Comparison of Three Nucleic Acid Amplification Tests and Culture for Detection of Group B Streptococcus from Enrichment Broth.

Ji H Shin,David T Pride,Sandra S Richter

doi:10.1128/jcm.01958-18

Ji H Shin, David T Pride + Show 1 more

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https://doi.org/10.1128/jcm.01958-18

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Abstract

Colonization of the gastrointestinal and genitourinary tracts of pregnant women with group B Streptococcus (GBS) can result in vertical transmission to neonates during labor/delivery. GBS infections in neonates can cause severe complications, such as sepsis, meningitis, and pneumonia. Accurate detection is critical because administration of intrapartum antibiotics can significantly reduce transmission. We compared the clinical sensitivities of three nucleic acid amplification tests (NAATs), the Hologic Panther Fusion GBS, Luminex Aries GBS, and Cepheid Xpert GBS LB assays, to that of the standard of care culture method recommended for GBS screening using 500 vaginal-rectal swab specimens after 18 to 24 h of broth enrichment. We identified 108 positive specimens (21.6%) by culture, while at least 1 of the 3 NAATs was positive for GBS in 155 specimens (31.0%). All 108 specimens positive by culture were also detected by the Panther Fusion assay, while 107/108 (99.1%) were detected by the Cepheid Xpert and Luminex Aries assays. Of the 61 specimens positive by at least 1 NAAT but negative by culture, 24 (39.3%) were positive by all 3 NAATs, suggesting that they represent true positives (TPs). NAATs offer less hands-on time, greater throughput, faster time to result, and potentially greater sensitivity than culture methods, and they should be considered the new gold standard for intrapartum GBS screening.

Highlights

Streptococcus agalactiae, known as group B Streptococcus (GBS), is a commensal Gram-positive bacterium that can transiently colonize the vagina, gastrointestinal tract, and urethra [1]
Vaginal-rectal GBS colonization has been reported to occur in about 18% of pregnant women worldwide [2] and in about 25% in the United States, according to the Centers for Disease Control and Prevention (CDC) [3]
The use of commercially available real-time PCR nucleic acid amplification tests (NAATs) for GBS screening in pregnant women has the potential to increase the overall sensitivity of GBS screening while reducing the time to obtaining results

Summary

Introduction

Streptococcus agalactiae, known as group B Streptococcus (GBS), is a commensal Gram-positive bacterium that can transiently colonize the vagina, gastrointestinal tract, and urethra [1]. Spread of GBS to newborn children occurs via vertical transmission from vaginal-rectal-colonized pregnant women during labor and childbirth, and the organism may ascend the vagina to the amniotic fluid after the onset of labor and/or rupture of membranes This transmission from the mother to the newborn occurs variably at an estimated rate of 40% to 73% [4], with about 1% to 2% of colonized newborns developing early-onset disease (EOD). Guidelines from the CDC recommend universal screening of antepartum women at 35 to 37 weeks of pregnancy to identify women colonized with GBS with the potential to transmit to their newborns during labor These guidelines recommend using enriched culture-based methods using a vaginal-rectal specimen, followed by intrapartum antibiotic prophylaxis for women in whom GBS colonization has been identified [5, 10]. NAATs on sample-to-answer platforms offer standardized processing technology for specimen extraction, amplification, and detection, provide a shorter turnaround time to result, and demonstrate improved GBS detection rates compared to those of culture [13,14,15,16,17,18,19,20,21,22,23]

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