Six Bacterial Vaginosis-Associated Species Can Form an In Vitro and Ex Vivo Polymicrobial Biofilm That Is Susceptible to Thymbra capitata Essential Oil

Abstract

Bacterial vaginosis (BV) is associated with serious gynaecologic and obstetric complications. The hallmark of BV is the presence of a polymicrobial biofilm on the vaginal epithelium, but BV aetiology is still a matter of debate. We have previously developed an in vitro biofilm model that included three BV-associated species, but, up to now, no studies are available whereby more bacterial species are grown together to better mimic the in vivo situation. Herein, we characterized the first polymicrobial BV biofilm consisting of six cultivable BV-associated species by using both in vitro and ex vivo vaginal tissue models. Both models revealed that the six species were able to incorporate the polymicrobial biofilm, at different bacterial concentrations. As it has been thought that this polymicrobial biofilm may increase the survival of BV-associated species when exposed to antibiotics, we also assessed if the Thymbra capitata essential oil (EO), which has recently been shown to be highly bactericidal against several Gardnerella species, could maintain its anti-biofilm activity against this polymicrobial biofilm. Under our experimental conditions, T. capitata EO exhibited a high antibacterial effect against polymicrobial biofilms, in both tested models, with a significant reduction in the biofilm biomass and the number of culturable cells. Overall, this study shows that six BV-associated species can grow together and form a biofilm both in vitro and when using an ex vivo model. Moreover, the data obtained herein should be considered in further applications of T. capitata EO as an antimicrobial agent fighting BV.

Chemical Composition, Antioxidant, and Antibiofilm Properties of Essential Oil from Thymus capitatus Plants Organically Cultured on the Greek Island of Lemnos

“…In two other similar studies by the same group, this EO was also found to present an important biomass removal effect on preformed Candida spp. biofilms (of 13 clinical isolates that belonged to four different species) [ 40 ], as well as a preformed polymicrobial biofilm that consisted of six cultivable bacterial vaginosis-associated bacterial species [ 41 ]. In another study, the EO from Italian C. capitatus at 1% v / v was found to inhibit biofilm formation and reduce preformed biofilms in about half of eleven clinical P. aeruginosa isolates from cystic fibrosis patients [ 42 ].…”

“…It is generally accepted that organic agricultural systems are more profitable and more environmentally friendly than conventional farming and deliver equivalent or higher-quality products that contain less (or no) pesticide residues [ 35 ]. While there are some previous antimicrobial and antibiofilm studies employing the EO from this aromatic and medicinal species [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ], wild plants have most of the times been used to extract the oil. In addition, to the best of our knowledge, no other study has ever tested the action of T. capitatus EO against the biofilms of the aforementioned three important pathogens.…”

Effect of a combination of pea protein, grape seed extract and lactic acid in an in vivo model of bacterial vaginosis

“…These include plant extracts, such as Prangos ferulacea, Myrtus communis , Zataria multiflora , essential oils, small antimicrobial peptides of animal origin, bacteriocins and various groups of plant compounds (such as triterpenoids, phenols, and flavonoids) with antimicrobial and antiviral activity 46 , 48 . In particular, studies conducted by Machado and Rosca 25 , 32 demonstrated the potential use of Thymbra capitata essential oil (EO) as a novel therapeutic agent in the treatment of BV thanks to its antimicrobial effect against several bacterial species associated with BV including Gardnerella species. The natural products can be used in combination with MET or probiotics to improve the efficacy of antimicrobial therapy and reduce the recurrence of vaginal infections 43 .…”

“…As biofilms allow Gardnerella spp. to persist in recurrent BV, it is important to identify new treatments capable to counteract BV-biofilm 24 , 25 . Currently, the therapeutic agents available for the management of BV are topical agents containing lactic acid, clindamycin and/or orally administered antibiotics 26 , among others.…”

“…However, oral administration of clindamycin (CLIN) and/or metronidazole (MET) long-term could negatively impact the gut microbiome and increase BV recurrence 27 , due to the rising number of antimicrobial resistant species 28 ; therefore, alternative treatments are needed for a better management of BV 26 , 29 . In the last decade, more attention was given to the use of natural substances for the treatment of vaginal dysbiosis, including BV 25 , 30 – 32 . Pea protein (PP) is derived from the plant of Pisum sativum ; it is rich in fiber and represents an important source of essential amino acids such as lysine 33 .…”