Estimation of Group B Streptococcus Colonization in High-Risk Neonates by PCR and Standard Culture

Group B Streptococcus (GBS) (Streptococcus agalactiae) is the leading cause of morbidity and mortality of newborn infants considered a leading factor causing septicemia after birth. The standard method for the diagnosis of GBS colonization is culture in a selective medium, but PCR has a high sensitivity and specificity. The goal of this study was to estimate the colonization of GBS in rectum of neonates of high-risk mothers by culture and PCR method. Samples were taken from rectal mucosa of 154 neonatesof high-risk mothers for GBS by swabs. Samples were tested by standard culture using Todd Hewitt broth and blood agar and also by PCR using primers specific for cfb gene. Of 154 neonates, Culture identified 17 (11%) neonates as colonized by GBS; and the PCR assay could identify 27 (17%) neonates with positive results for GBS. Mothers age range was 17-40 years (mean = 26.1 ± 5.1). Maternal age was significantly lower in PCR positive group (P = 0.038) and in culture positive group (P = 0.015). Using culture as the gold standard, sensitivity, NPV, specificity, and PPV of PCR were 100%, 100%, 92%, and 62%, respectively. The time required for PCR assay and culture were 2hours and 36hours, respectively. This study showed that the incidence of GBS in Iranian high-risk neonates is high, so we strongly recommend screening of high-risk neonates for detection of GBS