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Detection of group B Streptococcus during antenatal screening in Western Australia: a comparison of culture and molecular methods
Author(s) -
Furfaro L.L.,
Chang B.J.,
Payne M.S.
Publication year - 2019
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.14331
Subject(s) - streptococcus , streptococcus agalactiae , microbiology and biotechnology , streptococcaceae , group b , group a , group (periodic table) , biology , medicine , bacteria , chemistry , genetics , antibiotics , organic chemistry
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.