Abstract
Bacterial vaginosis (BV) is a common condition among women of reproductive age. A sensitive, quantitative and rapid assay is needed for the diagnosis of and, particularly, therapy monitoring for BV. Bacterial sialidase appears to play an important role in bacterial biofilms on vaginal epithelium, a condition closely associated with BV. Here, we report a biochemiluminescent sialidase assay that uses a substrate derivatized with firefly luciferin. In the presence of sialidase in the reaction, the substrate is cleaved to release luciferin, which is subsequently oxidized by firefly luciferase to generate a light signal. Thus, the light signal intensity can be used to detect and measure the relative concentration of sialidase in a vaginal sample as a means of BV diagnosis. All reagents are present in a reagent bead and sample buffer, enabling essentially a one-step assay. The assay is highly sensitive and quantitative, with a sensitivity and specificity of 95.40% and 94.94%, respectively, compared to the Amsel method. Interestingly, only 27.6% of those with BV had high levels of sialidase activity with a signal to cutoff ratio of 10 or more. The assay may be used for diagnosis of BV, risk assessment of BV patients in terms of sialidase activity levels, and monitoring antibiotic therapy.
Highlights
Bacterial vaginosis (BV) is a common condition[1,2,3,4,5,6]
When the light signal intensity of the luciferase reaction is dependent on the product of the sialidase reaction, i.e., luciferin, the signal intensity is expected to be proportional to sialidase activity, thereby enabling quantitative detection of the sialidase activity in the sample
Improvement in the treatment outcome of BV requires a better understanding of the etiology of this condition, which should in turn lead to better diagnostic and treatment monitoring methods
Summary
Bacterial vaginosis (BV) is a common condition[1,2,3,4,5,6]. Globally, 20–30% of women of reproductive age suffer from BV, a condition that is associated with an increased chance of preterm abortion, pelvic inflammatory disease (PID), sexually transmitted diseases including infection of human immunodeficiency virus (HIV), and even obesity[7,8,9,10,11,12]. It is commonly recognized that BV results from a change in vaginal conditions, which promote the growth of anaerobic bacterial species, thereby leading to a shift from aerobic bacterial flora to anaerobic bacterial flora in the vagina. One proposed etiological role of G. vaginalis in BV is that this bacterial species first establishes a biofilm on vaginal epithelium[15,16]. Biofilm is critical for the survival of G. vaginalis in the vagina as it creates an anaerobic environment, which in turn invites other anaerobic bacterial species. Sialidase appears to play an important role in biofilm formation by removing the polysaccharide substances on vaginal epithelium cells. Much higher sialidase activity was detected in vaginal samples from women with BV17,18. Sialidase has been associated with biofilm formation in the vagina[19,20,21,22]. A more sensitive and quantitative assay may be used for monitoring the efficacy of an antibiotic therapy
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