Prevalence, seasonal patterns, and microbial co-occurrence of selected genital tract microorganisms in women attending a gynecological counseling service in Southern Italy

Background: Sexually transmitted infections (STIs) represent a major global public health problem due to their potential to cause serious complications such as infertility, chronic pelvic pain, and increased susceptibility to HIV. Young adults, and especially women of reproductive age, are particularly vulnerable, underscoring the need for early diagnosis, routine screening, and targeted prevention efforts. However, not all genital tract infections are sexually transmitted, and distinguishing between STIs and non-sexually transmitted genital tract pathogens is essential for accurate epidemiological interpretation and clinical management. Methods: We conducted a cross-sectional study among women aged 18-60 years attending a gynaecological counseling service in Southern Italy. Endocervical and vaginal swabs were tested for a panel of pathogens, including classical STI agents (e.g., Chlamydia trachomatis, Neisseria gonorrhoeae) and non-sexually transmitted or opportunistic genital tract microorganisms. Multivariable Poisson regression, seasonal trends, and pairwise co-occurrence models were employed to investigate correlations of microorganism detection. Results: A total of 536 women were tested. Classical STI pathogens were rarely or not detected, with Chlamydia trachomatis and Neisseria gonorrhoeae showing very low prevalence. In contrast, non-STI genital tract pathogens were frequently identified, with Gardnerella vaginalis being the most prevalent, followed by Enterococcus faecalis and Staphylococcus aureus. Seasonal patterns were observed primarily among S. aureus and Pseudomonas spp. showing lower positivity rates in spring and summer compared to autumn and winter. Co-detection analysis revealed non-random associations mainly involving non-STI organisms, particularly between E. faecalis and Escherichia coli, and between G. vaginalis and Proteus spp. or Staphylococcus spp. Conclusions: In this population, classical STIs were infrequent, whereas non-sexually transmitted genital tract pathogens were more commonly detected and showed distinct epidemiological patterns. These findings highlight the importance of clearly distinguishing between STIs and other genital tract infections in both research and clinical practice, while maintaining targeted prevention and screening strategies for STIs. Trial registration: Territorial Ethics Committee of the Calabria Region (Protocol No. 168, dated May 30, 2024). Clinical trial number: Not applicable.