Population-based active surveillance for neonatal group B streptococcal infections in Alberta, Canada: implications for vaccine formulation

Sublingual immunisation with GBS serotype III capsular polysaccharide-tetanus toxoid conjugate vaccine induces systemic and mucosal antibody responses which are opsonophagocytic and inhibit GBS colonisation of vaginal epithelial cells

No vaccines are currently licensed against Group B streptococcus (GBS), an important cause of morbidity and mortality in babies and adults. Using a mouse model, and in vitro opsonophagocytosis and colonisation assays, we evaluated the potential of a sublingually-administered polysaccharide-conjugate vaccine against GBS serotype III. Sublingual immunisation of mice with 10 µg of GBS conjugate vaccine once a week for 5 weeks induced a substantial systemic IgG anti-polysaccharide response which was similar to the level induced by subcutaneous immunsation. In addition, sublingual immunisation also induced mucosal (IgA) antibody responses in the mouth, intestines and vagina. Immune sera and intestinal washes were functionally active at mediating killing of the homologous GBS serotype III in an opsonophagocytosis assay. In addition, intestinal and vaginal washes inhibited the colonisation of mouse vaginal epithelial cells by the vaccine homologous strain. These results suggest that, in addition to the induction of high levels of IgG antibodies that could be transduced from the immunised mother to the foetus to protect the newborn against GBS infection, sublingual immunisation can elicit a substantial mucosal antibody response which might play an important role in the prevention of GBS colonisation in immunised women, thereby eliminating the risk of GBS transmission from the mother to the baby during pregnancy or at birth.

Systematic review of Group B Streptococcal capsular types, sequence types and surface proteins as potential vaccine candidates

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Most comprehensive review of Group B Streptococcal serotypes through 2018.

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First systematic review of Group B Streptococcal strain type and protein data.

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Theoretically candidate vaccines may protect against 93-99% disease-causing strains.

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More studies on GBS strains in low- and middle-income countries are needed.

Background

21 million pregnant women worldwide (18%) are estimated to carry Group B Streptococcus (GBS), which is a risk for invasive disease in newborns, pregnant women, and stillbirths. Adults ≥ 60 years or with underlying health conditions are also vulnerable to invasive GBS disease. We undertook systematic reviews on GBS organism characteristics including: capsular polysaccharide (serotype), sequence type (multi-locus sequence types (MLST)), and virulence proteins. We synthesised data by at-risk populations, to inform vaccine development.

Methods

We conducted systematic reviews and meta-analyses to estimate proportions of GBS serotypes for at risk populations: maternal colonisation, invasive disease in pregnant women, stillbirths, infants 0–90 days age, and older adults (≥60 years). We considered regional variation and time trends (2001–2018). For these at-risk population groups, we summarised reported MLST and surface proteins.

Results

Based on 198 studies (29247isolates), 93–99% of GBS isolates were serotypes Ia, Ib, II, III, IV and V. Regional variation is likely, but data gaps are apparent, even for maternal colonisation which has most data. Serotype III dominates for infant invasive disease (60%) and GBS-associated stillbirths (41%). ST17 accounted for a high proportion of infant invasive disease (41%; 95%CI: 35–47) and was found almost exclusively in serotype III strains, less present in maternal colonisation (9%; 95%CI:6–13),(4%; 95%CI:0–11) infant colonisation, and adult invasive disease (4%, 95%CI:2–6). Percentages of strains with at least one of alp 1, alp2/3, alpha C or Rib surface protein targets were 87% of maternal colonisation, 97% infant colonisation, 93% infant disease and 99% adult invasive disease. At least one of three pilus islands proteins were reported in all strains.

Discussion

A hexavalent vaccine (serotypes Ia, Ib, II, III, IV and V) might provide comprehensive cover for all at-risk populations. Surveillance of circulating, disease-causing target proteins is useful to inform vaccines not targeting capsular polysaccharide. Addressing data gaps especially by world region and some at-risk populations (notably stillbirths) is fundamental to evidence-based decision-making during vaccine design.

The impact of Lactobacillus on group B streptococcal interactions with cells of the extraplacental membranes

Group B Streptococcus (GBS) causes adverse pregnancy outcomes and neonatal disease. The recommended preventative measure is intrapartum antibiotic prophylaxis, which can prevent early onset neonatal disease but not chorioamnionitis, preterm labor, stillbirth, or late-onset disease. Novel prevention methods are therefore needed. Use of probiotics including Lactobacillus spp., has been suggested given that they are dominant members of the lower reproductive tract microbiome. Although Lactobacillus was shown to reduce recto-vaginal colonization of GBS, no studies have examined how Lactobacillus impacts GBS in the extraplacental membranes. Since Lactobacillus has been detected in the placental membranes, we sought to characterize GBS-Lactobacillus interactions in vitro using a colonizing and invasive GBS strain. While live Lactobacillus did not affect growth or biofilms in GBS, co-culture with L. gasseri led to a 224-fold increase in GBS association with decidualized human endometrial stromal cells for both GBS strains (p < 0.005). Increased association did not result in increased invasion (p > 0.05) or host cell death, though some GBS and Lactobacillus combinations contributed to a significant reduction in host cell death (p < 0.05). Since Lactobacillus secretes many inhibitory compounds, the effect of Lactobacillus supernatants on GBS was also examined. The supernatants inhibited GBS growth, biofilm formation and invasion of host cells, though strain dependent effects were observed. Notably, supernatant from L. reuteri 6475 broadly inhibited growth in 36 distinct GBS strains and inhibited GBS growth to an average of 46.6% of each GBS strain alone. Together, these data show that specific Lactobacillus strains and their secreted products have varying effects on GBS interactions with cells of the extraplacental membranes that could impact pathogenesis. Understanding these interactions could help guide new treatment options aimed at reducing GBS-associated maternal complications and disease.

No. 298-The Prevention of Early-Onset Neonatal Group B Streptococcal Disease

OBJECTIVE

To review the evidence in the literature and to provide recommendations on the management of pregnant women in labour for the prevention of early-onset neonatal group B streptococcal disease. The key revisions in this updated guideline include changed recommendations for regimens for antibiotic prophylaxis, susceptibility testing, and management of women with pre-labour rupture of membranes.

OUTCOMES

Maternal outcomes evaluated included exposure to antibiotics in pregnancy and labour and complications related to antibiotic use. Neonatal outcomes of rates of early-onset group B streptococcal infections are evaluated.

EVIDENCE

Published literature was retrieved through searches of MEDLINE, CINAHL, and The Cochrane Library from January 1980 to July 2012 using appropriate controlled vocabulary and key words (group B streptococcus, antibiotic therapy, infection, prevention). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to May 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

The recommendations in this guideline are designed to help clinicians identify and manage pregnancies at risk for neonatal group B streptococcal disease to optimize maternal and perinatal outcomes. No cost-benefit analysis is provided.

SUMMARY STATEMENT

There is good evidence based on randomized control trial data that in women with pre-labour rupture of membranes at term who are colonized with group B streptococcus, rates of neonatal infection are reduced with induction of labour (I). There is no evidence to support safe neonatal outcomes with expectant management in this clinical situation.

RECOMMENDATIONS

Effectiveness of oral intake of Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 on Group B Streptococcus colonization during pregnancy: a midwifery-led double-blind randomized controlled pilot trial

OBJECTIVE

Group B streptococcus (GBS) vaginal/rectal colonization in pregnancy has been associated with early-onset GBS disease (EOGBSD), a leading cause of neonatal morbidity and mortality. In Canada, universal screening for GBS colonization is offered to pregnant people at 35-37 weeks' gestation and those who test positive are offered intrapartum antibiotic prophylaxis (IAP). Universal screening and treatment with IAP have not eradicated all cases of EOGBSD, and IAP has documented side effects. Probiotic supplements have been proposed as a possible way to reduce GBS colonization.

MATERIALS AND METHODS

Pregnant midwifery clients >18 years of age and <45 years of age and with a gestational age of <25 weeks at the time of enrolment were randomly assigned to receive two capsules of probiotics (Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14) or placebo orally daily for 12 weeks at 23-25 weeks' gestation. The primary aim was to determine the feasibility of a larger study. The rate of GBS vaginal/rectal colonization at 35-37 weeks' gestation was also assessed in both groups.

RESULTS

In total, 139 pregnant midwifery clients were randomized (probiotic group [N = 73] and placebo group [N = 66]). Of these, 113 were included in the final analysis (probiotic group [N = 57] and placebo group [N = 56]). Baseline characteristics between groups were similar with the exception of gestational age (p < .01). The recruitment rate was low at 12%, but the mean compliance rate was 87%. The eligibility/ineligibility criteria were too strict and changes to the study design will be required for the larger proposed study. The rates of vaginal/rectal GBS colonization did not differ significantly between groups (15.8 versus 21.43%; p = .48). No adverse effects were documented in the probiotic group.

CONCLUSION

This was the first midwifery-led trial involving a natural health product in the province of Ontario. Although treatment with oral probiotics is feasible, the results were not superior to placebo in reducing the rate of GBS colonization. An adequately powered, randomly controlled trial is required to assess the effectiveness of the two probiotic strains.

Perinatal Streptococcus agalactiae Epidemiology and Surveillance Targets

Streptococcus agalactiae, or group B streptococcus (GBS), is a major neonatal pathogen. Recent data have elucidated the global prevalence of maternal and neonatal colonization, but gaps still remain in the epidemiology of this species. A number of phenotypic and genotypic classifications can be used to identify the diversity of GBS strains, and some are more discriminatory than others. This review explores the main schemes used for GBS epidemiology and further details the targets for epidemiological surveillance. Current screening practices across the world provide a unique opportunity to gain detailed information on maternal colonizing strains and neonatal disease-causing strains, which is vital for monitoring and therapeutics, if sufficient detail can be extracted. Deciphering which isolates are circulating within specific populations and recording targets within invasive strains are crucial steps in monitoring the implementation of therapeutics, such as vaccines, as well as developing novel therapies against prevalent GBS strains. Having a detailed understanding of global GBS epidemiology will prove invaluable for understanding the pathogenesis of this organism and equipping future prevention strategies for success.

Infant Group B Streptococcal Disease Incidence and Serotypes Worldwide: Systematic Review and Meta-analyses

Background

Group B Streptococcus (GBS) remains a leading cause of neonatal sepsis in high-income contexts, despite declines due to intrapartum antibiotic prophylaxis (IAP). Recent evidence suggests higher incidence in Africa, where IAP is rare. We investigated the global incidence of infant invasive GBS disease and the associated serotypes, updating previous estimates.

Methods

We conducted systematic literature reviews (PubMed/Medline, Embase, Latin American and Caribbean Health Sciences Literature [LILACS], World Health Organization Library Information System [WHOLIS], and Scopus) and sought unpublished data regarding invasive GBS disease in infants aged 0–89 days. We conducted random-effects meta-analyses of incidence, case fatality risk (CFR), and serotype prevalence.

Results

We identified 135 studies with data on incidence (n = 90), CFR (n = 64), or serotype (n = 45). The pooled incidence of invasive GBS disease in infants was 0.49 per 1000 live births (95% confidence interval [CI], .43–.56), and was highest in Africa (1.12) and lowest in Asia (0.30). Early-onset disease incidence was 0.41 (95% CI, .36–.47); late-onset disease incidence was 0.26 (95% CI, .21–.30). CFR was 8.4% (95% CI, 6.6%–10.2%). Serotype III (61.5%) dominated, with 97% of cases caused by serotypes Ia, Ib, II, III, and V.

Conclusions

The incidence of infant GBS disease remains high in some regions, particularly Africa. We likely underestimated incidence in some contexts, due to limitations in case ascertainment and specimen collection and processing. Burden in Asia requires further investigation.

Incidence and serotype characterisation of Streptococcus agalactiae in a Portuguese hospital

AIMS

Streptococcus agalactiae, commonly known as group B Streptococcus (GBS), has been recognised as a worldwide causative pathogenic agent of neonatal sepsis, meningitis and pneumonia. To better understand the behaviour of S. agalactiae in pregnant women from a hospital from the North of Portugal, retrospective analyses were performed to describe epidemiological, clinical and microbiological characteristics of the isolates obtained.

METHODS

Based on laboratorial records and the hospital's patient files, a 6-year retrospective study was performed to analyse S. agalactiae isolates from screened pregnant women between 35 and 37 weeks of gestation and hospitalised neonates from pregnant women between 24 and 41 weeks of gestation admitted in Hospital Pedro Hispano. Serotype characterisation was also performed in 67 GBS strains.

RESULTS

In 6692 pregnant women between 35 and 37 weeks of gestation screened between 2011 and 2016, a total of 1377 S. agalactiae isolates (21%) were found. A high percentage (40%) of unknown colonisation status among hospitalised neonates from pregnant women between 24 and 41 weeks of gestations was also found. The incidence of neonatal sepsis was 8.7 (95% CI 7.0 to 10.8) cases per 1000 live births. Regarding serotype characterisation, serotype III (22.4%) was the most frequent, followed by serotype Ia (19.4%) and serotypes Ib and V (both with 17.9%).

CONCLUSION

High epidemiological values of GBS colonisation and incidence were found in this study. In Portugal studies on the epidemiology and behaviour of S. agalactiae remain limited, reinforcing the importance and need for S. agalactiae screening across the country.

Identification of Group B Streptococcus Capsule Type by Use of a Dual Phenotypic/Genotypic Assay

The group B streptococcus (GBS) capsular polysaccharide (CPS) is an important virulence factor which is also used for GBS typing. There are 10 CPS types (Ia, Ib, and II to IX). GBS that do not phenotypically type are considered nontypeable. All genes required for CPS synthesis are found on the GBS cps operon, which contains a highly variable CPS-determining region (cpsG-cpsK). The objective of this study was development of an assay to detect sialic acid on the GBS cell surface, followed by a genotypic PCR CPS typing assay. Sialic acid is located at the terminal end of the side chain of all known GBS CPS types. Sialic acid can be bound to commercially available lectins such as slug Limax flavus lectin. Biotinylated L. flavus-streptavidin-peroxidase complex was used in an enzyme immunoassay and dot blot assay to detect sialic acid. This was followed by a PCR typing scheme that was developed to target the serotype-determining region of the cps locus for Ia, Ib, and II to IX. Sialic acid from the CPS types Ia, Ib, and II to IX was detectable on the GBS cell surfaces of all previously identified CPS-typed GBS strains assayed. This was followed by the real-time PCR typing assay which successfully identified CPS Ia, Ib, and II to IX types. The combination of phenotypic and genotypic assays provides an accurate tool for detection of CPS expression and assignment of CPS typing. These assays have the potential to be used for CPS typing in large-scale epidemiological studies.

Prévention de l'infection néonatale à streptocoques du groupe B d'apparition précoce

OBJECTIF

Analyser les données issues de la littérature et formuler des recommandations sur la prise en charge des parturientes en vue de prévenir l'infection néonatale à streptocoques du groupe B d'apparition précoce. Parmi les révisions clés que renferme la présente directive clinique mise à jour, on trouve des modifications quant aux recommandations en ce qui concerne les schémas posologiques d'antibioprophylaxie, les épreuves de sensibilité et la prise en charge des femmes présentant une rupture prématurée des membranes.

ISSUES

Parmi les issues maternelles évaluées, on trouvait l'exposition aux antibiotiques au cours de la grossesse et du travail, ainsi que les complications associées à l'administration d'antibiotiques. Les issues néonatales associées aux taux d'infection néonatale à streptocoques du groupe B d'apparition précoce ont été évaluées. RéSULTATS: La littérature publiée a été récupérée par l'intermédiaire de recherches menées dans PubMed, CINAHL et The Cochrane Library entre janvier 1980 et juillet 2012, au moyen d'un vocabulaire contrôlé et de mots clés appropriés (« group B streptococcus », « antibiotic therapy », « infection », « prevention »). Les résultats ont été restreints aux analyses systématiques, aux essais comparatifs randomisés / essais cliniques comparatifs et aux études observationnelles. Aucune restriction n'a été appliquée en matière de date ou de langue. Les recherches ont été mises à jour de façon régulière et intégrées à la directive clinique jusqu'en mai 2013. La littérature grise (non publiée) a été identifiée par l'intermédiaire de recherches menées dans les sites Web d'organismes s'intéressant à l'évaluation des technologies dans le domaine de la santé et d'organismes connexes, dans des collections de directives cliniques, dans des registres d'essais cliniques et auprès de sociétés de spécialité médicale nationales et internationales.

VALEURS

La qualité des résultats est évaluée au moyen des critères décrits dans le rapport du Groupe d'étude canadien sur les soins de santé préventifs (Tableau 1). AVANTAGES, DéSAVANTAGES ET COûTS: Les recommandations que renferme la présente directive clinique sont conçues de façon à aider les cliniciens à identifier et à assurer la prise en charge des grossesses exposées à un risque d'infection néonatale à streptocoques du groupe B, en vue d'optimiser les issues maternelles et périnatales. Aucune analyse de rentabilité n'est fournie. DéCLARATION SOMMAIRE: Nous disposons de bonnes données (issues d'essais comparatifs randomisés) indiquant que, chez les femmes présentant une rupture prématurée des membranes à terme qui sont colonisées par des streptocoques du groupe B, le déclenchement du travail entraîne une baisse des taux d'infection néonatale. (I) Aucune donnée ne permet de soutenir que, dans une telle situation clinique, la prise en charge non interventionniste permet l'obtention de bonnes issues néonatales. RECOMMANDATIONS.

The Prevention of Early-Onset Neonatal Group B Streptococcal Disease

OBJECTIVE

To review the evidence in the literature and to provide recommendations on the management of pregnant women in labour for the prevention of early-onset neonatal group B streptococcal disease. The key revisions in this updated guideline include changed recommendations for regimens for antibiotic prophylaxis, susceptibility testing, and management of women with pre-labour rupture of membranes.

OUTCOMES

Maternal outcomes evaluated included exposure to antibiotics in pregnancy and labour and complications related to antibiotic use. Neonatal outcomes of rates of early-onset group B streptococcal infections are evaluated.

EVIDENCE

Published literature was retrieved through searches of MEDLINE, CINAHL, and The Cochrane Library from January 1980 to July 2012 using appropriate controlled vocabulary and key words (group B streptococcus, antibiotic therapy, infection, prevention). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to May 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

The recommendations in this guideline are designed to help clinicians identify and manage pregnancies at risk for neonatal group B streptococcal disease to optimize maternal and perinatal outcomes. No cost-benefit analysis is provided.

SUMMARY STATEMENT

There is good evidence based on randomized control trial data that in women with pre-labour rupture of membranes at term who are colonized with group B streptococcus, rates of neonatal infection are reduced with induction of labour (I). There is no evidence to support safe neonatal outcomes with expectant management in this clinical situation.

RECOMMENDATIONS

Challenges in reducing group B Streptococcus disease in African settings

Group B Streptococcus (GBS) is a leading cause of neonatal sepsis and meningitis in high-income settings and is associated with high rates of neonatal mortality and morbidity. There is now increasing evidence to suggest that there is a high GBS disease burden in resource-limited countries, and it is therefore critically important to identify suitable and practical preventive strategies. In Europe and North America, intrapartum antibiotic prophylaxis (IAP) has led to a dramatic reduction of early-onset GBS disease. However, the methods for identifying pregnant women who should receive IAP and how to reduce late-onset GBS disease are not without controversy and are challenging for most sub-Saharan African countries. GBS vaccines are approaching phase III trials but are still under development. This review aims to explore the current evidence related to strategies for reducing invasive GBS disease in an African setting, the development of a GBS vaccine and whether preventative measures against GBS disease can be practically implemented.

Differing mechanisms of surviving phagosomal stress among group B Streptococcus strains of varying genotypes

Group B Streptococcus (GBS), a leading cause of neonatal sepsis and meningitis, asymptomatically colonizes up to 30% of women and can persistently colonize even after antibiotic treatment. Previous studies have shown that GBS resides inside macrophages, but the mechanism by which it survives remains unknown. Here, we examined the ability of 4 GBS strains to survive inside macrophages and then focused on 2 strains belonging to sequence type (ST)-17 and ST-12, to examine persistence in the presence of antibiotics. A multiple stress medium was also developed using several stressors found in the phagosome to assess the ability of 30 GBS strains to withstand phagosomal stress. The ST-17 strain was more readily phagocytosed and survived intracellularly longer than the ST-12 strain, but the ST-12 strain was tolerant to ampicillin unlike the ST-17 strain. Exposure to sub-inhibitory concentrations of ampicillin and erythromycin increased the level of phagocytosis of the ST-17 strain, but had no effect on the ST-12 strain. In addition, blocking acidification of the phagosome decreased the survival of the ST-17 strain indicating a pH-dependent survival mechanism for the ST-17 strain. Congruent with the macrophage experiments, the ST-17 strain had a higher survival rate in the multiple stress medium than the ST-12 strain, and overall, serotype III isolates survived significantly better than other serotypes. These results indicate that diverse GBS strains may use differing mechanisms to persist and that serotype III strains are better able to survive specific stressors inside the phagosome relative to other serotypes.

Group B streptococcal immunisation of pregnant women for the prevention of early and late onset Group B streptococcal infection of the neonate as well as adult disease

INTRODUCTION

Early onset neonatal Group B streptococcal disease is preventable. Intrapartum antibiotic prophylaxis has resulted in a significant reduction in neonatal mortality and morbidity. National guidelines for the selection of women eligible for intrapartum antibiotic prophylaxis, whether screening-based or risk-based, differ according to the local burden of disease. Despite the introduction of intrapartum antibiotic prophylaxis, there remains a significant burden of disease, which can be resolved by better adherence to guidelines, rapid identification of maternal colonization or in the future, vaccination. Areas covered: The introduction of a vaccine to women in the third trimester is likely to further reduce the burden of disease and provide benefits beyond the prevention of early neonatal disease, including meningitis and disability following late onset disease. Development of specific polyvalent vaccines continues, but testing has challenges and may require surrogate markers or molecular-based techniques to manipulate antigenicity and immunogenicity. Expert commentary: Group B streptococcal vaccination using conjugated polyvalent vaccines against the major disease causing serotypes of Group B streptococcus, either alone, or in combination with a policy of intrapartum antibiotic prophylaxis, may decrease the burden of Group B streptococcus beyond that achieved by current use of intrapartum antibiotic prophylaxis alone.

Ongoing Cases of Early-Onset Group B Streptococcal Disease in the Era of Screening and Prophylaxis

OBJECTIVE

We reviewed cases of group B Streptococcus (GBS) sepsis in term infants at our institution to identify areas for potential prevention.

METHODS

We identified cases by searching our institution's microbiology databases for all positive GBS blood and cerebrospinal fluid cultures taken from infants between 2008 and 2013. Patients were included if the timing of the positive culture met the criteria for early-onset GBS disease (age 7 days or under). Charts that met inclusion criteria were abstracted for details related to antepartum screening, intrapartum care, and postpartum outcome.

RESULTS

There are an average of 10 000 deliveries per year in our institution. During the five-year period (2008-2013), we identified 13 cases representing early-onset GBS disease in term infants. Of the 13 cases, nine mothers screened negative for GBS, two screened positive, and two were screened unknown. Four cases qualified for intrapartum prophylaxis; of these, two did not receive appropriate prophylaxis, one because of parental refusal and one for unspecified reasons after the membranes had been ruptured for > 18 hours. All 13 infants had confirmed GBS bacteremia, and four had concurrent GBS meningitis. One infant died and one infant had neurologic sequelae.

CONCLUSION

Early-onset GBS disease in term infants continues to occur at our institution, and consequences for the infant can be severe. The majority of cases identified were screened and managed in accordance with current guidelines. Most cases were GBS negative when screened in the antepartum period, raising the question of whether a more sensitive test or a test closer to delivery could prevent further cases of early-onset GBS disease.

The changing epidemiology of group B streptococcus bloodstream infection: a multi-national population-based assessment

BACKGROUND

Population-based studies conducted in single regions or countries have identified significant changes in the epidemiology of invasive group B streptococcus (GBS) infection. However, no studies have concurrently compared the epidemiology of GBS infections among multiple different regions and countries over time. The study objectives were to define the contemporary incidence and determinants of GBS bloodstream infection (BSI) and assess temporal changes in a multi-national population.

METHODS

Population-based surveillance for GBS BSI was conducted in nine regions in Australia, Canada, Denmark, Sweden, Finland and the UK during 2000-2010. Incidence rates were age- and gender-standardised to the EU population.

RESULTS

During 114 million patient-years of observation, 3464 cases of GBS BSI were identified for an overall annual incidence of 3.4 patients per 100,000 persons. There were marked differences in the overall (range = 1.8-4.1 per 100,000 person-year) and neonatal (range = 0.19-0.83 per 1000 live births) incidences of GBS BSI observed among the study regions. The overall incidence significantly (p = 0.05) increased. Rates of neonatal disease were stable, while the incidence in individuals older than 60 years doubled (p = 0.003). In patients with detailed data (n = 1018), the most common co-morbidity was diabetes (25%). During the study period, the proportion of cases associated with diabetes increased.

CONCLUSIONS

While marked variability in the incidence of GBS BSI was observed among these regions, it was consistently found that rates increased among older adults, especially in association with diabetes. The burden of this infection may be expected to continue to increase in ageing populations worldwide.

Population structure and antimicrobial resistance of invasive serotype IV group B Streptococcus, Toronto, Ontario, Canada

Conjugate vaccines should include polysaccharide or virulence proteins of this serotype to provide complete protection.

We recently showed that 37/600 (6.2%) invasive infections with group B Streptococcus (GBS) in Toronto, Ontario, Canada, were caused by serotype IV strains. We report a relatively high level of genetic diversity in 37 invasive strains of this emerging GBS serotype. Multilocus sequence typing identified 6 sequence types (STs) that belonged to 3 clonal complexes. Most isolates were ST-459 (19/37, 51%) and ST-452 (11/37, 30%), but we also identified ST-291, ST-3, ST-196, and a novel ST-682. We detected further diversity by performing whole-genome single-nucleotide polymorphism analysis and found evidence of recombination events contributing to variation in some serotype IV GBS strains. We also evaluated antimicrobial drug resistance and found that ST-459 strains were resistant to clindamycin and erythromycin, whereas strains of other STs were, for the most part, susceptible to these antimicrobial drugs.

Group B streptococcal disease and genotypes in Australian infants

AIMS

Estimate the incidence, risk factors and clinical features of group B streptococcal (GBS) disease in Australian infants and compare bacterial genotypes between infant disease and maternal carriage.

METHODS

The Australian Paediatric Surveillance Unit conducted a study of invasive GBS disease in infants aged 0-90 days between July 2005 and June 2008. Clinical data were obtained by questionnaire. GBS isolates from affected infants and antenatal carriers were referred for genotyping.

RESULTS

One hundred fifty confirmed cases were reported: 88 early-onset (EOD; 0-6 days) and 62 late-onset disease (LOD). Based on review of selected laboratory records, they represented ∼1/3 of all cases. Estimated national EOD and LOD rates were 0.38 and 0.19/1000 live births, respectively. Admission to intensive care was common (44%), and 7% of infants died. One or more obstetric indications for intrapartum antibiotic prophylaxis (IAP) were identified in 51% of mothers; 53% of mothers were screened for GBS carriage, and screening was positive in 45%; only 25% of women with clinical or microbiological risk factors were given IAP (no significant differences between EOD and LOD groups). Distribution of GBS genotypes differed significantly between invasive and vaginal isolates: virulent serosubtype III-2/sequence type 17 was strongly associated with LOD but uncommon among EOD and vaginal isolates.

CONCLUSIONS

Estimated GBS disease rates remain relatively low despite poor predictive values of clinical and microbiological criteria for, and compliance with, IAP. Clinical and microbiological epidemiology of LOD differs significantly from that of EOD. Further reduction in infant morbidity and mortality from GBS disease will require new strategies.

Maternal group B Streptococcus-related stillbirth: a systematic review

BACKGROUND

Limited epidemiological data on the association between maternal rectovaginal group B Streptococcus (GBS) colonisation and stillbirth makes assessment of antenatal interventions for GBS stillbirth difficult.

OBJECTIVES

To systematically review the existing literature and evaluate the incidence of GBS-related stillbirth by region up to March 2015.

SEARCH STRATEGY

A systematic review of the published literature was completed using PubMed/MEDLINE, EMBASE, LILACS, and Cochrane Library, with Medical Subject Headings (MeSH) and search terms based upon the Centers for Disease Control and Prevention's (CDC) Active Bacterial Core Surveillance (ABCs) GBS-related stillbirth definition and chorioamnionitis.

SELECTION CRITERIA

Studies reporting original data on GBS-related stillbirth occurring ≥20 weeks of gestation, with GBS confirmed by autopsy or by culture from the placenta, amniotic fluid, or other normally sterile site samples from the stillborn.

DATA COLLECTION AND ANALYSIS

Descriptive analyses were performed with the absolute GBS-related stillbirth rates and proportion of stillbirths attributed to GBS calculated per study where possible. Differences in stillbirth definitions did not allow for pooled estimates to be calculated.

MAIN RESULTS

Seventeen studies reported GBS-related stillbirth rates varying from 0.04 to 0.9 per 1000 births, with the proportion of stillbirths associated with GBS ranging from 0 to 12.1%. Most studies reported data from before the year 2000 and from high-income countries.

CONCLUSIONS

The sparsely available epidemiological evidence was not reported consistently, emphasising the importance of standardised stillbirth definitions and diagnostic methods to optimally assess the effectiveness of any future antenatal interventions. Timing of stillbirth, GBS serotype, and global diversity were gaps in the current evidence.

TWEETABLE ABSTRACT

Systematic review finds Group B Streptococcus causes up to 12.1% of stillbirths, but more research is needed.

Direct identification of Streptococcus agalactiae and capsular type by real-time PCR in vaginal swabs from pregnant women

Most group B streptococcus (GBS) infections in newborns are with capsular type Ia, Ib, or III. To prevent these infections more effectively, we developed a real-time PCR method to simultaneously detect GBS species and identify these 3 capsular types in vaginal swab samples from women at 36-39 weeks of gestation. DNA to be detected included those of the dltS gene (encoding a histidine kinase specific to GBS) and cps genes encoding capsular types. PCR sensitivity was 10 CFU/well for a 33-35 threshold cycle. Results were obtained within 2 h. Direct PCR results were compared with results obtained from cultures. Samples numbering 1226 underwent PCR between September 2008 and August 2012. GBS positivity rates by direct PCR and after routine culture were 15.7% (n = 192) and 12.6% (n = 154), respectively. Sensitivity and specificity of direct PCR relative to culture were 96.1% and 95.9%. Of GBS positive samples identified by PCR, capsular types determined directly by real-time PCR were Ia (n = 24), Ib (n = 32), and III (n = 26). Real-time PCR using our designed cycling probe is a practical, highly sensitive method for identification of GBS in pregnant carriers, allowing use of prophylactic intrapartum antibiotics in time to cover the possibility of unexpected premature birth.

Management of the neonate at risk for early-onset Group B streptococcal disease (GBS EOD): new paediatric guidelines in Belgium

Despite group B streptococcal (GBS) screening in late pregnancy and intrapartum antimicrobial prophylaxis, early-onset sepsis in neonates remains a common source of neonatal morbidity and mortality especially in preterm neonates. The identification of neonates with early-onset sepsis is usually based on perinatal risk factors. Clinical signs are aspecific and laboratory tests are not sensitive. Therefore, many clinicians will overtreat at-risk infants. Inappropriate treatment with antibiotics increases the risk for late-onset sepsis, necrotizing enterocolitis, mortality, and prolongs hospitalisation and costs. In 2003, the Belgian Health Council published guidelines for the prevention of perinatal GBS infections. This report presents the Belgian paediatric management guidelines, which have been endorsed by the Belgian and Flemish societies of neonatology and paediatrics. The most imported changes in the 2014 guidelines are the following: recommendations for a lumbar puncture; clarification of normal spinal fluid parameters and blood neutrophil indices corrected for gestation age; specific timing for diagnostic testing after birth; no indication for diagnostic testing in asymptomatic newborns unless additional risk factors; a revised algorithm for management of neonates according to maternal and neonatal risk factors; and premature infants described as those below 35 weeks instead of 37 weeks. The guidelines were made on the basis of the best evidence and on expert opinion when inadequate evidence exists.

Association and virulence gene expression vary among serotype III group B streptococcus isolates following exposure to decidual and lung epithelial cells

Group B Streptococcus (GBS) causes severe disease in neonates, the elderly, and immunocompromised individuals. GBS species are highly diverse and can be classified by serotype and multilocus sequence typing. Sequence type 17 (ST-17) strains cause invasive neonatal disease more frequently than strains of other STs. Attachment and invasion of host cells are key steps in GBS pathogenesis. We investigated whether four serotype III strains representing ST-17 (two strains), ST-19, and ST-23 differ in their abilities to attach to and invade both decidual cells and lung epithelial cells. Virulence gene expression following host cell association and exposure to amnion cells was also tested. The ST-17 strains differed in their abilities to attach to and invade decidual cells, whereas there were no differences with lung epithelial cells. The ST-19 and ST-23 strains, however, attached to and invaded decidual cells less than both ST-17 strains. Although the ST-23 strain attached to lung epithelial cells better than ST-17 and -19 strains, none of the strains effectively invaded the lung epithelial cells. Notably, the association with host cells resulted in the differential expression of several virulence genes relative to basal expression levels. Similar expression patterns of some genes were observed regardless of cell type used. Collectively, these results show that GBS strains differ in their abilities to attach to distinct host cell types and express key virulence genes that are relevant to the disease process. Enhancing our understanding of pathogenic mechanisms could aid in the identification of novel therapeutic targets or vaccine candidates that could potentially decrease morbidity and mortality associated with neonatal infections.

Pilus distribution among lineages of group b streptococcus: an evolutionary and clinical perspective

Background

Group B Streptococcus (GBS) is an opportunistic pathogen in both humans and bovines. Epidemiological and phylogenetic analyses have found strains belonging to certain phylogenetic lineages to be more frequently associated with invasive newborn disease, asymptomatic maternal colonization, and subclinical bovine mastitis. Pilus structures in GBS facilitate colonization and invasion of host tissues and play a role in biofilm formation, though few large-scale studies have estimated the frequency and diversity of the three pilus islands (PIs) across diverse genotypes. Here, we examined the distribution of pilus islands (PI) 1, 2a and 2b among 295 GBS strains representing 73 multilocus sequence types (STs) belonging to eight clonal complexes. PCR-based RFLP was also used to evaluate variation in the genes encoding pilus backbone proteins of PI-2a and PI-2b.

Results

All 295 strains harbored one of the PI-2 variants and most human-derived strains contained PI-1. Bovine-derived strains lacked PI-1 and possessed a unique PI-2b backbone protein allele. Neonatal strains more frequently had PI-1 and a PI-2 variant than maternal colonizing strains, and most CC-17 strains had PI-1 and PI-2b with a distinct backbone protein allele. Furthermore, we present evidence for the frequent gain and loss of genes encoding certain pilus types.

Conclusions

These data suggest that pilus combinations impact host specificity and disease presentation and that diversification often involves the loss or acquisition of PIs. Such findings have implications for the development of GBS vaccines that target the three pilus islands.

Characterization of invasive group B streptococcus strains from the greater Toronto area, Canada

We determined the capsular polysaccharide (CPS) type of 600 group B Streptococcus (GBS) (also known as Streptococcus agalactiae) strains recovered from patients with invasive infections in the greater Toronto area, Canada, between 2009 and 2012. GBS strains of CPS type III were the most prevalent among infants (44% in those with early-onset disease, 75% in those with late-onset disease), while type V strains were most frequently isolated from adult patients (26% in patients≥19 years old). We next investigated the presence in our collection of GBS strains belonging to the hypervirulent multilocus sequence typing clonal complex 17 (CC17). We used a PCR test described as specific for the detection of CC17 strains, which targets the gene encoding the major virulence factor HvgA. We identified 91 hvgA-positive strains; of these, 88 were CPS type III, 2 were CPS type IV, and 1 was CPS type V. Using whole-genome sequencing, we showed that the two hvgA-positive CPS type IV strains are CC17 strains which underwent capsular switching. However, sequence analysis revealed that the hvgA-positive CPS type V strain does not belong to CC17 but instead is a bona fide CC1 strain which acquired hvgA, probably by recombination from a CC17 donor. Our findings underline the importance of recombination in GBS pathogenesis and caution against the use of single-gene-based PCR tests to detect CC17 GBS strains.

Associations between capsular serotype, multilocus sequence type, and macrolide resistance in Streptococcus agalactiae isolates from Japanese infants with invasive infections

SUMMARY Streptococcus agalactiae (group B streptococcus; GBS) isolates (n = 150) from infants with invasive infections between 2006 and 2011 were analysed for capsular serotype, multilocus sequence type, and antibiotic susceptibility. In cases with late-onset disease (n = 115), primary meningitis was predominant (62.6%), but represented only 39.1% in cases with early-onset disease (n = 23). The most common serotype was III (58.7%), followed by Ia (21.3%) and Ib (12.7%). Sequence types (STs) of serotype III strains included ST17 (50.0%), ST19 (26.1%), ST335 (18.2%), ST27 (4.5%), and ST1 (1.1%). Predominant STs of serotypes Ia and Ib were ST23 (81.3%) and ST10 (84.2%), respectively. No penicillin-resistant strains were detected, but 22·0% of strains had mef(A/E), erm(A), or erm(B) genes, which mediate macrolide resistance. A new ST335, possessing an mef(A/E) gene belonging to clonal complex 19 gradually increased in frequency. Improved prevention of invasive GBS infections in infants requires timely identification, and ultimately vaccine development.

Group B streptococcal epidemiology and vaccine needs in developed countries

Development of a group B streptococcal vaccine (GBS) vaccine is the most promising approach for the prevention of GBS infections in babies, given the potential adverse effects of intrapartum antibiotic prophylaxis as well as the need for effective prevention of both adult and late perinatal disease. There are numerous prevention strategies at this time but none are 100% effective in the eradication of neonatal early onset GBS disease and there are no preventative strategies for late onset disease. The need for a GBS vaccine is therefore, of utmost importance. Efforts applying genomics to GBS vaccine development have led to the identification of novel vaccine candidates. The publication of GBS whole genomes coupled with new technologies including multigenome screening and bioinformatics has also allowed researchers to overcome the serotype limitation of earlier vaccine preparations in the search of a universal effective vaccine against GBS. This review brings together the key arguments concerning the potential need of a GBS vaccine in developed countries and describes the current status with GBS epidemiology and microbiology in these countries.

Significance, management and prevention of Streptococcus agalactiae infection during the perinatal period

The highest annual death rate during the first five decades of life occurs in the first year, particularly during the perinatal period between the onset of labor and 72 h after birth. Invasive bacterial disease evoking the severe inflammatory response syndrome is a leading cause of perinatal morbidity and mortality. Group B streptococcus (Streptococcus agalactiae) is the most important pathogen in this period of life, although the concept of intrapartum antimicrobial prophylaxis has impressively reduced the rate of culture-proven invasive infection in neonates. This strategy, however, has considerable limitations since group B streptococcus-related stillbirths or prematurity and late-onset sepsis cannot be prevented. Moreover, the use of intrapartum antimicrobial prophylaxis has significantly increased the use of antibiotics during labor and therefore may select for intrapartum infections caused by other bacteria, including those resistant to antibiotics. Several advances in the development of vaccines and research on virulence factors and pathways involved in the immune response to group B streptococcus have been accomplished within the last years, including complete sequencing of the group B streptococcus genome. Development of effective vaccines and implementation of vaccination strategies will be one of the key challenges in the future for prevention of neonatal group B Streptococcus infections.

The prevention of early-onset neonatal group B streptococcal disease

OBJECTIVE

To review the evidence in the literature and to provide recommendations on the management of pregnant women in labour for the prevention of early-onset neonatal group B streptococcal disease. The key revisions in this updated guideline include changed recommendations for regimens for antibiotic prophylaxis, susceptibility testing, and management of women with pre-labour rupture of membranes.

OUTCOMES

Maternal outcomes evaluated included exposure to antibiotics in pregnancy and labour and complications related to antibiotic use. Neonatal outcomes of rates of early-onset group B streptococcal infections are evaluated.

EVIDENCE

Published literature was retrieved through searches of MEDLINE, CINAHL, and The Cochrane Library from January 1980 to July 2012 using appropriate controlled vocabulary and key words (group B streptococcus, antibiotic therapy, infection, prevention). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to May 2013. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

The recommendations in this guideline are designed to help clinicians identify and manage pregnancies at risk for neonatal group B streptococcal disease to optimize maternal and perinatal outcomes. No cost-benefit analysis is provided.

SUMMARY STATEMENT

There is good evidence based on randomized control trial data that in women with pre-labour rupture of membranes at term who are colonized with group B streptococcus, rates of neonatal infection are reduced with induction of labour. (I) There is no evidence to support safe neonatal outcomes with expectant management in this clinical situation.

RECOMMENDATIONS

1. Offer all women screening for colonization with group B streptococcus at 35 to 37 weeks' gestation with culture taken from one swab first to the vagina and then to the rectum (through the anal sphincter). (II-1A) This includes women with planned Caesarean delivery because of their risk of labour or ruptured membranes earlier than the scheduled Caesarean delivery. (II-2B) 2. Because of the association of heavy colonization with early onset neonatal disease, provide intravenous antibiotic prophylaxis for group B streptococcus at the onset of labour or rupture of the membranes to: • any woman positive for group B streptococcus by vaginal/rectal swab culture screening done at 35 to 37 weeks' gestation (II-2B); • any woman with an infant previously infected with group B streptococcus (II-3B); • any woman with documented group B streptococcus bacteriuria (regardless of level of colony-forming units) in the current pregnancy. (II-2A) 3. Manage all women who are < 37 weeks' gestation and in labour or with rupture of membranes with intravenous group B streptococcus antibiotic prophylaxis for a minimum of 48 hours, unless there has been a negative vaginal/rectal swab culture or rapid nucleic acid-based test within the previous 5 weeks. (II-3A) 4. Treat all women with intrapartum fever and signs of chorioamnionitis with broad spectrum intravenous antibiotics targeting chorioamnionitis and including coverage for group B streptococcus, regardless of group B streptococcus status and gestational age. (II-2A) 5. Request antibiotic susceptibility testing on group B streptococcus-positive urine and vaginal/rectal swab cultures in women who are thought to have a significant risk of anaphylaxis from penicillin. (II-1A) 6. If a woman with pre-labour rupture of membranes at ≥ 37 weeks' gestation is positive for group B streptococcus by vaginal/rectal swab culture screening, has had group B streptococcus bacteriuria in the current pregnancy, or has had an infant previously affected by group B streptococcus disease, administer intravenous group B streptococcus antibiotic prophylaxis. Immediate obstetrical delivery (such as induction of labour) is indicated, as described in the Induction of Labour guideline published by the Society of Obstetricians and Gynaecologist in September 2013. (II-2B) 7. At ≥ 37 weeks' gestation, if group B streptococcus colonization status is unknown and the 35- to 37-week culture was not performed or the result is unavailable and the membranes have been ruptured for greater than 18 hours, administer intravenous group B streptococcus antibiotic prophylaxis. (II-2B) 8. If a woman with pre-labour rupture of membranes at < 37 weeks' gestation has an unknown or positive group B streptococcus culture status, administer intravenous group B streptococcus prophylaxis for 48 hours, as well as other antibiotics if indicated, while awaiting spontaneous or obstetrically indicated labour. (II-3B).

Genital group B Streptococcus carrier rate and serotype distribution in Korean pregnant women: implications for group B streptococcal disease in Korean neonates

AIMS

We investigated the genital group B streptococcus (GBS) carrier rate in Korean pregnant women and the serotype distribution in face of the recent increase of late-onset GBS disease in Korea.

METHODS

GBS screening was performed on 4045 healthy pregnant women at 35-37 weeks' gestation. In case of positive GBS culture, serotyping was performed by using GBS typing antisera.

RESULTS

When both vaginal and anorectal culture were performed, the GBS carrier rate was 10.0% (n=121/1205), which is the highest rate ever reported in Korea. Type III was more common (36%), and type Ia (13%) and Ib (7%) were less prevalent.

CONCLUSIONS

Increased maternal genital GBS carrier rate and difference in serotype distribution pattern of GBS may be related to the recent increase of late-onset GBS disease in Korea.

International perspective on early-onset neonatal sepsis

Infections are a major cause of neonatal death in developing countries. High-quality information on the burden of early-onset neonatal sepsis and sepsis-related deaths is limited in most of these settings. Simple preventive and treatment strategies have the potential to save many newborns from sepsis-related death. Implementation of public health programs targeting newborn health will assist attainment of Millennium Development Goals of reduction in child mortality.

Molecular characterization and prophage DNA contents of Streptococcus agalactiae strains isolated from adult skin and osteoarticular infections

Skin and osteoarticular infections (SKI and OAI, respectively) account for almost one-third of Streptococcus agalactiae infections in nonpregnant adults. We evaluated the genetic diversity and phylogeny of 58 S. agalactiae strains responsible for adult SKI or OAI and of 61 S. agalactiae strains from cases of adult human colonization (HCol) by serotyping and multilocus sequence typing (MLST). We also assessed the prophage DNA content of the genomes of these strains by a PCR-based method. We found that 63% of SKI and 56% of OAI occurred in people aged 55 years and over. Overall, 71% of SKI strains were of serotype Ia or V, and 91% of OAI strains were of serotype Ia, III, or V. Strains of clonal complexes 1 and 23 (CC1 and CC23) were associated with 79% of SKI cases and 62% of OAI cases. Seven groups of strains, groups A, B, C, D, E, F, and G, were obtained by performing a hierarchical analysis on the basis of prophage DNA-PCR data. We found that 85% of CC1 strains clustered in DNA prophage group D, the group with the highest prophage DNA content (average, 4.4; average of absolute deviations [AVEDEV], 0.9). The CC23 strains displayed the greatest diversity in prophage DNA fragment content, but 47% of CC23 strains clustered in group B, which also had a high average prophage DNA content per strain (average, 2.3; AVEDEV, 0.6). Many (65%) of the OAI strains were in prophage DNA group D, whereas 83% of the SKI strains were in prophage DNA groups B and D. These data suggest that S. agalactiae strains from CC1 and CC23 may be subject to particular transduction mechanisms in gene recombination, rendering them particularly capable of invading the skin, bone, or joints in adults.

Commonly used molecular epidemiology markers of Streptococcus agalactiae do not appear to predict virulence

AIMS

Several virulent clones of group B streptococcus (GBS) are known to be associated with certain serotypes and molecular epidemiological markers. It is unclear, however, whether the clinical significance of GBS can be predicted based solely on such molecular markers. The aim of this study was to test the hypothesis that GBS virulence can be predicted by using the molecular epidemiology markers.

METHODS

We examined 912 human GBS isolates in which 18 distinct molecular markers (including virulence-associated mobile genetic elements, polysaccharide capsule determinants, variants of a surface antigen and invasin, and antibiotic resistance-related genes) were characterised using multiplex PCR based reverse line blot assay. All strains were classified in clinically relevant invasive and colonising categories. Relationships between molecular markers and clinical phenotypes were tested using statistical and machine learning analyses. Classifier performance was evaluated by the area under receiver operator characteristic curve (AUC).

RESULTS

The distribution of serotypes was comparable with those in previous reports (Ia, 22.1%; III, 34.7%; V, 17.7%). From single marker analyses, only alp3 (which encodes a surface protein antigen, commonly associated with serotype V) showed an increased association with invasive diseases (OR = 2.93, p = 0.0003). Molecular serotype (MS) II (OR = 10.0, p = 0.0007) had a significant association with early-onset neonatal disease when compared with late-onset diseases. Predictive analysis with logistic regression and machine learning classifiers, however, only yielded weak predictive power (AUC 0.56-0.71, stratified 10-fold cross-validation) across all the subgroups.

CONCLUSION

While some molecular epidemiological markers are important in defining GBS clusters, a definitive predictive relationship between the molecular markers and clinical outcomes may be lacking.

Selection, recombination, and virulence gene diversity among group B streptococcal genotypes

Transmission of group B Streptococcus (GBS) from mothers to neonates during childbirth is a leading cause of neonatal sepsis and meningitis. Although subtyping tools have identified specific GBS phylogenetic lineages that are important in neonatal disease, little is known about the genetic diversity of these lineages or the roles that recombination and selection play in the generation of emergent genotypes. Here, we examined genetic variation, selection, and recombination in seven multilocus sequence typing (MLST) loci from 94 invasive, colonizing, and bovine strains representing 38 GBS sequence types and performed DNA sequencing and PCR-based restriction fragment length polymorphism analysis of several putative virulence genes to identify gene content differences between genotypes. Despite the low level of diversity in the MLST loci, a neighbor net analysis revealed a variable range of genetic exchange among the seven clonal complexes (CCs) identified, suggesting that recombination is partly responsible for the diversity observed between genotypes. Recombination is also important for several virulence genes, as some gene alleles had evidence for lateral gene exchange across divergent genotypes. The CC-17 lineage, which is associated with neonatal disease, is relatively homogeneous and therefore appears to have diverged independently with an exclusive set of virulence characteristics. These data suggest that different GBS genetic backgrounds have distinct virulence gene profiles that may be important for disease pathogenesis. Such profiles could be used as markers for the rapid detection of strains with an increased propensity to cause neonatal disease and may be considered useful vaccine targets.

Multilocus sequence types associated with neonatal group B streptococcal sepsis and meningitis in Canada

Group B streptococci (GBS), a leading cause of neonatal sepsis and meningitis, are transferred to neonates from colonized mothers during childbirth. Prior studies using multilocus sequence typing (MLST) have found specific GBS clones (e.g., sequence type 17 [ST-17]) to be associated with neonatal disease in several geographic locations. Few population-based studies, however, have been conducted to determine the frequency of disease caused by specific GBS clones. MLST was used to assess the genetic diversity of 192 GBS strains from neonates and young children identified by population-based surveillance in Alberta, Canada, from 1993 to 2002. Comparisons were made to 232 GBS strains collected from colonized pregnant women, and all strains were characterized for one of nine capsule (cps) genotypes. A total of 47 STs were identified, and more than 80% of GBS strains were represented by 7 STs that have been shown to predominate in other populations. ST-17 and ST-19 were more prevalent in strains causing early onset disease (EOD) and late onset disease (LOD) than from pregnant women, whereas STs 1, 12, and 23 were more common in pregnant women. In addition, ST-17 strains and close relatives more frequently caused meningitis than sepsis and LOD versus EOD in this population of neonates. Further research is required to better understand why strains belonging to the ST-17 phylogenetic lineage are more likely to cause both LOD and meningitis and may provide clues into the pathogenesis of these conditions.

Genotypic diversity and serotype distribution of group B streptococcus isolated from women before and after delivery

BACKGROUND

Most studies of the dynamics of maternal group B Streptococcus (GBS) colonization have relied on capsular serotyping to define GBS acquisition or loss. Newer molecular methods that distinguish GBS clones may expand our knowledge and influence vaccination strategies. We used multilocus sequence typing (MLST) and GBS capsular gene cluster (cps) genotyping to investigate the dynamics of perinatal GBS colonization.

METHODS

A total of 338 GBS isolates obtained from 212 colonized women who were enrolled in a prior prospective cohort study were serotyped and genotyped by MLST and cps typing before (visit 1) and 6 weeks after (visit 2) delivery.

RESULTS

Of the 212 women, 126 were colonized at both visits, whereas 66 lost and 20 acquired GBS by visit 2. MLST of the 338 strains identified 29 sequence types marking distinct bacterial clones. A change in sequence type or cps and serotype occurred in 23 (18.3%) of the 126 women who were colonized at both visits. Specific sequence types were associated with GBS loss and persistence. Older maternal age and exclusive intrapartum antibiotic use were associated with persistent colonization.

CONCLUSIONS

Although most GBS-positive pregnant women were stably colonized during the peripartum period, we detected changes in capsule expression and recolonization with antigenically distinct GBS clones over time by applying MLST. Combining the epidemiologic and molecular typing data revealed host factors and clones associated with persistent colonization, as well as a clone that was more readily lost. This knowledge is useful for the development of prevention and intervention strategies to reduce the likelihood of maternal GBS colonization.

Characterisation of invasive group B streptococci based on investigation of surface proteins and genes encoding surface proteins

The joint distributions of the six genes bca, bac, epsilon/alp1, alp2, alp3 and rib (encoding alpha-C-protein, beta-C-protein, epsilon/Alp1, Alp2, Alp3, and Rib, respectively) and the proteins alpha-C-protein, beta-C-protein and Rib were investigated in invasive isolates of group B streptococcus (GBS). In total, 297 invasive isolates (123 from neonates, 174 from adults) from south-west Sweden were collected during a 13-year period. Genes were detected using multiplex and specific PCRs, and expression of the surface proteins was demonstrated using monoclonal antibodies. The genes studied were found alone or in combinations in 294 (99%) of the invasive isolates. The most common genes were rib (n = 127 isolates, 43%), alp3 (n = 78, 26%) and epsilon/alp1 (n = 42, 14%). The bac gene was never found alone, but was found in combination with one other gene in 36 isolates. The surface proteins studied were detected alone or in combinations in 152 (51%) isolates, with the most common being Rib (n = 80, 27%), alpha-C-protein (n = 68, 23%) and beta-C-protein (n = 24, 8%). Several genes were associated significantly with particular serotypes (e.g., epsilon/alp1 with serotype Ia; bca and bac with serotypes Ib and II; rib with serotype III; alp3 with serotype V). Overall, it was concluded that demonstration of different genes and surface proteins of GBS strains can be useful in epidemiological studies and in formulation of vaccines, but disappointingly, no single gene or surface protein included in the study was sufficiently common for it to be considered as the basis for a successful GBS vaccine.

Analysis of group B streptococcal isolates from infants and pregnant women in Portugal revealing two lineages with enhanced invasiveness

The populations of group B streptococcus (GBS) associated with vaginal carriage in pregnant women and invasive neonatal infections in Portugal were compared. GBS isolates were characterized by serotyping, pulsed-field gel electrophoresis (PFGE) profiling, and multilocus sequence typing (MLST). Serotypes III and V accounted for 44% of all colonization isolates (n = 269), whereas serotypes III and Ia amounted to 69% of all invasive isolates (n = 64). Whereas serotype Ia was associated with early-onset disease (EOD), serotype III was associated with late-onset disease (LOD). Characterization by PFGE and MLST identified very diverse populations in carriage and invasive disease. Serotype Ia was represented mainly by a single PFGE cluster defined by sequence type 23 (ST23) and the infrequent ST24. In contrast, serotype III was found in a large number of PFGE clusters and STs, but a single PFGE cluster defined by ST17 was found to be associated with invasive disease. Although serotype III was associated only with LOD, ST17 showed an enhanced capacity to cause both EOD and LOD. Our data reinforce the evidence for enhanced invasiveness of ST17 and identify a lineage expressing serotype Ia capsule and represented by ST23 and ST24 as having enhanced potential to cause EOD.

Risk factors for group B streptococcal colonization: potential for different transmission systems by capsular type

PURPOSE

Group B Streptococcus (GBS) is a common inhabitant of the bowel and vaginal flora, with known transmission routes including sexual contact and vertical transmission from mother to infant. Food-borne transmission is also possible, as GBS is a known fish and bovine pathogen. We conducted a prospective cohort study in order to identify risk factors for acquisition.

METHODS

We identified risk factors for GBS acquisition among college women (n = 129) and men (n = 128) followed at 3-week intervals for 3 months.

RESULTS

A doubling in sex acts significantly increased incidence of GBS capsular type V by 80% (95% confidence interval [CI]: 1.19, 2.58), and other non-Ia or -Ib types combined by 40% (95% CI: 1.00, 2.06; incidence of capsular type Ia (odds ratio [OR] = 1.2; 95% CI: 0.71, 1.88; p = 0.57) and Ib (OR = 1.5, 95% CI: 0.75, 2.86; p = 0.27) were elevated, although not significantly. After adjustment for sexual activity and sexual history, gender, and eating venue, fish consumption increased risk of acquiring capsular types Ia and Ib combined 7.3 fold (95% CI: 2.34, 19.50), but not of acquiring other capsular types. Beef and milk were not associated with GBS incidence.

CONCLUSIONS

Different GBS capsular types may have different transmission routes.

A practical method for subtyping of Streptococcus agalactiae serotype III, of human origin, using rolling circle amplification

Group B streptococcus (GBS; Streptococcus agalactiae) serotype III is one of the most common and virulent serotypes of the species. It can be divided into several subtypes, which vary in their distribution among invasive isolates from different patient groups. In this study, we used 91 well-characterized GBS serotype III isolates to compare three subtyping methods, and developed a novel padlock probe and rolling circle amplification (RCA) method to identify informative single nucleotide polymorphisms (SNPs) that define the major subtypes. There was good agreement between partial sequencing of the capsule polysaccharide synthesis (cps) gene cluster, a 3-set genotyping system and multilocus sequence typing (MLST). Serosubtype III-2/multilocus sequence type (ST)-17 represents a virulent clone which is significantly associated with late onset GBS neonatal infections. RCA provides a simple, reproducible method for rapid identification of the two most common GBS serotype III subtypes (III-1/ST-19 and III-2/ST-17).

Perinatal infection with Group B streptococci

Group B streptococcus (GBS) is a major cause of severe bacterial infection in newborns. Early neonatal GBS infection can be prevented by identifying high-risk pregnancies and administering intrapartum antibiotics. In the USA, a screening strategy has been introduced resulting in a reduction in early-onset GBS infection, but no decrease in late-onset neonatal GBS disease has been noted. In many European countries, a risk-based strategy is recommended. Vaccination may, in the future, be an alternative in preventing GBS infection in newborns.

Invasive Early-Onset Neonatal Group B Streptococcal Cases – Alaska, 2000–2004

OBJECTIVE

We conducted a review of invasive early-onset neonatal group B Streptococcus (GBS) infections that occurred during 2000-2004 in Alaska to determine the proportion of cases that might have been prevented by complete implementation of the 2002 Centers for Disease Control and Prevention (CDC) guidelines.

METHODS

Cases were identified from statewide laboratory-based surveillance conducted by the CDC Arctic Investigations Program, and from the Alaska Medicaid database using International Classification of Diseases 9 codes 038.0, 041.02, 320.2, and 482.3. Neonates were considered to have early-onset disease if clinical illness within 6 days after birth was accompanied by GBS isolation from a normally sterile site. Maternal and neonatal medical records were reviewed. Potentially preventable cases were those for whom the 2002 CDC GBS maternal screening and intrapartum antimicrobial prophylaxis (IAP) guidelines were not completely implemented. Preventability of events not related to clinician implementation of the guidelines were not considered.

RESULTS

Twenty-one neonates with invasive early-onset GBS disease were identified (0.42/1,000 live births). Three of the eight mothers for whom IAP was indicated, did not receive adequate IAP. Nine of the 13 mothers for whom there was no indication for IAP, had not been screened appropriately. Therefore, a total of 12 neonates were determined to have had potentially preventable GBS disease.

CONCLUSIONS

Over 50% of the invasive early-onset neonatal GBS cases in Alaska were potentially preventable. The majority of these cases may have been prevented by closer adherence to either specific IAP administration guidelines or to maternal screening guidelines.