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. 2012 Jan;43(1):253-60.
doi: 10.1590/S1517-838220120001000029. Epub 2012 Jun 1.

A combined enrichment/polymerase chain reaction based method for the routine screening of Streptococcus agalactiae in pregnant women

F M Munari  1 , F De-Paris, G D Salton, P S Lora, P Giovanella, A B M P Machado, L S Laybauer, K R P Oliveira, C Ferri, J L S Silveira, C C F C Laurino, R M Xavier, A L Barth, S Echeverrigaray, J P Laurino
Affiliations

A combined enrichment/polymerase chain reaction based method for the routine screening of Streptococcus agalactiae in pregnant women

F M Munari et al. Braz J Microbiol. 2012 Jan.

Abstract

Group B Streptococcus (GBS) is the most common cause of life-threatening infection in neonates. Guidelines from CDC recommend universal screening of pregnant women for rectovaginal GBS colonization. The objective of this study was to compare the performance of a combined enrichment/PCR based method targeting the atr gene in relation to culture using enrichment with selective broth medium (standard method) to identify the presence of GBS in pregnant women. Rectovaginal GBS samples from women at ≥36 weeks of pregnancy were obtained with a swab and analyzed by the two methods. A total of 89 samples were evaluated. The prevalence of positive results for GBS detection was considerable higher when assessed by the combined enrichment/PCR method than with the standard method (35.9% versus 22.5%, respectively). The results demonstrated that the use of selective enrichment broth followed by PCR targeting the atr gene is a highly sensitive, specific and accurate test for GBS screening in pregnant women, allowing the detection of the bacteria even in lightly colonized patients. This PCR methodology may provide a useful diagnostic tool for GBS detection and contributes for a more accurate and effective intrapartum antibiotic and lower newborn mortality and morbidity.

Keywords: Accuracy; Group B Streptococcus; Screening test; Streptococcus agalactiae; atr gene.

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Figures

Figure 1
Figure 1
Results for PCR assay with the atr-primers to the mix of DNA with and without S. agalactiae (A) and for the cultures of clinical isolates (B). Lane M- 100-bp molecular-size standard. Lane W/O- mix of DNA without S. agalactiae. Lane W- mix of DNA with S. agalactiae. Lane 1- Proteus mirabillis. Lane 2- S. agalactiae. Lane 3- Staphylococcus aureus. Lane 4-Staphylococcus epidermidis. Lane 5- Acinetobacter sp. Lane 6- Serratia sp. Lane 7- Salmonella sp. Lane 8- Morganella morganii. Lane 9- Citrobacter sp.
Figure 2
Figure 2
Flow diagram of the diagnostic accuracy study of a PCR assay to identify the presence of GBS in pregnant women.
See this image and copyright information in PMC

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