Comparison of qPCR and chromogenic culture methods for rapid detection of group B streptococcus colonization in Vietnamese pregnant women

Introduction

Neonatal infections can rapidly become severe, with delays in treatment often proving fatal. Streptococcus agalactiae (Group B Streptococcus, GBS) is a common cause, typically transmitted from colonized pregnant women to neonates during childbirth. In Vietnam, routine prenatal care lacks standardized GBS screening protocols. This study aims to compare enhanced qPCR methods with the culture method, evaluate the diagnostic accuracy of these qPCR procedures, and assess the frequency of GBS infection in pregnant Vietnamese women during their final trimester.

Materials and methods

Pregnant women aged 35 weeks gestation or more were recruited. Rectovaginal swabs were collected and analyzed for GBS using chromogenic culture, a commercial real-time PCR kit, and in-house real-time PCR assays targeting the cfb and sip genes. Clinical diagnostic values were calculated, and GBS prevalence was determined.

Results

The study included 259 pregnant women with a mean age of 30.2 ± 5.0 years. Of these, 96.6 % had gestational ages of 37 weeks or more at delivery. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the cfb-based and sip-based qPCR assays were 94.1/92.7, 99.0/99.5, 97.1/98.5, 97.8/97.3, and 97.6 %, respectively. The Kappa values were excellent (0.940 and 0.939), with results available in under 2 h. GBS prevalence was 24.7 % and 25.5 % by cfb-based and sip-based qPCR assays, aligning with the culture method (25.5 %).

Conclusions

Both direct real-time PCR assays demonstrated high accuracy and were comparable to chromogenic culture in diagnosing GBS. A significant prevalence of GBS colonization was found among Vietnamese pregnant women in their final trimester.