AUTHOR=He Yuanhui , Na Risu , Niu Xiaoxi , Xiao Bingbing , Yang Huixia 

TITLE=Lactobacillus rhamnosus and Lactobacillus casei Affect Various Stages of Gardnerella Species Biofilm Formation

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.568178

DOI=10.3389/fcimb.2021.568178

ISSN=2235-2988

ABSTRACT=<p>Bacterial vaginosis (BV) and its recurrence are most commonly associated with the formation of <italic>Gardnerella</italic> species biofilm. Probiotics are typically used to treat BV; however, the optimal period of <italic>Lactobacillus</italic> probiotic application in BV treatment remains uncertain. The present study aimed to explore the effects of <italic>Lactobacillus rhamnosus</italic> and <italic>Lactobacillus casei</italic> on various stages of biofilm formation in <italic>Gardnerella</italic> species. The biofilm-forming ability of seven strains, including one <italic>Gardnerella vaginalis</italic> ATCC 14018 and six clinically isolated <italic>Gardnerella</italic> species, was determined <italic>via</italic> gentian violet staining assay. Moreover, the sensitivity of the planktonic and biofilm forms toward metronidazole and clindamycin was assessed <italic>via</italic> microdilution broth method. <italic>L. rhamnosus</italic> Xbb-LR-1 and <italic>L. casei</italic> Xbb-LC-1 were added during various stages of biofilm formation in <italic>Gardnerella</italic> species and were cocultured for 24 h. The biofilm thickness of each sample was determined <italic>via</italic> confocal laser scanning microscopy (CLSM). The absolute quantities of <italic>Gardnerella</italic> species in each sample was obtained <italic>via</italic> real time polymerase chain reaction method, and the pH value was obtained using a pH indicator paper. Biofilm formation by <italic>Gardnerella</italic> species in a medium with distinct pH values was observed <italic>via</italic> gentian violet staining, CLSM, and scanning electron microscopy (SEM). The biofilm increased the resistance of <italic>Gardnerella</italic> species toward metronidazole and clindamycin. <italic>L. rhamnosus</italic> added at the initial biofilm formation stage in <italic>Gardnerella</italic> species exhibited highest inhibitory effect, with a percentage inhibition of 38.17% ± 1.35%. When the pH value of the culture medium was &lt;4.5 or &gt;6.5, ATCC 14018 could hardly form a biofilm; however, at pH ≥4.5 and ≤6.5, it was able to form a stronger biofilm. The amount of biofilm attained maximum value at optical density of 3.29 ± 0.28 (595 nm), pH 5.5, and at 36 h. Biofilm formation increases the resistance of <italic>Gardnerella</italic> species toward antibiotics. Maintaining an acidic vaginal environment with pH &lt;4.5 and a vaginal microbiota dominated by <italic>Lactobacillus</italic> remarkably prevents the formation of <italic>Gardnerella</italic> species biofilm at the initial stage, which further has a significant impact on the treatment and prevention of biofilm-related infections.</p>