Bacterial Vaginosis Assessed By Molecular Methods

Bacterial vaginosis (BV) is an aberrant state of the vaginal microbiota, which is characterized by a depletion of lactobacilli, an increased diversity of the bacterial population and an elevated pH. It is one the most common vaginal syndromes in fertile, premenopausal and pregnant women.

Women are most often diagnosed with bacterial vaginosis (BV) using microscopy based on Nugent scoring or Amsel criteria; however, the accuracy is less than optimal. To confirm the identity of known BV-associated composition profiles and evaluate indicators for BV, three molecular methods have been assessed.

Microbiologists at the Vrije Universiteit (Amsterdam, The Netherlands) and their colleagues studied the vaginal microbiota of 40 subjects, of which 20 BV-negative and 20 BV-positive, by selection of low (0–3) and high (7–10) Nugent scores, respectively. A standard cervical examination was performed and a cotton swab was used to remove abundant mucus prior to the collection of a sample for Chlamydia trachomatis and Neisseria gonorrhoeae screening. The diagnosis of BV was based on the Nugent Gram stain and the presence of three Amsel criteria characteristic vaginal discharge, clue cells, and positive amine test.

DNA was isolated and sequence analysis was performed on a 454 GS-FLX-Titanium Sequencer (454 Life Sciences, Branford, CT, USA). Evaluation of indicators for BV was carried out by 16S ribosomal ribonucleic acid (rRNA) amplicon sequencing of the V5-V7 region, a tailor-made 16S rRNA oligonucleotide-based microarray, and a polymerase chain reaction (PCR)-based profiling technique termed IS-profiling, which is based on fragment variability of the 16S-23S rRNA intergenic spacer region. The amplification of the IS-regions was performed with the IS-pro assay (IS-Diagnostics, Amsterdam, the Netherlands).

Analysis of the bacterial communities by 16S rRNA amplicon sequencing revealed two clusters in the BV negative women, dominated by either Lactobacillus iners or L. crispatus and three distinct clusters in the BV positive women. In the former, there was a virtually complete, negative correlation between L. crispatus and L. iners. BV positive subjects showed cluster profiles that were relatively high in bacterial species diversity and dominated by anaerobic species, including Gardnerella vaginalis, and those belonging to the Families of Lachnospiraceae and Leptotrichiaceae. Accordingly, the Gini-Simpson index of species diversity, and the relative abundance Lactobacillus species appeared consistent indicators for BV.

The authors concluded that an affordable and simple molecular test showing a depletion of the genus Lactobacillus in combination with an increased species diversity of vaginal microbiota could serve as an alternative and practical diagnostic method for the assessment of BV. The study was published on April 23, 2016, in the joournal BMC Infectious Diseases.

Related Links:
Vrije Universiteit
454 Life Sciences
IS-Diagnostics