Rapid detecting Group B Streptococci using a real-time polymerase chain reaction assay in newborn
Date Issued
2011
Date
2011
Author(s)
Hung, Yi-Li
Abstract
Background: Group B Streptococcus (GBS) infection has been the leading cause of early-onset neonatal sepsis for more than 30 years. Approximately 10-30% of pregnant women are colonized with GBS in their vagina or rectum and the vertical transmission rate was around 50%.The guidelines of CDC 2002 recommend that all pregnant women be screened for GBS carriage between GA 35 and 37 weeks and that intrapartum antibiotic prophylaxis (IAP) be given to carriers. This guideline significantly decreased incidence of GBS related neonatal sepsis. However, there are still some limitations of this culture-based screening strategy, including time consuming and the possibility of changing colonization status after testing in pregnant women. Moreover, infants born preterm have an elevated risk for early onset GBS disease but the colonization status is sometimes unknown at delivery. Recently, a real time polymerase chain reaction (RT-PCR) assay for GBS had been applied to the intrapartum pregnant women with higher sensitivities than the antepartum standard selective broth vaginal-rectal culture. This RT-PCR assay had never been applied directly to newborn in detecting GBS colonization status.
Purposes of Study: 1.To evaluate the performance of GBS RT-PCR assay in direct detecting GBS colonization status of newborn. 2. To access the association between neonatal respiratory distress and asymptomatic GBS colonization.
Method: Neonates born to a GBS colonization mother or neonates with respiratory distress within 1 hour after birth were enrolled from June, 2009 to May, 2010 in Cathay general hospital. Swabs were obtained from their external ear canals, nostrils, body surface of periumbilical area and subaxillary skin folds immediately after birth before their fist bath. Oral secretion or gastric juice was also collected. All specimens were sent for the IDI-Strep B PCR assay (Becton Dickinson & Co., Franklin Lakes, NJ, USA). Samples were plating and inoculated in the sheep blood agar plate at the same time. Ifβ-hemolytic colony was found on the agar plate, GBS grouping Latex kit was used to reconfirm it. Their urine was collected immediately and the urine latex test was performed to identify the GBS specific antigen. Using GBS culture as the gold standard, we compared the performance of the RT-PCR, urine antigen immunoassay, and correlated with their perinatal characters.
Result: The maternal vaginal-rectal GBS colonization rate at gestational age 35-37 weeks was 15.4%. Eighty-five neonates were born to GBS colonization mothers. Among them, 74 were born via vaginal delivery and 15 of them (20.2%) had positive GBS RT-PCR and 11 of them concurrently showed positive GBS culture. The vertical transmission rate of GBS was 14.9%.In the remaining 11 neonates who were born via Cesarean section, only 1 newborn had positive GBS RT-PCR and culture. The urine GBS antigen tests were negative in all enrolled candidates. Comparing neonates with positive or negative of GBS RT-PCR, there wasn’t significant difference in their gestational age, birth body weight, maternal leukocyte count, maternal age but neonates with shorter duration of IAP before delivery had a significant higher GBS PCR positive rate. There were 25 neonates suffering from respiratory distress within 1 hour after birth. Six of them (24%) were GBS PCR positive. A total of 100 paired GBS RT-PCR samples and GBS cultures were available. The sensitivity and specificity of the PCR test were 100% (95% CI 71.5~100) and 92% (95% CI 84.5~96.8), respectively. The time taken to undertake the RT-PCR assay was 90 minutes in average.
Conclusion: GBS RT-PCR assay maybe an alternative sensitive method to rapid detection GBS colonization status in newborn.
Subjects
Real-time polymerase chain reaction (RT-PCR)
Group B Streptococcus (GBS)
Intrapartum antibiotic prophylaxis (IAP)
Neonate
Respiratory distress
Type
thesis
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