Evaluation of the bacterial vaginosis in pregnant women by polymerase chain reaction techniques

Abstract

Bacterial vaginosis (BV) is the most common vaginal infection in women of reproductive age. Pregnancy with bacterial vaginosis is a higher risk for some complications of pregnancy especially of preterm delivery.  Screening and treating in BV positive pregnant women, particularly those that have a history of previous preterm delivery, may help to reduce the rate of preterm delivery. The laboratory diagnosis of BV is Gram stain-based Nugent score. This method requires the microbiologist for accurate diagnosis. The fastidious growth of BV-associated microorganisms makes identification by culture method difficult and not valuable for interpretation. Therefore, PCR methods have been developed and identified novel fastidious bacterial species in BV. The aim of this study was to evaluate the bacterial vaginosis in pregnant women by polymerase chain reaction (PCR) techniques by use of species-directed 16S rRNA which specific to Gardnerella vaginalis and Atopobium vaginae compare with the Nugent score. This prospective study was conducted in Srinagarind Hospital from September 2010 to March 2011. A total of two hundred and ninety-five pregnant women attending an antenatal clinic.  The pregnant women age between 28.2 ± 6 years and the gestational age between 21.3 ± 10 weeks. With using of Gram stain-based Nugent score, 131 (44.4 %) samples were classified as normal, 44 (15.0 %) were classified as intermediate, and 120 (40.6 %) were classified as BV.  Moreover, the BV patients have association with the maternal/fetal complications outcome, the overall rate was 48 (40.0 %) samples in BV and 22 (18.3 %) samples in intermediate. Compared to the Nugent score method, PCR technique which specific to Gardnerella vaginalis had a sensitivity, specificity, positive predictive value, negative predictive value and prevalence were of 78.7 %, 68.0 %, 75.4 %, 71.8 % and 58 %, respectively. Meanwhile the PCR technique which specific to Atopobium vaginae, had a sensitivity, specificity, positive predictive value, negative predictive value and prevalence of 49.0 %, 97.0 %, 95.3 %, 60.5 % and 29.0 % respectively. In conclusion, the PCR technique which specific to Gardnerella vaginalis may be suitable for diagnosis of BV and could be considered for routine use in clinical laboratories because of higher sensitivity. The prevalence of BV was 58% found in this method similar to 56.0 % in the Nugent method. But Atopobium vaginae had more specific for BV than Gardnerella vaginalis. However, the improved detection for quantitative method such as the real-time PCR should be use for increase sensitivity and specificity, or multiplex PCR of Gardnerella vaginalis and Atopobium vaginae will be helpful for identify the specific infection. Because Atopobium vaginae has also been reported to be highly resistant to metronidazole therapy.