State of the Art for Diagnosis of Bacterial Vaginosis

Abstract

Bacterial vaginosis (BV) is the most common cause of vaginal discharge among reproductive-age women. It is associated with multiple adverse health outcomes, including increased risk of acquisition of HIV and other sexually transmitted infections (STIs), in addition to adverse birth outcomes. While it is known that BV is a vaginal dysbiosis characterized by a shift in the vaginal microbiota from protective Lactobacillus species to an increase in facultative and strict anaerobic bacteria, its exact etiology remains unknown. The purpose of this minireview is to provide an updated overview of the range of tests currently used for the diagnosis of BV in both clinical and research settings. This article is divided into two primary sections: traditional BV diagnostics and molecular diagnostics. Molecular diagnostic assays, particularly 16S rRNA gene sequencing, shotgun metagenomic sequencing, and fluorescence in situ hybridization (FISH), are specifically highlighted, in addition to multiplex nucleic acid amplification tests (NAATs), given their increasing use in clinical practice (NAATs) and research studies (16S rRNA gene sequencing, shotgun metagenomic sequencing, and FISH) regarding the vaginal microbiota and BV pathogenesis. We also provide a discussion of the strengths and weaknesses of current BV diagnostic tests and discuss future challenges in this field of research.

Keywords: bacterial vaginosis; diagnosis; molecular diagnostics; vaginal infection.

FIG 1

Comparison of 16S rRNA gene sequencing and shotgun metagenomics sequencing results for bacterial microorganisms in woman who developed incident BV (34). The Nugent score is presented at the top and indicates normal (0 to 3), intermediate (4 to 6), or high (7 to 10), and the number of days prior to the day of incident BV (iBV) (day 0) is given at the bottom. Days sequenced using 16S rRNA gene sequencing are in green, while the same days sequenced using shotgun metagenomics are colored in purple. Each bacterial microorganism’s abundance is displayed as a log-normalized relative abundance.

FIG 2

Example of BV diagnosis using fluorescence in situ microscopy and PNA FISH probes. Lactobacillus-specific (Lac633-Alexa Fluor 488) and Gardnerella-specific (Gard162-Alexa Fluor 594) PNA FISH probes allowed a quick (<3-h) and accurate (85% sensitivity and 98% specificity) BV diagnosis following Ison and Hay’s criteria. The Lac633 probe marked the Lactobacillus spp. with a strong green signal, while Gard162 marked the Gardnerella spp. with a red signal. Sample A was obtained from a woman with a Nugent score of <3, while sample B was obtained from a woman with a Nugent score of >7. Some nonspecific fluorescence can be observed in both images, but the difference between the woman without BV and the woman with BV is evident. These images were obtained from a previous study (82).