Comparison of BD MAX GBS and GenomEra GBS assays for rapid intrapartum PCR detection of vaginal carriage of group B streptococci

Accuracy of real-time polymerase chain reaction test for Group B Streptococcus detection in pregnant women: A systematic review and meta-analysis

OBJECTIVES

This study aimed to determine the performance of RT PCR of GBS screening in pregnant women under different situations, especially compared to different reference methods (culture or composite standards) and preprocessing before detection (directly or enrichment).

MATERIALS AND METHODS

We searched PubMed, the Cochrane Library: Cochrane Database of Systematic Reviews, EMBASE, and Google Scholar, and clinical trial registries such as ClinicalTrials.gov and WHO ICTRP until March 2024. The assessment of each study quality was performed using a modified QUADAS-2 instrument. The meta-analysis included pooled sensitivity, specificity, summary receiver operating characteristic (SROC) curve, and AUC. Publication bias was examined using Deek's funnel plot. Sensitivity analysis was conducted to evaluate the robustness of the meta-analysis. Index (I-square) and Q-test were performed to analyze the heterogeneity, and subgroup analysis and logistic meta-regression were used to identify the potential causes.

RESULTS

A total of 81 reports, including 133 research, were involved in the analysis. The pooled sensitivity and specificity of RT-PCR for detection of Group B Streptococcus in pregnant women were 96 % (95 %CI: 94 %-97 %) and 98 % (95 %CI:97 %-98 %), respectively. The pooled AUC value was 0.99 (95 %CI:0.98-1.00). In subgroup studies, there were four groups, including Group A (Enrichment & culture), Group B (Direct & culture), Group C (Enrichment & composite standard), and Group D (Direct & composite standard). Group A's pooled sensitivity and specificity were 98 % (95 %CI: 97 %-99 %) and 94 % (95 %CI:92 %-96 %), respectively. Group B's pooled sensitivity and specificity were 92 % (95 %CI: 89 %-94 %) and 96 % (95 %CI:95 %-97 %), respectively. Group C's pooled sensitivity and specificity were 98 % (95 %CI: 97 %-99 %) and 99 % (95 %CI: 99 %-99 %), respectively. Group D's pooled sensitivity and specificity were 93 %(95 %CI: 87 %-97 %) and 100 % (95 %CI:99 %-100 %), respectively. The pooled AUC values of the SROC for groups A, B, C, and D were 0.99 (95 %CI: 0.98-1.00), 0.98(95 %CI: 0.97-0.99), 1.00 (95 %CI: 0.99-1.00), and 0.99(95 %CI: 0.99-1.00), respectively.

Rapid Point-of-care Testing to Inform Intrapartum Treatment of Group B Streptococcus-Colonized Women in Uganda

Introduction

Maternal Group B Streptococcus (GBS) rectovaginal colonization is an important risk factor for invasive disease in neonates, yet availability of culture-based methods for detection is limited in low-resource settings. We evaluated the diagnostic performance of the HiberGene (HG) GBS loop-mediated isothermal amplification (LAMP) assay for the rapid detection of GBS in rectal/vaginal swabs collected from women in Uganda. This work forms a part of the PROGRESS GBS study.

Methods

In phase 1, 1294 rectal and vaginal swabs were collected from pregnant women and inoculated in enrichment (Lim) broth, which was then tested using the HG GBS LAMP assay (sip gene target) and culture on chromogenic agar. In phase 2, 166 swabs from nonpregnant women were tested directly (without the enrichment step). For samples with discordant results, an additional method of testing against multiplex real-time polymerase chain reaction assay was used.

Results

Overall, the HG GBS LAMP assay detected more GBS-positive samples (31.3%; 452/1445) than culture-based methods (13.3%; 192/1445). Multiplex polymerase chain reaction-tested results were concordant with LAMP results in 96.3% of cases. The sensitivity and specificity of the LAMP assay, after adjusting for the tiebreaker results of discordant samples, were 94.4% (95% confidence interval, 86.2-99.4) and 99.0% (95% confidence interval, 94.3-100), respectively.

Conclusions

The results of this study demonstrate high sensitivity and specificity of the HG GBS LAMP assay for the detection of GBS rectovaginal colonization in our setting. Given its rapid turnaround time, the HG GBS LAMP assay could appropriately be used to screen women for GBS rectovaginal colonization during labor to enable provision of intrapartum antibiotic prophylaxis.

Applicability of an in-house extraction protocol in a Bruker Biotyper matrix-assisted laser desorption/ionization time-of-flight mass spectrometry system for the identification of Streptococcus agalactiae from broth-enriched vaginal/rectal swab specimens

BACKGROUND AND PURPOSE

Early laboratory identification of group B Streptococcus (GBS, Streptococcus agalactiae) in the birth canal of pregnant women is critical for prompt administration of antimicrobial therapy and may further reduce the mortality rate due to GBS neonatal infection.

METHODS

A total of 164 vaginal/rectal swab specimens collected from pregnant women at 35-37 weeks of gestation were screened for GBS vaginal colonization. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS, Bruker Biotyper, Bruker Daltonik GmbH, Bremen, Germany) system was used to detect GBS from Carrot broth and LIM broth enrichment using an in-house extraction protocol. The results were compared to those by conventional broth-enriched culture/identification methods as the gold standard. BD MAX™ GBS assay (Becton Dickinson, Sparks, MD, USA) was also performed for Carrot broth-enriched specimen. Discordant results were investigated using the GeneXpert® GBS PCR assay (Cepheid Inc., Sunnyvale, CA, USA).

RESULTS

Using the extraction protocol, 33 (20.1%) of the 164 specimens were positive in Carrot broth, and 19 (11.6%) were positive in LIM broth. Using the culture protocol, 38 (23.2%) samples in Carrot broth and 35 (21.3%) in LIM broth were positive. The sensitivity, specificity, and positive and negative predictive values using the extraction protocol in Carrot broth and LIM broth compared to the gold standard conventional culture/identification method were 86.8% and 50.0%, 100% and 100%, 100% and 100%, and 96.2% and 86.9%, respectively.

CONCLUSIONS

The extraction protocol with MALDI-TOF MS from Carrot broth-enriched samples provides a more rapid turnaround time, lower cost, and acceptable sensitivity and specificity to correctly identify pathogens when compared to conventional culture/identification methods.

Evaluation of two rapid commercial assays for detection of Streptococcus agalactiae from vaginal samples

INTRODUCTION

Streptococcus agalactiae, also known as group B streptococci (GBS), is associated with invasive infections in neonates. Identification of GBS vaginal colonization in pregnant women before delivery is essential for treatment with antibiotics to prevent intrapartum vertical transmission to the newborn. This study was designed to evaluate applicability of two rapid real-time PCRs in comparison to standard culture identification.

MATERIAL AND METHODS

We compared the Xpert GBS assay, hereafter referred to as Xpert, and GenomEra GBS PCR, hereafter referred to as GenomEra. The standard culture identification consisted of two different agar plates as well as an enrichment broth.

RESULTS

We analyzed vaginal samples of 260 pregnant women; 42 samples were tested GBS-positive by using standard culture as a gold standard, 30 by Xpert, and 37 by GenomEra. Xpert and GenomEra assays performed with sensitivities of 71.4% and 88.1% as well as specificities of 98.6% and 99.1%, respectively. Twelve vaginal samples were false-negative by Xpert and five samples by GenomEra. Interestingly, three negative Xpert results of standard culture-positive samples exhibited high Ct-values indicating the presence of GBS. If higher Ct-values are taken into consideration, the sensitivity of Xpert increases up to 78.6%. Moreover, only three Xpert PCRs had to be repeated, whereas two Genomera were invalid even after repetition and further 15 GenomEra PCRs were repeated because of borderline results or inhibition of the PCR test.

CONCLUSIONS

In this study, GenomEra assay performed with a higher sensitivity than the Xpert PCR. On the other hand, the Xpert assay needs less hands-on-time for a sample preparation and requires approximately four-fold less repetitions as compared to the GenomEra assay. This robust performance of the Xpert assay make it applicable as a rapid intrapartum point-of-care test, although a higher sensitivity would be desirable. Therefore, culture in the 35-37 week of gestation remains the gold standard to detect vaginal colonization.

Updates on Group B Streptococcus Infection in the Field of Obstetrics and Gynecology

Group B Streptococcus (GBS, Streptococcus agalactiae) is a Gram-positive bacterium that is commonly found in the gastrointestinal and urogenital tracts. However, its colonization during pregnancy is an important cause of maternal and neonatal morbidity and mortality worldwide. Herein, we specifically looked at GBS in relation to the field of Obstetrics (OB) along with the field of Gynecology (GY). In this review, based on the clinical significance of GBS in the field of OBGY, topics of how GBS is being detected, treated, and should be prevented are addressed.

An Application of Real-Time PCR and CDC Protocol May Significantly Reduce the Incidence of Streptococcus agalactiae Infections among Neonates

Streptococcus agalactiae is an important human opportunistic pathogen, especially infectious for pregnant women and neonates. This pathogen belongs to beta hemolytic Streptococcus spp. representatives and accounts for a significant part of early infections in newborns, including serious life-threatening infections. This research investigated the usefulness of Centers for Disease Control and Prevention (CDC) protocol for S. agalactiae DNA detection in 250 samples of recto-vaginal swabs collected from pregnant women (at 35-37 weeks of gestation) and pre-cultured overnight in liquid medium. With an application of the CDC protocol-based real-time PCR, the cfb gene was detected in 68 (27.2%) samples compared to 41 (16.4%) for the standard culture-based methodology. The applied molecular method presented high sensitivity (100.0%) and specificity (87.1%). Therefore, it allowed for more precise detection of S. agalactiae bacteria, compared to the reference diagnostic method, culture on solid media with the following strain identification. The increased sensitivity of GBS detection may result in a reduced number of infections in newborns and leads to more targeted antimicrobial prophylaxis therapy of GBS infections in pregnant women. In addition, the use of the molecular method allows for a significant reduction in the time needed to obtain a result for GBS detection, and interpretation of the results is relatively simple. Therefore, it enables a faster intervention in case of a necessity of an antibiotic therapy introduction in pregnant women whose GBS status is unknown at the time of delivery.

Performance of BD MAX Group B Streptococcus (GBS) Assay without Enrichment for the Detection of GBS

Group B streptococcus (GBS) is an important pathogen causing neonatal early-onset disease. We evaluated the diagnostic performance of BD Max GBS assay (Becton Dickinson, Franklin Lakes, NJ, USA) without enrichment (direct BDM) for detecting GBS using vaginal and rectal specimens in comparison with culture. In total, 716 specimens collected from 358 pregnant women between June 2018 and May 2020 were included in this study. Bacterial culture was performed using ChromID Strep B agar (bioMérieux, Marcy-l’Étoile, France), and species identification results were confirmed using the VITEK-MS system (bioMérieux). The sensitivity of direct BDM for vaginal and rectal specimens was 75.0% and 100%, respectively. Thirteen specimens showed discrepant results: 10 false-negative results in the vaginal specimens and three false-positive results in the rectal specimens. The overall agreement between direct BDM and culture was 98.9% (354/358). The final sensitivity and specificity of direct BDM were 98.5% and 99.0%, respectively. Discrepant results—one false-negative and three false-positives—were obtained for four specimens. Direct BDM shows a good diagnostic performance and will be useful for GBS screening within a few hours.

Application of the appropriate molecular biology-based method significantly increases the sensitivity of group B streptococcus detection results

BACKGROUND

Streptococcus agalactiae (group B streptococcus: GBS) is a leading cause of early- and late-onset diseases in neonates. Reliable results of GBS carriage investigation among pregnant women may decrease the incidence of neonatal infection and mortality.

AIM

To compare the results of conventional culture investigation with those of the US Food and Drug Administration-approved nucleic acid amplification test (BD Max GBS (Becton Dickinson)), and to establish our own protocols of standard polymerase chain reaction (PCR).

METHODS

A total of 250 vaginal-rectal swabs from three different hospitals in Bydgoszcz, Poland, were used to evaluate GBS carriage. Standard laboratory technique (overnight culture in broth enrichment media) results were compared with those of BD Max GBS assay (Becton Dickinson) and two standard PCR protocols, established to detect the cfb and 16S rRNA S. agalactiae genes, from the overnight cultures of the samples in the liquid enrichment media.

FINDINGS

The overall GBS carriage was estimated as 16.4-23.2%, depending on the applied detection method. The highest percentage of positive results, from each lab-oratory was obtained with the application of BD Max GBS assay. The differences in the number of positive results obtained with this particular method were statistically significant. Overall, 27 discrepancies were noted for the results obtained with the application of the methods compared.

CONCLUSIONS

The methods applied for GBS detection differ in sensitivity. A culture technique, though very specific, appears to be less sensitive at detecting S. agalactiae compared with the commercially available BD Max GBS assay or in-house PCR protocols established for this purpose.

A comparison of GenomEra® GBS PCR and GeneXpert ® GBS PCR assays with culture of GBS performed with and without broth pre-enrichment

This study was designed to compare the performance of GeneXpert® and GenomEra® group B streptococcus (GBS) PCR assays, held up against standard culture of GBS performed with and without broth pre-enrichment. In Denmark, the strategy for preventing early onset GBS infection (EOGBS) is risk factor based. Three hundred and sixty six women fulfilling one or more of the criteria for presence of risk factors for EOGBS were prospectively included. Rectovaginal swab samples were taken intrapartum and tested bed-site by the GenomEra® and the GeneXpert® GBS PCR assays and cultured at the microbiology laboratory using Granada agar plates with and without prior growth of sampling material in selective enrichment broth. Among 366 participants tested intrapartum, 99 were GBS-positive by culture, 95 by GenomEra, and 95 by GeneXpert. Compared with culture, the GenomEra and the GeneXpert performed with a sensitivity of 91.8% and 91.7% and a specificity of 98.1% and 97.3%, respectively. A combined reference standard was established by defining true positives as either culture-positive samples or culture-negative samples where both the GeneXpert and the GenomEra GBS PCR assays were positive. Using this, the sensitivity increased to 92.2% and the specificity to 99.6% for GenomEra and to 92.0% and 96.8% for GeneXpert. The use of selective broth enrichment found only three additional GBS culture-positive samples. The performance of the two PCR methods examined was very similar and close to the findings by culture, and both PCR assays are thus applicable as rapid intrapartum bed-site tests.