Molecular quantification of Gardnerella vaginalis and Atopobium vaginae loads to predict bacterial vaginosis
Authors: Jean-Pierre Menard
Florence Bretelle
Didier Raoult
Mireille Henry
Florence Fenollar
Journal: Clinical Infectious Diseases (2008)
Discipline: IMMUNOLOGY
Keywords: Bacterial vaginosis; Molecular analysis; Diagnostic tool; Real-time polymerase chain reaction; Gardnerella vaginalis
Affiliations: Unit√© des Rickettsies, IFR 48, CNRS UMR 6020, Facult√© de M√©decine, Universit√© de la M√©diterran√©e, Marseille, France.

Abstract:  Background: Bacterial vaginosis (BV) is a poorly detected public health problem that is associated with preterm delivery and for which no reliable diagnostic tool exists. Methods: Molecular analysis of 231 vaginal samples, classified by Gram stain-based Nugent score, was used to propose molecular criteria for BV; these criteria were prospectively applied to 56 new samples. A quantitative molecular tool targeting 8 BV-related microorganisms and a human gene was developed using a specific real-time polymerase chain reaction assay and serial dilutions of a plasmid suspension. The targeted microorganisms were Gardnerella vaginalis, Lactobacillus species, Mobiluncus curtisii, Mobiluncus mulieris, and Candida albicans (which can be identified by Gram staining), as well as Atopobium vaginae, Mycoplasma hominis, and Ureaplasma urealyticum (which cannot be detected by Gram staining). Results: With use of the Nugent score, 167 samples were classified as normal, 20 were classified as BV, and 44 were classified as intermediate. Except for U. urealyticum, M. mulieris, and Lactobacillus species, DNA of the tested bacteria was detected more frequently in samples demonstrating BV, but the predictive value of such detection was low. The molecular quantification of A. vaginae (DNA level, &gt; or = 10(8) copies/mL) and G. vaginalis (DNA level, &gt; or = 10(9) copies/mL) had the highest predictive value for the diagnosis of BV, with excellent sensitivity (95%), specificity (99%), and positive (95%) and negative (99%) predictive values; 25 (57%) of the samples demonstrating intermediate flora had a BV profile. When applied prospectively, our molecular criteria had total positive and negative predictive values of 96% and 99%, respectively. Conclusions: We report a highly reproducible, quantitative tool to objectively analyze vaginal flora that uses cutoff values for the concentrations of A. vaginae and G. vaginalis to establish the molecular diagnosis of BV. 

Retracted: No

PubPeer comments:
 In this paper, vaginal samples were obtained from 204 women during a pregnancy follow-up period at the Conception University Hospital of Marseille. A second cohort of 56 pregnant women was sampled at the North University Hospital of Marseille. * Could the authors please clarify if all or some women of the first cohort of 204 women were pregnant during sampling? Some wording ( Vaginal samples were used either for screening for BV during the first trimester for patients who had a prior preterm delivery or for screening for Streptococcus agalactiae during the third trimester. ) appeared to suggest that all women were pregnant during sampling, but the during a pregnancy follow-up period appeared to suggest it was after pregnancy. * Subjects in the first cohort gave informed consent, but was the same true for the second cohort? Was any ethical approval obtained from the Conception University Hospital or the North University Hospital, where the patients were sampled? I could not find any wording on that. ,