Figure 1.

(A) The mixed-biofilms are complex structures in which bacteria and/or fungi adhere to the vaginal wall surfaces, and they are encased in an extracellular matrix. The extracellular matrix is a physical barrier to the outside environment. (B) Microbes within the biofilm also exhibit antagonistic and synergistic interactions. Lactobacilli can attach to the surface of Candida albicans hyphae. Production of antimicrobials leads to the death of fungal filaments. In addition to antagonistic interactions, mutually beneficial interactions in mixed biofilm environments are also possible. For example, C. albicans can protect anaerobic bacteria by providing a low oxygen niche within the depths of the biofilm, even though the external environment is aerobic. (C) Antagonistic interactions are more likely to occur between probiotics and pathogens. Synergistic interactions are more likely to occur between pathogens. Different microbes can determine the course of mixed vaginitis. In interspecies interactions, many environmental cues (hypoxia, extracellular pH, body temperature and CO₂) and host immune factors could impact the formation of mixed vaginitis.