Human α-amylase present in lower-genital-tract mucosal fluid processes glycogen to support vaginal colonization by Lactobacillus

Lactobacillus colonization of the lower female genital tract provides protection from the acquisition of sexually transmitted diseases, including human immunodeficiency virus, and from adverse pregnancy outcomes. While glycogen in vaginal epithelium is thought to support Lactobacillus colonization in vivo, many Lactobacillus isolates cannot utilize glycogen in vitro. This study investigated how glycogen could be utilized by vaginal lactobacilli in the genital tract. Several Lactobacillus isolates were confirmed to not grow in glycogen, but did grow in glycogen-breakdown products, including maltose, maltotriose, maltopentaose, maltodextrins, and glycogen treated with salivary α-amylase. A temperature-dependent glycogen-degrading activity was detected in genital fluids that correlated with levels of α-amylase. Treatment of glycogen with genital fluids resulted in production of maltose, maltotriose, and maltotetraose, the major products of α-amylase digestion. These studies show that human α-amylase is present in the female lower genital tract and elucidates how epithelial glycogen can support Lactobacillus colonization in the genital tract.