Vaccination against Group B streptococcus

Characterization of clinical infection and drug resistance of group B streptococcus in Chengdu, China

OBJECTIVE

To investigate the clinical infection characteristics and antibiotic resistance of Group B Streptococcus (Streptococcus agalactiae, GBS) in Chengdu, China, from 2019 to 2021, as well as to provide data to support rational clinical drug use.

METHODS

This was a retrospective study to collect 203 culture-positive GBS strains isolated from January 2019 to December 2021 in Chengdu, China, all of which were identified by the VITEK 2 Compact automated microbial Bacterial identification instrument. Data were derived using WHONET 5.6 software. The sample type and ward distribution were counted. Pregnant women and newborns were screened from the original data and their pregnancy outcomes were calculated respectively.

RESULTS

GBS strains were mainly concentrated in obstetrics and neonatology departments, accounting for 40.9 % and 33.5 %. The types of specimens were mainly vaginal secretions, amniotic fluid and sputum, accounting for 25.6 %, 26.1 % and 18.7 %, respectively. Chorioamnionitis, premature rupture of membranes and preterm delivery occurred mainly in pregnant women after infection, accounting for 44.4 %, 31.5 % and 24.1 %. Neonates, on the other hand, were mainly diagnosed with neonatal pneumonia, neonatal sepsis, respiratory failure and septic meningitis, accounting for 91.8 %, 61.2 %, 44.9 % and 16.3 % of all positive neonates. 840 pregnant women were screened for GBS colonization from 2019 to 2021, and a total of 108 GBS positive pregnant women were identified, with a GBS colonization rate of 12.9 %. A total of 9 neonates from 108 GBS positive pregnant women developed early-onset disease. The morbidity in neonates was 8.3 %. No strains resistant to penicillin and ampicillin were found, while the resistance rates of tetracycline and clindamycin were higher than 50 %, respectively 60.1 % and 53.2 %.

CONCLUSION

GBS infection mainly affected pregnant women and newborns in Chengdu, China, which can lead to adverse maternal and infant outcomes. Attention should be paid to strengthening general screening of GBS in perinatal urogenital secretions and the prevention strategy of IAP (intrapartum antibiotic prophylaxis). Antimicrobial therapy should be administered with appropriate antibiotics. Penicillin was still the first line drug for the treatment of GBS. These initiatives were important to reduce mother-to-child transmission and neonatal infections.

Development in the Concept of Bacterial Polysaccharide Repeating Unit-Based Antibacterial Conjugate Vaccines

The surface of cells is coated with a dense layer of glycans, known as the cell glycocalyx. The complex glycans in the glycocalyx are involved in various biological events, such as bacterial pathogenesis, protection of bacteria from environmental stresses, etc. Polysaccharides on the bacterial cell surface are highly conserved and accessible molecules, and thus they are excellent immunological targets. Consequently, bacterial polysaccharides and their repeating units have been extensively studied as antigens for the development of antibacterial vaccines. This Review surveys the recent developments in the synthetic and immunological investigations of bacterial polysaccharide repeating unit-based conjugate vaccines against several human pathogenic bacteria. The major challenges associated with the development of functional carbohydrate-based antibacterial conjugate vaccines are also considered.

Group B Streptococcus and Pregnancy: Critical Concepts and Management Nuances

Importance

Group B Streptococcus (GBS) is a common pathogen with an effective treatment. However, it remains a significant cause of neonatal sepsis, morbidity, and mortality. The screening and management of this infection are some of the first concepts learned during medical training in obstetrics. However, effective screening and evidence-based management of GBS are nuanced with many critical caveats.

Objective

The objectives of this review are to discuss the essential aspects of GBS screening and management and to highlight recent changes to recommendations and guidelines.

Evidence Acquisition

Original research articles, review articles, and guidelines on GBS were reviewed.

Results

The following recommendations are based on review of the evidence and professional society guidelines. Screening for GBS should occur between 36 weeks and the end of the 37th week. The culture swab should go 2 cm into the vagina and 1 cm into the anus. Patients can perform their own swabs as well. Penicillin allergy testing has been shown to be safe in pregnancy. Patients with GBS in the urine should be treated at term with antibiotic prophylaxis, independent of the colony count of the culture. Patients who are GBS-positive with preterm and prelabor rupture of membranes after 34 weeks are not candidates for expectant management, as this population has higher rates of neonatal infectious complications. Patients with a history of GBS colonization in prior pregnancy who are GBS-unknown in this current pregnancy and present with labor should receive intrapartum prophylaxis. Work on the GBS vaccine continues.

Conclusions

Although all of the efforts and focus on neonatal early-onset GBS infection have led to lower rates of disease, GBS still remains a major cause of neonatal morbidity and mortality requiring continued vigilance from obstetric providers.

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.

Macrolide-resistance, capsular genotyping and associated factors of group B Streptococci colonized pregnant women in Isfahan, Iran

Background and Objectives:

Group B streptococcus (GBS) can cause severe and invasive infections in pregnant women, infants, and adults. This study aimed to investigate the risk factors of GBS colonization in pregnant women and determine the macrolide resistance and capsular type of isolates.

Materials and Methods:

In a cross-sectional study, a total of 200 pregnant women were screened for GBS colonization by phenotypic methods. Antibiotic susceptibility pattern of colonizing isolates and ermB, ermTR, mefA/E genes were detected. Also, molecular capsular types of isolates were distinguished.

Results:

The overall prevalence of colonization of participates with GBS was 13.5%. Statistical analysis showed that there was no association between risk factors and colonization with GBS. The highest resistance was observed to erythromycin (44.4%) followed by clindamycin (29.6%), penicillin, ampicillin, and ceftriaxone (18.5%), levofloxacin (11.1%), and 29.6% isolates were multidrug-resistant. ermTR and mefA/E genes were detected in 37% and 11.1% isolates; respectively and the ermB gene was not detected. The most common capsular type was type Ib (44.4%) followed by type III (40.7%), type II (11.1), and type Ia (3.7%).

Conclusion:

In the present study, the prevalence of GBS was in the medium range. Resistance to key antibiotic agents was relatively high. Also, capsular serotype Ib was the predominant serotype, which emphasizes the importance of monitoring the molecular typing of the GBS isolates regularly.

Meningitis vaccines in children: what have we achieved and where next?

PURPOSE OF REVIEW

This review highlights the recent impacts of vaccines against the major bacterial causes of meningitis in children, and the challenges for further prevention of bacterial meningitis, with a focus on Streptococcus pneumoniae, Neisseria meningitidis and group B Streptococcus.

RECENT FINDINGS

Conjugate vaccines against S. pneumoniae and N. meningitidis have resulted in dramatic reductions in bacterial meningitis globally where they have been used. Recent licensure and use of capsular group B meningococcal protein vaccines have further reduced meningococcal meningitis in infants, young children and adolescents for countries with endemic disease and during outbreaks.

SUMMARY

Existing vaccines to prevent bacterial meningitis in children should be utilized in countries with significant numbers of cases of pneumococcal and/or meningococcal meningitis. Vaccines, which are able to protect against more than 13 serotypes of S. pneumoniae are in clinical trials and should be able to further reduce pneumococcal meningitis cases. Cost effective meningococcal vaccines against non-A capsular groups are needed for low-resource countries. There remains an urgent need for a vaccine against group B Streptococcus, which is a major cause of neonatal meningitis globally and for which no vaccine currently exists.

Systematic review of the clinical development of group B streptococcus serotype-specific capsular polysaccharide-based vaccines

INTRODUCTION

Vaccination against group B Streptococcus (GBS) during pregnancy could provide protection against disease in the mother, fetus, and newborn. Immunity through transplacental acquired antibodies in the newborns could persist through early infancy, reducing the risk of early-onset (<7 days age) and late-onset (7-89 days age) disease. We conducted a systematic review of clinical trials on GBS capsular polysaccharide (CPS) vaccine to assess its safety and immunogenicity in pregnant and nonpregnant adults.

AREAS COVERED

We searched literature databases PubMed (Medline), Scopus, and the Cochrane library and identified 25 unique records on GBS CPS vaccines with or without conjugant protein.

EXPERT COMMENTARY

GBS vaccines were well tolerated, with mild local reactogenicity being the main solicited adverse event and no difference in reporting of other serious adverse events compared to placebo recipients. CPS vaccines conjugated to immunogenic proteins induced ≥fourfold increase of serotype-specific antibodies with high longevity (1-2 years); and capable of promoting homotypic GBS opsonophagocytic killing. Feto-maternal transplacental antibody ratio of serotype-specific IgG ranged between 0.49 and 0.81. The clinical relevance of these immunogenicity studies, however, need to be weighed against a correlate of protection against invasive GBS disease in infants, which is yet to be established using a universally accepted standardized assay.

Group B Streptococcal Colonization, Molecular Characteristics, and Epidemiology

Streptococcus agalactiae or group B streptococcus (GBS) is a leading cause of serious neonatal infections. GBS is an opportunistic commensal constituting a part of the intestinal and vaginal physiologic flora and maternal colonization is the principal route of GBS transmission. GBS is a pathobiont that converts from the asymptomatic mucosal carriage state to a major bacterial pathogen causing severe invasive infections. At present, as many as 10 serotypes (Ia, Ib, and II–IX) are recognized. The aim of the current review is to shed new light on the latest epidemiological data and clonal distribution of GBS in addition to discussing the most important colonization determinants at a molecular level. The distribution and predominance of certain serotypes is susceptible to variations and can change over time. With the availability of multilocus sequence typing scheme (MLST) data, it became clear that GBS strains of certain clonal complexes possess a higher potential to cause invasive disease, while other harbor mainly colonizing strains. Colonization and persistence in different host niches is dependent on the adherence capacity of GBS to host cells and tissues. Bacterial biofilms represent well-known virulence factors with a vital role in persistence and chronic infections. In addition, GBS colonization, persistence, translocation, and invasion of host barriers are largely dependent on their adherence abilities to host cells and extracellular matrix proteins (ECM). Major adhesins mediating GBS interaction with host cells include the fibrinogen-binding proteins (Fbs), the laminin-binding protein (Lmb), the group B streptococcal C5a peptidase (ScpB), the streptococcal fibronectin binding protein A (SfbA), the GBS immunogenic bacterial adhesin (BibA), and the hypervirulent adhesin (HvgA). These adhesins facilitate persistent and intimate contacts between the bacterial cell and the host, while global virulence regulators play a major role in the transition to invasive infections. This review combines for first time epidemiological data with data on adherence and colonization for GBS. Investigating the epidemiology along with understanding the determinants of mucosal colonization and the development of invasive disease at a molecular level is therefore important for the development of strategies to prevent invasive GBS disease worldwide.

Group B Streptococcus: developing a correlate of protection for a vaccine against neonatal infections

PURPOSE OF REVIEW

Maternal vaccination to prevent invasive Group B Streptococcus (GBS) disease in infants is an important alternative strategy to intrapartum antibiotic prophylaxis. Licensure of GBS vaccines could be expedited using immunological correlates of protection.

RECENT FINDINGS

Between 2014 and 2015, we identified two studies that demonstrated an inverse association between invasive GBS disease and maternal serotype III capsular antibody levels greater than 1 μg/ml and greater than 3 μg/ml, and higher maternal antibody levels were associated with protection against serotype Ia disease. Furthermore, serotype Ia and III antibody levels greater than 3 μg/ml were associated with a reduced risk of GBS colonization in pregnant women.Experimental studies have investigated the use of GBS surface proteins as vaccine candidates. Although the immunogenic potential of pilus island and other surface proteins has been shown in animal-model studies, no association between maternal pilus island antibody levels and invasive GBS disease was demonstrated in infants. Additionally, several novel innate immune mediators that prevent GBS infection have been described in human and experimental studies.

SUMMARY

Recent studies suggest that maternal capsular antibody thresholds may be used as immunological correlates of protection for vaccine licensure. Surface proteins, as candidate vaccines or conjugates to the polysaccharide-protein vaccine, may broaden protection against invasive GBS disease.

Evaluation of the Immunomodulatory Properties of Streptococcus suis and Group B Streptococcus Capsular Polysaccharides on the Humoral Response

Streptococcus suis and group B Streptococcus (GBS) are encapsulated streptococci causing septicemia and meningitis. Antibodies (Abs) against capsular polysaccharides (CPSs) have a crucial protective role, but the structure/composition of the CPS, including the presence of sialic acid, may interfere with the generation of anti-CPS Ab responses. We investigated the features of the CPS-specific Ab response directed against S. suis serotypes 2 and 14 and GBS serotypes III and V after infection or immunization with purified native or desialylated CPSs in mice. Whereas S. suis-infected mice developed a very low/undetectable CPS-specific IgM response, significant anti-CPS IgM titers were measured in GBS-infected animals (especially for type III GBS). No isotype switching was detected in S. suis- or GBS-infected mice. While the expression of sialic acid was essential for the immunogenicity of purified GBS type III CPS, this sugar was not responsible for the inability of purified S. suis types 2, 14 and GBS type V CPSs to induce a specific Ab response. Thus, other biochemical criteria unrelated to the presence of sialic acid may be responsible for the inaptitude of the host immune system to mount an effective response against certain S. suis and GBS CPS types.

Associations between nasopharyngeal carriage of Group B Streptococcus and other respiratory pathogens during early infancy

BACKGROUND

In West Africa, the carriage of Group B Streptococcus (GBS), among infants is poorly characterised. We investigated co-carriage of GBS with other respiratory pathogens in the infants' nasopharynx in The Gambia.

METHODS

We assessed the carriage, serotypes and antibiotic susceptibility of Beta-haemolytic Streptococci (BHS) groups A-G; along with the carriage of Streptococcus pneumoniae; Haemophilus influenzae; Staphylococcus aureus and Moraxella catarrhalis in 1200 two-month old infants.

RESULTS

The BHS prevalence was 20.0 % and GBS dominated (13.8 %), particularly serotypes V and II; serotype V being negatively associated with H. Influenzae carriage (OR 0.41 [95 % CI: 0.18-0.93], p = 0.033). Although co-colonization of GBS and other BHS was not seen, colonization with GBS was positively associated with S. aureus (OR 1.89 [95 % CI: 1.33-2.69], P < 0.001) and negatively associated with S. pneumoniae (OR 0.47 [95 % CI: 0.33-0.67], p < 0.001) and M. catarrhalis (OR 0.61 [95 % CI: 0.40-0.92], p = 0.017). ≥ 89 % of GBS isolates were susceptible to most antibiotics tested, except for tetracycline resistance, which was 89 %.

CONCLUSION

This study provides baseline data on the carriage of GBS in two month old infants from West Africa. The dominant serotypes of GBS in this setting are serotypes V and II. This may be important for future GBS vaccine development for the West African sub-region.

Serotype-Specific Cell-Mediated Immunity Associated With Clearance of Homotypic Group B Streptococcus Rectovaginal Colonization in Pregnant Women

We investigated the association between group B Streptococcus (GBS) serotype-specific capsular polysaccharide cellular immunity, measured with enzyme-linked immunospot (ELISPOT) interferon γ release assay at 20 weeks gestation in pregnant women, and its effect on rectovaginal serotype-specific GBS colonization up to 37 weeks gestation. Among women colonized by serotype III at enrollment, interferon γ ELISPOT positivity was more common in those in whom colonization was cleared (44.4%) than in those in whom colonization persisted (7.4%; P = .008), with a similar trend observed for serotype Ia. Presence of serotype-specific capsular polysaccharide cell-mediated immunity contributes to the clearance of GBS rectovaginal colonization.

Group B streptococcus infections of soft tissue and bone in California adults, 1995-2012

Group B streptococcus (GBS) is an increasing cause of disease in adults. We present long-term trends in incidence of overall infections and identify characteristics of patients with GBS cellulitis, bone and joint infections. Active, population-based surveillance was conducted from 1995-2012 in three California counties and the data were analysed retrospectively. All cases had isolation of GBS from a normally sterile site. Cases of cellulitis were classified based on clinical diagnosis. GBS bone or joint infection was defined as isolation of GBS from a bone or joint or a diagnosis of osteomyelitis or septic arthritis. Medical charts were reviewed for demographic and clinical information. There were 3917 cases of GBS; the incidence of disease increased from 5·8 to 8·3 cases/100 000 persons (P < 0·001) from 1995 to 2012. In adults aged ⩾40 years, the overall incidence of GBS increased from 8·5 to 14·2 cases/100 000 (P < 0·001) persons during the study period. The incidence of cellulitis increased from 1·6 to 3·8 cases/100 000 (P < 0·001), bone infection increased from 0·7 to 2·6 cases/100 000 (P < 0·001), and the incidence of joint infection remained approximately constant at an average rate of 1·0 case/100 000. The highest incidence rates were observed in men, persons aged ⩾80 years, non-Hispanic blacks and Hispanics. Diabetes was the most common underlying condition (51·2% cellulitis cases, 76·3% bone infections, 29·8% joint infections).

Natural acquired humoral immunity against serotype-specific group B Streptococcus rectovaginal colonization acquisition in pregnant women

Group B Streptococcus (GBS) rectovaginal colonization in pregnant women is associated with invasive GBS disease in newborns, preterm delivery and stillbirths. We studied the association of GBS serotype-specific capsular polysaccharide (CPS) antibody on new acquisition and clearance of rectovaginal GBS colonization in pregnant women from 20 weeks until 37 to 40 weeks' gestation. Serum serotype-specific CPS IgG antibody concentration was measured by multiplex enzyme-linked immunosorbent assay and opsonophagocytic activity (OPA) titres. Rectovaginal swabs were evaluated for GBS colonization, using standard culture methods and serotyping by latex agglutination, at five to six weekly intervals. Higher serotype III CPS antibody concentration was associated with lower risk of rectovaginal acquisition of serotype III during pregnancy (p 0.009). Furthermore, serotype-specific OPA titres to Ia and III were higher in women who remained free of GBS colonization throughout the study compared to those who acquired the homotypic serotype (p <0.001 for both serotypes). Serum CPS IgG values of ≥1μg/mL for serotype V and ≥3μg/mL for serotypes Ia and III were significantly associated with protection against rectovaginal acquisition of the homotypic serotype. A GBS vaccine that induces sufficient capsular antibody in pregnant women, including high OPA titres, could protect against rectovaginal colonization during the latter half of pregnancy.

Tyrosine-directed conjugation of large glycans to proteins via copper-free click chemistry

We have demonstrated that the insertion of alkyne-containing bifunctional linkers into the tyrosine residues of the carrier protein, followed by the copper mediated azide-alkyne [3 + 2] cycloaddition of carbohydrates, is a robust approach for the preparation of glycoconjugates with defined glycans, carrier, and connectivity. Conjugation of Group B Streptococcus (GBS) capsular polysaccharides to streptococcal pilus protein could extend the vaccine coverage to a variety of strains. Application of our protocol to these large charged polysaccharides occurred at low yields. Herein we developed a tyrosine-directed conjugation approach based on the copper-free click chemistry of sugars modified with cyclooctynes, which enables efficient condensation of synthetic carbohydrates. Most importantly, this strategy was demonstrated to be more effective than the corresponding copper catalyzed reaction for the insertion of GBS onto the tyrosine residues of GBS pilus proteins, previously selected as vaccine antigens through the so-called reverse vaccinology. Integrity of protein epitopes in the modified proteins was ascertained by competitive ELISA, and conjugation of polysaccharide to protein was confirmed by SDS page electrophoresis and immunoblot assays. The amount of conjugated polysaccharide was estimated by high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). The described technology is particularly suitable for proteins used with the dual role of vaccine antigen and carrier for the carbohydrate haptens.

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.

[Streptococcus agalactiae late-onset neonatal infections in Barcelona (1996-2010)]

OBJETIVE

To study the characteristics and evolution of group B Streptococcus (GBS) late-onset diseases, over a period of 15years in 8hospitals the Barcelona area and analyze the possible impact of prophylactic measures for the prevention of early-onset neonatal infections.

METHODS

Retrospective review of all patients diagnosed with late-onset neonatal disease due to GBS from 1996 to 2010.

RESULTS

A total of 143 patients were diagnosed. Of these, 51 were born in others hospitals. The overalll incidence was 0.42 per 1000 live births, varying between 0.14‰ in the year 2000 and 0.80‰ in 2009. A slight but sustained tendency of increased risk was observed over the years, 6.9% in the overall disease (with no statistical significance). Sepsis/bacteremia was detected in 63.6% of the newborns, meningitis in 32.8%, and arthritis/osteomyelitis in 3.5%. In cases with known obstetrics dates, 53% of mothers had been colonized by GBS during pregnancy, 53.8% received intrapartum antibiotic prophylaxis, and 41.2% had some obstetric risk factors, particularly premature birth in 35.9%. There was a 2.8% mortality rate in the neonates, and predominant serotypes were III and Ia.

CONCLUSIONS

The incidence of GBS late-onset disease has not decreased despite the control practices of early-onset disease, and possibility of this appearing must be taken into account.

Evaluation of Trans-Vag broth, colistin-nalidixic agar, and CHROMagar StrepB for detection of group B Streptococcus in vaginal and rectal swabs from pregnant women in South Africa

Maternal vaginal colonization with group B streptococcus (GBS) is a major risk factor for invasive GBS infection in newborns. The CDC-recommended method for detecting GBS colonization is to culture vaginal and rectal swabs in a selective broth followed by subculture on blood agar or a selective medium. A high incidence of antimicrobial resistance in the fecal microflora can compromise the recovery of GBS from the selective broth. Here, we compared CHROMagar StrepB (CA), Columbia colistin-nalidixic agar (CNA), and Trans-Vag selective broth enrichment for the isolation of GBS from 130 vaginal and 130 rectal swabs from pregnant women. The swabs were randomized for plating first on either CA or CNA, and they then were inoculated in Trans-Vag broth. GBS was cultured from 37.7% of the vaginal swabs and 33.1% of the rectal swabs. There were no differences in the detection rates for the vaginal swabs between CA (31.5%), CNA (26.2%), and the selective broth (30.0%). The sensitivities in relation to a composite score were 83.7%, 69.4%, and 79.6%, respectively. However, recovery of GBS from the rectal swabs was significantly higher from CA (29.2%; P<0.0001) and CNA (23.8%; P=0.002) than from the selective broth (9.2%). The sensitivities were 88.4%, 72.1%, and 27.9%, respectively. The order of plating on the solid medium was significant (P=0.003), with GBS detection rates of 30.8% and 24.6% when swabs were plated first and second, respectively. These findings show that a selective broth is not suitable for the recovery of GBS from rectal swabs in settings such as ours, due to masking of the GBS colonies by persistent microflora.

Transmission probabilities and durations of immunity for three pathogenic group B Streptococcus serotypes

Group B Streptococcus (GBS) remains a major cause of neonatal sepsis and is an emerging cause of invasive bacterial infections. The 9 known serotypes vary in virulence, and there is little cross-immunity. Key parameters for planning an effective vaccination strategy, such as average length of immunity and transmission probabilities by serotype, are unknown. We simulated GBS spread in a population using a computational model with parameters derived from studies of GBS sexual transmission in a college dormitory. Here we provide estimates of the duration of immunity relative to the transmission probabilities for the 3 GBS serotypes most associated with invasive disease: Ia, III, and V. We also place upper limits on the durations of immunity for serotype Ia (570 days), III (1125 days) and V (260 days). Better transmission estimates are required to establish the epidemiological parameters of GBS infection and determine the best vaccination strategies to prevent GBS disease.

Molecular characterization of capsular polysaccharides and surface protein genes in relation to genetic similarity of group B streptococci isolated from Polish pregnant women

Serotyping, subtyping and genotyping are important tools for epidemiological studies of group B streptococci (GBS). We investigated the genotype distribution of 353 GBS isolates originating from vaginal or rectal carriage to identify capsular serotypes and subtypes based on the surface protein genes of the alpha-like protein (Alp) family. GBS were recovered from 30% of 1176 pregnant women during the period 2007-2009, with a predominance of capsular genotypes III (35%), Ia (20%), V (17%), II (15%), Ib (8%) and IV (5%). The most common Alp gene was epsilon (26%), followed by rib (22%), alp2 (21%), bca (17%) and alp3 (14%). Several protein genes were significantly associated (G(2)=249·635, P<0·0001) with particular serotypes: epsilon with Ia, Ib, IV; bca with Ib, II; rib with II, III; alp3 with V; alp2 with III. High genetic diversity within GBS strains was observed using DNA macrorestriction. Serotypes Ib, II and III demonstrated the greatest genetic heterogeneity and serotype V the lowest heterogeneity (relative frequency coefficient ≥0·03 vs. -0·46, respectively). Macrolide-resistant strains with serotype V and alp3 gene, showed higher uniformity in genetic profile. The distribution of serotypes and surface proteins of GBS strains are necessary data to inform the design and formulation of new GBS vaccines for use in Poland and other countries.

Progress in the development of effective vaccines to prevent selected gram-positive bacterial infections

Infections caused by virulent Gram-positive bacteria, such as Staphylococcus aureus, group B streptococci and group A streptococci, remain significant causes of morbidity and mortality despite progress in antimicrobial therapy. Despite significant advances in the understanding of the pathogenesis of infection caused by these organisms, there are only limited strategies to prevent infection. In this article, we review efforts to develop safe and effective vaccines that would prevent infections caused by these 3 pathogens.

Group B streptococcal disease in infants: progress in prevention and continued challenges

The burden of early-onset disease caused by group B Streptococcus (GBS) has decreased dramatically in the United States over the past 20 years. Universal culture-based screening at 35 to 37 weeks gestational age and use of intrapartum antibiotic prophylaxis are the cornerstones of prevention measures that have led to this decline. GBS, however, remains the leading cause of early-onset neonatal sepsis in the United States. Revised guidelines for prevention of perinatal GBS are planned for issuance in 2010. This article discusses implementation challenges for clinicians caring for pregnant women and newborns and presents an updated algorithm for neonatal management.

Utilization of serologic assays to support efficacy of vaccines in nonclinical and clinical trials: meeting at the crossroads

In May 2009 the National Institute of Allergy and Infectious Diseases hosted a workshop on serologic assays that support vaccine efficacy evaluations. The meeting promoted exchange of ideas among investigators from varying disciplines who are working on anti-infectious agent vaccines at different stages of development. The presentations and discussions at the workshop illustrated the challenges common across various pathogens with recurring themes: (1) A thorough understanding of the science regarding the pathogen and the host response to disease and immunization is fundamental to assay selection. (2) The intended use of the immunoassay data must be clearly defined to ensure appropriate specificity, accuracy, and precision; a laboratory must also commit resources to assure data quality and reliability. (3) During vaccine development, an immunoassay may evolve with respect to quality, purpose, and degree of standardization, and, in some cases, must be changed or replaced as data are accumulated. (4) Collaboration on standardized reagents and methods, harmonization efforts, and multidisciplinary teams facilitate consistent generation of quality data. This report provides guidance for effective development and utilization of immunoassays based on the lessons learned from currently licensed vaccines. Investigators are encouraged to create additional opportunities for scientific exchange, noting that the discussed themes are relevant for immunoassays used for other purposes such as therapeutics and diagnostics.

Prevention of Group B Streptococcus early-onset disease: a toolkit by the California Perinatal Quality Care Collaborative

The California Perinatal Quality Care Collaborative (CPQCC) was organized in 1996 in an effort to improve perinatal outcomes in California. CPQCC has a robust infrastructure of quality improvement resources and expertise and uses a database of demographic and outcome data from neonatal intensive care units in California. In 2004, CPQCC developed a toolkit to provide an evidence-based framework and supporting documents for hospitals to use in systematically addressing persistent early-onset disease (EOD) because of Group B Streptococcus (GBS) in their centers. The CPQCC toolkit was based on the 2002 Centers for Disease Control guideline, 'Prevention of Perinatal Group B Streptococcal Disease.' This article presents an updated version of the CPQCC toolkit reflecting several population studies published since the 2002 guideline. Current epidemiological trends in incidence of EOD with GBS, changes in antibiotic sensitivity and the potential value of newer strategies are discussed.

Vaccines and biosimilarity: a solution or a problem?

Biosimilarity is a significant issue for vaccines and a reasonable approach to this could facilitate licensing of follow-on products of similar design. However, the definitions and guideline criteria developed for similar versions of biotherapeutics may be too restrictive for vaccines, as the molecular composition of their active substances can rarely be defined precisely, and immunogenicity is an essential rather than an undesirable characteristic. Similarity in antigenic composition may be more relevant. The criteria that determine biosimilarity need more careful definition; superficial similarity may conceal significant differences in performance that can only be disclosed by careful clinical evaluation. These issues have been reviewed in detail for current types of bacterial and viral vaccines. For truly biosimilar products, limited clinical studies could be acceptable provided that they permit side-by-side comparison with the original product or another suitable reference. The prospect of the development of biosimilar products also emphasizes the need for improved regulatory tests capable of detecting subtle but biologically significant differences in vaccines. The need for an acceptable definition of biosimilarity and guidelines relevant to vaccines is emphasized.

Streptococcus adherence and colonization

Streptococci readily colonize mucosal tissues in the nasopharynx; the respiratory, gastrointestinal, and genitourinary tracts; and the skin. Each ecological niche presents a series of challenges to successful colonization with which streptococci have to contend. Some species exist in equilibrium with their host, neither stimulating nor submitting to immune defenses mounted against them. Most are either opportunistic or true pathogens responsible for diseases such as pharyngitis, tooth decay, necrotizing fasciitis, infective endocarditis, and meningitis. Part of the success of streptococci as colonizers is attributable to the spectrum of proteins expressed on their surfaces. Adhesins enable interactions with salivary, serum, and extracellular matrix components; host cells; and other microbes. This is the essential first step to colonization, the development of complex communities, and possible invasion of host tissues. The majority of streptococcal adhesins are anchored to the cell wall via a C-terminal LPxTz motif. Other proteins may be surface anchored through N-terminal lipid modifications, while the mechanism of cell wall associations for others remains unclear. Collectively, these surface-bound proteins provide Streptococcus species with a "coat of many colors," enabling multiple intimate contacts and interplays between the bacterial cell and the host. In vitro and in vivo studies have demonstrated direct roles for many streptococcal adhesins as colonization or virulence factors, making them attractive targets for therapeutic and preventive strategies against streptococcal infections. There is, therefore, much focus on applying increasingly advanced molecular techniques to determine the precise structures and functions of these proteins, and their regulatory pathways, so that more targeted approaches can be developed.

Application of carbohydrate array technology to antigen discovery and vaccine development

Carbohydrate arrays are a new technology developed for high-throughput evaluation of interactions between carbohydrates and proteins, cells or viruses. Carbohydrate arrays contain many different carbohydrate structures on a solid support. The format allows one to probe hundreds or thousands of potential receptor-ligand interactions while using only tiny amounts of material. Recently, carbohydrate arrays have been applied to vaccine development in several ways. First, carbohydrate arrays have been utilized for the discovery and characterization of carbohydrate antigens. Second, they have been used to evaluate immune responses to vaccine candidates. Third, carbohydrate arrays have been used to identify and characterize reagents necessary for vaccine development. Although still at an early stage, carbohydrate array technology has tremendous potential for accelerating vaccine development.

Preventive strategies for group B streptococcal and other bacterial infections in early infancy: cost effectiveness and value of information analyses

OBJECTIVE

To determine the cost effectiveness of strategies for preventing neonatal infection with group B streptococci and other bacteria in the UK and the value of further information from research.

DESIGN

Use of a decision model to compare the cost effectiveness of prenatal testing for group B streptococcal infection (by polymerase chain reaction or culture), prepartum antibiotic treatment (intravenous penicillin or oral erythromycin), and vaccination during pregnancy (not yet available) for serious bacterial infection in early infancy across 12 maternal risk groups. Model parameters were estimated using multi-parameter evidence synthesis to incorporate all relevant data inputs.

DATA SOURCES

32 systematic reviews were conducted: 14 integrated results from published studies, 24 involved analyses of primary datasets, and five included expert opinion. Main outcomes measures Healthcare costs per quality adjusted life year (QALY) gained.

RESULTS

Current best practice (to treat only high risk women without prior testing for infection) and universal testing by culture or polymerase chain reaction were not cost effective options. Immediate extension of current best practice to treat all women with preterm and high risk term deliveries without testing (11% treated) would result in substantial net benefits. Currently, addition of culture testing for low risk term women, while treating all preterm and high risk term women, would be the most cost effective option (21% treated). If available in the future, vaccination combined with treating all preterm and high risk term women and no testing for low risk women would probably be marginally more cost effective and would limit antibiotic exposure to 11% of women. The value of information is highest (67m pounds sterling) if vaccination is included as an option.

CONCLUSIONS

Extension of current best practice to treat all women with preterm and high risk term deliveries is readily achievable and would be beneficial. The choice between adding culture testing for low risk women or vaccination for all should be informed by further research. Trials to evaluate vaccine efficacy should be prioritised.

Group B Streptococcus: global incidence and vaccine development

An ongoing public health challenge is to develop vaccines that are effective against infectious diseases that have global relevance. Vaccines against serotypes of group B Streptococcus (GBS) that are prevalent in the United States and Europe are not optimally efficacious against serotypes common to other parts of the world. New technologies and innovative approaches are being used to identify GBS antigens that overcome serotype-specificity and that could form the basis of a globally effective vaccine against this opportunistic pathogen. This Review highlights efforts towards this goal and describes a template that can be followed to develop vaccines against other bacterial pathogens.