Comparison of qPCR and culture methods for group B Streptococcus colonization detection in pregnant women: evaluation of a new qPCR assay

An improved procedure based on fluorescence immunochromatography for rapid detection of group B streptococcus from enrichment cultures

BACKGROUND

Group B streptococcus (GBS) is a major cause of perinatal infectious morbidity and mortality. Although intrapartum antibiotic prophylaxis (IAP) administration for ≥ 4 h is effective in preventing neonatal early-onset GBS diseases, the conventional culture-based approach to identify GBS often takes 24-72 h. This study aimed to find a strategy to improve the efficacy of GBS screening.

METHODS

We developed a fluorescence immunochromatographic test (FICT) strip to detect GBS within 15 min. The detection limit, analytical sensitivity, cross-reactivity and performance of the strip were evaluated. The performance of the strip on vaginal-rectal swabs with or without enrichment culture was compared with real-time quantitative polymerase chain reaction (qPCR) and colloidal gold immunochromatography (GIC) assay with conventional enrichment culture method as the reference method.

RESULTS

The detection limit of the strip ranges from 104 CFU/mL to 106 CFU/mL. Additionally, the strip has detected all of the positives from 48 h enrichment cultures (175/175). and 30 GBS strains representing different serotypes at cell density of 106 CFU/mL yielded positive results. Cross-reactivity test indicated no false-positive results. The sensitivity on direct samples was 34.48%, while 4 h enrichment in LIM broth prior to FICT has greatly increased the sensitivity to 90.91% with the specificity being 95.35%.

CONCLUSIONS

The improved procedure based on the FICT for GBS detection from short-term LIM broth cultures was expected to guide IAP administration in obstetrical emergencies.

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.

Comparison of qPCR and chromogenic culture methods for rapid detection of group B streptococcus colonization in Vietnamese pregnant women

Introduction

Neonatal infections can rapidly become severe, with delays in treatment often proving fatal. Streptococcus agalactiae (Group B Streptococcus, GBS) is a common cause, typically transmitted from colonized pregnant women to neonates during childbirth. In Vietnam, routine prenatal care lacks standardized GBS screening protocols. This study aims to compare enhanced qPCR methods with the culture method, evaluate the diagnostic accuracy of these qPCR procedures, and assess the frequency of GBS infection in pregnant Vietnamese women during their final trimester.

Materials and methods

Pregnant women aged 35 weeks gestation or more were recruited. Rectovaginal swabs were collected and analyzed for GBS using chromogenic culture, a commercial real-time PCR kit, and in-house real-time PCR assays targeting the cfb and sip genes. Clinical diagnostic values were calculated, and GBS prevalence was determined.

Results

The study included 259 pregnant women with a mean age of 30.2 ± 5.0 years. Of these, 96.6 % had gestational ages of 37 weeks or more at delivery. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the cfb-based and sip-based qPCR assays were 94.1/92.7, 99.0/99.5, 97.1/98.5, 97.8/97.3, and 97.6 %, respectively. The Kappa values were excellent (0.940 and 0.939), with results available in under 2 h. GBS prevalence was 24.7 % and 25.5 % by cfb-based and sip-based qPCR assays, aligning with the culture method (25.5 %).

Conclusions

Both direct real-time PCR assays demonstrated high accuracy and were comparable to chromogenic culture in diagnosing GBS. A significant prevalence of GBS colonization was found among Vietnamese pregnant women in their final trimester.

Development and performance evaluation of a qPCR-based assay for the fully automated detection of group B Streptococcus (GBS) on the Panther Fusion Open Access system

Streptococcus agalactiae [group B Streptococcus (GBS)] poses a major threat as the primary cause of early-onset neonatal invasive disease, particularly when mothers are colonized rectovaginally. Although culture remains the gold standard for antepartum GBS screening, quantitative polymerase chain reaction (qPCR) offers advantages in terms of sensitivity and turnaround time. The aim of this study was to validate the clinical utility of an automated qPCR laboratory-developed test (LDT) for antepartum GBS screening using the Panther Fusion Open Access system (Hologic, California, USA). The LDT targeted a conserved region of the GBS surface immunogenic protein gene, demonstrating no cross-reactivity and high coverage (99.82%-99.99%). The limit of detection (LoD) was 118 CFU/mL. Comparison with commercial qPCR assays (Panther Fusion GBS and VIASURE Streptococcus B Real-Time) revealed an overall agreement of 99.7%, with a robust Cohen's kappa coefficient of 0.992. Testing of 285 rectovaginal swabs from pregnant women and 15 external quality assessment samples demonstrated exceptional diagnostic performance of the LDT, achieving a diagnostic sensitivity and specificity of 100%, underscoring its accuracy. Prevalence and predictive values were also determined to reinforce test reliability. Our research highlights the limitations of culture-based screening and supports the suitability of our qPCR-based LDT for GBS detection in a clinical setting.IMPORTANCERectovaginal colonization by GBS is a major risk factor for early-onset invasive neonatal disease. The most effective approach to reducing the incidence of early-onset disease (EOD) has been described as universal screening, involving assessment of GBS colonization status in late pregnancy and intrapartum antibiotic prophylaxis. Despite its turnaround time and sensitivity limitations, culture remains the gold standard method for GBS screening. However, nucleic acid amplification-based tests, such as qPCR, have been utilized due to their speed and high sensitivity and specificity. This study validated the clinical usefulness of an automated qPCR-LDT for antepartum GBS screening through the Panther Fusion Open Access system (Hologic). Our study addresses the critical need for more robust, sensitive, and rapid strategies for GBS screening in pregnant women that could favorably impact the incidence of EOD.

Adherence to universal screening for group B Streptococcus in pregnancy and prevalence of colonised pregnancies in Caserta province, Italy

Group B Streptococcus (Streptococcus agalactiae; GBS) infection is a significant contributor to neonatal morbidity and mortality. In the early 1970s, the neonatal mortality rate for infants with invasive GBS disease was 55%. With the adoption of the first medical community guidelines to prevent GBS infection in the 1990s, the mortality rate decreased to approximately 5%. The main obstetric procedure for preventing vertical transmission of GBS infection involves universal screening of pregnant women using a vaginal-rectal swab (VRS) to identify those eligible for intrapartum antibiotic prophylaxis (IAP). The study analyzes the adherence of screening and the trend of GBS infection in pregnancy in the province of Caserta, Italy. Data were obtained from pregnant women who gave birth in a first level birthing center in 2022 from birth assistance certificate (CEDAP), obstetric and neonatal record. Postnatal evaluation collected through computer-assisted telephone interviews. 567 women delivered at our center during the study period. The average coverage of GBS testing in pregnancy was 99.2% (562), and the proportion of GBS colonised women was 12.6% (71) according with the national average, which is about 10-20%. The spread of positive cases appears to fluctuate among the various groups of pregnant women studied, indicating no significant statistical variance among presence of a partner, among women who have given birth multiple times, among Italian nationals, or across different ages, but a significant statistical excess is evident among mothers with less education. In 93% (66) of GBS carrier mothers, intrapartum antibiotic prophylaxis (IAP) was administered correctly, regardless of the type of delivery performed. Despite the successful integration of GBS screening, a significant gap remains between the ideal scenario and the actual implementation of IAP. At the three-month assessment, no child required hospitalization, consistent with the relatively low incidence of invasive GBS infection. Nevertheless, for those who are not eligible to VRS screening, such as preterm birth, or IAP, as in precipitous birth, the identification of biomarkers enabling early recognition of invasive GBS disease remains essential. Additionally, the emergence of vaccines administered during gestation, conferring passive immunity to newborns represents a promising possible new direction. Therefore, to ensure the practical application of GBS screening and actual IAP by healthcare providers, periodic audits and regular monitoring should be encouraged.

Establishment and application of a rapid molecular diagnostic platform for the isothermal visual amplification of group B Streptococcus based on recombinase polymerase

With growing concerns about Group B streptococcal (GBS) infections and their adverse effects on perinatal pregnancies, including infection, premature delivery, neonatal septicemia, and meningitis, it is urgent to promote GBS screening at all pregnancy stages. The purpose of this study is to establish a device-independent, fast, sensitive, and visual GBS detection method. Taking advantage of the characteristics of the recombinase polymerase isothermal amplification (RPA), the activity of the nfo nuclease cleavage base analog (tetrahydrofuran, THF) site, and the advantages of visual reading of the lateral flow chromatography strip (LFS), a GBS detection method was developed. This method focused on the conservative region of the Christie-Atkins-Munch-Petersen factor encoded by the cfb gene, a virulence gene specific to GBS. Two forward primers, two biotin-labeled reverse primers, and one fluorescein isothiocyanate (FITC)-labeled and C3spacer-blocked probe were designed. The study involved optimizing the primer pair and probe combination, determining the optimal reaction temperature and time, evaluating specificity, analyzing detection limits, and testing the method on 87 vaginal swabs from perinatal pregnant women. The results showed that the visual detection method of GBS-RPA-LFS, using the cfb-F1/R2/P1 primer probe, could detect GBS within 15 min at the temperature ranging from 39°C to 42°C. Furthermore, the method specifically amplified only GBS, without cross-reacting with pathogens like Lactobacillus iners, Lactobacillus crispatus, Candida albicans, Listeria monocytogenes, Yersinia enterocolitica, Klebsiella Pneumoniae, Enterobacter cloacae, Citrobacter freundii, Vibrio alginolyticus, Vibrio parahaemolyticus, Salmonella typhimurium, Staphylococcus aureus, Pseudomonas aeruginosa, or Trichomonas vaginalis. It could detect a minimum of 100 copies per reaction. In clinical 98 samples of vaginal swabs from pregnant women, the agreement rate between the GBS-RPA-LFS method and TaqMan real-time fluorescence quantification method was 95.92%. In conclusion, this study successfully established a combined RPA and LFS GBS in situ detection platform, with short reaction time, high sensitivity, high specificity, portability, and device independence, providing a feasible strategy for clinical GBS screening.

A small-scale external quality assessment for PCR detection of group B streptococcus in China

BACKGROUND

Group B streptococcus (GBS) is considered a leading cause of maternal and infant morbidity and mortality. Molecular diagnosis is a routinely used approach for GBS screening to protect pregnant women and prevent early-onset GBS neonatal disease. The objective of this study was to identify issues and guarantee the dependability of GBS molecular diagnosis by an external quality assessment (EQA) scheme.

METHODS

The EQA panel comprised eight samples spiked with 10-fold dilutions of GBS suspension (20-2,000,000 copies/mL), and 2 negative control samples. The panels were coded randomly and distributed to participating laboratories for GBS detection.

RESULTS

In total, 44 participating laboratories submitted results with eight commercial GBS PCR assays and one in-house assay. Among them, 36 obtained an acceptable or higher performance score, while 8 required improvement. Among the 440 results returned, 62 (14.1 %) were incorrect, including 5 false positives and 57 false negatives.

CONCLUSIONS

Our small-scale EQA showed that most participating laboratories have reliable diagnostic capacities for GBS PCR detection. Nonetheless, further improvements in the detection performance of some laboratories are required, particularly with low-concentration samples. Our survey also reinforces the use of EQA as an essential tool to evaluate the overall proficiency of clinical laboratories.

Quantitative real-time PCR and magnetic separation strategy for specific detection of group B streptococcus in perinatal Women's urine

Introduction

Group B streptococcus(GBS)often causes adverse outcomes such as urinary system infection, intrauterine infection, premature birth, and stillbirth in perinatal women. Perinatal screening of GBS is conducive to guiding clinical scientific intervention and improving delivery outcomes.This study quantitative real-time PCR (RT-qPCR) combined with magnetic separation was used for GBS detection.

Materials and methods

Sample pre-treatment in this study involved the utilization of magnetic separation (MS) technology, aiming to expedite the detection process and enhance detection sensitivity, and the cfb gene of group B streptococcus was used as the target gene to establish quantitative real-time PCR (RT-qPCR) to detect group B streptococcus.

Results

It was found that penicillin-functionalized magnetic beads had a good ability to enrich and capture group B Streptococcus.The findings revealed an exceptional detection sensitivity, with the ability to detect B streptococcus in urine samples at levels as low as 102 CFU/mL.

Conclusions

The utilization of MS technology in conjunction with the RT-qPCR (MS-RT-qPCR) assay, as demonstrated in this study, offers a viable approach for prenatal screening of group B streptococcus among perinatal women.

Group B streptococcal prevalence in internal organs and placentas of deceased neonates and stillbirths in South Asia

OBJECTIVE

Group B streptococcus (GBS) has been associated with adverse pregnancy outcomes, but few prospective studies have assessed its prevalence in low- and middle-income country settings. We sought to evaluate the prevalence of GBS by polymerase chain reaction (PCR) in internal organ tissues and placentas of deceased neonates and stillbirths.

DESIGN

This was a prospective, observational study.

SETTING

The study was conducted in hospitals in India and Pakistan.

POPULATION

Pregnant women with stillbirths or preterm births were recruited at delivery, as was a group of women with term, live births, to serve as a control group.

METHODS

A rectovaginal culture was collected from the women in Pakistan to assess GBS carriage. Using PCR, we evaluated GBS in various tissues of stillbirths and deceased neonates and their placentas, as well as the placentas of live-born preterm and term control infants.

MAIN OUTCOME MEASURES

GBS identified by PCR in various tissues and the placentas; rate of stillbirths and 28-day neonatal deaths.

RESULTS

The most obvious finding from this series of analyses from India and Pakistan was that no matter the country, the condition of the subject, the tissue studied or the methodology used, the prevalence of GBS was low, generally ranging between 3% and 6%. Among the risk factors evaluated, only GBS positivity in primigravidae was increased.

CONCLUSIONS

GBS diagnosed by PCR was identified in <6% of internal organs of stillbirths and neonatal deaths, and their placentas, and control groups in South Asian sites. This is consistent with other reports from South Asia and is lower than the reported GBS rates from the USA, Europe and Africa.

Determinants of Gastrointestinal Group B Streptococcus Carriage in Adults

Background

Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal Gram-positive bacterium found in the human gastrointestinal and urogenital tracts. Much of what is known about GBS relates to the diseases it causes in pregnant people and neonates. However, GBS is a common cause of disease in the general population with 90% of GBS mortality occurring in non-pregnant people. There are limited data about the predisposing factors for GBS and the reservoirs in the body. To gain an understanding of the determinants of gastrointestinal GBS carriage, we used stool samples and associated metadata to determine the prevalence and abundance of GBS in the gut microbiome of adults and find risk factors for GBS status.

Methods

We used 754 stool samples collected from adults in Wisconsin from 2016-2017 to test for the prevalence and abundance of GBS using a Taqman probe-based qPCR assay targeting two GBS-specific genes: cfp and sip. We compared the microbiome compositions of the stool samples by GBS status using 16S rRNA analysis. We compared associations with GBS status and 557 survey variables collected during sample acquisition (demographics, diet, overall health, and reproductive health) using univariate and multivariate analyses.

Results

We found 137/754 (18%) of participants had detectable GBS in their stool samples with a median abundance of 104 copies per nanogram of starting DNA. There was no difference in GBS status or abundance based on gender. Beta-diversity, Bray-Curtis and Unweighted UniFrac, was significantly different based on carrier status of the participant. Prior to p-value correction, 59/557 (10.6%) survey variables were significantly associated with GBS carrier status and 11/547 (2.0%) variables were significantly associated with abundance (p-value<0.05). After p-value correction, 2/547 (0.4%) variables were associated with GBS abundance: an increased abundance of GBS was associated with a decreased frequency since last dental checkup (p<0.001) and last dental cleaning (p<0.001). Increased GBS abundance was significantly associated with increased frequency of iron consumption (p=0.007) after p-value correction in multivariate models.

Conclusions

GBS is found in stool samples from adults in Wisconsin at similar frequencies as pregnant individuals screened with rectovaginal swabs. We did not find associations between risk factors historically associated with GBS in pregnant people, suggesting that risk factors for GBS carriage in pregnancy may differ from those in the general population. We found that frequency of iron consumption and dental hygiene are risk factors for GBS carriage in Wisconsin adults. Given that these variables were not assayed in previous GBS surveys, it is possible they also influence carriage in pregnant people. Taken together, this work serves as a foundation for future work in developing approaches to decrease GBS abundance in carriers.

Analysis of molecular characteristics of CAMP-negative Streptococcus agalactiae strains

Background

Streptococcus agalactiae can produce CAMP factor, which can promote the β-hemolysin activity of Staphylococcus aureus, forming an arrow-shaped hemolysis enhancement zone at the intersection of the two bacterial species on a blood agar plate. This characteristic feature of Streptococcus agalactiae has led to the widespread use of the CAMP test as an identification method.

Methods

Vaginal/rectal swabs, collected from women at 35-37  weeks of pregnancy, were first inoculated into a selective enrichment broth media, then subcultured onto GBS chromogenic agar and 5% sheep blood agar sequentially. The VITEK-2 automatic identification system and MALDI-TOF MS were initially employed for identification, followed by the CAMP test. CAMP-negative strains underwent 16S rDNA and cfb gene sequence analysis, as well as bacterial multilocus sequence typing.

Results

A total of 190 strains were isolated, with 15 identified as CAMP-negative. Further 16S rDNA gene sequence analysis confirmed that all 15 strains were Streptococcus agalactiae. The MLST typing assay revealed that these 15 strains were of the ST862 type. The cfb gene was amplified and electrophoresed, but no specific fragments were found, indicating that these strains lack the CAMP factor due to cfb gene deletion. Antibiotic susceptibility tests demonstrated no resistance to penicillin, ampicillin, vancomycin and linezolid among the GBS strains. However, there are significant differences in resistance rates to tetracycline.

Conclusion

This study found that 7.9% of GBS strains isolated from the vagina/rectum of pregnant women were CAMP-negative, suggesting that the CAMP test method or primers targeting the cfb gene should not be used as the sole presumptive test for GBS identification.

Do NAAT-Based Methods Increase the Diagnostic Sensitivity of Streptococcus agalactiae Carriage Detection in Pregnant Women?

The aim of the study was to evaluate particular polymerase chain reaction primers targeting selected representative genes and the influence of a preincubation step in a selective broth on the sensitivity of group B Streptococcus (GBS) detection by nucleic acid amplification techniques (NAAT). Research samples were vaginal and rectal swabs collected in duplicate from 97 pregnant women. They were used for enrichment broth culture-based diagnostics, bacterial DNA isolation, and amplification, using primers based on species-specific 16S rRNA, atr and cfb genes. To assess the sensitivity of GBS detection, additional isolation of samples preincubated in Todd-Hewitt broth with colistin and nalidixic acid was performed and then subjected to amplification again. The introduction of the preincubation step increased the sensitivity of GBS detection by about 33-63%. Moreover, NAAT made it possible to identify GBS DNA in an additional six samples that were negative in culture. The highest number of true positive results compared to the culture was obtained with the atr gene primers, as compared to cfb and 16S rRNA primers. Isolation of bacterial DNA after preincubation in enrichment broth significantly increases the sensitivity of NAAT-based methods applied for the detection of GBS from vaginal and rectal swabs. In the case of the cfb gene, the use of an additional gene to ensure the appropriate results should be considered.

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.

Adherence to screening and management guidelines of maternal Group B Streptococcus colonization in pregnancy

Aims

To investigate Group B Streptococcus (GBS) colonization in pregnancy; adherence to antenatal GBS screening and adherence to the intrapartum antibiotics protocol within two models of care (midwifery and non‐midwifery led).

Design

This retrospective quantitative study has employed a descriptive design using administrative health data.

Methods

Data from five maternity hospitals in metropolitan and regional Western Australia that included 22,417 pregnant women who gave birth between 2015 and 2019 were examined, applying descriptive statistics using secondary data analysis.

Results

The study revealed an overall GBS colonization rate of 21.7% with similar rates in the different cohorts. A lower adherence to screening was found in the midwifery led model of care (MMC, 68.76%, n = 7232) when compared with the non‐midwifery led model of care (NMMC, 90.49%, n = 10,767). Over the 5 years, screening rates trended down in the MMC with stable numbers in the counterpart. Adherence in relation to intrapartum antibiotic prophylaxis revealed discrepant findings between the study groups.

Conclusion

Adherence to screening and management guidelines of maternal GBS colonization in pregnancy is lower within the MMC when compared with the NMMC.

Impact

This is the first cohort study to describe the adherence to the recommended Western Australian GBS screening guidelines in the two different models of care. Findings may assist in the guidance and improvement of clinical protocols as well as the planning of clinical care in relation to GBS screening to reduce the risk of neonatal GBS infection.

Assessing standards for prevention of early onset group B streptococcal (GBS) disease in Ireland

BACKGROUND

Early onset group B streptococcal (GBS) disease can cause significant neonatal morbidity and mortality. There is currently no Irish national guideline for GBS screening, and protocols vary across maternity units. Polymerase chain reaction (PCR) testing at induction or labour onset informs triage for antibiotic prophylaxis; however, there are human and infrastructural resource requirements to enable widespread implementation.

AIM

Our aim was to identify current standard practices for GBS prevention in Irish obstetric and neonatal services and to utilise this data to inform the need for, and potential impact of implementation of, a national guideline.

METHODS

A questionnaire on GBS screening, management and existing resources was completed by an informed staff member from each of the 19 Irish maternity units, including questions regarding timing and method of screening, antibiotic usage, and neonatal management.

RESULTS

One unit (5.2%) performs routine GBS screening at 35-37 weeks of gestation. Twelve units (63%) screen for GBS following spontaneous rupture of membranes (SROM) after 37 weeks, of which two (17%) perform PCR and ten (83%) culture testing. Seventeen units (89.3%) have access to a GeneXpert PCR machine, and of these, two (11.7%) use the machine for rapid GBS testing. Two units screen patients for GBS at either the start of labour or induction of labour. Four units (21%) use the neonatal early onset sepsis (EOS) calculator. Sixteen units (84%) do not treat asymptomatic infants born to GBS-positive mothers.  CONCLUSION: There is a lack of consistency in the methods for GBS screening and disease prevention across the country, highlighting the need for a national guideline accompanied by an implementation plan and budget to standardise care.

Molecular detection of respiratory pathogens in community-acquired pneumonia involving adults

BACKGROUND

Community-acquired pneumonia (CAP) causes substantial morbidity and mortality in adults worldwide. The etiology of CAP often remains uncertain, and therapy is empirical. Thus, there is still room for improvement in the diagnosis of pneumonia.

METHODS

Adults aged >20 years who presented at the outpatient or emergency departments of Linkou and Keelung Chang Gung Memorial Hospital with CAP were prospectively included between November 2016 and December 2018. We collected respiratory specimens for culture and molecular testing and calculated the incidence rates of CAP according to pathogens.

RESULTS

Of 212 hospitalized adult patients with CAP, 69.3% were male, and the median age of the patients was 67.8 years. Bacterial pathogens were detected in 106 (50%) patients, viruses in 77 (36.3%), and fungal pathogens in 1 patient (0.5%). The overall detection rate (culture and molecular testing method) was 70.7% (n = 150). Traditional microbial culture yielded positive results in 36.7% (n = 78), molecular testing in 61.3% (n = 130). The most common pathogens were influenza (16.1%), followed by Klebsiella pneumoniae (14.1%), Pseudomonas aeruginosa (13.6%), human rhinovirus (11.8%), and Streptococcus pneumoniae (9.9%). Multiple pathogen co-infections accounted for 28.7% (n = 61), of which co-infection with K. pneumoniae and human rhinovirus comprised the largest proportion.

CONCLUSIONS

Molecular diagnostic testing could detect 23.6% more pathogens than traditional culture techniques. However, despite the current diagnostic tests, there is still the possibility that no pathogen was detected.

Analysis of Susceptibility to the Antimicrobial and Anti-Biofilm Activity of Human Milk Lactoferrin in Clinical Strains of Streptococcus agalactiae With Diverse Capsular and Sequence Types

Group B Streptococcus (GBS) is one of the leading infection-related causes of adverse maternal and neonatal outcomes. This includes chorioamnionitis, which leads to preterm ruptures of membranes and can ultimately result in preterm or stillbirth. Infection can also lead to maternal and neonatal sepsis that may contribute to mortality. Currently, treatment for GBS infection include a bolus of intrapartum antibiotic prophylaxis to mothers testing positive for GBS colonization during late pregnancy. Lactoferrin is an antimicrobial peptide expressed in human breast milk, mucosal epithelia, and secondary granules of neutrophils. We previously demonstrated that lactoferrin possesses antimicrobial and antibiofilm properties against several strains of GBS. This is largely due to the ability of lactoferrin to bind and sequester iron. We expanded upon that study by assessing the effects of purified human breast milk lactoferrin against a panel of phenotypically and genetically diverse isolates of GBS. Of the 25 GBS isolates screened, lactoferrin reduced bacterial growth in 14 and biofilm formation in 21 strains. Stratifying the data, we observed that colonizing strains were more susceptible to the growth inhibition activity of lactoferrin than invasive isolates at lactoferrin concentrations between 250-750 µg/mL. Treatment with 750 µg/mL of lactoferrin resulted in differences in bacterial growth and biofilm formation between discrete sequence types. Differences in bacterial growth were also observed between capsular serotypes 1a and III. Maternally isolated strains were more susceptible to lactoferrin with respect to bacterial growth, but not biofilm formation, compared to neonatal sepsis isolates. Finally, high biofilm forming GBS strains were more impacted by lactoferrin across all isolates tested. Taken together, this study demonstrates that lactoferrin possesses antimicrobial and antibiofilm properties against a wide range of GBS isolates, with maternally isolated colonizing strains being the most susceptible.

Use of Recombinant Endolysin to Improve Accuracy of Group B Streptococcus Tests

Group B Streptococcus (GBS) causes serious neonatal infection via vertical transmission. The prenatal GBS screening test is performed at the late stage of pregnancy to avoid risks of infection. In this test, enrichment culture is performed, followed by GBS identification. Selective medium is used for the enrichment; however, Enterococcus faecalis, which is a potential contaminant in swab samples, can interfere with the growth of GBS. Such bacterial contamination can lead to false-negative results. Endolysin, a bacteriophage-derived enzyme, degrades peptidoglycan in the bacterial cell wall; it is a promising antimicrobial agent for selectively eliminating specific bacterial genera/species. In this study, we used the recombinant endolysin EG-LYS, which is specific to E. faecalis; the endolysin potentially enriched GBS in the selective culture. First, in the false-negative model (coculture of GBS and E. faecalis, which disabled GBS detection in the subsequent GBS identification test), EG-LYS treatment at 0.1 mg/ml improved GBS detection. Next, we used 548 vaginal swabs to test the efficacy of EG-LYS treatment in improving GBS detection. EG-LYS treatment (0.1 mg/ml) increased the GBS-positive ratio to 17.9%, compared to 15.7% in the control (phosphate-buffered saline [PBS] treatment). In addition, there were an increased number of GBS colonies under EG-LYS treatment in some samples. The results were supported by the microbiota analysis of the enriched cultures. In conclusion, EG-LYS treatment of the enrichment culture potentially improves the accuracy of the prenatal GBS screening test. IMPORTANCE Endolysin is a bacteriophage-derived enzyme that degrades the peptidoglycan in the cell wall of host bacteria; it could be used as an antimicrobial agent for selectively eliminating specific bacterial genera/species. Group B Streptococcus (GBS) causes neonatal infection via vertical transmission; prenatal GBS screening test, in which enrichment culture is followed by bacterial identification, is used to detect the presence of GBS in pregnant women. However, the presence of commensal bacteria such as Enterococcus faecalis in clinical specimens can inhibit GBS growth in the selective enrichment culture, resulting in false-negative result. Here, we demonstrated that the application of originally isolated endolysin in the enrichment culture improved the test accuracy by inhibiting unwanted E. faecalis growth and therefore avoiding false-negative results, not only in experimental settings, but also in tests using vaginal swabs.

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.

Visual multiple cross displacement amplification for the rapid identification of S. agalactiae immediately from vaginal and rectal swabs

Streptococcus agalactiae (S. agalactiae) is an important pathogen that can lead to neonatus and mother infection. The current existing techniques for the identification of S. agalactiae are limited by accuracy, speed and high-cost. Therefore, a new multiple cross displacement amplification (MCDA) assay was developed for test of the target pathogen immediately from vaginal and rectal swabs. MCDA primers screening were conducted targeting S. agalactiae pcsB gene, and one set of MCDA primers with better rapidity and efficiency was selected for establishing the S. agalactiae-MCDA assay. As a result, the MCDA method could be completed at a constant temperature of 61 °C, without the requirement of special equipment. The detection limit is 250 fg (31.5 copies) per reaction, all S. agalactiae strains displayed positive results, but not for non-S. agalactiae strains. The visual MCDA assay detected 16 positive samples from 200 clinical specimen, which were also detected positive by enrichment/qPCR. While the CHROMagar culture detected 6 positive samples. Thus, the MCDA assay is prefer to enrichment/qPCR and culture for detecting S. agalactiae from clinical specimen. Particularly, the whole test of MCDA takes about 63.1 min, including sample collection (3 min), DNA preparation (15 min), MCDA reaction (45 min) and result reporting (6 s). In addition, the cost was very economic, with only US$ 4.9. These results indicated that our S. agalaciae-MCDA assay is a rapid, sensitive and cost-efficient technique for target pathogen detection, and is more suitable than conventional assays for an urgent detection, especially for 'on-site' laboratories and resource-constrained settings.

Group B Streptococcus Screening Guidelines in Pregnancy: A Critical Review of Compliance

INTRODUCTION

Colonization with Group B Streptococcus in pregnancy is a major risk factor for neonatal infection. Universal screening for maternal streptococcal colonization and the use of intrapartum antibiotic prophylaxis has resulted in substantial reductions of neonatal early-onset Group B Streptococcus disease. To achieve the best neonatal outcomes, it is imperative for maternity healthcare providers to adhere to screening and management guidelines.

AIM

This literature review uses a systematic approach and aims to provide a synthesis of what is known about compliance with Group B Streptococcus screening protocols in a variety of global settings, including maternity homes, private obstetric practice, and hospital clinical environments.

METHODS

The review was carried out using electronic databases as well as hand-searching of reference lists. Included papers reported primarily on compliance with Group B Streptococcus screening guidelines, potential factors which influence compliance rates, and implementations and outcomes of interventions.

RESULTS

Six international studies have been retained which all focused on adherence to Group B Streptococcus screening guidelines and demonstrated that different factors might have an influence on adherence to GBS screening protocols such as financial aspects and high caesarean section rates. Findings of relatively low compliance rates led to recognizing the need of developing improved strategies for optimising antenatal GBS screening adherence.

CONCLUSION

Adhering to Group B Streptococcus screening guidelines to prevent neonatal infection is crucial. Various factors influence compliance rates such as financial aspects and high proportions of caesarean sections. The implementation of strategies and different forms of education can result in improved compliance rates.

Highly Sensitive and Rapid Identification of Streptococcus agalactiae Based on Multiple Cross Displacement Amplification Coupled With Lateral Flow Biosensor Assay

Streptococccus agalactiae (S. agalactiae) is an important neonatal pathogen that is associated with mortality and morbidity. Therefore, we developed a rapid, accurate, and sensitive method based on multiple cross displacement amplification (MCDA) for the detection of the target pathogen. Four sets of MCDA primers were designed for targeting the S. agalactiae-specific groEL gene, and one set of MCDA primers with the optimum amplification efficiency was screened for establishing the S. agalactiae-MCDA assay. As a result, the newly-developed assay could be conducted at a fixed temperature (61°C) for only 30 min, eliminating the use of complex instruments. A portable and user-friendly nanoparticle-based lateral flow biosensor (LFB) assay was employed for reporting MCDA results within 2 min. Our results suggested that the detection limit of the S. agalactiae-MCDA-LFB assay is 300 fg per reaction, and no cross-reaction occurred with non-S. agalactiae strains. For 260 vaginal and rectal swabs, the detection rate of the MCDA-LFB assay was 7.7%, which was in accordance with the reference method of enrichment/qPCR, and higher by 4.6% than the CHROMagar culture. Moreover, the total procedure time of the MCDA-LFB assay was around 50 min, including sample collection, template preparation, MCDA reaction, and result reporting. Therefore, the MCDA-LFB assay is superior to enrichment/qPCR and CHROMagar culture and has great promise for point-of-care testing of S. agalactiae from vaginal and rectal swabs of pregnant women in resource-limited settings.

Development of a droplet digital PCR method for detection of Streptococcus agalactiae

Background

Streptococcus agalactiae (GBS) is the causative pathogen of puerperal sepsis in pregnant women and pneumonia, sepsis and meningitis in infants. Infection of GBS is responsible for the increased morbidity in pregnant women and the elderly, and bring challenges to clinical diagnosis and treatment. However, culture-based approaches to detect S.agalactiae is time-consuming with limited sensitivity. Besides, real-time quantitative PCR demands expensive instruments with tedious steps. Thus, we aim to establish a new detection method for more accurate and rapid detection of S.agalactiae.

Results

The ddPCR primer targeted the CpsE gene showed better amplified efficiency in the reaction. The limit of detection for GBS DNA with ddPCR was able to reach 5 pg/μL. Moreover, no positive amplified signals could be detected in the reactions which served 11 non-GBS strains DNA as templates. Furthermore, the coefficient of variation of this method was 4.5%, indicating excellent repeatability of ddPCR assay.

Conclusions

In our study, ddPCR was performed as a rapid detection of S.agalactiae with high sensitivity and specificity. This technique can promote the accuracy of the diagnosis of GBS infection and provide a scientific basis for clinical treatment.

Development and analytical validation of real-time PCR for the detection of Streptococcus agalactiae in pregnant women

Background

Group B Streptococcus (GBS) is the leading cause of invasive neonatal infection. In this study, we aimed to evaluate the analytical validation of qualitative real-time polymerase chain reaction (qPCR) as a means to detect GBS.

Methods

Genomic DNA (gDNA) was purified from 12 ATCC bacterial strains, two belonging to GBS and the remainder acting as negative controls. Additionally, gDNA was isolated from 21 strains of GBS from various serotypes (Ia, Ib and II-VIII). All gDNA was used to evaluate the analytical validation of the qPCR method employing a specific Taqman probe. Inclusivity, exclusivity, anticipated reportable range, the limit of detection and robustness were evaluated. The methods used are described in international guidelines and other existing reports. The performance of this qPCR method for detecting GBS was compared to other microbiological methods used with vaginal-rectal samples from pregnant women.

Results

Our qPCR method for detecting GBS was analytically validated. It has a limit of detection of 0.7 GE/μL and 100% analytical specificity. It detects all strains of GBS with the same level of performance as microbiological methods.

Conclusion

Data suggest that this qPCR method performs adequately as a means to detect GBS in vaginal-rectal swabs from pregnant women.

Group B Streptococcus colonisation and their antimicrobial susceptibility among pregnant women attending antenatal clinics in tertiary care hospitals in the Western Province of Sri Lanka

The proportion of Group B Streptococcus (GBS) colonisation in pregnant women >35 weeks of gestation was 18% and 49% by culture and real-time PCR respectively in selected hospitals from the Western Province of Sri Lanka. A Descriptive cross-sectional study was conducted from January to April 2019. Two low vaginal and rectal swabs were collected from 100 pregnant women. Identification of GBS was done by culture and real-time PCR. GBS isolates were found to be sensitive to penicillin, ampicillin, cefotaxime, vancomycin, while 5 and 4 isolates out of 18 were resistant to erythromycin and clindamycin, respectively. Further, there was a significant association between GBS colonisation and a history of vaginal discharge and unemployment.IMPACT STATEMENTWhat is already known on this subject? Prevalence of GBS colonisation in the vagina and rectum of pregnant women in developing countries ranges from 8.5% to 22%. The Conventional method of culture has been considered the gold standard for diagnosis, however, the culture method does not give positive results for all cases of GBS. Polymerase chain reaction (PCR) has been found to be more sensitive for the detection of GBS than culture. In Sri Lanka, ante-natal screening for GBS is not practiced as the prevalence of GBS is still unlcear due to non-availably of data. Only a few scattered studies have been conducted using culture in Sri Lanka. Thus there is an urgent need to determine the magnitude of the GBS colonisers of ante-natal women in order to set up guidelines for screening and management of GBS.What do the results of this study add? In this study, the overall GBS colonisation rate which was detected using both culture and PCR was 50% in Western Province of Sri Lanka. That was a high figure when compared to the figures which were detected previously in Sri Lanka using only conventional culture methods. The risk factors for GBS colonisation were found to have a significant relationship with the history of abnormal vaginal discharge. Further, it was found that when Candida species coexisted with GBS, the existence of GBS was enhanced. Penicillin remains the antibiotic of choice for GBS.What are the implications of these findings for clinical practice and/or further research? This study emphasises the importance of establishing national policies for screening of pregnant women of >35 weeks of gestation to reduce the risk of neonatal infection. Further, it gives an insight into the options of antibiotics that can be used for treatment of these GBS colonisers from Sri Lanka.

Group B Streptococcus DNA Copy Numbers Measured by Digital PCR Correlates with Perinatal Outcomes

Group B Streptococcus (GBS) is a one of the main causes of perinatal disease, yet the method for GBS detection, broth-enriched culture, is time-consuming and has low sensitivity and accuracy. We aimed to develop a GBS digital PCR (GBS-dPCR) assay for detecting GBS colonization. More rapid and accurate detection of GBS colonization could increase GBS diagnosis and treatment closer to delivery. A single-center, retrospective, case-controlled study was performed. A total of 182 rectovaginal swabs from pregnant women, who were undergoing prenatal screening by broth-enriched culture, were evaluated using GBS-dPCR targeting the cfb gene of GBS. Pregnant women with GBS colonization were followed up for correlation analysis between GBS DNA copy numbers and perinatal outcomes. The results of the GBS-dPCR assay were compared to those from the broth-enriched culture, which is the gold standard for GBS detection. The sensitivity and specificity of GBS-dPCR were 98% and 92.5%, respectively. By discrepant result analysis, the specificity of GBS-dPCR was raised to 97.4%. The incidence of premature rupture of membrane (PROM) and neonatal infection were statistically significantly positively correlated with GBS DNA copy numbers. GBS-dPCR has the advantage of directly detecting GBS colonization from swabs with high specificity and sensitivity, while reducing turnaround time (<4 h). Analysis of clinical samples with GBS-dPCR shows that GBS DNA copy numbers are positively correlated with the incidence of PROM and neonatal infection, suggesting that dPCR is a promising method for detection of GBS colonization during pregnancy.

[Group B streptococcus colonization in pregnant women and group B streptococcus infection in their preterm infants]

OBJECTIVE

To study the incidences of group B streptococcus (GBS) colonization in pregnant women and GBS infection in their preterm infants, and to investigate the risk factors for GBS colonization in preterm infants.

METHODS

A total of 859 women who delivered before term from January 2017 to January 2018 were enrolled in this prospective cohort study. Bacterial culture was performed for GBS using the swabs collected from the rectum and the lower 1/3 of the vagina of the pregnant women on admission. A total of 515 of the above cases underwent real-time PCR assay for testing of GBS DNA. Bacterial culture was performed for GBS using the oropharyngeal secretion, gastric fluid or blood samples in preterm infants born to the 859 pregnant women. Peripheral blood samples from the pregnant women and umbilical cord blood samples from their preterm infants were collected to determine the level of anti-GBS capsular polysaccharide antibody. The incidence of GBS infection and perinatal risk factors for GBS colonization in the preterm infants were examined.

RESULTS

The positive rate for GBS in the rectal and vaginal cultures was 14.8% (127/859) among the 859 pregnant women, and the positive rate in the GBS DNA testing was 15.1% (78/515). There were 976 live-birth preterm infants delivered by 859 pregnant women, and 4.4% (43/976) of whom were GBS positive. Four preterm infants had early-onset GBS diseases, including pneumonia in two cases and sepsis in two cases. In 127 preterm infants delivered by 127 GBS-positive pregnant women, the preterm infant group with a gestational age between 34 and 37 weeks had a significantly lower GBS positive rate and a significantly higher level of anti-GBS capsular polysaccharide antibody compared with the preterm infant group with a gestational age of less than 34 weeks (P=0.013 and 0.001 respectively). A multivariate logistic regression analysis revealed that premature rupture of membranes time >18 hours and chorioamnionitis were independent risk factors for GBS colonization in preterm infants (OR=6.556 and 6.160 respectively; P<0.05).

CONCLUSIONS

GBS positive rate and anti-GBS capsular polysaccharide antibody level in preterm infants are correlated with gestational age. premature rupture of membranes time >18 hours and chorioamnionitis may increase the risk of GBS colonization in preterm infants.