Enhanced antenatal detection of group B streptococcus colonization

A Multicenter Study on the Utility of Selective Enrichment Broth for Detection of Group B Streptococcus in Pregnant Women in Japan

Universal screening for Streptococcus agalactiae, Group B Streptococcus (GBS), in pregnant women is important for the prevention of severe infectious diseases in neonates. The subculture method using selective enrichment broth significantly improves GBS detection rates in the United States; however, this method is not widely utilized in Japan mainly because of the lack of large-scale validation. Therefore, we aimed to validate the utility of the subculture method in collaboration with multiple facilities. A total of 1957 vaginal-rectal swab specimens were obtained from pregnant women at 35-37 gestational weeks from March 1, 2020, to August 30, 2020, at Fukushima Medical University Hospital, Aiiku Hospital, Kitano Hospital, and the University of the Ryukyus Hospital. Conventional direct agar plating, subculture using selective enrichment broth, and direct latex agglutination (LA) testing with incubated broth were performed for GBS detection, and discrepant results were confirmed using real-time PCR. The GBS detection rates for direct agar plating, subculture, and direct LA testing were 18.2% (357/1957), 21.6% (423/1957), and 22.3% (437/1957), respectively. The use of selective enrichment broth showed promise for GBS detection with high sensitivity and is therefore recommended for GBS screening to prevent GBS-related infectious diseases in neonates in Japan.

Group B Streptococcus in Pregnancy

To decrease risk of early-onset neonatal sepsis from group B streptococcus (GBS), pregnant patients should undergo screening between 36 0/7 and 37 6/7 weeks' gestation. Patients with a positive vaginal-rectal culture, GBS bacteriuria , or history of newborn with GBS disease should receive intrapartum antibiotic prophylaxis (IAP) with an agent targeting GBS. If GBS status is unknown at time of labor, IAP should be administered in cases of preterm birth, rupture of membranes for >18 hours, or intrapartum fever. The antibiotic of choice is intravenous penicillin; alternatives should be considered in cases of penicillin allergy depending on allergy severity.

Vaginal-perianal or vaginal-perineal compared with vaginal-rectal culture-based screening for Group B Streptococci (GBS) colonization during the third trimester of pregnancy: a systematic review and meta-analysis

BACKGROUND

Screening for maternal anogenital Group B streptococci (GBS) colonization in pregnancy with initiation of intravenous intrapartum antibiotic prophylaxis as indicated has led to a significant reduction in the incidence of neonatal GBS infection. This study aims to evaluate the agreement between vaginal-perianal or vaginal-perineal culture and the more typically used vaginal-rectal culture for screening for maternal anogenital GBS colonization in the third trimester of pregnancy.

METHODS

Eligible English-language studies published until January 2020 were retrieved from Scopus, Web of Science, PubMed, Embase, and ClinicalTrials.gov databases. Studies were compiled that assessed for GBS colonization utilizing vaginal-perianal or vaginal-perineal culture and vaginal-rectal culture during the third trimester of pregnancy. Nonoriginal research articles and studies that did not assess pregnant patients, did not use culture-based screening, or did not compare vaginal-perianal or vaginal-perineal culture with vaginal-rectal culture were excluded. The search identified 559 articles with three prospective cohort studies that met inclusion criteria, including 643 participants. Quality was assessed using the Newcastle-Ottawa Scale, and risk of bias was assessed using the Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool. Patient characteristics and associated pain with specimen collection were abstracted. Meta-analyses of both the raw agreement and the Cohen's kappa statistic were performed.

RESULTS

Within the three included studies, the range of GBS detection was 17.6-34.0%, consistent with the anticipated prevalence of GBS colonization reported in earlier publications. For both raw agreement and Cohen's kappa coefficient, the test for heterogeneity was not significant, indicating low heterogeneity among studies. The pooled estimate of the raw agreement was 0.97 (95%CI 0.95-0.98) and of the Cohen's kappa coefficient was 0.91 (95% CI: 0.87-0.95), indicating (according to the Landis and Koch criteria) an "almost perfect" agreement between the compared clinical tests. In the two studies that assessed procedure-related patient discomfort, vaginal-rectal swabbing caused more discomfort.

CONCLUSION

Use of vaginal-perineal culture for assessment of maternal GBS colonization is comparable to the more typically utilized vaginal-rectal culture and is associated with less discomfort.

Development and Clinical Evaluation of a CRISPR-Based Diagnostic for Rapid Group B Streptococcus Screening

Vertical transmission of group B Streptococcus (GBS) is among the leading causes of neonatal illness and death. Colonization with GBS usually is screened weeks before delivery during pregnancy, on the basis of which preventive measures, such as antibiotic prophylaxis, were taken. However, the accuracy of such an antenatal screening strategy has been questionable because of the intermittent nature of GBS carriage. We developed a simple-to-use, rapid, CRISPR-based assay for GBS detection. We conducted studies in a prospective cohort of 412 pregnant women and a retrospective validation cohort to evaluate its diagnostic performance. We demonstrated that CRISPR-GBS is highly sensitive and offered shorter turnaround times and lower instrument demands than PCR-based assays. This novel GBS test exhibited an overall improved diagnostic performance over culture and PCR-based assays and represents a novel diagnostic for potential rapid, point-of-care GBS screening.

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.

Prevention of Group B Streptococcal Early-Onset Disease in Newborns: ACOG Committee Opinion, Number 782

Group B streptococcus (GBS) is the leading cause of newborn infection. The primary risk factor for neonatal GBS early-onset disease (EOD) is maternal colonization of the genitourinary and gastrointestinal tracts. Approximately 50% of women who are colonized with GBS will transmit the bacteria to their newborns. Vertical transmission usually occurs during labor or after rupture of membranes. In the absence of intrapartum antibiotic prophylaxis, 1-2% of those newborns will develop GBS EOD. Other risk factors include gestational age of less than 37 weeks, very low birth weight, prolonged rupture of membranes, intraamniotic infection, young maternal age, and maternal black race. The key obstetric measures necessary for effective prevention of GBS EOD continue to include universal prenatal screening by vaginal-rectal culture, correct specimen collection and processing, appropriate implementation of intrapartum antibiotic prophylaxis, and coordination with pediatric care providers. The American College of Obstetricians and Gynecologists now recommends performing universal GBS screening between 36 0/7 and 37 6/7 weeks of gestation. All women whose vaginal-rectal cultures at 36 0/7-37 6/7 weeks of gestation are positive for GBS should receive appropriate intrapartum antibiotic prophylaxis unless a prelabor cesarean birth is performed in the setting of intact membranes. Although a shorter duration of recommended intrapartum antibiotics is less effective than 4 or more hours of prophylaxis, 2 hours of antibiotic exposure has been shown to reduce GBS vaginal colony counts and decrease the frequency of a clinical neonatal sepsis diagnosis. Obstetric interventions, when necessary, should not be delayed solely to provide 4 hours of antibiotic administration before birth. This Committee Opinion, including , , and , updates and replaces the obstetric components of the CDC 2010 guidelines, "Prevention of Perinatal Group B Streptococcal Disease: Revised Guidelines From CDC, 2010."

Rapid and visual detection of Group B streptococcus using recombinase polymerase amplification combined with lateral flow strips

Conventional culture method for detecting Group B streptococcus (GBS), a common pathogen of neonatal meningitis and sepsis, is time-consuming and unsensitive. Even though real-time fluorescence PCR-based molecular method is more accurate, it need special instrument and elaborate protocol. Here, we established a novel molecular method combining recombinase polymerase amplification with lateral flow strips for detecting GBS. The cAMP factor (cfb) gene is a highly specific and sensitive biomarker to identify GBS and is detectable by using 100 genomic copies as the amplification template. Clinical performance of this assay was evaluated by testing 130 samples, in comparison with culture method and real-time fluorescence PCR, and the results achieved 100% accuracy, which were the same with those of real-time fluorescence PCR, and were better than those of culture method with false-negative detection. This study provides a rapid and visual method, with clinical potential, for the detection of GBS infection of patients.

Group B Streptococci Colonization in Pregnant Guatemalan Women: Prevalence, Risk Factors, and Vaginal Microbiome

Background

Infection causes 1 of every 5 neonatal deaths globally. Group B Streptococcus (GBS) is the most significant pathogen, although little is known about its epidemiology and risk in low-income countries.

Methods

A cross-sectional study in 2015 at a public hospital in Guatemala City enrolled women ≥35 weeks’ gestation. Vaginal and rectal swabs were processed using Lim broth and GBS CHROMagar then agglutination testing. Risk factors were assessed using multivariate analysis. Vaginal microbiota were profiled by 16S ribosomal ribonucleic acid sequencing in a subset of 94 women.

Results

Of 896 pregnant women, 155 (17.3%; 95% confidence interval [CI], 14.9–19.9) were GBS colonized. Colonization was associated with history of previous infant with poor outcome (odds ratio [OR], 1.94; 95% CI, 1.15–3.27) and increasing maternal age (OR, 1.05; 95% CI, 1.02–1.09). Multiparity was protective (OR, .39; 95% CI, .21–.72). Four (6%) GBS-exposed infants had early-onset neonatal sepsis. Vaginal microbiome composition was associated with previous antibiotic exposure (P = .003) and previous low birth weight infant (P = .03), but not GBS colonization (P = .72). Several individual taxa differed in abundance between colonized and noncolonized women.

Conclusions

Group B Streptococcus is prevalent in pregnant women from Guatemala with different risk factors than previously described. Although the vaginal microbiome was not altered significantly in GBS-colonized women, use of antibiotics had an effect on its composition.

Group B Streptococcus vaccine development: present status and future considerations, with emphasis on perspectives for low and middle income countries

Globally, group B Streptococcus (GBS) remains the leading cause of sepsis and meningitis in young infants, with its greatest burden in the first 90 days of life. Intrapartum antibiotic prophylaxis (IAP) for women at risk of transmitting GBS to their newborns has been effective in reducing, but not eliminating, the young infant GBS disease burden in many high income countries. However, identification of women at risk and administration of IAP is very difficult in many low and middle income country (LMIC) settings, and is not possible for home deliveries. Immunization of pregnant women with a GBS vaccine represents an alternate pathway to protecting newborns from GBS disease, through the transplacental antibody transfer to the fetus in utero. This approach to prevent GBS disease in young infants is currently under development, and is approaching late stage clinical evaluation. This manuscript includes a review of the natural history of the disease, global disease burden estimates, diagnosis and existing control options in different settings, the biological rationale for a vaccine including previous supportive studies, analysis of current candidates in development, possible correlates of protection and current status of immunogenicity assays. Future potential vaccine development pathways to licensure and use in LMICs, trial design and implementation options are discussed, with the objective to provide a basis for reflection, rather than recommendations.

Evaluation of an in-house real-time polymerase chain reaction method to identify group B streptococcus colonization in pregnancy

AIM

The aim of this study was to evaluate the performance of in-house real-time polymerase chain reaction (qPCR) in detecting group B streptococcus (GBS) colonization compared with the standard culture method in a cohort of pregnant women.

MATERIAL AND METHODS

A total of 134 rectovaginal swabs were collected from 125 pregnant women, of whom 108 were known carriers or presented with preterm prelabor rupture of membranes. The swabs were placed in Standard Methods Broth (Todd-Hewitt broth supplemented with 6 μg/mL gentamicin and 15 μg/mL nalidixic acid) for culture identification of GBS. An in-house qPCR was also performed from the broth and after overnight incubation of the broth.

RESULTS

The detection rate of GBS in this cohort was 30.6% and 50.7% using standard culture method and qPCR, respectively. GBS-specific qPCR assay gave sensitivities of 97.6% and 100%, specificities of 73.1% and 71.0%, and negative predictive values of 98.6% and 100% from direct specimen and from broth after overnight incubation, respectively.

CONCLUSIONS

The in-house qPCR test has high sensitivity in detecting GBS colonization. The high negative predictive value helps to avoid unnecessary use of antibiotics in uncolonized women.

Diagnosis and management of group B streptococcus in pregnancy

Group B streptococcus (GBS) can cause significant maternal and neonatal morbidity. Over the past 30 years, reductions in early-onset GBS neonatal sepsis in the United States have been attributable to the guidelines from the Centers for Disease Control and Prevention for antepartum screening and treating this organism during labor. This article highlights the clinical implications, screening, diagnosis, prophylactic interventions, and future therapies for mothers with GBS during the peripartum period.

Intrapartum GBS screening and antibiotic prophylaxis: a European consensus conference

Group B streptococcus (GBS) remains worldwide a leading cause of severe neonatal disease. Since the end of the 1990s, various strategies for prevention of the early onset neonatal disease have been implemented and have evolved. When a universal antenatal GBS screening-based strategy is used to identify women who are given an intrapartum antimicrobial prophylaxis, a substantial reduction of incidence up to 80% has been reported in the USA as in other countries including European countries. However recommendations are still a matter of debate due to challenges and controversies on how best to identify candidates for prophylaxis and to drawbacks of intrapartum administration of antibiotics. In Europe, some countries recommend either antenatal GBS screening or risk-based strategies, or any combination, and others do not have national or any other kind of guidelines for prevention of GBS perinatal disease. Furthermore, accurate population-based data of incidence of GBS neonatal disease are not available in some countries and hamper good effectiveness evaluation of prevention strategies. To facilitate a consensus towards European guidelines for the management of pregnant women in labor and during pregnancy for the prevention of GBS perinatal disease, a conference was organized in 2013 with a group of experts in neonatology, gynecology-obstetrics and clinical microbiology coming from European representative countries. The group reviewed available data, identified areas where results were suboptimal, where revised procedures and new technologies could improve current practices for prevention of perinatal GBS disease. The key decision issued after the conference is to recommend intrapartum antimicrobial prophylaxis based on a universal intrapartum GBS screening strategy using a rapid real time testing.

Usefulness of a rapid real-time PCR assay in prenatal screening for group B streptococcus colonization

Background

Group B streptococcus (GBS) infection is a leading cause of neonatal morbidity and mortality worldwide. Here, we present the analytical and diagnostic usefulness of a new real-time PCR-based assay (Xpert GBS; Cepheid, USA) for rapid and accurate prenatal GBS screening.

Methods

We enrolled 175 pregnant women who were between 35 and 39 weeks of gestation. The analytical performance of the Xpert GBS assay was first tested using a reference GBS strain. Next, to test diagnostic performance, rectovaginal swabs were obtained from pregnant women who visited the hospital for regular antenatal screening after 34 weeks of gestation. The results of the Xpert GBS assay were compared to those of standard culture for the detection of prenatal GBS colonization.

Results

When any positive result from Xpert GBS or culture was considered a true positive, the sensitivity of the Xpert GBS assay and culture were 91% (20/22; 95% CI [confidence interval], 72-98) and 68% (15/22; 95% CI, 47-84), respectively. The specificity of both methods was 100% (153/153; 95% CI, 97-100). The sensitivity and specificity of the Xpert GBS assay, using the culture results as a reference, were 86.7% and 95.6%, respectively. In the Xpert GBS assay, the median threshold cycle of vaginally colonized samples was significantly lower than rectally colonized samples (P<0.01).

Conclusions

The Xpert GBS assay is an accurate, rapid, easy-to-use test for the detection of maternal GBS colonization in prenatal screening that might be especially useful in clinical settings where standard culture is not feasible.

Prevention of neonatal group B streptococcus disease in the 21st century

There have been significant reductions in early-onset neonatal group B streptococcus (GBS) disease following implementation of maternal intrapartum antibiotic prophylaxis (IAP) policies. Nevertheless, GBS remains a leading cause of neonatal sepsis in Australia and New Zealand resulting in considerable morbidity and mortality, particularly among preterm infants. In the United States, the universal screening-based approach for identifying women for IAP results in apparently lower rates of early-onset neonatal GBS infection than risk-based assessment. In addition, IAP has altered the profile of newborn infants who develop early-onset disease. Many affected infants lack the typical intrapartum risk factors for GBS infection, are born to mothers with a negative GBS screen or represent missed opportunities for prevention. Clinicians should remain alert for signs of sepsis in any newborn infant. We provide an update of GBS preventative management strategies in the perinatal period taking into account recent United States, Australian and New Zealand guidelines.

Early-onset group B streptococcal disease following culture-based screening in Japan: a single center study

AIM

We investigated trends in early-onset group B streptococcal disease (EOD) after the introduction of culture-based screening in Japan.

MATERIAL AND METHODS

A retrospective cohort study examined EOD trends in 9506 pregnancies and 10 715 neonates at our center from 2002 to 2009.

RESULTS

EOD occurred in four neonates (4/7332: 0.55/1000 live births). The EOD incidence among infants born to women positive for GBS by screening was 0.90 cases per 1000 live births (1/1107). In contrast, the EOD incidence among infants negative by GBS screening was 0.48 cases per 1000 live births (3/6225). Thus, of the four affected neonates, three had mothers who tested negative on antepartum GBS screening. Two neonates had symptoms of infection during labor and intrapartum antibiotic agents were administered. The other two neonates received no antibiotics because deliveries were uneventful and they were negative on GBS screening.

CONCLUSION

The incidence of EOD is 0.90 cases per 1000 live births among GBS-positive women and 0.48 cases per 1000 live births among GBS-negative women. The results of our study implied that EOD can develop regardless of GBS screening and intrapartum clinical course, although the method of sample collection, indications for antibiotic prophylaxis, and the antibiotics regimen should be considered.

Comparison of scpB gene and cfb gene polymerase chain reaction assays with culture on Islam medium to detect Group B Streptococcus in pregnancy

PURPOSE

The purpose of the current study was to evaluate two low-costing PCR assays for rapid detection of Group B Streptococcus (GBS) in comparison to a pigment-based culture method.

MATERIALS AND METHODS

One-hundred and fifty vaginal swabs were collected from pregnant women at 35-40 weeks of gestation. Vaginal swabs were inoculated in selective enrichment broth medium, and examined using Islam medium, cfb PCR and scpB PCR assays. The demographic data were analysed to identify independent predictors of GBS colonization (age and gravidity), with GBS status as the dependent variable.

RESULTS

There was a significant association of age and gravidity with GBS colonization. GBS was detected in 25.3% of isolates by Islam medium, in 30.6% by using the cfb PCR assay and in 30% by using the scpB PCR assay.

CONCLUSION

Older pregnant women (≥30 years) and multigravida (>3 pregnancies) are at higher risk of GBS colonization. Both scpB-gene and cfb-gene-based PCR methods are highly sensitive techniques (100% sensitivity) compared to culture method. However, the specificities of the scpB and cfb PCR assays were 93.75 and 92.85%, respectively.

Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women

Background

Streptococcus agalactiae (group B streptococcus; GBS) is a significant cause of perinatal and neonatal infections worldwide. To detect GBS colonization in pregnant women, the CDC recommends isolation of the bacterium from vaginal and anorectal swab samples by growth in a selective enrichment medium, such as Lim broth (Todd-Hewitt broth supplemented with selective antibiotics), followed by subculture on sheep blood agar. However, this procedure may require 48 h to complete. We compared different sampling and culture techniques for the detection of GBS.

Methods

A total of 300 swabs was taken from 100 pregnant women at 35-37 weeks of gestation. For each subject, one rectovaginal, one vaginal and one rectal ESwab were collected. Plating onto Columbia CNA agar (CNA), group B streptococcus differential agar (GBSDA) (Granada Medium) and chromID Strepto B agar (CA), with and without Lim broth enrichment, were compared. The isolates were confirmed as S. agalactiae using the CAMP test on blood agar and by molecular identification with tDNA-PCR or by 16S rRNA gene sequence determination.

Results

The overall GBS colonization rate was 22%. GBS positivity for rectovaginal sampling (100%) was significantly higher than detection on the basis of vaginal sampling (50%), but not significantly higher than for rectal sampling (82%). Direct plating of the rectovaginal swab on CNA, GBSDA and CA resulted in detection of 59, 91 and 95% of the carriers, respectively, whereas subculturing of Lim broth yielded 77, 95 and 100% positivity, respectively. Lim broth enrichment enabled the detection of only one additional GBS positive subject. There was no significant difference between GBSDA and CA, whereas both were more sensitive than CNA. Direct culture onto GBSDA or CA (91 and 95%) detected more carriers than Lim broth enrichment and subculture onto CNA (77%). One false negative isolate was observed on GBSDA, and three false positives on CA.

Conclusions

In conclusion, rectovaginal sampling increased the number GBS positive women detected, compared to vaginal and/or rectal sampling. Direct plating on CA and/or GBSDA provided rapid detection of GBS that was at least as sensitive and specific as the CDC recommended method of Lim broth subcultured onto non chromogenic agar.

The effect of a chlorhexidine-based surgical lubricant during pelvic examination on the detection of group B Streptococcus

OBJECTIVE

The objective of the study was to estimate whether surgical lubricant used during pelvic examination alters the detection of group B Streptococcus (GBS).

STUDY DESIGN

We conducted a prospective cohort study of patients undergoing GBS screening at the prenatal clinics of a New York City public hospital. Two specimens were collected from each patient, before and after a pelvic examination with Surgilube (Fougera and Co, Melville, NY), a bacteriostatic surgical lubricant. Test performance indices using GBS status pre-pelvic examination as the reference were calculated.

RESULTS

Over 10 months, 168 patients were enrolled in the study. Twenty of 168 patients (11.9%; 95% confidence interval, 7.4-17.8%) tested GBS positive before the pelvic examination. Of the initial 20 GBS-positive patients, 10 tested GBS positive after the pelvic examination with surgical lubricant. The sensitivity of detecting GBS after the examination with surgical lubricant was 50%.

CONCLUSION

Because pelvic examination with surgical lubricant may decrease the detection of GBS, obstetric practitioners should collect GBS screening cultures before the use of surgical lubricant.

Group B streptococcus infection in pregnancy

Group B streptococcus (streptococcus agalactiae), a gram-positive coccus, is one of the major causes of maternal or neonatal severe infection and sepsis. Maternal infection associated with GBS includes acute chorioamnionitis, endometritis, and urinary tract infection.

Perinatal group B streptococcal disease prevention, Minnesota

In 2002, revised guidelines for preventing perinatal group B streptococcal disease were published. In 2002, all Minnesota providers surveyed reported using a prevention policy. Most screen vaginal and rectal specimens at 34–37 weeks of gestation. The use of screening-based methods has increased dramatically since 1998.

Comparison of two culture media and three sampling techniques for sensitive and rapid screening of vaginal colonization by group B streptococcus in pregnant women

The Centers for Disease Control and Prevention (CDC) recommend universal screening of all pregnant women between 35 and 37 weeks of gestation for group B streptococci (GBS) by use of a selective broth medium. Recent reports suggest that Granada medium can be used for rapid and direct visual identification of GBS colonies. However, studies comparing the Granada medium method to the selective broth method are few, and while some report comparable sensitivities, others have found significant differences in detection rates between the two methods. This prospective study compared a method using Granada agar to a Todd-Hewitt broth method with subculture to blood agar in order to determine which GBS detection method is more sensitive and less labor-intensive and has a more rapid turnaround time. Detection rates for three sampling techniques (rectovaginal, vaginal only, and cervical only) were also compared. Consecutive specimens for GBS screening received over a 6-month period from 1,635 pregnant women were included. Overall, GBS was detected in 390 (23.8%) women. The Granada medium gave positive results for 348 of these women, and the selective broth gave positive results for 385, indicating sensitivities of 89.2% for the Granada medium and 98.7% for the selective broth. These findings show that the Granada medium method is less sensitive than the selective broth method and should not replace it as the only method for screening pregnant women for GBS. However, the Granada medium method reduced detection time to 1 day and also reduced the use of ancillary tests in approximately 90% of positive cases. Additionally, no significant differences were noted in the detection rates with rectovaginal, vaginal, and cervical specimens.

Multicenter Study of a Rapid Molecular-Based Assay for the Diagnosis of Group B Streptococcus Colonization in Pregnant Women

BACKGROUND

Current prevention of infection due to group B Streptococcus (GBS) involves giving intrapartum antibiotics to women on the basis of either antenatal culture colonization status or presence of risk factors.

METHODS

We prospectively compared the performance characteristics of a rapid molecular diagnostic test (IDI-Strep B; Infectio Diagnostic) with culture for intrapartum GBS detection after 36 weeks' gestation in 5 North American centers during the period September 2001-May 2002. Antenatal GBS screening was done according to the usual practice of participating hospitals. Two combined vaginal/anal specimens were obtained from participants during labor by use of standard techniques and processed by the same laboratories that processed the antenatal specimens. Each swab sample was processed simultaneously by culture and with IDI-Strep B. The collected specimens were randomized for order of testing of the swab samples by culture or the rapid test.

RESULTS

Of enrolled women, 803 (91.1%) were eligible for analysis. The overall intrapartum GBS colonization rate by culture was 18.6% (range, 9.1%-28.7%). Compared with intrapartum culture, the molecular test had a sensitivity of 94.0% (range, 90.1%-97.8%), specificity of 95.9% (range, 94.3%-97.4%), positive predictive value of 83.8% (range, 78.2%-89.4%), and negative predictive value of 98.6% (range, 97.7%-99.5%). The molecular test was superior to antenatal cultures (sensitivity, 94% vs. 54%; P<.0001) and prediction of intrapartum status on the basis of risk factors (sensitivity, 94% vs. 42%; P<.0001).

CONCLUSION

Use of this test for determination of GBS colonization during labor is highly sensitive and specific and may lead to a further reduction in rates of neonatal GBS disease.

Screening protocols for group B streptococcus: are transport media appropriate?

Objective: To evaluate group B streptococcus (GBS) detection in an in vitro setting, using a low and controlled inoculum from swabs directly inoculated into a selective medium, as compared to delayed inoculation following a period in a commercial Amies transport medium with charcoal (Venturi Transystem^™ Copan, Italy).

Study design: Clinical isolates of GBS (n = 103), were inoculated into the Amies transport medium with charcoal in a concentration of 100 colony-forming units (cfu)/ml (10 cfu/swab). Swabs were then transferred to an enrichment broth (NPC) at time intervals of 0, 2, 4, 6 and 24 hours. Broths were then incubated for 18–24 hours at 35^°C in air, before being transferred to New Granada Medium Modified (NGM) for GBS detection and incubated for a further 18–24 hours at 35^°C in air. If the characteristic orange pigmented colonies were observed after this period, the specimen was recorded as + (1–10 colonies) or ++ (more than 10 colonies).

Results: Overall 92.2% (95/103) of isolates were detected in all tubes and at all times. An additional two isolates were non-hemolytic, non-pigment forming GBS. Of note, 3.9% (4/103) were negative until 2 hours delayed inoculation and 1.9% (2/103) gave inconsistent results, likely due to the low inoculum used.

Conclusion: Delayed inoculation into selective enrichment broth following a period in transport medium, even with a low inoculum, gave a similar and acceptable GBS detection rate to direct inoculation. Hence, Amies transport medium with charcoal is an appropriate transport medium to use, where it is not practical for clinical specimens to be directly inoculated into selective enrichment broth and as endorsed in the Centers for Diseases Control (CDC) Guidelines, 2002.

[Comparative study of three culture media for detecting group B Streptococcus colonization in pregnant women]

OBJECTIVE

To compare the efficacy of three culture media to detect vaginal and rectal colonization by group B streptococci (GBS) in pregnant women.

METHODS

We processed 1334 samples from 861 pregnant women: in 388 patients only vaginal swab was cultured (Group A) and in 473 vaginal and rectal swabs were cultured (Group B). Samples were inoculated on blood agar with colistin-nalidixic acid (BA-CNA), on plates with Granada medium, and on Todd-Hewitt broth (THB) with amikacin followed by subculture in BA-CNA.

RESULTS

GBS was isolated in 181 samples (13.6%): 114 vaginal swabs (13.2%) and 67 rectal swabs (14.2%). Among the positive samples, GBS was isolated on BA-CNA in 60.5% of vaginal swabs and in 59.7% of rectal swabs, on Granada medium in 80.7% of vaginal swabs and in 91% of rectal swabs, and on THB in 97.4% of vaginal swabs and in 97% of rectal swabs.We detected 130 GBS carriers, 54 (13.9%) in Group A and 76 (16.1%) in Group B. The percent of carriers detected in groups A and B, respectively, was 59.3% and 75% with BA-CNA, 77.8% and 93.4% with Granada medium, and 96.3% and 97.4% with THB.

CONCLUSIONS

THB was the most reliable medium for the detection of GBS. Use of Granada medium allows fast detection of about 87% of carriers. The combination of THB and an initial plate of Granada medium or BA-CNA allows detection of more than 99% of GBS carriers.

Invasive group B streptococcal infections in Finland: a population-based study

We analyzed surveillance data on group B streptococcus (GBS) infection in Finland from 1995 to 2000 and reviewed neonatal cases of early-onset GBS infection in selected hospitals in 1999 to 2000. From 1995 to 2000, 853 cases were reported (annual incidence 2.2-3.0/100,000 population). We found 32-38 neonatal cases of early-onset GBS disease per year (annual incidence 0.6-0.7/1,000 live births). In five hospitals, 35% of 26 neonatal cases of early-onset GBS infection had at least one risk factor: prolonged rupture of membranes, preterm delivery, or intrapartum fever. Five of eight mothers screened for GBS were colonized. In one case, disease developed despite intrapartum chemoprophylaxis. Although the incidence of early-onset GBS disease in Finland is relatively low, some geographic variation exists, and current prevention practices are suboptimal. Establishing national guidelines to prevent perinatal GBS is likely to reduce the incidence of the disease.

Epidemiology and predictive values of risk factors for neonatal group B streptococcal sepsis

OBJECTIVES

To determine the incidence of and factors affecting risk factors for neonatal group B streptococcal (GBS) sepsis and their predictive values for intrapartum GBS carriage; to calculate the proportions of women eligible for intrapartum antibiotic prophylaxis (IAP) using different selection protocols.

DESIGN

Cohort study.

SETTING

Antenatal clinics and labour wards of a community hospital and a tertiary referral centre in western Sydney

POPULATION

Women attending antenatal clinics during the study periods were invited to participate.

METHODS

Approximately 500 women attending antenatal clinics were screened for GBS carriage at 26-32 weeks gestation and at delivery, using several screening methods. Clinical risk factors for neonatal sepsis were recorded during labour.

MAIN OUTCOME MEASURES

Incidence of antenatal anovaginal GBS carriage and clinical risk factors during labour, their predictive values for intra-partum GBS carriage and their relationship, if any, to demographic and obstetric factors.

RESULTS

Antenatal and intra-partum GBS carriage rates were similar but varied from 18% to 27%, depending on screening methods. The best positive and negative predictive values of antenatal GBS culture, for intra-partum carriage, were 69% (95% confidence interval (CI) 64-74) and 92% (95% CI 50-94) respectively Clinical risk factors occurred in similar proportions of GBS carriers and non-carriers.

CONCLUSIONS

Neither early antenatal screening nor clinical risk factors are reliable predictors of intra-partum GBS carriage. Intra-partum antibiotic prophylaxis based on GBS carriage or risk factors when carrier status is unknown would involve approximately 35% of women, compared with approximately 16% if based on risk factors only Both strategies would prevent similar proportions of neonatal deaths from GBS sepsis. Compliance with a preventive protocol is the most likely determinant of its overall effectiveness.

Evaluation of methods to increase the sensitivity and timeliness of detection of Streptococcus agalactiae in pregnant women

Direct culture of rectovaginal specimens on Granada agar was compared to culture on sheep blood agar plate (SBAP) and AccuProbe detection of group B streptococcus from overnight LIM broth enhancement cultures (LIM-SBAP). Both broth-enhanced methods demonstrated excellent sensitivity (97.5% for LIM-SBAP and 93.5% for AccuProbe), while Granada agar demonstrated a sensitivity of only 40.3%.

Early-onset neonatal group B streptococcal infection: 2002 guidelines for prevention

In 1996, the Centers for Disease Control and Prevention (CDC) and relevant professional organizations jointly released guidelines for prevention of early-onset neonatal group B streptococcal infections. The guidelines recommended that all obstetric providers and institutions providing intrapartum services follow one of two strategies. This year, on the basis of multistate surveillance data collected since prevention strategies were initiated, the CDC has released revised prevention recommendations. This article reviews the new guidelines and discusses clinical implications for practice in a variety of settings.

Early-onset group B streptococcus prevention protocols in New Zealand public hospitals

OBJECTIVE

Determine group B streptococcus (GBS) prevention protocols.

METHODS

Questionnaire survey of 19 hospitals accounting for 73% of New Zealand births.

RESULTS

Prevention policies were reported by 16 (84%) hospitals (bacteriological-screening n = 4, risk-factor determination n = 8, both strategies n = 4). Only five out of 12 (42%) centres using risk-assessment administered antibiotics for all high-risk criteria. Inadequate specimen collection and culture methods meant no hospital maximised culture-based strategies. Nevertheless, hospitals with prevention policies had lower early-onset GBS disease rates (0.46 versus 1.44 per 1,000 births; OR 0.32; (95% CI 0.12, 0.98)).

CONCLUSIONS

Prevention strategies can be further improved by hospitals fully implementing nationally agreed guidelines.

Late antenatal carriage of group B Streptococcus by New Zealand women

OBJECTIVES

To determine in New Zealand women the prevalence of group B Streptococcus (GBS) carriage late in pregnancy and to identify GBS colonisation risk factors, antibiotic susceptibility and serotype distribution.

DESIGN

Prospective, observational study.

SETTING

Community and hospital antenatal clinics in Wellington and Auckland during 1998-1999.

SAMPLE

Convenience sample of 240 women between 35-37 weeks gestation.

METHODS

Sociodemographic data, obstetric details and anogenital swabs were collected from each subject. Swabs were inoculated into selective media. GBS isolates underwent serotyping and antibiotic susceptibility testing.

RESULTS

Two hundred and forty women (9% Maori, 11% Pacific) aged 15-41 years were recruited. Fifty-two (22%; 95% CI 17, 27) were colonised by GBS. Carriage was independently associated with younger age (59% < or = 30 years; adjusted OR 3.25; 95% CI 1.53, 6.95) and least social deprivation (57% NZ Dep 96 score +/- 3; adjusted OR 1.22; 95% CI 1.06,1.39). All GBS isolates were penicillin-susceptible, but resistance to clindamycin (15%) and erythromycin (7.5%) was detected and associated with serotype V strains. Predominant serotypes were: III (29%), Ia (21%), Ib (20%) and V (20%).

CONCLUSIONS

Approximately 20% of New Zealand women carry GBS late in pregnancy, with young age a major risk factor. Increased risk in the socially advantaged, development of resistance to erythromycin and clindamycin, and emergence of new GBS serotypes are findings with important implications for prevention strategies requiring further confirmation.

Maternal screening and treatment for group B streptococcus

Maternal group B streptococcus colonization can result in complications for both mother and fetus. There are two protocols for decreasing the risk of infection: antenatal cultures and intrapartum risk-factor screening. Compliance with guidelines improves with the active participation of nurses who monitor women at risk, notify clinicians when treatment is appropriate, and provide patient support and education.

Antibacterial properties of human amnion and chorion in vitro

OBJECTIVE

The purpose of the present study was to explore the direct effects of amnion and chorion on bacterial growth in vitro including the antibacterial spectrum. Chorioamniotic membranes were obtained under sterile conditions from 13 healthy women undergoing elective cesarean section at term. Likewise, chorioamniotic membranes were obtained from 10 healthy women with spontaneous vaginal delivery at term. Five strains of Hemolytic streptococci group B (GBS) were tested and one clinical isolate of the following species or bacterial groups: Hemolytic streptococcus group A, Staphylococcus aureus, Staphylococcus saprophyticus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter calcoaceticus and Lactobacillus species. Bacteriological media included (1) blood-agar medium; (2) a transparent agar medium for submerged cultures; and (3) a nutrient broth medium.

RESULTS

An inhibitory effect of fetal membranes against a range of bacteria was found. Consistent results were obtained in experiments with cultures on agar and cultures suspended in agar (membranes from eight women in both studies). In experiments with liquid cultures (seven women) only chorion showed a marginal inhibitory effect. All strains were inhibited, but the most pronounced inhibition was obtained for streptococcus group A, S. aureus and S. saprophyticus by both chorion and amnion.

CONCLUSION

This study demonstrated an inhibitory effect of the fetal membranes on a diverse panel of bacteria

Neonatal group B streptococcal infection. Results of 33 months of universal maternal screening and antibioprophylaxis

OBJECTIVE

To assess the efficacy and pitfalls of a protocol of generalized screening for group B Streptococcus (GBS) and intra-partum treatment of all carriers in a clinical setting.

DESIGN

A descriptive study and comparison with an historical group.

SETTING

A tertiary perinatal center.

POPULATION

All women attending prenatal care in our center and delivered after 37 weeks were eligible. Study period ranged from January 1994 to September 1996. Comparison group consisted in deliveries of years 1992 and 1993.

METHODS

Vaginal cultures were performed at 36 weeks on non-selective medium followed by intra-partum treatment of all carrier mothers. Rate of carriage, incidence of neonatal GBS sepsis, influence of risk factors and the reasons for failures were analysed. Comparison was made with an historical group. Statistical analysis was performed using a Chi-square test.

RESULTS

There were 5374 term deliveries during the study. 3906 were screened (72.7%) and 559 of them found positive for GBS (14.3%). We observed 46 early-onset GBS diseases (0.86% of term-births). 43.5% of infections occurred in babies born from mothers without risks factors at delivery. Negative GBS cultures at sampling accounted for 43.5% of protocol failures. Comparison of the incidence of early-onset GBS disease with the previous two years showed a significant drop (1.45-0.86%, P<0.05).

CONCLUSIONS

Our protocol revealed feasible and effective in reducing the incidence of early-onset GBS disease. Improvements must be studied particularly as to the predictive value of screening cultures.

Neonatal group B streptococcal disease: how infection control teams can contribute to prevention efforts

Group B streptococcal (GBS) disease is a leading cause of morbidity and mortality among newborns. Many cases of newborn GBS disease can be prevented by the administration of intrapartum antibiotic prophylaxis. Current consensus guidelines for prevention of perinatal GBS disease have led to substantial declines in the incidence of GBS disease occurring in newborns <7 days of age (early-onset disease). Despite declines in the incidence of early-onset disease, approximately 20% of pregnant women are colonized with GBS at the time of labor and thus have the risk of transmitting the bacteria to their newborns. Consequently, continued and improved implementation of prevention efforts is essential. Infection control teams can contribute uniquely to prevention of perinatal GBS disease by serving as hospital champions of GBS disease prevention. In particular, teams can coordinate with administration and staff to encourage establishment and effective implementation of GBS prevention policies; facilitate improved laboratory processing of prenatal GBS screening specimens; monitor any adverse consequences of increased use of intrapartum antibiotics within the hospital; and investigate GBS cases that occur to determine whether they could have been prevented. By spearheading efforts to improve implementation of perinatal GBS disease prevention at the hospital level, hospital epidemiologists and infection control practitioners can play an important role in reducing the burden of early-onset GBS disease.

Development of Conventional and Real-Time PCR Assays for the Rapid Detection of Group B Streptococci

Background: Group B streptococci (GBS), or Streptococcus agalactiae, are the leading bacterial cause of meningitis and bacterial sepsis in newborns. Currently available rapid methods to detect GBS from clinical specimens are unsuitable for replacement of culture methods, mainly because of their lack of sensitivity.

Methods: We have developed a PCR-based assay for the rapid detection of GBS. The cfb gene encoding the Christie-Atkins-Munch-Petersen (CAMP) factor was selected as the genetic target for the assay. The PCR primers were initially tested by a conventional PCR method followed by gel electrophoresis. The assay was then adapted for use with the LightCyclerTM. For this purpose, two fluorogenic adjacent hybridization probes complementary to the GBS-specific amplicon were designed and tested. In addition, a rapid sample-processing protocol was evaluated by colony-forming unit counting and PCR. A total of 15 vaginal samples were tested by both standard culture method and the two PCR assays.

Results: The conventional PCR assay was specific because it amplified only GBS DNA among 125 bacterial and fungal species tested, and was able to detect all 162 GBS isolates from various geographical areas. This PCR assay allowed detection of as few as one genome copy of GBS. The real-time PCR assay was comparable to conventional PCR assay in terms of sensitivity and specificity, but it was more rapid, requiring only ∼30 min for amplification and computer-based data analysis. The presence of vaginal specimens had no detrimental effect on the sensitivity of the PCR with the sample preparation protocol used. All four GBS-positive samples identified by the standard culture method were detected by the two PCR assays.

Conclusion: These assays provide promising tools for the rapid detection and identification of GBS.

Two-year survey of Alberta laboratories processing of antenatal group B streptococcal (GBS) screening specimens: implications for GBS screening programs

We evaluated specimen types received and methods used by laboratories to process screening GBS specimens from pregnant women. Surveys during 1995 and 1997 of all laboratories in the province of Alberta, Canada that culture GBS from screening genital specimens were completed. Between surveys, there was dissemination of information about appropriate culture techniques. Survey completion rates were 100% in both years (38/38 in 1995 and 20/20 in 1997). During 1995 as compared to 1997, laboratories were less likely to a) have a specific written protocol for identification of genital GBS screening specimens (1995: 78.2% versus 1997: 100%, p = 0.08) b) be receiving combined vaginal-anorectal swabs (1995: 18% of all swabs received versus 1997: 60.4%, p < 0.001), and c) be using selective GBS culture media (1995: 45.5% versus 1997: 86.7%, p = 0.01). Regions using screening based approaches for GBS prevention need to ensure that their laboratories are using adequate techniques for GBS detection.

Group B streptococcal infections

Group B streptococcal infection is the most common cause of neonatal sepsis and is responsible for significant neonatal morbidity and mortality. Group B streptococcus is also the causative agent in 50,000 maternal infections per year. Approximately 30% of women have asymptomatic group B streptococcal colonization at some time during pregnancy, but the neonatal attack rate is only about 2 per 1,000 deliveries. Maternal and neonatal risk factors contribute to the rates of vertical transmission and symptomatic neonatal disease. Options that have been investigated for prevention of neonatal group B streptococcal disease include identification of at-risk pregnancies as well as antenatal, intrapartum, and neonatal treatment. The intrapartum treatment of women at risk for vertical transmission of group B streptococcus to their neonates unequivocally has been shown to decrease the rate of neonatal colonization. Practitioners should implement one of two strategies that incorporate intrapartum prophylaxis for prevention of perinatal group B disease.

Epidemiology of group B streptococcal disease in the United States: shifting paradigms

Since its emergence 25 years ago, group B streptococcus has become recognized as a cause of serious illness in newborns, pregnant women, and adults with chronic medical conditions. Heavy colonization of the genital tract with group B streptococcus also increases the risk that a woman will deliver a preterm low-birthweight infant. Early-onset infections (occurring at < 7 days of age) are associated with much lower fatality than when they were first described, and their incidence is finally decreasing as the use of preventive antibiotics during childbirth increases among women at risk. New serotypes of group B streptococcus have emerged as important pathogens in adults and newborns. Clinical and laboratory practices--in obstetrics, pediatrics, and clinical microbiology--have an impact on disease and/or its prevention, and protocols established at the institutional level appear to be critical tools for the reduction of perinatal disease due to group B streptococcus. Since intrapartum antibiotics will prevent at best only a portion of the full burden of group B streptococcal disease, critical developments in vaccine evaluation, including study of polysaccharide-protein conjugate vaccines, offer the potential for enhanced prevention in the relatively near future.

Maternal colonization with group B Streptococcus and prelabor rupture of membranes at term: the role of induction of labor. TermPROM Study Group

OBJECTIVES

Our purpose was to determine the effect of induction of labor on neonatal infection if mothers are group B streptococci positive and have prelabor rupture of membranes at term.

STUDY DESIGN

In the TermPROM study 5041 women were randomized to induction with intravenous oxytocin, induction with vaginal prostaglandin E2 gel, or expectant management with induction, if needed. Of these, 4834 women had vaginal or introital swabs for group B streptococci taken at entry. We used logistic regression to test for effects of treatment within group B streptococci subgroups.

RESULTS

Group B streptococci were predictive of neonatal infection for the induction with vaginal prostaglandin E2 gel and expectant groups but not for the induction with oxytocin group. For women positive for group B streptococci the rates of neonatal infection were 2.5% for the induction with oxytocin group and > 8% for all other groups.

CONCLUSIONS

Induction of labor with intravenous oxytocin may be preferable for group B streptococci-positive women with prelabor rupture of membranes at term.

A comparison of the yield of positive antenatal group B Streptococcus cultures with direct inoculation in selective growth medium versus primary inoculation in transport medium followed by delayed inoculation in selective growth medium

OBJECTIVE

Our purpose was to compare the yield of positive group B Streptococcus cultures with standard medium for transport of culture swabs compared with use of selective medium during transport.

STUDY DESIGN

Cultures of introitus, perineum, and rectum were obtained on prenatal patients; one was placed in standard transport medium, and the other directly in selective growth medium. Swabs in standard transport medium were plated for routine culture and then transferred to selective growth medium, Todd-Hewitt broth, in the laboratory.

RESULTS

A total of 307 of 1222 (25.1%) patients had a positive result by any method. With direct inoculation into selective growth medium at the time of sampling, 4.6% of positive cultures were missed. With delayed inoculation into selective growth medium, 16.3% were missed (p < 0.001). Without use of selective media (routine culture), 31.9% were missed (p < 0.001).

CONCLUSIONS

Use of standard transport medium with subsequent transfer into selective growth medium results in a significantly decreased yield of positive group B Streptococcus cultures.