A maternal vaccine against group B Streptococcus: past, present, and future

Serotype distribution, antimicrobial resistance, and molecular characterization of group B Streptococcus isolates from Chinese pregnant woman

OBJECTIVE

This study was aimed to investigate the serotypes, antibiotic susceptibilities, and multi-locus sequence type (MLST) profiles of group B Streptococcus (GBS) in the Beijing area.

METHODS

Lower vaginal and rectal swabs were obtained from pregnant women of 35-37 gestational weeks (GWs) who attended the Beijing Obstetrics and Gynecology Hospital. All GBS isolates were identified with Gram staining, catalase reaction assays, and CAMP tests, followed by antibiotic susceptibility testing, serotype identification, multilocus sequence typing and erythromycin resistance gene analysis (ermB and mefE).

RESULTS

From July 2020 to June 2022, 311 (5.17%) of 6012 pregnant women that were screened for GBS colonization were detected positive. Of the eight serotypes identified (III, Ia, Ib, IV, II, VIII, V, and NT), serotypes III (43.09%), Ia (34.08%) and Ib (17.04%) were the predominant species. In the antimicrobial susceptibility experiments, the resistant rates measured for erythromycin, clindamycin, levofloxacin, and tetracycline were 76.21%, 63.99%, 50.80%, and 81.03%, respectively, and 7.6% of GBS isolates showed inducible clindamycin in resistance (D-test phenotype). Meanwhile, the multilocus sequence typing analysis showed that sequence type 19 (ST19) (30.34%) and ST10 (18.62%) were the dominant sequence types. Among the 237 erythromycin-resistant isolates, 176 harbored ermB (128, 54.00%) or mefE (48, 20.30%) gene alone.

CONCLUSION

The infection rates, serotypes or MSLT distribution, and antimicrobial resistance of GBS in Beijing area were investigated, which may be applied in analyses of the epidemiological characteristics of GBS. This contributes to the basic knowledge required for successful GBS vaccine development suited for disease prevention and treatment in China, as well as the implementation of effective clinical antimicrobials.

Using Surface Immunogenic Protein as a Carrier Protein to Elicit Protective Antibody to Multiple Serotypes for Candidate Group B Streptococcal Glycan Conjugate Vaccines

Group B Streptococcus (GBS) is a life-threatening opportunistic pathogen, particularly in pregnant women, infants, and the elderly. Currently, maternal vaccination is considered the most viable long-term option for preventing GBS mother-to-infant infection, and two polysaccharide conjugate vaccines utilizing CRM197 as a carrier protein have undergone clinical phase II trials. Surface immunogenic protein (Sip), present in all identified serotypes of GBS strains so far, is a protective surface protein of GBS. In this study, the type Ia capsular polysaccharide (CPS) of GBS was utilized as a model to develop candidate antigens for a polysaccharide conjugate vaccine by coupling it with the Sip of GBS and the traditional carrier protein CRM197. Serum analysis from immunized New Zealand rabbits and CD1 mice revealed that there was no significant difference in antibody titers between the Ia-Sip group and Ia-CRM197 group; however, both were significantly higher than those observed in the Ia polysaccharide group. Opsonophagocytosis and passive immune protection results using rabbit serum indicated no significant difference between the Ia-Sip and Ia-CRM197 groups, both outperforming the Ia polysaccharide group. Furthermore, serum from the Ia-Sip group had a cross-protective effect on multiple types of GBS strains. The challenge test results in CD1 mice demonstrated that the Ia-Sip group provided complete protection against lethal doses of bacteria and also showed cross-protection against type III strain. Our study demonstrates for the first time that Ia-Sip is immunogenic and provides serotype-independent protection in glycan conjugate vaccines, which also indicates Sip may serve as an excellent carrier protein for GBS glycan conjugate vaccines and provide cross-protection against multiple GBS strains.

Immune responses against group B Streptococcus monovalent and pentavalent capsular polysaccharide tetanus toxoid conjugate vaccines in Balb/c mice

Immunization of pregnant women with Group B Streptococcus (GBS) capsular polysaccharide (CPS) conjugate vaccine (CV) could protect young infants against invasive GBS disease. We evaluated the immunogenicity of investigational five GBS monovalent (serotypes Ia, Ib, II, III, and V) CPS-tetanus toxoid (TT)-CV with adjuvant and GBS pentavalent CPS-TT-CV with adjuvant (GBS5-CV-adj) and without adjuvant (GBS5-CV-no-adj), in Balb/c mice. Aluminum phosphate was the adjuvant in the formulations, where included. The homotypic immunoglobulin G (IgG) geometric mean concentration (GMC) and opsonophagocytic activity (OPA) geometric mean titer (GMT) did not differ after the third dose of the GBS5-CV-adj vaccine compared with the monovalent counterparts for all five serotypes. The GBS5-CV-adj induced higher post-vaccination serotype-specific IgG GMCs and OPA GMTs compared to GBS5-CV-no_adj. The GBS5-CV with and without adjuvant should be considered for further development as a potential vaccine for pregnant women to protect their infants against invasive GBS disease.

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: Virulence Factors and Pathogenic Mechanism

Group B Streptococcus (GBS) or Streptococcus agalactiae is a major cause of neonatal mortality. When colonizing the lower genital tract of pregnant women, GBS may cause premature birth and stillbirth. If transmitted to the newborn, it may result in life-threatening illnesses, including sepsis, meningitis, and pneumonia. Moreover, through continuous evolution, GBS can use its original structure and unique factors to greatly improve its survival rate in the human body. This review discusses the key virulence factors that facilitate GBS invasion and colonization and their action mechanisms. A comprehensive understanding of the role of virulence factors in GBS infection is crucial to develop better treatment options and screen potential candidate molecules for the development of the vaccine.

Updates on Group B Streptococcus Infection in the Field of Obstetrics and Gynecology

Group B Streptococcus (GBS, Streptococcus agalactiae) is a Gram-positive bacterium that is commonly found in the gastrointestinal and urogenital tracts. However, its colonization during pregnancy is an important cause of maternal and neonatal morbidity and mortality worldwide. Herein, we specifically looked at GBS in relation to the field of Obstetrics (OB) along with the field of Gynecology (GY). In this review, based on the clinical significance of GBS in the field of OBGY, topics of how GBS is being detected, treated, and should be prevented are addressed.

Estimation of invasive Group B Streptococcus disease risk in young infants from case-control serological studies

Background

Group B Streptococcus (GBS) infections are a major cause of invasive disease (IGbsD) in young infants and cause miscarriage and stillbirths. Immunization of pregnant women against GBS in addition to intrapartum antibiotic prophylaxis could prevent disease. Establishing accurate serological markers of protection against IGbsD could enable use of efficient clinical trial designs for vaccine development and licensure, without needing to undertake efficacy trials in prohibitively large number of mother-infant dyads. The association of maternal naturally acquired serotype-specific anti-capsular antibodies (IgG) against serotype-specific IGbsD in their infants has been studied in case-control studies. The statistical models used so far to estimate IGbsD risk from these case-control studies assumed that the antibody concentrations measured sharing the same disease status are sampled from the same population, not allowing for differences between mothers colonised by GBS and mothers also potentially infected (e.g urinary tract infection or chorioamnionitis) by GBS during pregnancy. This distinction is relevant as infants born from infected mothers with occult medical illness may be exposed to GBS prior to the mother developing antibodies measured in maternal or infant sera.

Methods

Unsupervised mixture model averaging (MMA) is proposed and applied here to accurately estimate infant IGbsD risk from case-control study data in presence or absence of antibody concentration subgroups potentially associated to maternal GBS carriage or infection. MMA estimators are compared to non-parametric disease risk estimators in simulation studies and by analysis of two published GBS case-control studies.

Results

MMA provides more accurate relative risk estimates under a broad range of data simulation scenarios and more accurate absolute disease risk estimates when the proportion of IGbsD cases with high antibody levels is not ignorable. MMA estimates of the relative and absolute disease risk curves are more amenable to clinical interpretation compared to non-parametric estimates with no detectable overfitting of the data. Antibody concentration thresholds predictive of protection from infant IGbsD estimated by MMA from maternal and infant sera are consistent with non-parametric estimates.

Conclusions

MMA is a flexible and robust method for design, accurate analysis and clinical interpretation of case-control studies estimating relative and absolute IGbsD risk from antibody concentrations measured at or after birth.

Group B Streptococcal Colonization in African Countries: Prevalence, Capsular Serotypes, and Molecular Sequence Types

Streptococcus agalactiae or group B streptococcus (GBS) is a commensal of the gastrointestinal and genitourinary tracts of healthy women and an important cause of neonatal invasive infections worldwide. Transmission of bacteria to the newborn occurs at birth and can be prevented by intrapartum antibiotic prophylaxis. However, this not available in resource limited settings in Africa, which carries a particular high burden of disease. Serotype based vaccines are in development and present a suitable alternative to prevent neonatal infections. To be able to assess vaccine efficacy, knowledge and surveillance of GBS epidemiological data are required. This review summarizes investigations about the serotype distribution and the multi-locus sequence types (MLST) found in different African countries. While most serotypes and MLST data are comparable to findings from other continents, some specific differences exist. Serotype V is predominant among colonizing maternal strains in many different African countries. Serotypes that are rarely detected in western industrialized nations, such as serotypes VI, VII and IX, are prevalent in studies from Ghana and Egypt. Moreover, some specific MLST sequence types that seem to be more or less unique to Africa have been detected. However, overall, the data confirm that a hexavalent vaccine can provide broad coverage for the African continent and that a protein vaccine could represent a promising alternative.

Maternal vaccination with a type-III glycoconjugate protects mouse neonates against Group B Streptococcus intranasal infection

Group B Streptococcus (GBS) is generally an asymptomatic colonizer of human mucosa but it occasionally infects pregnant women and neonates through vertical transmission, causing disease during the first weeks of life with frequent and severe complications. Preclinical studies have shown that maternal vaccination with polysaccharide-based vaccines protects mothers and offspring from GBS mucosal colonization and consecutive infection. In these models, bacteria were inoculated in mouse either intravaginally in the last trimester of pregnancy or systemically in pups. Here, we investigated whether maternal vaccination with glycoconjugate vaccines may also prevent GBS-mediated colonization and disease in neonates using an infection route that more closely mimics inhalation or ingestion of bacteria during human delivery. To address this point, mice aged less than two days were intranasally challenged with epidemiologically relevant GBS strains. Bacteria were found to colonize nose and intestine, reaching in some cases lungs and blood during the first days of life. Bacteria were also found in vagina of a fraction of colonized female mice within the first month of life. GBS-specific IgG induced by maternal vaccination with a glycoconjugate vaccine formulation were found in blood and mucosal tissues of newborns. Finally, when intranasally challenged with GBS serotype III strains, pups delivered by vaccinated mothers were partially protected against mucosal colonization and deeper infection.

Future vaccines in pregnancy

Vaccination in pregnancy provides an important opportunity to target illnesses that are known to impact pregnant women, fetal development, and newborns in particular. The ability to create antibodies through safe vaccination that cross the placenta can provide protection against maternal, congenital, and newborn infections. At present, multiple vaccines are being developed which have direct benefits for pregnant women and their newborns. Group B streptococcus, Respiratory Syncytial Virus, Cytomegalovirus, Zika, Ebola, Malaria, and Coronavirus SARS-CoV-2 are all being researched with the view to develop a safe vaccine available for pregnant women. There is also an increased movement towards the inclusion of pregnant women in vaccine development and trials - challenging the historical, ethical, and medicolegal arguments against their involvement in such research.

Control of Streptococcal Infections: Is a Common Vaccine Target Achievable Against Streptococcus agalactiae and Streptococcus pneumoniae

Both Streptococcus agalactiae [group B streptococcus (GBS)] and Streptococcus pneumoniae (pneumococcus) remain significant pathogens as they cause life threatening infections mostly in children and the elderly. The control of diseases caused by these pathogens is dependent on antibiotics use and appropriate vaccination. The introduction of the pneumococcal conjugate vaccines (PCVs) against some serotypes has led to reduction in pneumococcal infections, however, the subsequent serotype switching, and replacement has been a serious challenge. On the other hand, no vaccine is yet licensed for use in the control of GBS diseases. In this review, we provide an overview of the history and global disease burden, disease pathophysiology and management, vaccines update, and the biology of both pathogens. Furthermore, we address recent findings regarding structural similarities that could be explored for vaccine targets across both mucosal pathogens. Finally, we conclude by proposing future genomic sequence comparison using the wealth of available sequences from both species and the possibility of identifying more related structural components that could be exploited for pan-pathogen vaccine development.

Heme controls the structural rearrangement of its sensor protein mediating the hemolytic bacterial survival

Hemes (iron-porphyrins) are critical for biological processes in all organisms. Hemolytic bacteria survive by acquiring b-type heme from hemoglobin in red blood cells from their animal hosts. These bacteria avoid the cytotoxicity of excess heme during hemolysis by expressing heme-responsive sensor proteins that act as transcriptional factors to regulate the heme efflux system in response to the cellular heme concentration. Here, the underlying regulatory mechanisms were investigated using crystallographic, spectroscopic, and biochemical studies to understand the structural basis of the heme-responsive sensor protein PefR from Streptococcus agalactiae, a causative agent of neonatal life-threatening infections. Structural comparison of heme-free PefR, its complex with a target DNA, and heme-bound PefR revealed that unique heme coordination controls a >20 Å structural rearrangement of the DNA binding domains to dissociate PefR from the target DNA. We also found heme-bound PefR stably binds exogenous ligands, including carbon monoxide, a by-product of the heme degradation reaction.

Phylogeny, recombination, and invasiveness of group B Streptococcus revealed by genomic comparisons of its global strains

Capsular polysaccharide (CPS) genes and pilus islands encode important virulence factors for group B Streptococcus (GBS) genomes. This study aims to detect phylogenetic inconsistency in CPS genes and pilus islands in GBSs and to explore its relationship with invasiveness. A total of 1016 GBS genomes were downloaded from the NCBI public database. The multi-locus sequence typing (MLST) and Bayesian analysis of Population Structure (BAPS) analyses were both conducted for phylogeny construction. Serotyping and pilus typing were determined in silico using the genomic sequences. The CPS and pilus typing results were generally consistent with MLST and BAPS clustering. GBS isolates of serotype II and of the PI-1 + PI-2b and PI-2a types were more prone to phylogenetic inconsistency than the others. Isolates of serotype Ib and of PI-1 + PI-2a were more likely to appear as colonizing strains, whereas PI-2b was more likely to appear in invasive strains. For serotype V, phylogenetic inconsistency occurred more commonly in colonizing isolates, while for serotype III, the opposite occurred. The present study profiles for the first time the phylogenetic inconsistency of CPS genes and pilus islands in global GBS isolates, which is helpful for infection control and the development of new vaccines for the prevention of GBS occurrence.

Streptococcus agalactiae in pregnant women: serotype and antimicrobial susceptibility patterns over five years in Eastern Sicily (Italy)

Streptococcus agalactiae (also known Group B Streptococcus or GBS) represents the main pathogen responsible for early- and late-onset infections in newborns. The present study aimed to determine the antimicrobial susceptibility pattern and the capsular serotypes of GBS isolated in Eastern Sicily over 5 years, from January 2015 to December 2019. A total of 3494 GBS were isolated from vaginal swabs of pregnant women (37–39 weeks), as recommended by the Centers for Disease Control and Prevention. Capsular polysaccharide’s typing of GBS was determined by a commercial latex agglutination test containing reagents to serotypes I–IX. The antimicrobial resistance pattern of GBS was determined through the disk diffusion method (Kirby-Bauer) and the double-disk diffusion test on Mueller-Hinton agar plates supplemented with 5% defibrinated sheep blood, according to the guidelines of the Clinical and Laboratory Standards Institute. Serotypes III (1218, 34.9%) and V (1069, 30.6%) were the prevalent colonizers, followed by not typable (570, 16.3%) and serotypes Ia (548, 15.7%), Ib (47, 1.3%), II (40, 1.1%), and IV (2, 0.1%). All 3494 clinical isolates were susceptible to cefditoren and vancomycin. Resistance to penicillin, ampicillin, levofloxacin, clindamycin, and erythromycin was observed in 6 (0.2%), 5 (0.1%), 161 (4.6%), 1090 (31.2%), and 1402 (40.1%) of the strains, respectively. Most of erythromycin-resistant GBS (1090/1402) showed the cMLS_B phenotype, 276 the M phenotype, and 36 the iMLS_B phenotype. Our findings revealed a higher prevalence of serotype III and a relevant resistance rate, among GBS strains, to the most frequently used antibiotics in antenatal screening.

Immunization with a recombinant BibA surface protein confers immunity and protects mice against group B Streptococcus (GBS) vaginal colonization

Streptococcus agalactiae or group B Streptococcus (GBS) is a Gram-positive bacterium divided into ten distinct serotypes that colonizes the vaginal and rectal tracts of approximately 30% of women worldwide. GBS is the leading cause of invasive infection in newborns, causing sepsis, pneumoniae and meningitis. The main strategy to prevent GSB infection in newborns includes the use of intrapartum antibiotic therapy, which does not prevent late-onset diseases and may select resistant bacterial strains. We still do not have a vaccine formulation specific for this pathogen approved for human use. Conserved surface proteins are potential antigens that could be targets for recognition by antibodies and activation of cell opsonization. We used a serotype V GBS (GBS-V)-derived recombinant surface protein, rBibA, and evaluated the potential protective role of the induced antigen-specific antibodies after parenteral or mucosal immunizations in C57BL/6 mice. In vitro and in vivo assays demonstrated that vaccine formulations containing BibA combined with different adjuvants induced serum IgG and/or secreted IgA antibodies, leading to enhanced opsonophagocytosis of GBS-V cells and reduced invasion of epithelial cells. One BibA-based vaccine formulation adjuvanted with a nontoxic derivative of the heat-labile toxin produced by enterotoxigenic Escherichia coli (ETEC) strains was capable of inducing protection against vaginal colonization and lethal parenteral challenge with GBS-V. Serum collected from vaccinated mice conferred passive protection against vaginal colonization in naïve mice challenged with GBS-V. Taken together, the present data demonstrate that the BibA protein is a promising antigen for development of a vaccine to protect against GBS infection.

[Relationship of group B streptococcus colonization in late pregnancy with perinatal outcomes]

OBJECTIVE

To investigate the relationship of group B streptococcus (GBS) colonization in late pregnancy with perinatal outcome.

METHODS

Pregnant women who underwent antenatal check-up at General Hospital of PLA Eastern Theater Command and the First Affiliated Hospital of Nanjing Medical University from January 2016 to December 2018 were enrolled in the study. The vaginal and rectal swab samples were collected for GBS culture at 35-37 weeks of pregnancy. The perinatal outcomes of positive and negative GBS groups were compared. The GBS-positive group samples were tested for antibiotic susceptibility. In GBS positive group the maternal and child perinatal outcomes were compared between pregnant women with antibiotics treatment and those without antibiotics.

RESULTS

A total of 13 000 pregnant women were enrolled, and the overall colonization rate of GBS was 3.65%(475/13 000). The colonization rate of GBS in the vagina was 2.33%(303/13 000), and the colonization rate in the rectum was 1.75%(227/13 000). Through the collection and detection of rectal specimens, the positive rate of GBS increased by 56.77%(172/303). The monthly colonization rate of GBS showed significant fluctuations with the highest in March and October (all P < 0.05). The sensitivity of 475 GBS-positive specimens to ceftriaxone, vancomycin and linezolid were 100%, and the sensitivity to ampicillin and penicillin were 97.26%and 93.47%, respectively. The resistance rates of the strains to levofloxacin, clindamycin, erythromycin and tetracycline were 30.11%, 48.00%, 52.21%and 88.63%. The incidence of premature rupture of membranes, postpartum hemorrhage, puerperal infection, neonatal pneumonia and sepsis in GBS positive group were significantly higher than those in GBS negative group (all P < 0.01). In pregnant women with positive GBS, the incidence of puerperal infection, neonatal infection and admission to the NICU in the antibiotic group were significantly lower than those in the non-antibiotic group ( P < 0.05 or P < 0.01).

CONCLUSIONS

The total colonization rate of GBS is low. The detection of GBS can be significantly improved by supplementing rectal examination. Ceftriaxone, ampicillin and penicillin are currently the drugs of choice for the prevention and treatment of GBS-related diseases. GBS infection can increase the incidence of maternal and child complications. The use of antibiotics during labor can improve the outcome of mothers and infants.

Phenotypic and Genotypic Characterization of Resistance to Macrolides and Lincosamides in Streptococcus agalactiae Isolated from Pregnant Women in Misiones, Argentina

The aim of this work was to determine the susceptibility, molecular profile, and clonal relationship in Streptococcus agalactiae (group B Streptococcus [GBS]) isolated from vaginal-rectal swab samples. We worked with 200 isolates collected from pregnant women between 35 and 37 weeks of gestation. The macrolide-lincosamide-streptogramin B (MLS_B) resistance phenotypes were determined using the double-disc assay. Susceptibility to erythromycin (ERI) and clindamycin (CLI) was performed with the E-test. Resistance genes ermB and ermTR were detected by polymerase chain reaction. Clonal studies were performed using the random amplification of polymorphic DNA. Twelve (6%) of the isolates were resistant to ERI and 10 (5%) of them to CLI. Fifty percent of the resistant strains corresponded to serotype III, 25% to serotype V, and the remaining 25% to serotype Ia, II, and nontypeable strains. The cMLS_B phenotype was detected in eight strains (66.67%) and the iMLS_B phenotype in four (33.33%). The minimum inhibitory concentration values were between 1.5 and 16 μg/mL for ERI, and between 1 and 32 μg/mL for CLI. Out of the 25 strains susceptible to ERI and CLI, the presence of the ermB gene was detected in eight of them and the ermTR gene in one strain. The ermB gene was detected in the 12 strains that initially had some macrolide resistance phenotype. The ermTR gene was detected in three out of the four strains with the iMLS_B phenotype. The resistance to macrolides in the province of Misiones is due to multiclonal spread. The phenotypic and genotypic characterization of macrolide resistance in GBS strains are crucial to contribute to the correct intrapartum prophylactic antibiotic therapy of allergic pregnant women and the epidemiological surveillance of these strains.

Prevalence and capsular type distribution of group B Streptococcus isolated from vagina of pregnant women in Nghe An province, Vietnam

BACKGROUND AND OBJECTIVES

Identification of GBS serotypes provides helpful information for appropriate the development of suitable vaccines; however, no reports from Vietnam have been published. This study has been performed to find the prevalence and serotypes of group B Streptococcus isolated from vagina of pregnant women in Nghe An province, Vietnam.

MATERIALS AND METHODS

Vaginal swabs were collected from pregnant women at 35-37 weeks of gestation at the Nghe An Obstetrics and Pediatrics Hospital, Vietnam between May 2018 and July 2019. The swabs were cultured on 5% sheep blood agar for isolation of GBS. All isolates were identified using the Gram staining, CAMP test and specific PCR. GBS strains were serotyped using the multiplex PCR assays.

RESULTS

The prevalence of vaginal GBS colonization was 9.20% of 750 participants. Among the isolates, serotypes III (39.13%) and V (31.89%) were the most frequent, followed by serotypes Ia (11.59%), VI (11.59%), Ib (2.90%), II (1.45%) and VII (1.45%), respectively. Serotypes IV, VIII and IX were not found.

CONCLUSION

The prevalence of GBS in the Nghe An province of central Vietnam was similar to reports from other parts of the world. The predominat GBS serotypes (III, V, Ia and VI) were slightly different from those previously described from other regions around the world. The high frequency of serotype VI was a notable feature of the strains from pregnant women in Vietnam.

Regioselective Glycosylation Strategies for the Synthesis of Group Ia and Ib Streptococcus Related Glycans Enable Elucidating Unique Conformations of the Capsular Polysaccharides

Group B Streptococcus serotypes Ia and Ib capsular polysaccharides are key targets for vaccine development. In spite of their immunospecifity these polysaccharides share high structural similarity. Both are composed of the same monosaccharide residues and differ only in the connection of the Neu5Acα2-3Gal side chain to the GlcNAc unit, which is a β1-4 linkage in serotype Ia and a β1-3 linkage in serotype Ib. The development of efficient regioselective routes for GlcNAcβ1-3[Glcβ1-4]Gal synthons is described, which give access to different group B Streptococcus (GBS) Ia and Ib repeating unit frameshifts. These glycans were used to probe the conformation and molecular dynamics of the two polysaccharides, highlighting the different presentation of the protruding Neu5Acα2-3Gal moieties on the polysaccharide backbones and a higher flexibility of Ib polymer relative to Ia, which can impact epitope exposure.

Vaccination With a Latch Peptide Provides Serotype-Independent Protection Against Group B Streptococcus Infection in Mice

Streptococcus agalactiae (group B streptococcus [GBS]) is a leading cause of invasive diseases in neonates and severe infections in elderly individuals. GBS serine-rich repeat glycoprotein 1 (Srr1) acts as a critical virulence factor by facilitating GBS invasion into the central nervous system through interaction with the fibrinogen Aα chain. This study revealed that srr1 is highly conserved, with 86.7% of GBS clinical isolates expressing the protein. Vaccination of mice with different Srr1 truncated peptides revealed that only Srr1 truncates containing the latch domain protected against GBS meningitis. Furthermore, the latch peptide alone was immunogenic and elicited protective antibodies, which efficiently enhanced antibody-mediated opsonophagocytic killing of GBS by HL60 cells and provided heterogeneous protection against 4 different GBS serogroups. Taken together, these findings indicated that the latch domain of Srr1 may constitute an effective peptide vaccine candidate for GBS.

Subspecies Typing of Streptococcus agalactiae Based on Ribosomal Subunit Protein Mass Variation by MALDI-TOF MS

Background: A ribosomal subunit protein (rsp)-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method was developed for fast subspecies-level typing of Streptococcus agalactiae (Group B Streptococcus, GBS), a major cause of neonatal sepsis and meningitis.

Methods: A total of 796 GBS whole genome sequences, covering the genetic diversity of the global GBS population, were used to in silico predict molecular mass variability of 28 rsp and to identify unique rsp mass combinations, termed “rsp-profiles”. The in silico established GBS typing scheme was validated by MALDI-TOF MS analysis of GBS isolates at two independent research sites in Europe and South East Asia.

Results: We identified in silico 62 rsp-profiles, with the majority (>80%) of the 796 GBS isolates displaying one of the six rsp-profiles 1–6. These dominant rsp-profiles classify GBS strains in high concordance with the core-genome based phylogenetic clustering. Validation of our approach by in-house MALDI-TOF MS analysis of 248 GBS isolates and external analysis of 8 GBS isolates showed that across different laboratories and MALDI-TOF MS platforms, the 28 rsp were detected reliably in the mass spectra, allowing assignment of clinical isolates to rsp-profiles at high sensitivity (99%) and specificity (97%). Our approach distinguishes the major phylogenetic GBS genotypes, identifies hyper-virulent strains, predicts the probable capsular serotype and surface protein variants and distinguishes between GBS genotypes of human and animal origin.

Conclusion: We combine the information depth of whole genome sequences with the highly cost efficient, rapid and robust MALDI-TOF MS approach facilitating high-throughput, inter-laboratory, large-scale GBS epidemiological and clinical studies based on pre-defined rsp-profiles.

Prevalence and capsular type distribution of Streptococcus agalactiae isolated from pregnant women in Namibia and South Africa

Background

Streptococcus agalactiae or Group B Streptococcus (GBS) is the leading cause of neonatal morbidity and mortality resulting in septicaemia, bacteraemia and meningitis. Long term problems in children range from loss of hearing to mental retardation. While Intrapartum Antibiotic Prophylaxis (IAP) has reduced the incidence of S. agalactiae infection, it still remains the leading cause of disease in neonates. GBS has ten capsular types whose distribution varies across the world. Therefore, this study sought to determine the prevalence of GBS in Namibia and South Africa amongst pregnant women between 35 and 37 weeks gestation and elucidate the capsular types.

Methods

Lower vaginal and rectal swabs were collected from pregnant women between 35 and 37 weeks gestation. Five hundred and thirty pregnant women were recruited into the study in Windhoek, Namibia while one hundred pregnant women were recruited in the Eastern Cape, South Africa. The swabs were cultured on 5% sheep blood agar (Biomerieux, New Jersey, USA) for isolation of GBS. Presumptive isolates were confirmed using both the Vitek (2) and molecular techniques targeting the scpB gene. Capsular typing was performed in a multiplex PCR with capsular specific primer pairs.

Results

The prevalence of GBS in Namibia was 13.6 and 37% in South Africa respectively. In both countries most women were dually colonised with GBS. Capsular types II, III and V were the most prevalent.

Conclusions

The prevalence of GBS in Namibia was lower than in South Africa in this study. The prevalence in both countries was not different from those reported in other African countries and around the world. The predominant capsular types in this study are the ones commonly associated with adverse maternal outcomes.

Maternal immunisation to improve the health of HIV-exposed infants

HIV-exposed but uninfected (HEU) infants are at an increased risk of many infectious diseases that can contribute to the high mortality seen among HEU children. Maternal immunisation could be a promising strategy to reduce infections in HEU infants. However, very little research has explored the effect of HIV on the immunogenicity and effectiveness of vaccines given during pregnancy. We review the available evidence on maternal immunisation among women living with HIV (WLWH) for all vaccines recommended, considered, or being investigated for routine or risk-based use during pregnancy. Of the 11 vaccines included, only three have been investigated in WLWH. Available evidence suggests that maternal HIV infection limits the immunogenicity of several vaccines, leaving HEU infants more susceptible to infection during their first few months of life. Whether maternal immunisation reduces the infectious morbidity and mortality associated with infectious diseases in HEU children remains unknown. We conclude the Review by identifying future research priorities.

Maternal vaccine knowledge in low- and middle-income countries-and why it matters

Maternal vaccines have the potential to reduce the global burden of neonatal morbidity and mortality by accessing the infant immune system before a vaccine administered in childhood would be effective. Maternal vaccines for influenza, tetanus, and pertussis have been shown to reduce neonatal disease and mortality, and other candidate vaccines for group B streptococcus and respiratory syncytial virus are being developed to continue this trend. However, safe and effective maternal vaccines will only successfully reduce neonatal illness if mothers decide to receive them. Maternal knowledge, attitudes, and beliefs around vaccines are key determinants to vaccine acceptance or vaccine hesitancy, and yet this issue is often understudied in low and middle-income country settings. A deeper understanding of these factors and how they influence maternal decision-making will allow public health practitioners and global and national policymakers to design more effective interventions. Addressing barriers to immunization at the policy and programmatic levels such as mothers' knowledge, attitudes, and beliefs of maternal vaccines is essential to increasing vaccination rates at a global scale and reducing global vaccine-preventable neonatal deaths.

Obesity, Diabetes, and the Risk of Invasive Group B Streptococcal Disease in Nonpregnant Adults in the United States

Background

Rates of invasive group B Streptococcus (GBS) disease, obesity, and diabetes have increased in US adults. We hypothesized that obesity would be independently associated with an increased risk of invasive GBS disease.

Methods

We identified adults with invasive GBS disease within Active Bacterial Core surveillance during 2010–2012 and used population estimates from the Behavioral Risk Factor Surveillance System to calculate invasive GBS incidence rates. We estimated relative risks (RRs) of invasive GBS using Poisson analysis with offset denominators, with obesity categorized as class I/II (body mass index [BMI] = 30–39.9 kg/m²) and class III (BMI ≥ 40.0 kg/m²).

Results

In multivariable analysis of 4281 cases, the adjusted RRs of invasive GBS disease were increased for obesity (class I/II: RR, 1.52; 95% confidence interval [CI], 1.14–2.02; and class III: RR, 4.87; 95% CI, 3.50–6.77; reference overweight) and diabetes (RR, 6.04; 95% CI, 4.77–7.65). The adjusted RR associated with class III obesity was 3-fold among persons with diabetes (95% CI, 1.38–6.61) and nearly 9-fold among persons without diabetes (95% CI, 6.41–12.46), compared with overweight. The adjusted RRs associated with diabetes varied by age and BMI, with the highest RR in young populations without obesity. Population attributable risks of invasive GBS disease were 27.2% for obesity and 40.1% for diabetes.

Conclusions

Obesity and diabetes were associated with substantially increased risk of infection from invasive GBS. Given the population attributable risks of obesity and diabetes, interventions that reduce the prevalence of these conditions would likely reduce the burden of invasive GBS infection.

Identification of Streptococcus mitis321A vaccine antigens based on reverse vaccinology

Streptococcus mitis (S. mitis) may transform into highly pathogenic bacteria. The aim of the present study was to identify potential antigen targets for designing an effective vaccine against the pathogenic S. mitis321A. The genome of S. mitis321A was sequenced using an Illumina Hiseq2000 instrument. Subsequently, Glimmer 3.02 and Tandem Repeat Finder (TRF) 4.04 were used to predict genes and tandem repeats, respectively, with DNA sequence function analysis using the Basic Local Alignment Search Tool (BLAST) in the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Cluster of Orthologous Groups of proteins (COG) databases. Putative gene antigen candidates were screened with BLAST ahead of phylogenetic tree analysis. The DNA sequence assembly size was 2,110,680 bp with 40.12% GC, 6 scaffolds and 9 contig. Consequently, 1,944 genes were predicted, and 119 TRF, 56 microsatellite DNA, 10 minisatellite DNA and 154 transposons were acquired. The predicted genes were associated with various pathways and functions concerning membrane transport and energy metabolism. Multiple putative genes encoding surface proteins, secreted proteins and virulence factors, as well as essential genes were determined. The majority of essential genes belonged to a phylogenetic lineage, while 321AGL000129 and 321AGL000299 were on the same branch. The current study provided useful information regarding the biological function of the S. mitis321A genome and recommends putative antigen candidates for developing a potent vaccine against S. mitis.

Status of group B streptococcal vaccine development

Streptococcus agalactiae (group B streptococcus, GBS) is a leading causal organism of neonatal invasive diseases and severe infections in the elderly. Despite significant advances in the diagnosis and treatment of GBS infections and improvement in personal hygiene standards, this pathogen is still a global health concern. Thus, an effective vaccine against GBS would augment existing strategies to substantially decrease GBS infection. In 2014, World Health Organization convened the first meeting for consultation on GBS vaccine development, focusing on the GBS maternal immunization program, which was aimed at reducing infections in neonates and young infants worldwide. Here, we review the history of GBS infections, the current vaccine candidates, and the current status of immunogenicity assays used to evaluate the clinical efficacy of GBS vaccines.

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.

Intrinsic Maturational Neonatal Immune Deficiencies and Susceptibility to Group B Streptococcus Infection

Although a normal member of the gastrointestinal and vaginal microbiota, group B Streptococcus (GBS) can also occasionally be the cause of highly invasive neonatal disease and is an emerging pathogen in both elderly and immunocompromised adults. Neonatal GBS infections are typically transmitted from mother to baby either in utero or during passage through the birth canal and can lead to pneumonia, sepsis, and meningitis within the first few months of life. Compared to the adult immune system, the neonatal immune system has a number of deficiencies, making neonates more susceptible to infection. Recognition of GBS by the host immune system triggers an inflammatory response to clear the pathogen. However, GBS has developed several mechanisms to evade the host immune response. A comprehensive understanding of this interplay between GBS and the host immune system will aid in the development of new preventative measures and therapeutics.

Development of a multiplexed opsonophagocytic killing assay (MOPA) for group B Streptococcus

Group B Streptococcus (GBS) is a leading cause of sepsis in infants as well as chorioamnionitis in pregnant women. Opsonophagocytic killing assays (OPAs) are an essential technique in vaccine studies of encapsulated bacteria for estimating serotype-specific functional antibody levels in vitro. Here, we developed a three-fold multiplexed OPA (MOPA) to enable practical, large-scale assessment of GBS vaccine immunogenicity, including against serotypes Ia, III, and V. First, three target bacteria strains resistant to streptomycin, spectinomycin, or kanamycin were generated by natural selection through exposure to increasing antibiotic concentrations. Since a high level of nonspecific killing (NSK) of serotype V was observed in a 12.5% baby rabbit complement (BRC) solution, the BRC concentration was optimized. The final GBS-MOPA BRC concentration was 9%, which resulted in less than 20% NSK. The specificity was measured by preabsorbing serum with inactivated GBS. The opsonic index (OI) of preabsorbed serum with the homologous serotype GBS was significantly reduced in all three serotypes tested. The accuracy of the MOPA was compared with that of a single OPA (SOPA) with 35 serum samples. The OIs of the MOPA correlated well with those of the SOPA, and the r² values were higher than 0.950 for all three serotypes. The precision of the MOPA assay was assessed in five independent experiments with five serum samples. The inter-assay precision of the GBS-MOPA was 12.5% of the average coefficient of variation. This is the first report to develop and standardize a GBS-MOPA, which will be useful for GBS vaccine development and evaluation.

Genetic evidence for a novel variant of the pilus island 1 backbone protein in group B Streptococcus

PURPOSE

Pili contribute significantly to the pathogenesis of infection of group B Streptococcus (GBS) by facilitating adhesion and invasion of host cells. GBS pilin subunits (the backbone pilin protein, BP, and the ancillary pilin proteins, AP) as well as the specific enzymes required for pilus assembly are encoded by genes located in two separate genomic regions, known as pilus island 1 (PI-1) and PI-2. Our aim was to characterize the pilus profile of a collection of GBS isolates from metropolitan Toronto, Canada.

METHODOLOGY

The pilus profile of 1332 invasive and colonizing GBS isolates was determined by PCR and, in selected cases, by whole genome sequencing.

RESULTS

While investigating the pilus profile of a collection of GBS organisms, we discovered that 51 isolates possessed a novel variant of the PI-1 BP, which we named BP-1b. The predicted translated sequences of archetypical GBS BP-1 and novel BP-1b variants shared only 63 % amino acid sequence homology. The novel BP-1b variant was most common among strains of serotype Ib and VI, but was also found among strains of serotypes Ia, II, III and VIII.

CONCLUSION

We describe a relatively frequent occurrence of a novel PI-1 BP that cannot be detected by a commonly used multiplex PCR scheme, which could lead to strains being mistyped as PI-1 negative. We present PCR primers that can easily be incorporated into the multiplex PCR assay to identify strains with novel BP-1b variant.

Colonization prevalence and antibiotic susceptibility of Group B Streptococcus in pregnant women over a 6-year period in Dongguan, China

This study investigated the prevalence of recto-vaginal Group B Streptococcus (GBS) colonization, serotype distribution, and antimicrobial susceptibility patterns among pregnant women in Dongguan, China. Recto-vaginal swabs were collected from pregnant women at gestational age 35–37 weeks between January 1^st 2009 and December 31^st 2014. Isolates were serotyped by latex-agglutination and were tested against seven antimicrobials by disk diffusion. Of 7,726 pregnant women who completed GBS testing, 636 (8.2%) were GBS carriers. Of 153 GBS isolates available for typing, 6 serotypes (Ia, Ib, III, V, VI and VIII) were identified with type III being predominant, while 9 (5.9%) were non-typable isolates. All isolates were sensitive to penicillin, ceftriaxone, linezolid and vancomycin, whereas 52.4% were resistant to clindamycin, 25.9% were resistant to levofloxacin and 64.9% were resistant to erythromycin. This study showed the recto-vaginal colonization prevalence of GBS in Dongguan is significant. Due to 100% susceptibility to penicillin of all GBS samples, penicillin remains the first recommendation for treatment and prevention against GBS infection. Susceptibility testing should be performed for women allergic to penicillin in order to choose the most appropriate antibacterial agents for treatment and prevention of vertical transmission to neonates. In addition, we suggest establishing standard processes for GBS culture and identification in China as early as possible.

Update on community-acquired bacterial meningitis: guidance and challenges

BACKGROUND

The existing heterogeneity in diagnostic work-up and treatment strategies in bacterial meningitis was the incentive to develop a European evidence-based guideline, which was published in 2016 by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group on Infections of the Brain (ESGIB).

AIMS

To summarize salient features of the guideline, identify recent developments and challenges currently faced.

SOURCES

The ESCMID guideline, ongoing trial registries.

CONTENT

Epidemiology, clinical symptoms, diagnostic work-up and therapy strategies of acute bacterial meningitis.

IMPLICATIONS

The incidence of bacterial meningitis has decreased following pneumococcal and meningococcal conjugate vaccine introduction. In the diagnosis of bacterial meningitis the clinical characteristics and laboratory parameters are of limited diagnostic accuracy and therefore cerebrospinal fluid analysis remains the principal contributor to the final diagnosis. The ESCMID guideline advises to start empiric treatment within one hour of arrival in all suspected meningitis cases, and choice of antibiotics needs to be differentiated according to the patient's age, risk factors, and local resistance rates of pneumococci. Dexamethasone is the only proven adjunctive treatment and should be started together with the antibiotics. The follow-up of surviving patients should include evaluation for hearing loss and pneumococcal vaccination to prevent recurrences. Future perspectives include further development and implementation of vaccines, and new treatments aimed at further reducing the inflammatory response. Studies on implementation of the new guideline should determine adherence and evaluate whether improved prognosis can be achieved by following protocolled management strategies.

Neonatal Group B Streptococcus Infections: Prevention Strategies, Clinical and Microbiologic Characteristics in 7 Years of Surveillance

BACKGROUND

The characteristics of group B streptococcus (GBS) neonatal disease in a period of 7 years are reported.

METHODS

The estimation of the neonatal GBS disease risk and prevention strategies adopted at delivery in absence of national guidelines was evaluated by the analysis of 3501 questionnaires. Notification of 194 neonatal GBS infections was recorded. In addition, 115 strains from neonatal early-onset disease (EOD) and late-onset disease, respectively, plus 320 strains from pregnant women were analyzed by molecular typing methods and for antibiotic resistance.

RESULTS

Preterm deliveries, precipitous labor and GBS negatively screened mothers were the prominent causes for an inadequate or lack of intrapartum antibiotic prophylaxis and EOD occurrence. The superimposable serotype distribution of GBS strains from EOD and from antenatal screening confirmed the vertical transmission from mother to neonate as the cause of disease. On the contrary, late-onset disease was almost exclusively caused by the internationally diffused clonal complex 17. Erythromycin resistance was detected in 17% of strains. Resistance to clindamycin was 15.3 %.

CONCLUSIONS

The administration of intrapartum antibiotic prophylaxis to negatively GBS screened women in presence of risk factors was a deviation from the recommendations issued by the Centers for Disease Control and Prevention, and it should deserve further consideration. Routine surveillance and molecular typing of circulating clones are essential for the effective management of the neonatal GBS disease.

From Immunologically Archaic to Neoteric Glycovaccines

Polysaccharides (PS) are present in the outermost surface of bacteria and readily come in contact with immune cells. They interact with specific antibodies, which in turn confer protection from infections. Vaccines with PS from pneumococci, meningococci, Haemophilus influenzae type b, and Salmonella typhi may be protective, although with the important constraint of failing to generate permanent immunological memory. This limitation has in part been circumvented by conjugating glycovaccines to proteins that stimulate T helper cells and facilitate the establishment of immunological memory. Currently, protection evoked by conjugated PS vaccines lasts for a few years. The same approach failed with PS from staphylococci, Streptococcus agalactiae, and Klebsiella. All those germs cause severe infections in humans and often develop resistance to antibiotic therapy. Thereby, prevention is of increasing importance to better control outbreaks. As only 23 of more than 90 pneumococcal serotypes and 4 of 13 clinically relevant Neisseria meningitidis serogroups are covered by available vaccines there is still tremendous clinical need for PS vaccines. This review focuses on glycovaccines and the immunological mechanisms for their success or failure. We discuss recent advances that may facilitate generation of high affinity anti-PS antibodies and confer specific immunity and long-lasting protection.

Immunogenicity and protective efficacy induced by self-amplifying mRNA vaccines encoding bacterial antigens

Nucleic acid vaccines represent an attractive approach to vaccination, combining the positive attributes of both viral vectors and live-attenuated vaccines, without the inherent limitations of each technology. We have developed a novel technology, the Self-Amplifying mRNA (SAM) platform, which is based on the synthesis of self-amplifying mRNA formulated and delivered as a vaccine. SAM vaccines have been shown to stimulate robust innate and adaptive immune responses in small animals and non-human primates against a variety of viral antigens, thus representing a safe and versatile tool against viral infections. To assess whether the SAM technology could be used for a broader range of targets, we investigated the immunogenicity and efficacy of SAM vaccines expressing antigens from Group A (GAS) and Group B (GBS) Streptococci, as models of bacterial pathogens. Two prototype bacterial antigens (the double-mutated GAS Streptolysin-O (SLOdm) and the GBS pilus 2a backbone protein (BP-2a)) were successfully expressed by SAM vectors. Mice immunized with both vaccines produced significant amounts of fully functional serum antibodies. The antibody responses generated by SAM vaccines were capable of conferring consistent protection in murine models of GAS and GBS infections. Inclusion of a eukaryotic secretion signal or boosting with the recombinant protein resulted in higher specific-antibody levels and protection. Our results support the concept of using SAM vaccines as potential solution for a wide range of both viral and bacterial pathogens, due to the versatility of the manufacturing processes and the broad spectrum of elicited protective immune response.

Immunological Outcomes of Antibody Binding to Glycans Shared between Microorganisms and Mammals

Glycans constitute basic cellular components of living organisms across biological kingdoms, and glycan-binding Abs participate in many cellular interactions during immune defense against pathogenic organisms. Glycan epitopes are expressed as carbohydrate-only entities or as oligomers or polymers on proteins and lipids. Such epitopes on glycoproteins may be formed by posttranslational modifications or neoepitopes resulting from metabolic-catabolic processes and can be altered during inflammation. Pathogenic organisms can display host-like glycans to evade the host immune response. However, Abs to glycans, shared between microorganisms and the host, exist naturally. These Abs are able to not only protect against infectious disease, but also are involved in host housekeeping functions and can suppress allergic disease. Despite the reactivity of these Abs to glycans shared between microorganisms and host, diverse tolerance-inducing mechanisms permit the B cell precursors of these Ab-secreting cells to exist within the normal B cell repertoire.

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

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

Molecular Characterization of Streptococcus agalactiae Causing Community- and Hospital-Acquired Infections in Shanghai, China

Streptococcus agalactiae, a colonizing agent in pregnant women and the main cause of neonatal sepsis and meningitis, has been increasingly associated with invasive disease in nonpregnant adults. We collected a total of 87 non-repetitive S. agalactiae isolates causing community-acquired (CA) and hospital-acquired (HA) infections in nonpregnant adults from a teaching hospital in Shanghai between 2009 and 2013. We identified and characterized their antibiotic resistance, sequence type (ST), serotype, virulence, and biofilm formation. The most frequent STs were ST19 (29.9%), ST23 (16.1%), ST12 (13.8%), and ST1 (12.6%). ST19 had significantly different distributions between CA- and HA-group B Streptococci (GBS) isolates. The most frequent serotypes were III (32.2%), Ia (26.4%), V (14.9%), Ib (13.8%), and II (5.7%). Serotype III/ST19 was significantly associated with levofloxacin resistance in all isoates. The HA-GBS multidrug resistant rate was much higher than that of CA-GBS. Virulence genes pavA, cfb were found in all isolates. Strong correlations exist between serotype Ib (CA and HA) and surface protein genes spb1 and bac, serotype III (HA) and surface protein gene cps and GBS pilus cluster. The serotype, epidemic clone, PFGE-based genotype, and virulence gene are closely related between CA-GBS and HA-GBS, and certain serotypes and clone types were significantly associated with antibiotic resistance. However, CA-GBS and HA-GBS still had significant differences in their distribution of clone types, antibiotic resistance, and specific virulence genes, which may provide a basis for infection control.

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.

Streptococcus agalactiae Serotype Distribution and Antimicrobial Susceptibility in Pregnant Women in Gabon, Central Africa

Neonatal invasive disease due to Streptococcus agalactiae is life threatening and preventive strategies suitable for resource limited settings are urgently needed. Protective coverage of vaccine candidates based on capsular epitopes will relate to local epidemiology of S. agalactiae serotypes and successful management of critical infections depends on timely therapy with effective antibiotics. This is the first report on serotype distribution and antimicrobial susceptibility of S. agalactiae in pregnant women from a Central African region. Serotypes V, III, and Ib accounted for 88/109 (81%) serotypes and all isolates were susceptible to penicillin and clindamycin while 13% showed intermediate susceptibility to erythromycin.

Group B Streptococci serotype distribution in pregnant women in Ghana: assessment of potential coverage through future vaccines

OBJECTIVE

Group B streptococcal (GBS) colonization of pregnant women can lead to subsequent infection of the new-born and potentially fatal invasive disease. Data on GBS colonization prevalence and serotype distribution from Africa are scarce, although GBS-related infections are estimated to contribute substantially to infant mortality. In recent years, GBS vaccine candidates provided promising results in phase I and II clinical trials. We aimed to assess the prevalence and serotype distribution of GBS in Ghana since this knowledge is a prerequisite for future evaluation of vaccine trials.

METHODS

This double-centre study was conducted in one rural and one urban hospital in central Ghana, West Africa. Women in late pregnancy (≥35 weeks of gestation) attending the antenatal care clinic (ANC) provided recto-vaginal swabs for GBS testing. GBS isolates were analysed for serotype and antibiotic susceptibility. GBS-positive women were treated with intrapartum antibiotic prophylaxis (IAP) according to current guidelines of the Center for Disease Control and Prevention (CDC).

RESULTS

In total, 519 women were recruited at both study sites, recto-vaginal swabs were taken from 509. The overall prevalence of GBS was 19.1% (18.1% in rural Pramso and 23.1% in urban Kumasi, restrospectively). Capsular polysaccharide serotype (CPS) Ia accounted for the most frequent serotype beyond all isolates (28.1%), followed by serotype V (27.1%) and III (21.9%). No resistance to Penicillin was found, resistances to second line antibiotics clindamycin and erythromycin were 3.1% and 1%, respectively.

DISCUSSION

Group B Streptococcus serotype distribution in Ghana is similar to that worldwide, but variations in prevalence of certain serotypes between the urban and rural study site were high. Antibiotic resistance of GBS strains was surprisingly low in this study.

[Development of new vaccines]

Recent and important advances in the fields of immunology, genomics, functional genomics, immunogenetics, immunogenomics, bioinformatics, microbiology, genetic engineering, systems biology, synthetic biochemistry, proteomics, metabolomics and nanotechnology, among others, have led to new approaches in the development of vaccines. The better identification of ideal epitopes, the strengthening of the immune response due to new adjuvants, and the search of new routes of vaccine administration, are good examples of advances that are already a reality and that will favour the development of more vaccines, their use in indicated population groups, or its production at a lower cost. There are currently more than 130 vaccines are under development against the more wished (malaria or HIV), difficult to get (CMV or RSV), severe re-emerging (Dengue or Ebola), increasing importance (Chagas disease or Leishmania), and nosocomial emerging (Clostridium difficile or Staphylococcus aureus) infectious diseases.

Anti-Group B Streptococcus Glycan-Conjugate Vaccines Using Pilus Protein GBS80 As Carrier and Antigen: Comparing Lysine and Tyrosine-directed Conjugation

Gram-positive Streptococcus agalactiae or group B Streptococcus (GBS) is a leading cause of invasive infections in pregnant women, newborns, and elderly people. Vaccination of pregnant women represents the best strategy for prevention of neonatal disease, and GBS polysaccharide-based conjugate vaccines are currently under clinical testing. The potential of GBS pilus proteins selected by genome-based reverse vaccinology as protective antigens for anti-streptococcal vaccines has also been demonstrated. Dressing pilus proteins with surface glycan antigens could be an attractive approach to extend vaccine coverage. We have recently developed an efficient method for tyrosine-directed ligation of large glycans to proteins via copper-free azide-alkyne [3 + 2] cycloaddition. This method enables targeting of predetermined sites of the protein, ensuring that protein epitopes are preserved prior to glycan coupling and a higher consistency in glycoconjugate batches. Herein, we compared conjugates of the GBS type II polysaccharide (PSII) and the GBS80 pilus protein obtained by classic lysine random conjugation and by the recently developed tyrosine-directed ligation. PSII conjugated to CRM197, a carrier protein used for vaccines in the market, was used as a control. We found that the constructs made from PSII and GBS80 were able to elicit murine antibodies recognizing individually the glycan and protein epitopes on the bacterial surface. The generated antibodies were efficacious in mediating opsonophagocytic killing of strains expressing exclusively PSII or GBS80 proteins. The two glycoconjugates were also effective in protecting newborn mice against GBS infection following vaccination of the dams. Altogether, these results demonstrated that polysaccharide-conjugated GBS80 pilus protein functions as a carrier comparably to CRM197, while maintaining its properties of protective protein antigen. Glycoconjugation and reverse vaccinology can, therefore, be combined to design vaccines with broad coverage. This approach opens a path to a new generation of vaccines. Tyrosine-ligation allows creation of more homogeneous vaccines, correlation of the immune response to defined connectivity points, and fine-tuning of the conjugation site in glycan-protein conjugates.

Early-onset neonatal group B streptococcus sepsis following national risk-based prevention guidelines

BACKGROUND

Neonatal infection with group B streptococcus (GBS) is an important cause of infant mortality. Intrapartum antibiotics reduce early-onset GBS sepsis, but recommendations vary as to whether they should be offered following antenatal screening or based on risk factors alone. We aimed to determine the incidence of early-onset GBS sepsis in New Zealand five years after the publication of national risk-based GBS prevention guidelines.

MATERIALS AND METHODS

Prospective surveillance of early-onset GBS sepsis (defined as infection in the first 48 h of life) was undertaken between April 2009 and March 2011 through the auspices of the New Zealand Paediatric Surveillance Unit as part of a survey of infection presenting in the first week of life.

RESULTS

There were 29 cases of confirmed early-onset GBS sepsis, including one case of meningitis, giving an incidence rate of 0.23 per 1000 (95% CI 0.16-0.33) live births. Three infants (10.3%) died. In 16 cases (55%), a maternal risk factor qualifying the mother for intrapartum antibiotics was present, but only five (31%) received this intervention. A retrospective review of the major hospital laboratory databases for this period identified two additional cases. A secondary sensitivity analysis taking account of these cases provided an estimated national incidence of 0.26 (95% CI 0.18-0.37) per 1000 live births.

CONCLUSIONS

Ten years after a similar survey and five years after promoting a single, risk-based prevention protocol nationally, the incidence of early-onset GBS disease in New Zealand has more than halved, but opportunities remain to further reduce the rate.

Characteristics of group B Streptococcus isolated from infants with invasive infections: a population-based study in Japan

Group B Streptococcus (GBS) is one of the leading causes of neonatal bacterial infections. Population-based surveillance of GBS-related invasive diseases among newborns and infants from 10 prefectures in Japan was performed between 2007 and 2012. The characteristics of cases and isolated GBS are described in this study. The incidence rate of GBS-related invasive diseases was 0.13 per 1,000 live births. Analysis of GBS samples obtained from 60 invasive cases showed that the most frequent serotypes were III (48.3%), Ia (30.0%), and Ib (10.0%). All isolates were susceptible to penicillin G, ampicillin, cefotaxime, imipenem, and panipenem. However, 14, 2, and 7 isolates were resistant to erythromycin, clindamycin, and both erythromycin and clindamycin, respectively. Multilocus sequence typing revealed that GBS sequence type (ST) 23, ST17, and ST335 caused higher incidences of meningitis. These data show that serotypes III, Ia, and Ib together caused more than 80% of invasive infections in Japanese infants, and that GBS strains are still susceptible to β-lactam antibiotics.