Screening for Streptococcus agalactiae in pregnancy – do we need to take a step forward?

Abstract

Abstract Background: Streptococcus agalactiae is the leading infectious cause of morbidity among neonates. Majority of early onset neonatal infections can be prevented using antimicrobial prophylaxis during labour. Different diagnostic procedures can be employed to detect maternal colonization during pregnancy and labour. In the present study we analysed diagnostic characteristics of two common methods for detection of S. agalactiae. Methods: One hundred and one consecutive vaginal or combined vaginal-rectal swabs were included in this prospective study. All samples were tested with enrichment culture and molecular illumigene GBS assay. Results of repeatedly disconcordant samples were retested and confirmed with a different molecular assay. Sensitivity, specificity, positive and negative predicted values were determined for both assays. Results: Mean age of women was 33 years. Prevalence of colonisation in the sample was 23,8 %. Positivity rates using enrichment culture only, illumigene GBS assay only and combination of both assays were 19,8 %, 22,7 % and 23,8 %, respectively. Sensitivity, specificity, positive and negative predictive values were 83,3 %, 100 %, 100 % in 95,1 % for enrichment culture and 95,8 %, 100 %, 100 % in 98,7 % for illumigene GBS assay, respectively. Combining both methods 20 % more colonized women were detected compared to enrichment culture alone. Conclusions: With a combination of enrichment culture and illumigene GBS assay we can detect substantially more colonized women compared to currently most frequently used method of enrichment culture. Comprehensive evaluation of current strategies for prevention of S. agalactiae early neonatal infection is warranted in Slovenia.