Screening for group B Streptococcus (GBS) at labour onset using PCR: accuracy and potential impact - a pilot study

The acceptability of group B streptococcal bacteria (GBS) testing to women, including self-swabbing procedures: A qualitative study

BACKGROUND

Group B streptococcus (GBS) is a bacterium carried by 20-25 % of pregnant women in the UK, which can be transmitted from pregnant women to their babies at the time of birth. Women can be tested for GBS in pregnancy using a vaginal-rectal swab, however, this testing is currently not routinely offered in the UK. A large clinical trial is underway to determine the clinical and cost-effectiveness of routine testing (ISRCTN reference number ISRCTN49639731). A crucial part of understanding whether this type of test should be implemented is women's views on the acceptability of being offered GBS tests, their preferences towards testing procedures and their willingness to receive these tests.

AIM

To explore women's views on the acceptability of different methods of Group B streptococcal bacteria (GBS) testing in pregnancy, including self-swabbing procedures.

METHODS

A convenience sample of 19 women (5 pregnant and 14 postpartum) were interviewed using a semi-structured interview guide. Interviews were transcribed and analysed using systematic thematic analysis.

RESULTS

Findings show that many of the women interviewed were not concerned about being offered a GBS test, were willing to provide a sample and felt positive towards samples being taken to detect GBS. Women varied in their preferences on the best time for sampling. Some thought being approached during pregnancy gave them time to understand the purpose of testing, prepare for what may happen next and ask questions about potential treatment if needed. Others thought labour was a good time to provide accurate results on GBS carriage at birth and reduce unnecessary worry during pregnancy. However, women were concerned that they may be unable to make an informed decision in labour due to time, pain and the prospect of birthing quickly. Women perceived clinician swabbing as more accurate than self-sampling; however, many thought clinician swabbing might be embarrassing so self-swabs should be available to increase uptake for some women.

CONCLUSIONS

Overall, women thought both pregnancy and labour were acceptable times to test for GBS. The majority found both clinician and self-swabbing procedures acceptable; however, many had a preferred swabbing option and thought women should be given the choice of the swabbing procedure most acceptable to them. It is important that women are given information about GBS testing and its procedures in pregnancy regardless of when the GBS swabbing is performed.

Possible Rates of Detection of Neonatal Sepsis Pathogens in the Context of Microbiological Diagnostics in Mothers - Real World Data

Objective

The aim of this study was to identify the rate of detection of neonatal sepsis pathogens in maternal microbiological smears.

Study Design

This is a retrospective study conducted at a Level 1 perinatal center in the context of routine care from 2014 to 2019. For all premature infants and neonates with neonatal sepsis, the neonatal and maternal microbiological findings were examined to see if there was a match.

Results

During the study period, a total of 948 premature or newborn infants were identified as having a neonatal infection. Among all of the premature or newborn infants, 209 (22%) met the diagnostic criteria for neonatal sepsis; of these, 157 were premature births and 52 were full-term births. We evaluated the microbiological findings for these 209 mother and child pairs. No pathogens were detected in 27 out of 157 mothers of premature infants (17.1%) and in 31 out of 52 mothers of full-term infants (59.6%). In the premature infant group there were pairs with matching pathogens in 30 out of 130 cases (23.1%, 95% CI: 16.1-31.3), and in the full-term infant group there was a match in 4 out of 21 cases (19%, 95% CI: 5.4-41.9). The number needed to test to have a 90% probability of success for pathogen detection varies between 9 and 11 in the most favorable case and 26 and 32 in the least favorable case, depending on the evaluation method.

Conclusion

In cases of neonatal sepsis, the sepsis-causing pathogen was successfully detected through prior analysis of a maternal smear in 7% of full-term infants and in 19% of premature infants. The number needed to test was relatively high in all groups. The value of maternal smears for identifying neonatal sepsis-causing pathogens needs to be critically questioned.

Early-onset group B streptococcal disease in African countries and maternal vaccination strategies

Invasive group B streptococcal (GBS) disease is the commonest perinatally-acquired bacterial infection in newborns; the burden is higher in African countries where intrapartum antibiotic prophylaxis strategies are not feasible. In sub-Saharan Africa, almost one in four newborns with GBS early-onset disease will demise, and one in ten survivors have moderate or severe neurodevelopmental impairment. A maternal GBS vaccine to prevent invasive GBS disease in infancy is a pragmatic and cost-effective preventative strategy for Africa. Hexavalent polysaccharide protein conjugate and Alpha family surface protein vaccines are undergoing phase II clinical trials. Vaccine licensure may be facilitated by demonstrating safety and immunological correlates/thresholds suggestive of protection against invasive GBS disease. This will then be followed by phase IV effectiveness studies to assess the burden of GBS vaccine preventable disease, including the effect on all-cause neonatal infections, neonatal deaths and stillbirths.

Maternity care provider acceptance of a future Group B Streptococcus vaccine - A qualitative study in three countries

INTRODUCTION

There are vaccines in clinical trials that target the bacterium Group B Streptococcus (GBS). When approved, GBS vaccines will be intended for administration to pregnant women to prevent infection in their infants. The success of any vaccine will depend on its' uptake in the population. Experience with prior maternal vaccines, e.g. influenza, Tdap and COVID-19 vaccines, teaches us that acceptance of vaccines, especially if novel, is challenging for pregnant women, and that provider recommendation is a key driver of vaccine uptake.

METHODS

This study investigated attitudes of maternity care providers towards the introduction of a GBS vaccine in three countries (the United States (US), Ireland, and the Dominican Republic (DR)) with different GBS prevalence and prevention practices. Semi-structured interviews with maternity care providers were transcribed and coded for themes. The constant comparative method, and inductive theory building were used to develop conclusions.

RESULTS

Thirty-eight obstetricians, 18 general practitioners and 14 midwives participated. There was variability in provider attitudes towards a hypothetical GBS vaccine. Responses ranged from enthusiasm to doubts over the need for a vaccine. Attitudes were influenced by perceived additional benefits of a vaccine over current strategy and confidence in the safety of vaccines during pregnancy. Knowledge, experience and approaches to GBS prevention differed geographically and according to provider type, and influenced how participants assessed the risks and benefits of a GBS vaccine.

CONCLUSION

Maternity care providers are engaged in the topic of GBS management and there is opportunity to leverage attitudes and beliefs that will support a strong recommendation for a GBS vaccine. However, knowledge of GBS, and of the limitations of current prevention strategies vary among providers in different regions, and between different provider types. Targeted educational efforts with antenatal providers should focus on highlighting safety data the potential benefits of vaccination over current strategies.

Performance of the HiberGene Group B Streptococcus kit, a loop-mediated isothermal amplification-based assay for GBS screening during pregnancy

Timely and accurate detection of Group B Streptococcus (GBS) carriage in pregnant women allows for targeted peripartum prophylaxis. Replacing culture-based screening by molecular biology assays enables faster results obtention, better targeted antibiotic prophylaxis, and reduces the laboratory workload. Here, we present a comparative analysis between a Loop Mediated Isothermal Amplification assay (HiberGene GBS kit) and culture (gold-standard). The HiberGene GBS kit showed a sensitivity of 97.9% and a specificity of 96.8% compared with culture. The limit of detection was estimated at 10³ cfu/ml and results were obtained within 30 min. HiberGene GBS assay can be used for peripartum GBS screening and targeted antibiotic prophylaxis provided sample processing can be swiftly performed around the clock.

Group B Streptococcus real-time PCR may potentially reduce intrapartum maternal antibiotic treatment

BACKGROUND

Protocols for preventing early-onset group B streptococcal (GBS) neonatal infection may result in unnecessary antibiotics administration. Real-time polymerase chain reaction (PCR) can provide a result within 30-60 min and has been found to be specific and sensitive for defining intrapartum GBS status.

OBJECTIVE

To evaluate whether implementation of GBS fast real-time PCR to all women who require GBS prophylaxis may reduce the use of maternal prophylactic antibiotics.

METHODS

This prospective cohort study included women admitted to a single delivery ward who required prophylactic antibiotics either due to a positive antepartum GBS culture screening performed at 35-37 weeks or due to an unknown GBS status with an intrapartum risk factor. All the women were tested by a double vaginal swab (real-time PCR and culture) as soon as it became apparent, they required antibiotic prophylaxis and prior to its administration.

RESULTS

Between May 2019 and August 2020, 303 women met eligibility criteria and were enrolled, but four were excluded from the analysis due to failed culture or PCR tests. Of 299 women included in the study, 208 (69.5%) and 180 (60.2%) women, showed no evidence of GBS on intrapartum culture or PCR, respectively. Of 89 GBS antepartum carriers, 43 (48.3%) and 32 (35.9%) had negative intrapartum culture and PCR results, respectively. Of the 210 women with risk factors, 165 (78.5%) were culture negative and 148 (70.4%) had a negative PCR. Using intrapartum culture as the gold standard, intrapartum GBS real-time PCR was found to have a sensitivity of 97.8% (95% confidence interval [CI] 92.3, 99.7) and a specificity of 85.6% (95% CI 80.1, 90.1).

CONCLUSIONS

Compared with antepartum universal culture screening or intrapartum risk-factor assessment, the need for maternal antibiotic treatment may be substantially reduced by implementation of intrapartum GBS real-time PCR, without compromising the sensitivity of GBS detection.

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.

Intrapartum PCR-assay for detection of Group B Streptococci (GBS)

Objective

We have recently introduced intrapartum PCR-testing for group B streptococcus (GBS) in women in labor with prolonged rupture of membranes or preterm delivery to offer intrapartum antibiotic prophylaxis only for GBS positive women.

The goal of the present study is to report our experience and results from the first half year of GBS testing.

Study design

This is a retrospective study. Rectovaginal swabs from 321 women presenting in the labor ward with pre-labor rupture of membranes for >14 h/rupture of membranes during delivery for >14 h, or labor between gestational weeks 35 0/7 and 36 6/7 from February 7, 2017 to August 6, 2017, were tested.

We performed a molecular GBS test (Xpert GBS®, Cepheid Ltd., Sunnyvale, USA).

Data from patient files including mode of delivery, use of antibiotics, infection of mother and child are presented in more detail.

Data on the PCR results from the first year of testing were also collected.

Results

In the first half-year of testing a positive GBS test result was found in 58 (18.1%) and a negative test result in 263 women (81.9%). No invalid test result was achieved.

The indication for performing PCR testing was PROM > 14 h or rupture of membranes during labor for >14 h in 266 women (82.9%) and labor in gestational weeks 35 0/7–36 6/7 in 44 women (13.7%). In the remaining 11 women, the PCR test was performed for other reasons.

Of the 321 women tested 126 (39%) received antibiotics during labor.

Ten women (3.4%) were treated after delivery on suspicion of infection. 25 newborns (7.8%) were treated with antibiotics. In 11 cases, the treatment was stopped after 2–4 days as there were no signs of infection.

Conclusions

The introduction of the intrapartum GBS test in selected groups of women who gave birth in our department has been well accepted by the women, the midwifes and doctors. The result of the test is available within two hours, and as we only offer intrapartum antibiotic prophylaxis to GBS-positive women, we have reduced the use of antibiotics to approximately 40% in the groups tested, without an increase of infection in mother or child.

Clinical impact of rapid polymerase chain reaction (PCR) test for group B Streptococcus (GBS) in term women with ruptured membranes

BACKGROUND

Early-onset group B Streptococcus (EOGBS/GBS) infection remains a significant cause of neonatal morbidity and mortality.

AIMS

Aiming to improve antimicrobial stewardship and reduce unnecessary maternal and infant exposure to intrapartum antibiotic prophylaxis (IAP), this study assessed the clinical use of a commercially available GBS polymerase chain reaction (PCR) assay for term women with pre-labour rupture of membranes.

METHODS

This was a retrospective study in a tertiary level maternity unit of term women with pre-labour rupture of membranes (ROM), without any clinical suspicion of infection performed between November and December 2017. GBS PCR tests were cross-referenced with patient clinical data. PCR test results, the impact of testing on antibiotic administration, pyrexia in labour, induction, interventional delivery rates and neonatal outcomes were analysed.

RESULTS

Of 200 patients included in the study, 29 were positive (14.5%) and 166 were negative (83%), with five invalid results (2.5%). One hundred and twenty three women had > 18-h ruptured membranes and 86 women (70%) who would have been eligible for IAP based on risk factors avoided antibiotic therapy following a negative PCR test. There were no significant differences in induction or interventional delivery rates between GBS-positive and GBS-negative women following PCR testing. During the study period, there were no cases of EOGBS.

CONCLUSIONS

In a centre adhering to a risk-factor-based GBS policy, the introduction of limited rapid GBS screening for term women with pre-labour rupture of membranes resulted in a clinically significant reduction in prophylactic antibiotic use.