Chlamydia trachomatis infection prevalence and serovar distribution in a high-density urban area in the North of Italy

Chlamydia trachomatis (CT) is the causative agent of the most common bacterial sexually transmitted infection (STI) worldwide. CT molecular typing plays a fundamental role in finding associations between serovars and epidemiological features and can be crucial for therapeutic appropriateness. The aim of this study was to assess CT infection prevalence and serovar distribution in a high density urban area in the North of Italy, by comparing different groups of subjects divided on the basis of care providers they referred to. From January 2011 to May 2014, data about all the urogenital and extra-genital samples (anorectal and/or pharyngeal swabs) submitted to the Microbiology of St. Orsola Hospital in Bologna for CT detection were collected. The specimens were obtained from three different groups of patients: subjects attending the STI Outpatients Clinic of the Hospital, patients attending gynecological clinics or people referring to general practitioners. All the samples were processed by a real-time PCR (Versant CT/GC DNA 1.0 Assay; Siemens) and in case of positivity, molecular genotyping based on RFLP analysis was performed. A P < 0.05 was considered statistically significant. Overall CT infection prevalence was 8.1% with significant differences between sub-groups (P<0.01), but stable during the study period. STI Clinic was mainly responsible for CT diagnosis, whereas the lowest prevalence was detected in gynecological clinics, despite a high number of tests performed. Extra-genital samples were almost exclusively collected from males at the STI Clinic. Interestingly, 4.4% of CT positive cases would have been missed if extra-genital sites had not been tested. CT serovar distribution was influenced by gender, age, anatomic site (P<0.01) and care providers (P=0.01). L2 serovar was detected only in extra-genital samples from males at the STI Clinic. First, significant differences in the contribution of CT testing and diagnosis between care providers were noticed. Secondly, extra-genital testing need to be encouraged, especially outside the STI Clinic. Finally, CT typing is crucial for the appropriate management in specific settings, such as LGV in extra-genital samples of high-risk populations