The prevalence of Gardnerella vaginalis in Portuguese pregnant women and the search for novel alternatives for the treatment of bacterial vaginosis

Worldwide, bacterial vaginosis (BV) is the most common gynaecological infection in women in reproductive age, being related with pregnancy complications. This vaginal infection is characterized by the replacement of beneficial microflora (often lactobacilli) and concurrent overgrowth of anaerobic bacteria. Being polymicrobial in nature, BV etiology remains unclear. Nevertheless, it is commonly accepted that BV involves the presence of multispecies biofilm, mainly composed by Gardnerella vaginalis. A major issue related to BV is the recurrent failure of conventionally antibiotic therapies. So, the main aims of this work were to determine the prevalence of G. vaginalis and BV in Portuguese pregnant women and to search for novel strategies to treat this vaginal infection. To achieve this, we first conducted a cross-sectional study among pregnant women in the Northern region of Portugal. Our epidemiological findings showed that BV frequency was low (3.88%) but G. vaginalis colonization was high (67.48%) among pregnant women. Furthermore, a higher risk of G. vaginalis colonization was found in women with BV, basic educational level, smokers and during the second trimester of pregnancy. In contrast, past history of chronic disease, preterm delivery and colonization by G. vaginalis were identified as BV risk factors during pregnancy. Next, we performed a series of in vitro assays in order to determine the influence of environmental conditions in G. vaginalis biofilm formation. Using optimized in vitro conditions, we demonstrated that G. vaginalis biofilms display a higher tolerance to antibiotics and other antimicrobial agents than planktonic cultures. Lastly, we evaluated the potential therapeutic of Thymbra capitata essential oil and its main component (carvacrol) against G. vaginalis biofilms. We found that both T. capitata essential oil and carvacrol displayed a potent antibacterial activity against G. vaginalis planktonic cultures. However, only the intact oil was able to reduce significantly G. vaginalis biofilms. Interestingly, it presented a lower antimicrobial activity on vaginal lactobacilli. Thus, T. capitata essential oil stands up as a promising therapeutic agent for BV.