To explore the effect of vulvovaginal candidiasis (VVC) on the vaginal-cervical microbiome in women.

Women who participated in cervical and breast cancer screening (aged 35-65 years) were recruited from 2018 to 2019 at the Suzhou National New and Hi-tech Industrial Development Zone of Suzhou, China. Cervical samples and volunteer's information were collected. Then, 123 women among them were selected, including 36 women with VVC and 87 healthy women as controls. Metagenomic shotgun sequencing was performed on the cervical samples, and the relationship between the vaginal microbiome and VVC was then analyzed.

Principal coordinate analysis (PCoA) showed that there was a significant difference in the vaginal microbiome between the healthy women and women with VVC (PERMANOVA test, P=0.003). The proportion of Lactobacillus iners-dominated microbiota was significantly higher in women with VVC (VVC group: 61.11%; controls: 32.18%), but Lactobacillus crispatus showed little difference between the two groups. In addition, the proportion of Prevotella-dominated microbiota, especially P. bivia-dominated microbiota declined in women with VVC (VVC group: 0; controls: 8.05%). Markers such as L. iners were enriched in women with VVC obviously (Q＜0.05), while Veillonellaceae and Sneathia amnii decreased (P＜0.05, Q＞0.05).

Compared with healthy women, the vaginal-cervical microbiome has a remarkable difference in women with VVC, suggesting that VVC could cause an imbalance in the vaginal microbiome. High relative abundance of Lactobacillus iners can enhance the risk of VVC. The evaluation of the vaginal-cervical microbiome in women with VVC provides a basis for the diagnosis, treatment, and evaluation of prognosis of VVC.