The presence of the putative Gardnerella vaginalis sialidase A gene in vaginal specimens is associated with bacterial vaginosis biofilm

Bacterial vaginosis (BV) is a difficult-to-treat recurrent condition in which health-associated lactobacilli are outnumbered by other anaerobic bacteria, such as Gardnerella vaginalis. Certain genotypes of G. vaginalis can produce sialidase, while others cannot. Sialidase is known to facilitate the destruction of the protective mucus layer on the vaginal epithelium by hydrolysis of sialic acid on the glycans of mucous membranes. This process possibly facilitates adhesion of bacterial cells on the epithelium since it has been linked with the development of biofilm in other pathogenic conditions. Although it has not been demonstrated yet, it is probable that G. vaginalis benefits from this mechanism by attaching to the vaginal epithelium to initiate biofilm development. In this study, using vaginal specimens of 120 women enrolled in the Ring Plus study, we assessed the association between the putative G. vaginalis sialidase A gene by quantitative polymerase chain reaction (qPCR), the diagnosis of BV according to Nugent score, and the occurrence of a BV-associated biofilm dominated by G. vaginalis by fluorescence in situ hybridisation (FISH). We detected the putative sialidase A gene in 75% of the G. vaginalis-positive vaginal specimens and found a strong association (p<0.001) between the presence of a G. vaginalis biofilm, the diagnosis of BV according to Nugent and the detection of high loads of the G. vaginalis sialidase A gene in the vaginal specimens. These results could redefine diagnosis of BV, and in addition might guide research for new treatment

The presence of the putative <i>Gardnerella vaginalis</i> sialidase A gene in vaginal specimens is associated with bacterial vaginosis biofilm

<div><p>Bacterial vaginosis (BV) is a difficult-to-treat recurrent condition in which health-associated lactobacilli are outnumbered by other anaerobic bacteria, such as <i>Gardnerella vaginalis</i>. Certain genotypes of <i>G</i>. <i>vaginalis</i> can produce sialidase, while others cannot. Sialidase is known to facilitate the destruction of the protective mucus layer on the vaginal epithelium by hydrolysis of sialic acid on the glycans of mucous membranes. This process possibly facilitates adhesion of bacterial cells on the epithelium since it has been linked with the development of biofilm in other pathogenic conditions. Although it has not been demonstrated yet, it is probable that <i>G</i>. <i>vaginalis</i> benefits from this mechanism by attaching to the vaginal epithelium to initiate biofilm development. In this study, using vaginal specimens of 120 women enrolled in the Ring Plus study, we assessed the association between the putative <i>G</i>. <i>vaginalis</i> sialidase A gene by quantitative polymerase chain reaction (qPCR), the diagnosis of BV according to Nugent score, and the occurrence of a BV-associated biofilm dominated by <i>G</i>. <i>vaginalis</i> by fluorescence in situ hybridisation (FISH). We detected the putative sialidase A gene in 75% of the <i>G</i>. <i>vaginalis</i>-positive vaginal specimens and found a strong association (p<0.001) between the presence of a <i>G</i>. <i>vaginalis</i> biofilm, the diagnosis of BV according to Nugent and the detection of high loads of the <i>G</i>. <i>vaginalis</i> sialidase A gene in the vaginal specimens. These results could redefine diagnosis of BV, and in addition might guide research for new treatment.</p></div

Overview of different subsets of samples analysed with fluorescence in situ hybridisation (n = 462), Nugent score (n = 527), <i>G</i>. <i>vaginalis</i> quantitative polymerase chain reaction (n = 528) and <i>G</i>. <i>vaginalis</i> sialidase quantitative polymerase chain reaction (n = 393).

<p>Overview of different subsets of samples analysed with fluorescence in situ hybridisation (n = 462), Nugent score (n = 527), <i>G</i>. <i>vaginalis</i> quantitative polymerase chain reaction (n = 528) and <i>G</i>. <i>vaginalis</i> sialidase quantitative polymerase chain reaction (n = 393).</p

The association between quantitative polymerase chain reaction results for <i>G</i>. <i>vaginalis</i> and <i>G</i>. <i>vaginalis</i> sialidase of vaginal samples and fluorescence in situ hybridisation and Nugent score results of vaginal slides.

<p>The association between quantitative polymerase chain reaction results for <i>G</i>. <i>vaginalis</i> and <i>G</i>. <i>vaginalis</i> sialidase of vaginal samples and fluorescence in situ hybridisation and Nugent score results of vaginal slides.</p

Characteristics of vaginal samples.

<p>Characteristics of vaginal samples.</p

Superimposed confocal laser scanning microscopy images with 400x magnification of <i>Gardnerella vaginalis</i> biofilm, in three vaginal samples: vaginal epithelial cells DAPI in blue and <i>G</i>. <i>vaginalis</i> specific PNA-probe Gard162 with Alexa Fluor 647 in red.

<p>2A shows an example of dispersed-only <i>G</i>. <i>vaginalis</i> (negative for biofilm), 2B shows a light <i>G</i>. <i>vaginalis</i> biofilm (a small number of bacteria are adhering to the vaginal epithelial cells) and 2C is an example of a heavy <i>G</i>. <i>vaginalis</i> biofilm (the vaginal epithelial cells are covered by bacteria).</p