Rapid detection of Group B streptococcus directly from vaginal-rectal specimens using liquid swabs and the BD Max GBS assay

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.

PhenoMATRIX™ for the screening of Group B Streptococcus (GBS) carriage in pregnant women: ready to get rid of the LIM broth?

There is a constant need to reduce turn-around times and keep costs as low as possible for the carriage screening of GBS in pregnant patients. Laboratory automation might provide an edge in this field. The objectives of the present study were: i) to compare the performance of the direct chromID™ Strepto B agar (CA) plating against LIM-broth enriched plating on CA for the detection of GBS from vagino-rectal screening-swabs; and ii) to assess the usage of PhenoMATRIX™ for the automated screening of GBS. Between January 2021 and December 2023, 9'107 vagino-rectal specimens were collected from pregnant women at Geneva University Hospitals and were used to address the first objective. There was a small difference in the GBS detection rates between direct CA plating (13.2%; 1'202/9'107) and LIM-broth enriched plating on CA (13.2%; 1'198/9'107). Based on the LIM-broth enrichment results, the sensitivity and specificity of the direct CA plating were 98.3% (95% CI, 97.3%-98.9%) and 99.7% (95% CI, 99.5%-99.8%), respectively. Importantly, for 25 specimens, GBS growth was only detected by direct CA plating. We used a random set of 8'768 CA plate pictures for the machine learning of PhenoMATRIX™. The validation was carried out on an additional set of 830 CA plate pictures. The sensitivity and specificity of PhenoMATRIX™ were 100% (95% CI, 96.6%-100.0%) and 90.2% (95% CI, 87.8%-92.1%), respectively. We established that for GBS screening, the performance of direct CA plating is not inferior to the LIM-broth enriched approach. By relying on PhenoMATRIX™, the negative predictive value for GBS screening reaches 100% (95% CI, 99.4%-100.0%), enabling the automatic release of GBS-negative cases within 24 h.

Neonatal bacteraemia in Ireland: A ten-year single-institution retrospective review

Neonatal sepsis is a catastrophic condition of global concern, with reported mortality rates exceeding 10%. Bloodstream infections are an important cause of sepsis, and epidemiological studies of these infections are crucial for predicting the most common aetiological agents and antimicrobial susceptibility patterns and for developing antimicrobial guidelines. For the ten-year study period from July 2013 to June 2023, all neonatal bacteraemia cases were reviewed prospectively using an enhanced surveillance protocol. The patients were stratified according to their age at the time of blood culture collection: early onset if diagnosed in the first 72 hours of life, and late onset if diagnosed after that time. During the study period, 170 blood cultures were positive from 144 patients, of which 89 specimens from 64 patients represented the growth of significant pathogens. Coagulase-negative staphylococci (CoNS) were the most common pathogens identified (52%, 33/64), followed by Escherichia coli (14%, 9/64), Group B Streptococcus (GBS: 11%, 7/64) and Staphylococcus aureus (11%, 7/64). GBS was more commonly identified in early onset patients, while CoNS were predominantly associated with late onset. The presence of an intravascular catheter, maternal urinary tract infections and the receipt of total parenteral nutrition or transfused blood were identified as significant risk factors. The fatality rate was 8% (5/64). in summary, this study provides a detailed overview of the epidemiology of neonatal bacteraemia in a large teaching hospital in the Midwest of Ireland over a decade.

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.

False-positive detection of Group B Streptococcus (GBS) in chromogenic media (Strep B Carrot Broth) due to presence of Enterococcus faecalis in High Vaginal swabs

Introduction. Vaginal colonization of Group B Streptococcus (GBS) is associated with preterm births and neonatal sepsis. Thus routine screening of GBS in prenatal care is recommended.Hypothesis. Chromogenic media (carrot broth) aids in specific and rapid detection of GBS.Aim. To investigate the efficiency of Strep B Carrot Broth for detection of GBS in high vaginal swabs from pregnant women.Methods. In this study 201 vaginal swab samples were collected from pregnant women. Swabs were inoculated in chromogenic media (Strep B Carrot Broth). The positive and negative cultures were inoculated on blood agar and crome agar plates. The colonies were subjected to 16S rRNA sequencing and gene-specific PCR for confirmation. The Christie Atkins Munch Peterson (CAMP) and bile esculin agar (BEA) tests were used for biochemical confirmation. PCR was performed on genomic DNA isolated from uncultured vaginal swabs.Results. It was found that 20/201 (9.9 %) vaginal swab samples were positive in the Strep B Carrot Broth and 17/20 (85 %) and 19/20 (95 %) of these samples yielded colonies on blood agar and crome agar, respectively. Of the 181 carrot broth-negative samples, 1 (0.5 %) and 38 (20.9 %) yielded colonies on blood agar and crome agar plates, respectively. However, 16 s rRNA sequencing revealed that none of the 20 carrot broth-positive cultures were GBS and had sequence similarities to Enterococcus faecalis. This was also confirmed by using gene-specific PCR and BEA positivity. Furthermore, E. faecalis was detected by PCR in DNA isolated from 57 uncultured vaginal swabs samples, GBS could only be detected by PCR in four samples.Conclusion. Carrot broth-based culture can lead to false-positive detection due to the presence of E. faecalis. Thus GBS-positive results in carrot broth must be confirmed by the other molecular and biochemical tests before making a final diagnosis.

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.

Diagnostic Performance of Various Methodologies for Group B Streptococcus Screening in Pregnant Woman in China

Maternal vaginal/rectal colonization of group B streptococcus (GBS) is a main risk for neonatal invasive infection. Efficient determination of GBS colonization in pregnant women is crucial. This study aimed to investigate the prevalence of GBS carriage and evaluate the diagnostic performance of six methodologies for GBS screening conducted in China, including blood agar plate, liquid chromogenic medium, and loop-mediated isothermal amplification (LAMP) without pre-enrichment, chromogenic agar plate with pre-enrichment, and GBS antigen detection without and with pre-enrichment in comparison with the standard reference method (Lim broth-enriched subculture with plating on 5% sheep blood agar). Vaginal/rectal swabs were collected from 1,281 pregnant women at 35–37 weeks of gestation. Of them, 309 were taken in triplicate, one for Lim broth-enriched subculture, one for blood agar plate, and the third for GBS antigen detection (Reagent W); 177 were acquired in duplicate, one for Lim broth-enriched subculture and the other for GBS antigen detection (Reagent H); 502 were obtained in duplicate, one for Lim broth-enriched subculture and the other for liquid chromogenic medium; 158 were collected in duplicate, one for Lim broth-enriched subculture and the other for LAMP; and 135 were inoculated in Lim broth-enriched for GBS antigen detection (Reagent W) and subculture with chromogenic agar plate and 5% blood agar plate. The overall prevalence of GBS carriage was 10.1% (130/1,281, 95% CI: 8.5–12.1%) according to the standard reference method. Compared with the standard reference method, the LAMP had excellent performance of sensitivity (100%, 95%CI: 83.4–100%), specificity (94%, 95%CI: 88.1–97.1%), and Yoden index (0.940); as well as the blood agar plate with sensitivity (81.5%, 95%CI: 61.3–93.0%), specificity (100%, 95%CI: 98.3–100.0%), and Yoden index (0.815). The other four methods were not sufficient to reach the threshold in terms of sensitivity or specificity compared to the standard reference method. Furthermore, for LAMP, results can be obtained within 0.5–1 h, while for blood agar plate, which needed 24–48 h, and further identification was required. Our data suggested that the performance of LAMP was highly comparable to the standard Lim broth-enriched subculture and LAMP is considered as an alternative for fast and accurate GBS screening.

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.

Increasing Cytomegalovirus Detection Rate from Respiratory Tract Specimens by a New Laboratory-Developed Automated Molecular Diagnostic Test

Lots of automated molecular methods for detecting cytomegalovirus (CMV) DNA in the blood are available, but seldom for various clinical specimens. This study was designed to establish a highly sensitive automated assay to detect CMV DNA in non-blood specimens. We designed a new QMT assay using QIAGEN artus CMV RG polymerase chain reaction (Q-CMV PCR) kit applied on the BD MAX system and compared with the other assays, including an RGQ assay (LabTurbo auto-extraction combined Q-CMV PCR kit on Rotor-Gene-Q instrument), and in-house PCR assay. A total of 1067 various clinical samples, including 426 plasma, 293 respiratory tract specimens (RTS), 127 stool, 101 cerebral spinal fluid, 90 vitreous humours were analysed. Examining CMV DNA in simultaneous specimens of the same immunocompromised patient with respiratory symptoms, the detection rate of RTS (93.6%, 88/94) was significant higher than plasma (65.9%, 62/94). The positive rates for plasma samples with a low CMV viral load (<137 IU/mL) and diagnostic sensitivity of QMT, RGQ, and in-house assays were 65% and 99.1%, 45% and 100%, 5% and 65.5%, respectively. The QMT assay performs better, with shorter operational and turnaround time than the other assays, enabling the effective and early detection of CMV infection in various clinical specimens, particularly for RTS.

Emerging serotype III sequence type 17 group B streptococcus invasive infection in infants: the clinical characteristics and impacts on outcomes

BACKGROUND

Group B Streptococcus (GBS) is an important pathogen that causes high mortality and morbidity in young infants. However, data on clinical manifestations between different GBS serotypes and correlation with molecular epidemiology are largely incomplete. The aim of this study was to determine the serotype distribution, antimicrobial resistance, clinical features and molecular characteristics of invasive GBS isolates recovered from Taiwanese infants.

METHODS

From 2003 to 2017, 182 non-duplicate GBS isolates that caused invasive disease in infants less than one year of age underwent serotyping, multilocus sequence typing (MLST) and antibiotic susceptibility testing. The clinical features of these infants with GBS disease were also reviewed.

RESULTS

Of the 182 patients with invasive GBS disease, 41 (22.5%) were early-onset disease, 121 (66.5%) were late-onset disease and 20 (11.0%) were late late-onset disease (> 90 days of age). All these patients were treated with effective antibiotics on time. Among them, 51 (28.0%) had meningitis, 29 (16.0%) had neurological complications, 12 (6.6%) died during hospitalization, and 15 (8.8%) out of 170 patients who survived had long-term neurological sequelae at discharge. Serotype III GBS strains accounted for 64.8%, followed by serotype Ia (18.1%) and Ib (8.2%). MLST analysis revealed 11 different sequence types among the 182 isolates and ST-17 was the most dominant sequence type (56.6%). The correlation between serotype III and ST17 was evident, as ST17 accounted for 87.3% of all serotype III isolates. There was an obvious increasing trend of type III/ST-17 GBS that caused invasive disease in infants. All isolates were susceptible to penicillin, cefotaxime, and vancomycin, while 68.1 and 65.9% were resistant to erythromycin and clindamycin, respectively.

CONCLUSIONS

Despite timely and appropriate antibiotic treatment, a significant proportion of invasive GBS disease still inevitably causes adverse outcomes. Further study to explore preventive strategies and development of serotype-based vaccines will be necessary in the future.

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

Objective

To compare the diagnostic performance of BD MAX and GenomEra PCR assays for a rapid PCR detection of vaginal carriage of group B streptococci at delivery.

Methods

This is a retrospective laboratory analysis of vaginal swab samples taken intrapartum from a randomly selected cohort of pregnant women giving birth at a single childbirth and maternity unit.

Results

Ninety-one culture-positive and 279 culture-negative vaginal samples were included from a cohort of 902 women. One-hundred-and-two specimens were found positive with the BD MAX and 84 with the GenomEra PCR assay. No statistically significant difference was observed compared to culture, sensitivity of BD MAX 84.6% (77/91) [95%CI 75.5–91.3] and of GenomEra 71.4% (65/91) [95%CI 61.0–80.4]. When compared to a combined reference standard, no statistically significant differences were seen between culture, BD MAX and GenomEra PCR assays. The sensitivities were 82.7% (91/110) [95%CI 74.3–89.3], 87.3% (96/110) [95%CI 79.6–92.9], and 79.1% (87/110) [95%CI 70.3–86.3], respectively.

Conclusion

Both PCR assays performed comparably to culture of the intrapartum vaginal samples. In particular, the GenomEra assay is potentially an easy and rapid on-site PCR test for intrapartum detection of vaginal carriage of group B streptococci at a maternity ward to identify women who should receive intrapartum antibiotic prophylaxis.

Detection and genomic analysis of genital group B streptococcus in pregnant Korean women

AIM

Group B streptococcus (GBS) is a leading cause of life-threatening bacterial infections among newborns, and neonates born to heavily colonized women may be subject to vertical transmission. We sought to determine an appropriate detection method for genital GBS in pregnant women by comparing culture-based methods and real-time polymerase chain reaction (PCR). In addition, we performed molecular serotyping and multilocus sequence typing (MLST) on isolates.

METHODS

A total of 150 pregnant women were enrolled and underwent vaginal-rectal swabbing at 16-40 weeks of gestation. GBS was identified by conventional culture and real-time PCR with or without enrichment. Molecular serotyping and MLST were performed on isolates.

RESULTS

Overall genital GBS positive rate among the 150 study subjects was 17.3%. Direct culture identified 18 (12.0%) positive specimens, enrichment culture 22 (14.6%), direct PCR 24 (16.0%) and enrichment PCR 25 (16.6%). The sensitivity and specificity by direct and enrichment PCR were as follows: for direct PCR, 90.9% and 96.9%, respectively; and for enrichment PCR, 95.5% and 96.9%, respectively. Resistance rates to clindamycin and erythromycin were 33.3% and 19.1%, respectively. Serotype III-1 was the most common (26.3%), followed by serotype Ib (21.1%), III-3 (15.8%), V (15.8%), II (10.5%), IV (5.3%) and VI (5.3%). Most common sequence types (ST) were ST-1, ST-19 and ST-862 (15.8%), followed by ST-2 and ST-654 (10.5%).

CONCLUSION

Direct real-time PCR using vaginal-rectal specimen could be used for detecting GBS in emergent conditions. Molecular serotypes III, Ib and V were most common. MLST analysis frequently presented ST-1, ST-19 and ST-862.