Group B streptococcus

Diet influences community dynamics following vaginal group B streptococcus colonization

The vaginal microbiota plays a pivotal role in reproductive, sexual, and perinatal health and disease. Unlike the well-established connections between diet, metabolism, and the intestinal microbiota, parallel mechanisms influencing the vaginal microbiota and pathogen colonization remain overlooked. In this study, we combine a mouse model of Streptococcus agalactiae strain COH1 [group B Streptococcus (GBS)] vaginal colonization with a mouse model of pubertal-onset obesity to assess diet as a determinant of vaginal microbiota composition and its role in colonization resistance. We leveraged culture-dependent assessment of GBS clearance and culture-independent, sequencing-based reconstruction of the vaginal microbiota in relation to diet, obesity, glucose tolerance, and microbial dynamics across time scales. Our findings demonstrate that excessive body weight gain and glucose intolerance are not associated with vaginal GBS density or timing of clearance. Diets high in fat and low in soluble fiber are associated with vaginal GBS persistence, and changes in vaginal microbiota structure and composition due to diet contribute to GBS clearance patterns in nonpregnant mice. These findings underscore a critical need for studies on diet as a key determinant of vaginal microbiota composition and its relevance to reproductive and perinatal outcomes.IMPORTANCEThis work sheds light on diet as a key determinant influencing the composition of vaginal microbiota and its involvement in group B Streptococcus (GBS) colonization in a mouse model. This study shows that mice fed diets with different nutritional composition display differences in GBS density and timing of clearance in the female reproductive tract. These findings are particularly significant given clear links between GBS and adverse reproductive and neonatal outcomes, advancing our understanding by identifying critical connections between dietary components, factors originating from the intestinal tract, vaginal microbiota, and reproductive outcomes.

An opportunistic pathogen under stress: how Group B Streptococcus responds to cytotoxic reactive species and conditions of metal ion imbalance to survive

Group B Streptococcus (GBS; also known as Streptococcus agalactiae) is an opportunistic bacterial pathogen that causes sepsis, meningitis, pneumonia, and skin and soft tissue infections in neonates and healthy or immunocompromised adults. GBS is well-adapted to survive in humans due to a plethora of virulence mechanisms that afford responses to support bacterial survival in dynamic host environments. These mechanisms and responses include counteraction of cell death from exposure to excess metal ions that can cause mismetallation and cytotoxicity, and strategies to combat molecules such as reactive oxygen and nitrogen species that are generated as part of innate host defence. Cytotoxicity from reactive molecules can stem from damage to proteins, DNA, and membrane lipids, potentially leading to bacterial cell death inside phagocytic cells or within extracellular spaces within the host. Deciphering the ways in which GBS responds to the stress of cytotoxic reactive molecules within the host will benefit the development of novel therapeutic and preventative strategies to manage the burden of GBS disease. This review summarizes knowledge of GBS carriage in humans and the mechanisms used by the bacteria to circumvent killing by these important elements of host immune defence: oxidative stress, nitrosative stress, and stress from metal ion intoxication/mismetallation.

The association between maternal colonization with Group B Streptococcus and infectious morbidity following transcervical Foley catheter-assisted labor induction

OBJECTIVES

To determine whether maternal colonization with Group B Streptococcus increases the risk for infectious morbidity following transcervical Foley catheter-assisted cervical ripening.

METHODS

A retrospective cohort study comparing infectious morbidity and other clinical outcomes by Group B Streptococcus colonization status between all women with singleton pregnancies who underwent Foley catheter-assisted cervical ripening labor induction at a single tertiary medical center during 2011-2021. Multivariable logistic regression explored the relationship between Group B Streptococcus colonization to adverse outcomes while adjusting for relevant clinical variables.

RESULTS

A total of 4,409 women were included of whom 886 (20.1 %) were considered Group B Streptococcus carriers and 3,523 (79.9 %) were not. Suspected neonatal sepsis rate was similar between Group B Streptococcus carriers and non-carriers (5.2 vs. 5.0 %, respectively, p=0.78). Neonatal sepsis was confirmed in 7 (0.02 %) cases, all born to non-carriers. Group B Streptococcus carriers had a higher rate of maternal bacteremia compared to non-carriers (1.2 vs. 0.5 %, respectively, p=0.01). Group B Streptococcus colonization was independently associated with maternal bacteremia (adjusted odds ratio 3.05; 95 %CI 1.39, 6.66).

CONCLUSIONS

Group B Streptococcus colonization among women undergoing Foley catheter-assisted cervical ripening does not seem to increase the risk for neonatal infection. However, higher rates of maternal bacteremia were detected.

Improved disk diffusion method for simple detection of group B streptococci with reduced penicillin susceptibility (PRGBS)

We used 73 group B Streptococcus with reduced penicillin susceptibility (PRGBS) isolates and determined more rational cutoff values of previously developed disk diffusion method for detecting PRGBS using oxacillin, ceftizoxime, and ceftibuten disks. Using the novel cutoff values, the three disks showed high sensitivity and specificity, which were above 90.0%.

Interspecies recombination, not de novo mutation, maintains virulence after β-lactam resistance acquisition in Streptococcus pneumoniae

As opposed to de novo mutation, β-lactam resistance in S. pneumoniae is often conferred via homologous recombination during horizontal gene transfer. We hypothesize that β-lactam resistance in pathogenic streptococci is restricted to naturally competent species via intra-/interspecies recombination due to in vivo fitness trade-offs of de novo penicillin-binding protein (PBP) mutations. We show that de novo mutant populations have abrogated invasive disease capacity and are difficult to evolve in vivo. Conversely, serially transformed recombinant strains efficiently integrate resistant oral streptococcal DNA, gain penicillin resistance and tolerance, and retain virulence in mice. Large-scale changes in pbp2X, pbp2B, and non-PBP-related genes occur in recombinant isolates. Our results indicate that horizontal transfer of β-lactam resistance engenders initially favorable or minimal cost changes in vivo compared with de novo mutation(s), underscoring the importance of recombination in the emergence of β-lactam resistance and suggesting why some pathogenic streptococci lacking innate competence remain universally susceptible.

Group B Streptococcus Screening and Treatment Adherence in Pregnancy: A Retrospective Cohort Study and Opportunities for Improvement

Introduction

Pregnancy is a time of increased healthcare screening, and past adherence to evolving guidelines informs best practices. Although studies of Group B Streptococcus guideline adherence have focused primarily on treatment of Group B Streptococcus carriers, this study broadly evaluated long-term adherence to both Group B Streptococcus screening and treatment guidelines. Adherence was evaluated across provider types (obstetrics and gynecology, certified nurse midwives, and family medicine).

Methods

We conducted a retrospective cohort study. Demographic and clinical information were extracted from all prenatal care and delivery patients at a single institution in a single year. Vancomycin prescriptions in pregnancy were tracked for 10 years to determine long-term adherence. Adherence was defined as no deviation from 2010 Group B Streptococcus screening and treatment guidelines.

Results

Adherence occurred in 89% (1,610/1,810) of patients. Reasons for deviations from guidelines could not always be determined. There was no significant difference in maternal age, race, prenatal provider type, provider type at delivery, gestational age at delivery, delivery mode, or whether antibiotic sensitivities were performed between compliant and noncompliant groups. Significant differences in adherence were found between obstetric clinics (high-risk obstetrics clinic, maternal‒fetal medicine fellows clinic, continuity of care clinic, and faculty private clinic) (p<0.0001) and between the faculty family medicine clinic and resident family medicine clinic (p=0.001). Vancomycin prescription practice did not change significantly over the10-year period.

Conclusions

High rates of adherence to Group B Streptococcus screening and treatment guidelines in pregnancy have positive implications for reducing antibiotic resistance. Given evolving guidelines, there is a need to periodically evaluate adherence and to re-educate providers about standard practices and best documentation practices.

Bifidobacterium Species Colonization in Infancy: A Global Cross-Sectional Comparison by Population History of Breastfeeding

Bifidobacterium species are beneficial and dominant members of the breastfed infant gut microbiome; however, their health benefits are partially species-dependent. Here, we characterize the species and subspecies of Bifidobacterium in breastfed infants around the world to consider the potential impact of a historic dietary shift on the disappearance of B. longum subsp. infantis in some populations. Across populations, three distinct patterns of Bifidobacterium colonization emerged: (1) The dominance of Bifidobacterium longum subspecies infantis, (2) prevalent Bifidobacterium of multiple species, and (3) the frequent absence of any Bifidobacterium. These patterns appear related to a country’s history of breastfeeding, with infants in countries with historically high rates of long-duration breastfeeding more likely to be colonized by B. longum subspecies infantis compared with infants in countries with histories of shorter-duration breastfeeding. In addition, the timing of infant colonization with B. longum subsp. infantis is consistent with horizontal transmission of this subspecies, rather than the vertical transmission previously reported for other Bifidobacterium species. These findings highlight the need to consider historical and cultural influences on the prevalence of gut commensals and the need to understand epidemiological transmission patterns of Bifidobacterium and other major commensals.

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.

Human Milk Oligosaccharides versus Streptococcus: How a Human-Made Natural Product Protects Us from Pathogens

Group B Streptococcus (GBS) is a Gram-positive bacterium that colonizes the lower gastrointestinal tract, and in females, the urogenital tract, in up to 30% of healthy adults. However, GBS is a leading cause of mortality and morbidity in newborns due to ascending infection of the womb or by neonatal acquisition during vaginal passage. GBS neonatal disease manifests as pneumonia, sepsis, or meningitis, and an estimated 4 million newborns die each year globally. This commentary reflects on recent work by Mejia and colleagues (M. E. Mejia, S. Ottinger, A. Vrbanac, P. Babu, et al., mSphere 6:e00885-21, 2022, https://doi.org/10.1128/msphere.00885-21) that has examined human milk oligosaccharides (HMOs) as a natural product with anti-GBS activity. They show that HMOs reduce GBS vaginal colonization without impacting the normal vaginal microbiota. This study advances the possibility of using novel therapeutics to limit GBS maternal colonization and subsequent neonatal disease.

The Diverse Antimicrobial Activities of Human Milk Oligosaccharides against Group B Streptococcus

Streptococcus agalactiae or Group B Streptococcus (GBS) is a Gram-positive bacterial pathobiont that is the etiological cause of severe perinatal infections. GBS can colonize the vagina of pregnant patients and invade tissues causing ascending infections of the gravid reproductive tract that lead to adverse outcomes including preterm birth, neonatal sepsis, and maternal or fetal demise. Additionally, transmission of GBS during labor or breastfeeding can also cause invasive infections of neonates and infants. However, human milk has also been shown to have protective effects against infection; a characteristic that is likely derived from antimicrobial and immunomodulatory properties of molecules that comprise human milk. Recent evidence suggests that human milk oligosaccharides (HMOs), short-chain sugars that comprise 8-20 % of breast milk, have antimicrobial and anti-biofilm activity against GBS and other bacterial pathogens. Additionally, HMOs have been shown to potentiate the activity of antibiotics against GBS. This review presents the most recent published work that studies the interaction between HMOs and GBS.

Maternal Intake of Probiotics to Program Offspring Health

PURPOSE OF REVIEW

Probiotics intake may be considered beneficial by prospective and pregnant mothers, but their effects on offspring development are incompletely understood. The purpose of this review was to examine recent pre-clinical and clinical studies to understand how maternal probiotics exposure affects offspring health outcomes.

RECENT FINDINGS

Effects were investigated in the context of supporting offspring growth, intestinal health, and gut microbiota, preventing allergic diseases, supporting neurodevelopment, and preventing metabolic disorders in pre-clinical and clinical studies. Most human studies focused on infancy outcomes, whereas pre-clinical studies also examined outcomes at adolescence and young adulthood. While still understudied, both pre-clinical and clinical studies propose epigenetic modifications as an underlying mechanism. Optimal timing of intervention remains unclear. Administration of selected probiotics to mothers has programming potential for sustaining life-long health of offspring. Administration protocols, specific windows of susceptibility, and individual-specific responses need to be further studied.

Maternal immunization with Group B Streptococcus six-valent polysaccharide conjugate vaccine supported by lack of toxicity in rat and rabbit fertility and developmental toxicity studies

A maternal Group B Streptococcus (GBS) six-valent polysaccharide conjugate vaccine (GBS6) is being developed to protect neonates and infants up to 3 months of age through passive transfer of antibodies from the mother to the infant. Fertility and developmental toxicity studies were conducted in female Sprague Dawley rats and New Zealand White rabbits with GBS6 (20 μg capsular polysaccharide/serotype formulated with or without AlPO₄ , the highest clinical dose). Females were administered the full human dose of the GBS6 formulation intramuscularly twice prior to mating and twice during gestation, to ensure that high antibody levels were maintained throughout gestation and lactation. Approximately, half of the rats and rabbits were evaluated at the end of gestation, and the remainder were evaluated at the end of lactation. Maternal blood for GBS6 serology, to measure antibody titers to the GBS6 antigens, was collected prior to the first dose, prior to mating, and at each necropsy. Blood for serology was also collected from offspring at the end of gestation and lactation. In both species, there was no evidence of vaccine-related effects on fertility, embryo-fetal development, or postnatal development of the offspring, supporting regulatory guidance that single-species evaluation would have been sufficient. Functional serum antibodies to all six serotypes in the vaccine were confirmed in maternal animals and functional serum antibodies to one or more of the six serotypes was also confirmed in some rat offspring and most of the rabbit offspring. The results of these studies supported the safety of GBS6 vaccine administration to pregnant women.

Streptococcus pneumoniae, S. pyogenes and S. agalactiae membrane phospholipid remodelling in response to human serum

Streptococcus pneumoniae, S. pyogenes (Group A Streptococcus; GAS) and S. agalactiae (Group B Streptococcus; GBS) are major aetiological agents of diseases in humans. The cellular membrane, a crucial site in host–pathogen interactions, is poorly characterized in streptococci. Moreover, little is known about whether or how environmental conditions influence their lipid compositions. Using normal phase liquid chromatography coupled with electrospray ionization MS, we characterized the phospholipids and glycolipids of S. pneumoniae, GAS and GBS in routine undefined laboratory medium, streptococcal defined medium and, in order to mimic the host environment, defined medium supplemented with human serum. In human serum-supplemented medium, all three streptococcal species synthesize phosphatidylcholine (PC), a zwitterionic phospholipid commonly found in eukaryotes but relatively rare in bacteria. We previously reported that S. pneumoniae utilizes the glycerophosphocholine (GPC) biosynthetic pathway to synthesize PC. Through substrate tracing experiments, we confirm that GAS and GBS scavenge lysoPC, a major metabolite in human serum, thereby using an abbreviated GPC pathway for PC biosynthesis. Furthermore, we found that plasmanyl-PC is uniquely present in the GBS membrane during growth with human serum, suggesting GBS possesses unusual membrane biochemical or biophysical properties. In summary, we report cellular lipid remodelling by the major pathogenic streptococci in response to metabolites present in human serum.

Group B Streptococcus chimeric capsular polysaccharides as novel multivalent vaccine candidates

The capsular polysaccharide of the human pathogen Group B Streptococcus is a key virulence factor and vaccine candidate that induces protective antibodies when conjugated to carrier proteins. It consists of long polymeric chains of oligosaccharide repeating units, and each of the ten capsular serotypes described so far presents a unique chemical structure with distinct antigenic properties; therefore, broad protection against this pathogen could be achieved by a combination of ten glycoconjugates. Capsular polysaccharide biosynthesis and assembly follow a polymerase-dependent pathway that is widespread in encapsulated bacteria and is encoded by a polycistronic operon. Here we exploited the sequence similarity between the capsule operons of types V and IX to generate hybrid polysaccharides incorporating epitopes of both serotypes in a single molecule, by co-expressing their specific CpsM, O, I glycosyltransferases in a single isolate. Physicochemical and immunochemical methods confirmed that an engineered strain produced a high molecular weight chimeric polysaccharide, combining antigenic specificities of both type V and IX. By optimizing the copy number of key glycosyltransferase genes, we were able to modulate the ratio between type-specific epitopes. Finally, vaccination with chimeric glycoconjugates significantly decreased the incidence of disease in pups born from immunized mice challenged with either serotype. This study provides proof of concept for a new generation of glycoconjugate vaccines that combine the antigenic specificity of different polysaccharide variants in a single molecule, eliciting a protective immune response against multiple serotype variants.

Cytokine Profiles Before and After Exchange Transfusions in Severe Late-Onset Neonatal Group B Streptococcus Meningitis: A Case Report

Streptococcus agalactiae or group B streptococcus (GBS) is a pathogen that causes severe neonatal infections, resulting in sepsis, pneumonia, and meningitis. Neonatal GBS meningitis has a poor neurological prognosis and a high mortality rate. GBS disease is classified as early- and late-onset if the onset age is 0-6 and 7-89 days after birth, respectively. There is currently no effective preventive strategy against late-onset GBS (LOGBS) disease. Here, we report a case of female infant with LOGBS meningitis who recovered from the septic shock by two exchange transfusions (ExTs) but still experienced severe neurological sequela. She was born at a gestational age of 39 weeks via caesarian section due to oligohydramnios and had fever 11 days after birth. GBS was detected in her cerebrospinal fluid (CSF) and blood but not in the vaginal or breast-milk cultures of the mother. The patient was treated with intravenous antibiotic administration; however, she suddenly developed pulseless ventricular tachycardia and asystole the next day. Her heart rate was normalized via cardiopulmonary resuscitation. We also performed two ExTs, and she recovered from the septic shock. Cytokine-profile analysis revealed that the serum and CSF levels of various pro-inflammatory and anti-inflammatory cytokines were elevated before the ExTs, after which the serum levels of several of these cytokines decreased. Two ExTs were effective in saving the life of the patient but did not improve the neurological prognosis. Given that neonatal GBS meningitis has high fatality and sequela rates; thus, it is necessary to establish a preventive strategy.

An original infection model identifies host lipoprotein import as a route for blood-brain barrier crossing

Pathogens able to cross the blood-brain barrier (BBB) induce long-term neurological sequelae and death. Understanding how neurotropic pathogens bypass this strong physiological barrier is a prerequisite to devise therapeutic strategies. Here we propose an innovative model of infection in the developing Drosophila brain, combining whole brain explants with in vivo systemic infection. We find that several mammalian pathogens are able to cross the Drosophila BBB, including Group B Streptococcus (GBS). Amongst GBS surface components, lipoproteins, and in particular the B leucine-rich Blr, are important for BBB crossing and virulence in Drosophila. Further, we identify (V)LDL receptor LpR2, expressed in the BBB, as a host receptor for Blr, allowing GBS translocation through endocytosis. Finally, we show that Blr is required for BBB crossing and pathogenicity in a murine model of infection. Our results demonstrate the potential of Drosophila for studying BBB crossing by pathogens and identify a new mechanism by which pathogens exploit the machinery of host barriers to generate brain infection.

Identification of Zinc-Dependent Mechanisms Used by Group B Streptococcus To Overcome Calprotectin-Mediated Stress

Group B Streptococcus (GBS) asymptomatically colonizes the female reproductive tract but is a common causative agent of meningitis. GBS meningitis is characterized by extensive infiltration of neutrophils carrying high concentrations of calprotectin, a metal chelator. To persist within inflammatory sites and cause invasive disease, GBS must circumvent host starvation attempts. Here, we identified global requirements for GBS survival during calprotectin challenge, including known and putative systems involved in metal ion transport. We characterized the role of zinc import in tolerating calprotectin stress in vitro and in a mouse model of infection. We observed that a global zinc uptake mutant was less virulent than the parental GBS strain and found calprotectin knockout mice to be equally susceptible to infection by wild-type (WT) and mutant strains. These findings suggest that calprotectin production at the site of infection results in a zinc-limited environment and reveals the importance of GBS metal homeostasis to invasive disease.

Nutritional immunity is an elegant host mechanism used to starve invading pathogens of necessary nutrient metals. Calprotectin, a metal-binding protein, is produced abundantly by neutrophils and is found in high concentrations within inflammatory sites during infection. Group B Streptococcus (GBS) colonizes the gastrointestinal and female reproductive tracts and is commonly associated with severe invasive infections in newborns such as pneumonia, sepsis, and meningitis. Although GBS infections induce robust neutrophil recruitment and inflammation, the dynamics of GBS and calprotectin interactions remain unknown. Here, we demonstrate that disease and colonizing isolate strains exhibit susceptibility to metal starvation by calprotectin. We constructed a mariner transposon (Krmit) mutant library in GBS and identified 258 genes that contribute to surviving calprotectin stress. Nearly 20% of all underrepresented mutants following treatment with calprotectin are predicted metal transporters, including known zinc systems. As calprotectin binds zinc with picomolar affinity, we investigated the contribution of GBS zinc uptake to overcoming calprotectin-imposed starvation. Quantitative reverse transcriptase PCR (qRT-PCR) revealed a significant upregulation of genes encoding zinc-binding proteins, adcA, adcAII, and lmb, following calprotectin exposure, while growth in calprotectin revealed a significant defect for a global zinc acquisition mutant (ΔadcAΔadcAIIΔlmb) compared to growth of the GBS wild-type (WT) strain. Furthermore, mice challenged with the ΔadcAΔadcAIIΔlmb mutant exhibited decreased mortality and significantly reduced bacterial burden in the brain compared to mice infected with WT GBS; this difference was abrogated in calprotectin knockout mice. Collectively, these data suggest that GBS zinc transport machinery is important for combatting zinc chelation by calprotectin and establishing invasive disease.

The effect of group B streptococcus on maternal and infants' prognosis in Guizhou, China

Group B Streptococcus (GBS) is a kind of opportunistic pathogenic bacteria and mainly strikes the lower digestive tract and genitourinary tract. It is a major risk factor for neonatal babies, seriously threatening their lives. In the present study, we aimed to detect the GBS colonization in late pregnant women, and to study the effect of GBS on maternal and infants’ prognosis. Pregnant women with a gestational age of 35–37 weeks were enrolled in the study. Real-time polymerase chain-reaction (RT-PCR) was used to detect the colonization of GBS in the vaginal and rectal secretions for late pregnant women according to the screening guidelines. Chi-square test was applied to analyze the relationship between GBS colonization and clinical characteristics. A follow-up of 6 weeks was performed on the puerpera and infants after delivery. The positive rate of GBS was 12.6% in late pregnant women. GBS carrier state was positively related to several pregnancy outcomes, including intrauterine infection, premature rupture of membranes, postpartum hemorrhage, fetal distress and puerperal infection, as well as to part neonatal outcomes, containing neonatal infection, neonatal pneumonia and neonatal sepsis (all P < 0.05). GBS infection in late pregnant women results in adverse effects on maternal and neonatal outcomes.

Increasing incidence of group B streptococcus neonatal infections in the Netherlands is associated with clonal expansion of CC17 and CC23

Group B streptococcus (GBS) is the leading cause of neonatal invasive disease worldwide. In the Netherlands incidence of the disease increased despite implementation of preventive guidelines. We describe a genomic analysis of 1345 GBS isolates from neonatal (age 0–89 days) invasive infections in the Netherlands reported between 1987 and 2016. Most isolates clustered into one of five major lineages: CC17 (39%), CC19 (25%), CC23 (18%), CC10 (9%) and CC1 (7%). There was a significant rise in the number of infections due to isolates from CC17 and CC23. Phylogenetic clustering analysis revealed that this was caused by expansion of specific sub-lineages, designated CC17-A1, CC17-A2 and CC23-A1. Dating of phylogenetic trees estimated that these clones diverged in the 1960s/1970s, representing historical rather than recently emerged clones. For CC17-A1 the expansion correlated with acquisition of a new phage, carrying gene encoding a putative cell-surface protein. Representatives of CC17-A1, CC17-A2 and CC23-A1 clones were identified in datasets from other countries demonstrating their global distribution.

High prevalence of group B streptococcus ST17 hypervirulent clone among non-pregnant patients from a Hungarian venereology clinic

Background

Although Streptococcus agalactiae is the leading causative agent of neonatal sepsis and meningitis, recently it is increasingly isolated from non-pregnant adults. The relation between its presence in the genitourinary tract and manifested clinical symptoms of STD patients remains an open question. In this study, a complex epidemiological investigation of GBS isolates from a venerology clinic was performed.

Methods

Ninety-six GBS isolates were serotyped and their genetic relatedness determined by PFGE. MLST was also performed for a subset of 20 isolates. The antibiotic susceptibility was tested with agar dilution. Surface proteins and the ST-17 hypervirulent clone was detected by PCR.

Results

The serotype prevalence was the following: V (29.2%), III (27.1%), Ia (22.9%), IV (10.4%), II (5.2%) and Ib (4.2%). A strong association was demonstrated between surface protein genes and serotypes. All isolates were fully susceptible to penicillin, but erythromycin and clindamycin resistance was high (41.7 and 35.4%, respectively), and 8 phenotypically macrolide sensitive isolates carried the ermB gene.

21.9% of all strains belonged to the hypervirulent ST17 clone, most being of serotype III and all were rib +. We found a few serotype IV isolates belonging to several STs and one serotype V/ST110 strain, containing a 44-bp deletion in the atr allele.

Conclusions

The presence of silent ermB genes is of worry, as their expression upon macrolide exposure could lead to unforeseen therapeutic failure, while clindamycin is used for intrapartum antibiotic prophylaxis, in case of penicillin allergy. The other alarming result is the high prevalence of ST17 among these strains from STD patients, who could be sources of further infections.

This is the first report from Hungary providing both serotyping and genotyping data of GBS isolates. These results could be helpful for vaccine production as the major vaccine candidates are capsular antigens or surface proteins.

Cas9 Contributes to Group B Streptococcal Colonization and Disease

Group B Streptococcus (GBS) is a major opportunistic pathogen in certain adult populations, including pregnant women, and remains a leading etiologic agent of newborn disease. During pregnancy, GBS asymptomatically colonizes the vaginal tract of 20-30% of healthy women, but can be transmitted to the neonate in utero or during birth resulting in neonatal pneumonia, sepsis, meningitis, and subsequently 10-15% mortality regardless of antibiotic treatment. While various GBS virulence factors have been implicated in vaginal colonization and invasive disease, the regulation of many of these factors remains unclear. Recently, CRISPR-associated protein-9 (Cas9), an endonuclease known for its role in CRISPR/Cas immunity, has also been observed to modulate virulence in a number of bacterial pathogens. However, the role of Cas9 in GBS colonization and disease pathogenesis has not been well-studied. We performed allelic replacement of cas9 in GBS human clinical isolates of the hypervirulent sequence-type 17 strain lineage to generate isogenic Δcas9 mutants. Compared to parental strains, Δcas9 mutants were attenuated in murine models of hematogenous meningitis and vaginal colonization and exhibited significantly decreased invasion of human brain endothelium and adherence to vaginal epithelium. To determine if Cas9 alters transcription in GBS, we performed RNA-Seq analysis and found that 353 genes (>17% of the GBS genome) were differentially expressed between the parental WT and Δcas9 mutant strain. Significantly dysregulated genes included those encoding predicted virulence factors, metabolic factors, two-component systems (TCS), and factors important for cell wall formation. These findings were confirmed by qRT-PCR and suggest that Cas9 may regulate a significant portion of the GBS genome. We studied one of the TCS regulators, CiaR, that was significantly downregulated in the Δcas9 mutant strain. RNA-Seq analysis of the WT and ΔciaR strains demonstrated that almost all CiaR-regulated genes were also significantly regulated by Cas9, suggesting that Cas9 may modulate GBS gene expression through other regulators. Further we show that CiaR contributes to GBS vaginal colonization and persistence. Altogether, these data highlight the potential complexity and importance of the non-canonical function of Cas9 in GBS colonization and disease.

Epidemiology of Meningitis in Canadian Neonatal Intensive Care Units

BACKGROUND

Meningitis is a serious disease that occurs more commonly in the neonatal period than in any other age group. Recent data from large national cohorts are needed to determine if the epidemiology of neonatal meningitis (NM) has changed.

AIM

To assess the rates, causative organisms, risk factors, temporal trends and short-term outcomes of NM in Canadian Neonatal Intensive Care Units (NICUs).

METHODS

A retrospective review of newborn infants admitted to NICUs participating in the Canadian Neonatal Network between January 2010 and December 2016. Patients with meningitis were reviewed. Outcomes of patients with meningitis were compared with 1:2 matched (for gestation, sex and birth weight) neonates without meningitis.

RESULTS

Rates of NM ranged between 2.2 and 3.5/1000 NICU admissions during the 7-year study period with the majority of patients (87%) having late-onset meningitis (at >3 days after birth). The most common bacterial organism for both early- and late-onset meningitis was Escherichia coli followed by group B streptococci. Only 31% [95% confidence interval (CI): 24.06-38.63) of neonates with meningitis had simultaneous bacteremia. NM was associated with increased seizures [odds ratio (OR): 8.63; 95% CI: 4.73-15.7], retinopathy of prematurity (OR: 3.23; 95% CI: 1.30-8.02), bronchopulmonary dysplasia (OR: 1.93; 95% CI: 1.11-3.35), days of mechanical ventilation (OR: 1.03; 95% CI: 1.02-1.04) and length of hospital stay (OR: 1.02; 95% CI: 1.01-1.02), but not with mortality before discharge (OR: 1.29; 95% CI: 0.74-2.23).

CONCLUSIONS

The rate of NM remains largely unchanged in Canadian NICUs. NM was associated with increased major morbidities and longer hospital stay but not with mortality before discharge.

A comparison of Streptococcus agalactiae septic arthritis and non-Streptococcus agalactiae septic arthritis

INTRODUCTION

Streptococcus agalactiae (Group B Streptococcus, GBS) is an uncommon cause of septic arthritis in the adult population. In recent years, there has been an increase in the incidence of GBS septic arthritis. This study aims to compare the clinical presentation, investigations, microbiology and outcome of management in patients with GBS and non-GBS septic arthritis.

METHODS

Retrospective review of hospital surgical records was done to identify all patients treated surgically at our institution from January 2011 to January 2016 for primary septic arthritis. Patients were categorised into two groups: those with culture-proven GBS septic arthritis and those with causative pathogens that were not GBS. Patients who were medically unfit for surgical intervention as well as those who declined interventional procedures were excluded from the study.

RESULTS

A total of 83 patients were included in the study: 62 (74.7%) had non-GBS septic arthritis and 21 (25.3%) had GBS septic arthritis. Patients with GBS septic arthritis were more likely to have polyarticular involvement (p < 0.001) and involvement of less common sites such as the elbow joint. They were also more likely to have elevated inflammatory markers (C-reactive protein > 150 mg/L; p = 0.017) and positive blood cultures (p = 0.02), and were typically healthy adults with no medical comorbidities (p = 0.012).

CONCLUSION

Patients with GBS septic arthritis were more likely to present with polyarticular involvement, positive blood cultures and higher levels of C-reactive protein on admission, and tended to be healthier individuals with no medical comorbidities.

Is a positive Christie-Atkinson-Munch-Peterson (CAMP) test sensitive enough for the identification of Streptococcus agalactiae?

Background

For a long time, the Christie-Atkinson-Munch-Peterson (CAMP) test has been a standard test for the identification of Streptococcus agalactiae, and a positive result for S.agalactiae has been considered sensitive enough.

Methods

To confirm whether a positive CAMP test is a requirement for the identification of S.agalactiae, five suspected CAMP-negative S.agalactiae isolates from two hospitals, confirmed as Gram-positive and catalase-negative streptococci, were verified by the CAMP test in three batches of plates from two manufacturers and identified by the Phoenix system, MALDI-TOF MS, the PCR assay and the 16S rDNA gene sequencing.

Results

All five suspected strains were S.agalactiae, four of which were CAMP-negative and one of which was not S.agalactiae by the PCR assay.

Conclusions

A positive CAMP test was lacking sensitivity for the identification of S.agalactiae, and the question of whether the cfb gene is worthy of targeting should be further studied.

Changes in the incidence and epidemiology of neonatal group B Streptococcal disease over the last two decades in Crete, Greece

Group B streptococcus (GBS) remains a leading cause of neonatal disease. However, GBS rates and prevention strategies vary considerably worldwide. Herein, we investigated the burden and epidemiological trends of neonatal GBS infections in our area (Greece) over the last two decades. We conducted a multicenter retrospective study that includes all cases of culture-proven GBS disease in infants <90 days old in the last 22 years. Neonatal GBS incidence was 0.17/1000 live births (95%CI: 0.11-0.21). A significant increase was noted during the second decade (0.23 vs 0.10/1000, P<0.05). Late onset disease (LOD) significantly increased during the second decade (0.08 vs 0.02, P<0.05). Infants in the LOD group had a higher risk of meningitis (RR 1.8, 95%CI: 1.23-2.71). Long-term neurological sequelae were reported in 42.8% of meningitis cases. The mortality rate was 8%. The incidence of neonatal GBS disease in our area is among the lowest reported, but an increase was noted the last decade mainly due a rise in the LOD. The burden of LOD, the mortality and long-term disability are still substantial, thus effective prevention strategies − including maternal vaccination for neonatal GBS − are needed.

Phenotypic and molecular analysis of nontypeable Group B streptococci: identification of cps2a and hybrid cps2a/cps5 Group B streptococcal capsule gene clusters

The Group B streptococcus (GBS) can express a capsular polysaccharide (CPS). There are ten recognized CPSs (Ia, Ib, and II-IX). A GBS isolate is considered nontypeable (NT) when CPS cannot be identified as one of ten types. Two groups of GBS NT isolates were studied, isolates without surface sialic acid (sia(-)) and isolates with surface sialic acid (sia(+)). The first objective was to characterize NT sia(-) isolates that failed CPS identification by an immunodiffusion antisera typing assay and a RT-PCR capsule typing assay. NT sia(-) isolates were characterized by assaying phenotypic changes and identifying covR/S mutations that may potentially have a role in the altered phenotypes. The second objective was to characterize NT sia(+) isolates that failed to identify as one of the ten CPS types by an immundiffusion antisera-based typing assay and a RT-PCR capsule typing assay yet expressed capsule. Fifteen NT sia(-) isolates displayed increased β hemolysis/orange pigmentation, decreased CAMP activity, inability to form biofilm, and susceptibility to phagocytosis by human blood. DNA sequence analysis of the covR/S genes in the sia(-) isolates found mutations in 14 of 15 isolates assayed. These mutations in the covR/S genes may potentially contribute to lack of expression of phenotypic traits assayed in vitro. For the three NT sia(+) isolates, whole-genome sequence analyses identified two isolates with cps gene clusters identical to the recently described and uncommon CPSIIa type. The third isolate possessed a hybrid cluster containing cps genes for both CPSIIa and CPSV suggesting recombination between these two gene clusters.

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

Background

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

Methods

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

Results

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

Conclusions

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

High isolation rate and multidrug resistance tendency of penicillin-susceptible group B Streptococcus with reduced ceftibuten susceptibility in Japan

Group B Streptococcus (GBS) clinical isolates with reduced penicillin susceptibility (PRGBS) have emerged through acquisition of amino acid substitutions in penicillin-binding protein 2X (PBP2X). Moreover, we also reported the emergence of penicillin-susceptible GBS clinical isolates with reduced ceftibuten susceptibility (CTB^r PSGBS) due to amino acid substitutions in PBPs. However, whether or not these amino acid substitutions are responsible for the reduced ceftibuten susceptibility (RCTBS) profile remains unclear. Furthermore, the rate of CTB^r PSGBS isolation and their multidrug resistance tendency remain uncertain. Therefore, we collected 377 clinical GBS isolates from multiple regions in Japan between August 2013 and August 2015. These isolates were characterized by determining MICs and sequencing the pbp2x gene. The isolation rate of CTB^r PSGBS was 7.2% (27/377). CTB^r PSGBS isolate harbor two types of amino acid substitutions in PBP2X [(T394A type) and (I377V, G398A, Q412L, and H438H type)]. The relevance of the amino acid substitutions found to the RCTBS was confirmed with allelic exchange techniques. Allelic exchange recombinant clones acquired two types of amino acid substitutions in PBP2X showed RCTBS. Furthermore, total ratio of resistance and non-susceptibility to both macrolides and fluoroquinolones in CTB^r PSGBS was 51.9% (14/27). The isolation rate of CTB^r PSGBS is non-negligibly high and the CTB^r PSGBS tends to exhibit resistance and non-susceptible profile to both macrolides and fluoroquinolones.

What is the result of vaginal cleansing with chlorhexidine during labour on maternal and neonatal infections? A systematic review of randomised trials with meta-analysis

BACKGROUND

Infection with vaginal microorganisms during labour can lead to maternal and neonatal mortality and morbidity. The objective of this systematic review is to review the effectiveness of intrapartum vaginal chlorhexidine in the reduction of maternal and neonatal colonisation and infectious morbidity.

METHODS

Search strategy - Eight databases were searched for articles published in any language from inception to October 2016. Selection criteria - Randomised controlled trials were included. Data Collection and analysis - Publications were assessed for inclusion. Data were extracted and assessed for risk of bias. Relative risks from individual studies were pooled using a random effects model and the heterogeneity of treatment was evaluated using Chi2 and I2 tests.

RESULTS

Eleven randomised controlled trials (n = 20,101) evaluated intrapartum vaginal chlorhexidine interventions. Meta-analysis found no significant differences between the intervention and control groups for any of the four outcomes: maternal or neonatal colonization or infection. The preferred method for chlorhexidine administration was vaginal irrigation.

CONCLUSIONS

Meta-analysis did not demonstrate improved maternal or neonatal outcomes with intrapartum vaginal chlorhexidine cleansing, however this may be due to the limitations of the available studies. A larger, multicentre randomised controlled trial, powered to accurately evaluate the effect of intrapartum vaginal chlorhexidine cleansing on neonatal outcomes may still be informative; the technique of douching may be the most promising.

Comparison of 4 commercially available group B Streptococcus molecular assays using remnant rectal-vaginal enrichment broths

The incidence of neonatal Group B streptococcal (GBS) disease has significantly declined since the widespread implementation of prenatal screening of expectant mothers for urogenital and gastrointestinal tract GBS colonization. Screening methods have evolved from exclusively culture-based approaches to more rapid and highly sensitive molecular methods. We chose to evaluate the performance of 4 commercially available GBS molecular tests for detection of GBS colonization using 299 antepartum rectal-vaginal specimens submitted to our laboratory for routine GBS screening. In 97% of instances, there was agreement between all 3 systems. When testing 1, 6, and 12 samples simultaneously, all methods performed comparably, but the ARIES® GBS assay required the least total hands-on time and the illumigene^® Group B Streptococcus assay required the most hands-on time.

New Mutations of Penicillin-Binding Proteins in Streptococcus agalactiae Isolates from Cattle with Decreased Susceptibility to Penicillin

Streptococcus agalactiae is a causal agent of bovine mastitis and is treated by β-lactam antibiotics (BLAs). Compared to penicillin-resistant S. agalactiae from humans, resistant strains in bovine are rarely reported. In this study, we aimed to investigate BLA resistance and mutations in penicillin-binding proteins (PBPs) of S. agalactiae in central and northeast China. The minimum inhibitory concentrations (MICs) of 129 penicillin-resistant S. agalactiae isolates from cows with mastitis were determined, and the related PBP genes were detected and sequenced. All strains were unsusceptible to penicillin G and mostly resistant to ampicillin, cefalexin, and ceftiofur sodium. One hundred twenty-nine strains were divided into 4 clonal groups and 8 sequence types by multilocus sequence typing analysis. We found a set of new substitutions in PBP1B, PBP2B, and PBP2X from most strains isolated from three provinces. The strains with high PBP mutations showed a broader unsusceptible spectrum and higher MICs than those with few or single mutation. Our research indicates unpredicted mutations in the PBP genes of S. agalactiae isolated from cows with mastitis treated by BLAs. This screening is the first of S. agalactiae from cattle.

High Incidence of Pathogenic Streptococcus agalactiae ST485 Strain in Pregnant/Puerperal Women and Isolation of Hyper-Virulent Human CC67 Strain

Group B streptococcus (GBS) is the major pathogen causing diseases in neonates, pregnant/puerperal women, cows and fish. Recent studies have shown that GBS may be infectious across hosts and some fish GBS strain might originate from human. The purpose of this study is to investigate the genetic relationship of CC103 strains that recently emerged in cows and humans, and explore the pathogenicity of clinical GBS isolates from human to tilapia. Ninety-two pathogenic GBS isolates were identified from 19 patients with different diseases and their evolution and pathogenicity to tilapia were analyzed. The multilocus sequence typing revealed that clonal complex (CC) 103 strain was isolated from 21.74% (20/92) of patients and ST485 strain was from 14.13% (13/92) patients with multiple diseases including neonates. Genomic evolution analysis showed that both bovine and human CC103 strains alternately form independent evolutionary branches. Three CC67 isolates carried gbs2018-C gene and formed one evolutionary branch with ST61 and ST67 strains that specifically infect dairy cows. Studies of interspecies transmission to tilapia found that 21/92 (22.83%) isolates including all ST23 isolates were highly pathogenic to tilapia and demonstrated that streptococci could break through the blood-brain barrier into brain tissue. In conclusions, CC103 strains are highly prevalent among pathogenic GBS from humans and have evolved into the highly pathogenic ST485 strains specifically infecting humans. The CC67 strains isolated from cows are able to infect humans through evolutionary events of acquiring CC17-specific type C gbs2018 gene and others. Human-derived ST23 pathogenic GBS strains are highly pathogenic to tilapia.

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.

Implication of Soluble Forms of Cell Adhesion Molecules in Infectious Disease and Tumor: Insights from Transgenic Animal Models

Cell adhesion molecules (CAMs) are surface ligands, usually glycoproteins, which mediate cell-to-cell adhesion. They play a critical role in maintaining tissue integrity and mediating migration of cells, and some of them also act as viral receptors. It has been known that soluble forms of the viral receptors bind to the surface glycoproteins of the viruses and neutralize them, resulting in inhibition of the viral entry into cells. Nectin-1 is one of important CAMs belonging to immunoglobulin superfamily and herpesvirus entry mediator (HVEM) is a member of the tumor necrosis factor (TNF) receptor family. Both CAMs also act as alphaherpesvirus receptor. Transgenic mice expressing the soluble form of nectin-1 or HVEM showed almost complete resistance against the alphaherpesviruses. As another CAM, sialic acid-binding immunoglobulin-like lectins (Siglecs) that recognize sialic acids are also known as an immunoglobulin superfamily member. Siglecs play an important role in the regulation of immune cell functions in infectious diseases, inflammation, neurodegeneration, autoimmune diseases and cancer. Siglec-9 is one of Siglecs and capsular polysaccharide (CPS) of group B Streptococcus (GBS) binds to Siglec-9 on neutrophils, leading to suppress host immune response and provide a survival advantage to the pathogen. In addition, Siglec-9 also binds to tumor-produced mucins such as MUC1 to lead negative immunomodulation. Transgenic mice expressing the soluble form of Siglec-9 showed significant resistance against GBS infection and remarkable suppression of MUC1 expressing tumor proliferation. This review describes recent developments in the understanding of the potency of soluble forms of CAMs in the transgenic mice and discusses potential therapeutic interventions that may alter the outcomes of certain diseases.

Epidemiology of invasive group B streptococcal disease in infants from urban area of South China, 2011-2014

Background

Group B Streptococcus (GBS) is a leading cause of morbidity and mortality in infants in both developed and developing countries. To our knowledge, only a few studies have been reported the clinical features, treatment and outcomes of the GBS disease in China. The severity of neonatal GBS disease in China remains unclear. Population-based surveillance in China is therefore required.

Methods

We retrospectively collected data of <3 months old infants with culture-positive GBS in sterile samples from three large urban tertiary hospitals in South China from Jan 2011 to Dec 2014. The GBS isolates and their antibiotic susceptibility were routinely identified in clinical laboratories in participating hospitals. Serotyping and multi-locus sequence typing (MLST) were also conducted for further analysis of the neonatal GBS disease.

Results

Total 70 cases of culture-confirmed invasive GBS infection were identified from 127,206 live births born in studying hospitals, giving an overall incidence of 0.55 per 1000 live births (95% confidence interval [CI] 0.44–0.69). They consisted of 49 with early-onset disease (EOD, 0.39 per 1000 live births (95% CI 0.29–0.51)) and 21 with late-onset disease (LOD, 0.17 per 1000 live births (95% CI 0.11–0.25)). The incidence of EOD increased significantly over the studying period. Five infants (4 EOD and 1 LOD) died before discharge giving a mortality rate of 7.1% and five infants (7.1%, 2 EOD and 3 LOD) had neurological sequelae. Within 68 GBS isolates from GBS cases who born in the studying hospitals or elsewhere, serotype III accounted for 77.9%, followed by Ib (14.7%), V (4.4%), and Ia (2.9%). MLST analysis revealed the presence of 13 different sequence types among the 68 GBS isolates and ST-17 was the most frequent sequence type (63.2%). All isolates were susceptible to penicillin, ceftriaxone, vancomycin and linezolid, while 57.4% and 51.5% were resistant to erythromycin and clindamycin, respectively.

Conclusions

This study gains the insight into the spectrum of GBS infection in south China which will facilitate the development of the guidance for reasonable antibiotics usage and will provide evidence for the implementation of potential GBS vaccines in the future.

Electronic supplementary material

The online version of this article (10.1186/s12879-017-2811-0) contains supplementary material, which is available to authorized users.

Effectiveness of intrapartum antibiotic prophylaxis for early-onset group B Streptococcal infection: An integrative review

BACKGROUND

In some countries, up to 30% of women are exposed to intrapartum antibiotic prophylaxis for prevention of early-onset group B Streptococcal infection. Intrapartum antibiotic prophylaxis aims to reduce the risk of neonatal morbidity and mortality from this infection. The intervention may adversely affect non-pathogenic bacteria which are passed to the newborn during birth and are considered important in optimising health. Since many women are offered intrapartum antibiotic prophylaxis, effectiveness and implications of this intervention need to be established. This review considers clinical trials and observational studies analysing the effectiveness of intrapartum antibiotic prophylaxis.

METHODS

An integrative literature review was conducted. One systematic review, three clinical trials and five observational studies were identified for appraisal.

FINDINGS

Randomised controlled trials found intrapartum antibiotic prophylaxis effective but all retrieved randomised clinical trials had significant methodological flaws. High quality observational studies reported high rates of effectiveness but revealed less than optimal adherence to screening and administration of the prophylaxis. Scant consideration was given to short term risks, and long-term consequences were not addressed.

DISCUSSION

Studies found intrapartum antibiotic prophylaxis to be effective. However, evidence was not robust and screening and prophylaxis have limitations. Emerging evidence links intrapartum antibiotic prophylaxis to adverse short and longer-term neonatal outcomes.

CONCLUSION

Our review found high quality evidence of the effectiveness of intrapartum antibiotic prophylaxis was limited. Lack of consideration of potential risks of the intervention was evident. Women should be enabled to make informed decisions about GBS management. More research needs to be done in this area.

Preterm Birth Associated With Group B Streptococcus Maternal Colonization Worldwide: Systematic Review and Meta-analyses

BACKGROUND

Preterm birth complications are the leading cause of deaths among children <5 years of age. Studies have suggested that group B Streptococcus (GBS) maternal rectovaginal colonization during pregnancy may be a risk factor for preterm delivery. This article is the fifth of 11 in a series. We aimed to assess the association between GBS maternal colonization and preterm birth in order to inform estimates of the burden of GBS.

METHODS

We conducted systematic literature reviews (PubMed/Medline, Embase, Latin American and Caribbean Health Sciences Literature [LILACS], World Health Organization Library Information System [WHOLIS], and Scopus) and sought unpublished data from investigator groups on the association of preterm birth (<37 weeks' gestation) and maternal GBS colonization (GBS isolation from vaginal, cervical, and/or rectal swabs; with separate subanalysis on GBS bacteriuria). We did meta-analyses to derive pooled estimates of the risk and odds ratios (according to study design), with sensitivity analyses to investigate potential biases.

RESULTS

We identified 45 studies for inclusion. We estimated the risk ratio (RR) for preterm birth with maternal GBS colonization to be 1.21 (95% confidence interval [CI], .99-1.48; P = .061) in cohort and cross-sectional studies, and the odds ratio to be 1.85 (95% CI, 1.24-2.77; P = .003) in case-control studies. Preterm birth was associated with GBS bacteriuria in cohort studies (RR, 1.98 [95% CI, 1.45-2.69]; P < .001).

CONCLUSIONS

From this review, there is evidence to suggest that preterm birth is associated with maternal GBS colonization, especially where there is evidence of ascending infection (bacteriuria). Several biases reduce the chance of detecting an effect. Equally, however, results, including evidence for the association, may be due to confounding, which is rarely addressed in studies. Assessment of any effect on preterm delivery should be included in future maternal GBS vaccine trials.

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.

Analysis of multidrug resistant group B streptococci with reduced penicillin susceptibility forming small, less hemolytic colonies

Group B streptococci (GBS; Streptococcus agalactiae) are the leading cause of neonatal invasive diseases and are also important pathogens for elderly adults. Until now, nearly all GBS with reduced penicillin susceptibility (PRGBS) have shown β-hemolytic activity and grow on sheep blood agar. However, we have previously reported three PRGBS clinical isolates harboring a CylK deletion that form small less hemolytic colonies. In this study, we examined the causes of small, less hemolytic colony formation in these clinical isolates. Isogenic strains were sequenced to identify the mutation related to a small colony size. We identified a 276_277insG nucleic acid insertion in the thiamin pyrophosphokinase (tpk) gene, resulting in premature termination at amino acid 103 in TPK, as a candidate mutation responsible for small colony formation. The recombinant strain Δtpk, which harbored the 276_277insG insertion in the tpk gene, showed small colony formation. The recombinant strain ΔcylK, which harbored the G379T substitution in cylK, showed a reduction in hemolytic activity. The phenotypes of both recombinant strains were complemented by the expression of intact TPK or CylK, respectively. Moreover, the use of Rapid ID 32 API and VITEK MS to identify strains as GBS was evaluated clinical isolates and recombinant strains. VITEK MS, but not Rapid ID 32 API, was able to accurately identify the strains as GBS. In conclusion, we determined that mutations in tpk and cylK caused small colonies and reduced hemolytic activity, respectively, and characterized the clinical isolates in detail.

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

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

Genomic comparison of virulent and non-virulent serotype V ST1 Streptococcus agalactiae in fish

Streptococcus agalactiae or Group B Streptococcus (GBS) is the major pathogen causing pneumonia and meningitis in human, mastitis in dairy cows, and streptococcal disease in tilapia. Previous studies have shown that fish GBS strains are correlated with human GBS strains in evolution and might have cross-host infection ability. Although the invasive disease caused by ST1 GBS in non-pregnant adults and cows is increasing worldwide, infection of fish by ST1 GBS has not been reported. The aim of this study was to determine whether ST1 GBS was virulent in fish and to investigate the genomic characteristics of ST1 GBS strains with different pathogenicity in tilapia. The human-derived serotype V ST1 GBS strains NNA048 and NNA038 were used to intraperitoneally challenge Nile tilapia (Oreochromis niloticus) with doses of 1.0×10⁹CFU/fish, 1.0×10⁷CFU/fish, and 1.0×10⁵CFU/fish, respectively. The cumulative mortality rates of NNA048 infection at three different doses were 100.00%, 83.33%, and 40.00%. In contrast, there were no any sick or dead fish in NNA038 infection group. Histopathological results indicated that challenge of tilapia with NNA048 caused different degree of degeneration and necrosis in brain, liver, spleen, head kidney, and gut, and a large number of blue-stained Streptococcus granules were observed in the tissues. In contrast, there were no any lesions in the tissues of tilapia that were challenged with NNA038. Genome comparison showed that the major genome differences between NNA048 and NNA038 were attributed to the different phage sequences, and there was a 49.8kb length, intact phage sequence encoding 68 proteins in NNA048 genome. SNV and Indels analysis between NNA038 and NNA048 genomes indicated that there were a total of 96 SNVs, 5 deletions and 1 insert. Taken together, serotype V ST1 GBS was comprised of virulent and nonvirulent strains to tilapia, and gene rearrangement might be the main reason of causing different levels of virulence between strains.

Opsonophagocytic Antibodies to Serotype Ia, Ib, and III Group B Streptococcus among Korean Infants and in Intravenous Immunoglobulin Products

Group B streptococcus (GBS) infection is a leading cause of sepsis and meningitis among infants, and is associated with high rates of morbidity and mortality in many countries. Protection against GBS typically involves antibody-mediated opsonization by phagocytes and complement components. The present study evaluated serotype-specific functional antibodies to GBS among Korean infants and in intravenous immunoglobulin (IVIG) products. An opsonophagocytic killing assay (OPA) was used to calculate the opsonization indices (OIs) of functional antibodies to serotypes Ia, Ib, and III in 19 IVIG products from 5 international manufacturers and among 98 Korean infants (age: 0-11 months). The GBS Ia, Ib, and III serotypes were selected because they are included in a trivalent GBS vaccine formulation that is being developed. The OI values for the IVIG products were 635-5,706 (serotype Ia), 488-1,421 (serotype Ib), and 962-3,315 (serotype III), and none of the IVIG lots exhibited undetectable OI values (< 4). The geometric mean OI values were similar for all 3 serotypes when we compared the Korean manufacturers. The seropositive rate among infants was significantly lower for serotype Ia (18.4%), compared to serotype Ib and serotype III (both, 38.8%). Infant age of ≥ 3 months was positively correlated with the seropositive rates for each serotype. Therefore, only a limited proportion of infants exhibited protective immunity against serotype Ia, Ib, and III GBS infections. IVIG products that exhibit high antibody titers may be a useful therapeutic or preventive measure for infants. Further studies are needed to evaluate additional serotypes and age groups.

Group B Streptococcus and perinatal mortality

The World Health Organization estimates that every year, one million neonatal deaths occur because of neonatal infection. Furthermore, an equal number of stillbirths are thought to be caused by infections. Here we discuss the role of Streptococcus agalactiae (group B Streptococcus, GBS) in neonatal disease and stillbirth.

Immunity to uropathogens: the emerging roles of inflammasomes

Urinary tract infections (UTIs) cause a huge burden of morbidity worldwide with recurrent UTIs becoming increasingly frequent owing to the emergence of antibiotic-resistant bacterial strains. Interactions between the innate and adaptive immune responses to pathogens colonizing the urinary tract have been the focus of much research. Inflammasomes are part of the innate immune defence and can respond rapidly to infectious insult. Assembly of the multiprotein inflammasome complex activates caspase-1, processes proinflammatory cytokines IL-1β and IL-18, and induces pyroptosis. These effector pathways, in turn, act at different levels to either prevent or resolve infection, or eliminate the infectious agent itself. In certain instances, inflammasome activation promotes tissue pathology; however, the precise functions of inflammasomes in UTIs remain unexplored. An improved understanding of inflammasomes could provide novel approaches for the design of diagnostics and therapeutics for complicated UTIs, enabling us to overcome the challenge of drug resistance.

Neonatal Group B Streptococcal Disease in Otherwise Healthy Infants: Failure of Specific Neonatal Immune Responses

Only a small proportion of newborn infants exposed to a pathogenic microorganism develop overt infection. Susceptibility to infection in preterm infants and infants with known comorbidities has a likely multifactorial origin and can be often attributed to the concurrence of iatrogenic factors, environmental determinants, underlying pathogenic processes, and probably genetic predisposition. Conversely, infection occurring in otherwise healthy full-term newborn infants is unexplained in most cases. Microbial virulence factors and the unique characteristics of the neonatal immune system only partially account for the interindividual variability in the neonatal immune responses to pathogens. We here suggest that neonatal infection occurring in otherwise healthy infants is caused by a failure of the specific protective immunity to the microorganism. To explain infection in term and preterm infants, we propose an extension of the previously proposed model of the genetic architecture of infectious diseases in humans. We then focus on group B streptococcus (GBS) disease, the best characterized neonatal infection, and outline the potential molecular mechanisms underlying the selective failure of the immune responses against GBS. In light of the recent discoveries of pathogen-specific primary immunodeficiencies and of the role of anticytokine autoantibodies in increasing susceptibility to specific infections, we hypothesize that GBS disease occurring in otherwise healthy infants could reflect an immunodeficiency caused either by rare genetic defects in the infant or by transmitted maternal neutralizing antibodies. These hypotheses are consistent with available epidemiological data, with clinical and epidemiological observations, and with the state of the art of neonatal physiology and disease. Studies should now be designed to comprehensively search for genetic or immunological factors involved in susceptibility to severe neonatal infections.

Development and performance evaluation of a recombinase polymerase amplification assay for the rapid detection of group B streptococcus

Background

Despite the implementation of prevention guidelines, group B Streptococcal (GBS) infection remains a leading cause of sepsis, pneumonia, and meningitis, resulting in significant neonatal morbidity and mortality. Preventive approaches that identify women at risk of transmitting GBS have reduced the incidence of neonatal GBS disease, and dramatically decreased the associated mortality rates. However, there is an on-going requirement for a near-patient diagnostic test for GBS that can be carried out at the time of delivery, ideally in the labour ward setting, particularly for women of unknown GBS colonisation status at the time of delivery.

Methods

In this study, a Recombinase Polymerase Amplification (RPA) assay was developed and performance evaluated for the detection of group B Streptococcus in vaginal swabs. The assay uses the cAMP factor (cfb) gene of GBS as the target gene. The analytical performance of the assay was evaluated by testing a panel of GBS reference strains and clinical isolates, and non-GBS organisms. The limit of detection was determined and the clinical performance was evaluated by testing 124 vaginal swabs from women with both GBS positive and negative status.

Results

Based on specificity testing carried out the assay was shown to be specific for the target of interest. The limit of detection of the assay was shown to be between six and 12 genome copies and was comparable to that of a real-time PCR assay, both achieving a limit of detection below 12.5 genome copies. The performance of both assays when applied to clinical samples was identical.

Conclusion

A specific, sensitive RPA assay for GBS was developed. The performance of the assay for testing of clinical samples is within the acceptable range.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0836-y) contains supplementary material, which is available to authorized users.

Toll-like receptor-dependent discrimination of streptococci

Streptococcus pneumoniae and Streptococcus agalactiae cause distinct infectious diseases in small children. Similarly, these bacteria elicit very different host-cell responses in vitro. Inactivated S. agalactiae by far exceeds S. pneumoniae in the activation of inflammatory cytokines and upstream signaling intermediates such as the MAP kinase JNK. The inflammatory response to both Streptococcus spp. is mediated by MyD88, an essential adapter protein of Toll-like receptors (TLRs), although the specific TLRs that are involved have not been fully resolved. Furthermore, during logarithmic growth, S. pneumoniae releases pneumolysin that interacts with TLR4 whereas S. agalactiae releases diacylated molecules that interact with TLR2/6. Interaction of these soluble bacterial products with their cognate TLRs is critical for limiting bacterial dissemination and and systemic inflammation in mice. This might be due, in part, to TLR-mediated apoptosis induced by these factors. In conclusion related streptococcal species induce specific events in TLR-mediated signal transduction. Comparative analysis of the host-cell response to these bacteria reveals molecules such as JNK as valuable targets for adjunctive sepsis therapy.

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.