The human vagina: normal flora considered as an in situ tissue-associated, adherent biofilm

Abstract

Objective: A method that would allow in situ comparison of the degrees of adherence to genital epithelia by the biofilms of the normal flora.

Subjects: Four healthy women.

Setting: Departments of Biological Sciences, University of Calgary, and of Medicine, University of British Columbia.

Methods: In situ, scraped specimens were taken from the vagina and ectocervix before and after vigorous vaginal washes, and colony counts of associated bacteria were compared. In vitro, cells from the vulva, vagina and ectocervix were vortexed, centrifuged and sonicated and remaining associated bacteria quantitated by light microscopy.

Results: Anaerobic lactobacilli were notably tissue-adherent as colony counts of postwash specimens were comparable to those of their paired prewash specimens, but crucially were higher than those of their paired wash specimens (p less than 0.05, Wilcoxon signed rank test). However, vaginal and ectocervical coagulase-negative staphylococci and ectocervical Lancefield group B streptococci were loosely tissue-adherent, because counts in postwash specimens were lower than those in prewash or wash specimens (p less than 0.05, Wilcoxon signed rank test). In vitro, only vulvar scrapings and vaginal postwash specimens showed a significant decrease in associated bacteria after shear stressing (p less than 0.05, Wilcoxon signed rank test).

Conclusions: The normal flora of the female genitalia features both avidly and loosely tissue-adherent bacterial biofilm populations whose adherence can be influenced partly by their location. Our scraping/washing method can contribute to further characterisation of this phenomenon. The superior adherence of anaerobic lactobacilli may reflect a potential in maintaining or restoring normality.