing detection by two nucleic acid amplification tests (NAAT). Other microbes causing genitourinary tract infections, such as the human papillomavirus (HPV), herpes simplex virus (HSV), Mycoplasma genitalium and human herpesvirus 6 (HHV-6) may also contribute to the epidemiology of C. trachomatis. C. trachomatis promotes its survival inside the host cell through secreted effector proteins. The transcriptional expression of the genes encoding these effectors has mainly been studied using C. trachomatis reference strains propagated in cultured cells and not with currently circulating strains. In this thesis, the C. trachomatis genotype distribution and the occurrence of the Swedish nvCT in Finland was studied with real-time polymerase chain reaction (PCR) in urogenital specimens. The three most prevalent C. trachomatis genotypes were E, F, and G. The percentage of infections due to genotypes F and G increased slightly in 1987–2008, but otherwise the proportion of genotypes has remained quite stable in Finland during the last ten years. The Swedish nvCT was rare in Finland, as only two specimens (0.4%) containing the variant plasmid were detected. The prevalence of the LGV types in extragenital specimens in Finland was investigated with real-time PCR. Among the C. trachomatis positive samples, nine samples (8%) contained LGV types and one sample (1%) contained both non-LGV and LGV types. The LGV types were detected mainly in rectal swabs. Altogether nine LGV positive patients were identified and they were all MSM, and all except one were human immunodeficiency virus (HIV) positive. LGV infections among MSM also occur in Finland, which should be taken into account when considering the management of rectal C. trachomatis infections. The prevalence of HSV, HHV-6, HPV and M. genitalium in urogenital samples of C. trachomatis NAAT positive and negative young women in Finland was analysed with real-time PCR. The prevalence of HPV was significantly higher among the C. trachomatis positives than the negatives (66% vs. 25%). The prevalence of HSV, HHV-6, and M. genitalium was not significantly different between the C. trachomatis positives and negatives or between those who cleared the C. trachomatis infection and those who did not. The high prevalence of HPV among the C. trachomatis positives suggests greater sexual activity and increased risk for sexually transmitted pathogens. Low-passage-number C. trachomatis clinical isolates originating from cervical swabs and reference strains were used to study the expression of C. trachomatis protease (cpaf), phosphoprotein (tarp) and cytotoxin (tox) genes in a cell line during the chlamydial developmental cycle with real-time reverse transcriptase PCR (RT-PCR). Dissimilarities were observed in the gene expression patterns of cpaf and tox between the clinical isolates and the reference strains. All the strains had a similar tarp expression profile. Most clinical isolates showed slower growth kinetics compared to the reference strains. The use of low-passage-number C. trachomatis clinical isolates instead of reference strains in the gene expression studies might better reflect the situation during human infection.