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Original article
Assessment of Atopobium vaginae and Gardnerella vaginalis concentrations in a cohort of pregnant South African women


Objectives The purpose of this cross-sectional study was to assess Atopobium vaginae and Gardnerella vaginalis concentrations in pregnant women of different age groups, gestational age groups, vaginal flora categories and HIV status, and also to determine which DNA concentrations best discriminated between bacterial vaginosis (BV)-positive and non-BV categories.

Methods Self-collected vaginal swabs were obtained from 220 pregnant women attending an antenatal clinic in Pretoria, Gauteng, South Africa, from July 2012 to December 2012. BV was detected with the Nugent scoring system, and A. vaginae and G. vaginalis DNA was quantified with a multiplex quantitative real-time PCR assay.

Results Median concentrations of A. vaginae and G. vaginalis were not significantly different among various age groups (A. vaginae p=0.98 and G. vaginalis p=0.18) or different trimesters (A. vaginae p=0.31 and G. vaginalis p=0.19), but differed significantly among the vaginal flora categories (A. vaginae p<0.001 and G. vaginalis p<0.001) and HIV status (A. vaginae p<0.001 and G. vaginalis p=0.004). The presence of A. vaginae (OR=5.8; 95% CI 1.34 to 25.21 and p value=0.02) but not that of G. vaginalis (OR=1.90; 95% CI 0.81 to 4.43 and p value=0.14) was associated with HIV infection. An A. vaginae DNA concentration of ≥107 copies/mL together with a positive G. vaginalis result (≥100 copies/mL) best discriminated between BV-positive (39/220) and non-BV categories (181/220) with a sensitivity of 85% (95% CI 0.70 to 0.94) and a specificity of 82% (95% CI 0.76 to 0.88).

Conclusions A. vaginae and G. vaginalis were present in high numbers and concentrations in this pregnant cohort. Threshold concentrations should be established for specific populations to ensure sensitive molecular assays for BV detection.

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  • Handling editor Jackie A Cassell

  • Twitter Follow Mathys Redelinghuys @ShaneRed72

  • Contributors MJR is the project leader and was involved in concept design, sample procurement, laboratory work, data analysis and writing of the manuscript. MMK is the principal investigator and budget owner, and together with MME, was involved in the concept design of the study as well as review of the manuscript. PJB and JEB were involved in data and statistical analyses, and JEB participated in the interpretation of results. All authors read and approved the final manuscript.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Student Research Ethics Committee of the Faculty of Health Sciences, University of Pretoria. The approved protocol number for this project was S6/2012.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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