Detection of group B Streptococcus during antenatal screening in Western Australia: a comparison of culture and molecular methods

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Abstract

Aim: Global screening strategies for Group B Streptococcus (GBS) include risk- or culture-based methods to guide intrapartum prophylaxis. In Western Australia (WA), antenatal culture-based screening is routine; however, numerous culture methods exist, in addition to molecular methods. We aimed to assess the comparability of research and diagnostic screening approaches. Methods and Results: Vaginal and rectal swabs were self-collected by pregnant women (n = 531) from King Edward Memorial Hospital, WA, in parallel to routine screening (35–37 weeks of gestation). Research methods involved culture (Strep B Carrot Broth™ and StrepB CHROMagar™) and molecular methods (real-time PCR) and were compared to routine diagnostic screening (Lim Broth and Granada agar). Overall, GBS detection was comparable between research and diagnostic approaches (3–5% discrepancy, kappa = 0·76). Specificity/sensitivity of Carrot Broth was 100%/89%, while that of CHROMagar was 73%/100%, respectively. Direct PCR was unable to detect GBS in ~18% of specimens which were culture positive; however, it exhibited 100% specificity. Conclusions: This clinical evaluation of GBS screening methods provides support for current practice. Significance and Impact of the Study: Although CHROM was highly sensitive, further testing is recommended due to a high false-positive rate. Molecular assays are useful for rapid detection; however, low-titre samples may require additional enrichment prior to molecular analysis to improve sensitivity.

Original languageEnglish
Pages (from-to)598-604
Number of pages7
JournalJournal of Applied Microbiology
Volume127
Issue number2
DOIs
Publication statusPublished - 1 Aug 2019

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