GBS Pathogenesis Research Articles

Strain-level genomic analysis of serotype, genotype and virulence gene composition of group B streptococcus

IntroductionGBS (group B streptococcus) is an opportunistic pathogen that can colonize healthy individuals but presents significant challenges in clinical obstetrics and gynecology, as it can cause miscarriage, preterm birth, and invasive infections in newborns. To develop specific and personalized preventative strategies, a better understanding of the epidemiological characteristics and pathogenic features of GBS is essential.MethodsWe conducted a comprehensive strain-level genomic analysis of GBS, examining serotype and genotype distributions, as well as the composition and correlations of virulence genes using the blastn-short mode of the BLAST program(v2.10.0+), mlstsoftware (https://github.com/tseemann/mlst), Snippy (v4.6.0), FastTree (v2.1.11) and iTOL. The coding sequence region of virulence factors was annotated by Prodigal (v2.6.3) and Glimmer(v3.02b). We further identified host protein interacting with Srr2 by mass spectrometry analysis.ResultsWhile certain genotypes showed strong serotype consistency, there was no significant association between overall serotypes and genotypes. However, the composition of virulence genes was more closely related to the phylogeny of GBS, among which simultaneous presence of Srr2 and HygA exhibit significant association with hypervirulence. Tubulin emerged as the most distinct and abundant hit. The specific interaction of Tubulin with Srr2-BR, rather than Srr1-BR, was further confirmed by immunoblotting.DiscussionConsidering the impact of cytoskeleton rearrangement on GBS pathogenesis, this observation offers a plausible explanation for the hypervirulence triggered by Srr2. Collectively, our findings indicate that in the future clinical practice, virulence gene detection should be given more attention to achieve precise GBS surveillance and disease prevention.

The Streptococcus agalactiae LytSR two-component regulatory system promotes vaginal colonization and virulence in vivo.

Streptococcus agalactiae (or group B Streptococcus, GBS) is a leading cause of neonatal sepsis and meningitis globally. To sense and respond to variations in its environment, GBS possesses multiple two-component regulatory systems (TCSs), such as LytSR. Here, we aimed to investigate the role of LytSR in GBS pathogenicity. We generated an isogenic lytS knockout mutant in a clinical GBS isolate and used a combination of phenotypic in vitro assays and in vivo murine models to investigate the contribution of lytS to the colonization and invasive properties of GBS. Deletion of the lytS gene in the GBS chromosome resulted in significantly higher survival rates in mice during sepsis, accompanied by reduced bacterial loads in blood, lung, spleen, kidney, and brain tissues compared to infection with the wild-type strain. In a mouse model of GBS vaginal colonization, we also observed that the lytS knockout mutant was cleared more readily from the vaginal tract compared to its wild-type counterpart. Interestingly, lower levels of proinflammatory cytokines were found in the serum of mice infected with the lytS mutant. Our results demonstrate that the LytSR TCS plays a key role in GBS tissue invasion and pathogenesis, and persistence of mucosal colonization.IMPORTANCEStreptococcus agalactiae (group B Streptococcus, or GBS) is a common commensal of the female urogenital tract and one of WHO's priority pathogens. The bacterium has evolved mechanisms to adapt and survive in its host, many of which are regulated via two-component signal transduction systems (TCSs); however, the exact contributions of TCSs toward GBS pathogenicity remain largely obscure. We have constructed a TCS lytS-deficient mutant in a CC-17 hypervirulent GBS clinical isolate. Using murine models, we showed that LytSR regulatory system is essential for vaginal colonization via promoting biofilm production. We also observed that lytS deficiency led to significantly attenuated virulence properties and lower levels of proinflammatory cytokines in blood. Our findings are of significant importance in that they unveil a previously unreported role for LytSR in GBS and pave the way toward a better understanding of its ability to transition from an innocuous commensal to a deadly pathogen.

Multidrug Resistant Group B Streptococcus Isolates from Pregnant Women in Delta State, Nigeria.

&lt;b&gt;Background and Objective:&lt;/b&gt; Group B &lt;i&gt;Streptococci&lt;/i&gt; (GBS) are globally recognized as a major risk factor for neonatal infections and various obstetric complications. More so, biofilm formation has been suggested to be important for GBS pathogenesis. The aim of this study was to determine the prevalence and antibiotic susceptibility pattern of GBS among pregnant women and their capacity to form biofilm. &lt;b&gt;Materials and Methods:&lt;/b&gt; A total of 87 pregnant women at 34 to 37 weeks' gestation aged 17-45 years were recruited from 3 healthcare centres in Delta State, Nigeria. Cultures for the isolation of GBS were carried out using recto-vaginal swabs, according to standard microbiological methods. All strains isolated were used for susceptibility tests to various antibiotics as recommended by CLSI using the disk-diffusion method. &lt;b&gt;Results:&lt;/b&gt; The overall prevalence of GBS colonization among pregnant women was 43.6% (38/87). The &lt;u&gt;<&lt;/u&gt;30 age group had the highest rate of GBS colonization. Resistance to erythromycin and vancomycin was 48.2 and 66.4%, respectively. The fluoroquinolones had the lowest resistant rates with no isolate showing resistance to ofloxacin. Multidrug resistance (MDR) (&lt;u&gt;>&lt;/u&gt;3 drug classes) was detected in 73.7% (28/38) of the GBS isolates. All GBS isolated in this study were either strong, moderate or weak biofilm producers. However, most 28 (73.7%) were strong biofilm producers. Resistance of GBS isolates to erythromycin and vancomycin, drugs used for treating GBS infection was high. &lt;b&gt;Conclusion:&lt;/b&gt; This suggested the importance of testing antimicrobial susceptibilities in GBS colonized pregnant women in order to guide antibiotic therapy and minimize newborn infection and co-morbidity.

Guillain–Barré syndrome after COVID‐19 vaccination with suspected concurrent cytomegalovirus reactivation

AbstractBackgroundGuillain–Barré syndrome (GBS) is an immune‐mediated polyneuropathy most commonly associated with antecedent infections, such as Campylobacter jejuni or viral infections, but vaccination is also known as an antecedent event. In recent years, due to the worldwide pandemic, vaccination against coronavirus disease 2019 (COVID‐19) has widely spread throughout the world. Although surveillance of vaccination‐associated adverse effects is still ongoing, multiple cases of GBS after COVID‐19 vaccination have been reported. However, the exact pathophysiology of COVID‐19 vaccination causing GBS has not been clarified. Not only new‐onset infection, but also reactivation of dormant viral agents, is known to trigger GBS. This reactivation might occur after COVID‐19 vaccination; however, there are no reports of this phenomenon in association with post‐vaccination GBS.Case PresentationA 44‐year‐old immunocompetent woman presented with acute onset weakness in all four limbs 6 days after COVID‐19 vaccination. Neurological examination showed dysphagia, symmetrical weakness, absent tendon reflexes and distal dominant sensory disturbance in all four extremities. Nerve conduction studies were compatible with demyelinating neuropathy, and serum was positive for anti‐GD1a‐IgG antibody. A diagnosis of acute inflammatory demyelinating neuropathy was made. Serological examination on admission suggested concomitant cytomegalovirus reactivation. Plasma exchange rapidly improved her symptoms, including weakness and sensory disturbance, and she was discharged without residual symptoms.ConclusionsThe present case suggests that cytomegalovirus reactivation might play a role in the pathogenesis of GBS associated with COVID‐19 vaccination. Accounting for cytomegalovirus reactivation might reveal unidentified pathophysiology of GBS after COVID‐19 vaccination.

Group B Streptococcus Cas9 variants provide insight into programmable gene repression and CRISPR-Cas transcriptional effects

Group B Streptococcus (GBS; S. agalactiae) causes chorioamnionitis, neonatal sepsis, and can also cause disease in healthy or immunocompromised adults. GBS possesses a type II-A CRISPR-Cas9 system, which defends against foreign DNA within the bacterial cell. Several recent publications have shown that GBS Cas9 influences genome-wide transcription through a mechanism uncoupled from its function as a specific, RNA-programmable endonuclease. We examine GBS Cas9 effects on genome-wide transcription through generation of several isogenic variants with specific functional defects. We compare whole-genome RNA-seq from Δcas9 GBS with a full-length Cas9 gene deletion; dcas9 defective in its ability to cleave DNA but still able to bind to frequently occurring protospacer adjacent motifs; and scas9 that retains its catalytic domains but is unable to bind protospacer adjacent motifs. Comparing scas9 GBS to the other variants, we identify nonspecific protospacer adjacent motif binding as a driver of genome-wide, Cas9 transcriptional effects in GBS. We also show that Cas9 transcriptional effects from nonspecific scanning tend to influence genes involved in bacterial defense and nucleotide or carbohydrate transport and metabolism. While genome-wide transcription effects are detectable by analysis of next-generation sequencing, they do not result in virulence changes in a mouse model of sepsis. We also demonstrate that catalytically inactive dCas9 expressed from the GBS chromosome can be used with a straightforward, plasmid-based, single guide RNA expression system to suppress transcription of specific GBS genes without potentially confounding off-target effects. We anticipate that this system will be useful for study of nonessential and essential gene roles in GBS physiology and pathogenesis.

The S Protein of Group B Streptococcus Is a Critical Virulence Determinant That Impacts the Cell Surface Virulome.

Group B Streptococcus (GBS, S. agalactiae) is a human commensal and occasional pathogen that remains a leading cause of neonatal sepsis and meningitis with increasing disease burden in adult populations. Although programs for universal screening in pregnancy to guide intrapartum prophylaxis have reduced GBS invasive disease burden resulting from mother-to-newborn transfer during birth, better knowledge of disease mechanisms may elucidate new strategies to reduce antibiotic exposure. In our efforts to expand the knowledge base required for targeted anti-virulence therapies, we identified a GBS homolog for a recently identified virulence determinant of group A Streptococcus, S protein, and evaluated its role in GBS pathogenesis. A GBS S protein deletion mutant, Δess, showed altered cell-surface properties compared to the WT parent strain, including defective retention of its surface polysaccharide. Quantitative proteome analysis of enzymatically shaved surface epitopes of the GBS Δess mutant revealed a dysregulated cell surface virulome, with reduced abundance of several protein and glycoprotein components. The Δess mutant showed markedly attenuated virulence in a murine model of GBS systemic infection, with increased proteasome activity detected in the spleens of animals infected with the Δess mutant. These results expand the key roles S protein plays in streptococcal pathogenesis and introduces a new GBS virulence determinant and potential target for therapy development.

P-PN006. Guillain barré syndrome treatment related fluctuation (GBS-TRF) following meningococcus vaccination: A case report

Introduction . GBS is an autoimmune neurological disorder, characterized by acute limb weakness and areflexia. The pathogenesis of GBS is triggered mostly by infection process. However, the consequence of vaccination can cause GBS has been widely discussed. Some studies address the potential relationship of GBS to influenza vaccination, while other vaccination is rarely described. In this study, we reported a case of GBS-TRF after administration of meningococcus vaccination. Case presentation: A 64-year-old man presented with glove-stocking hypoesthesia followed by flaccid tetraparesis, which occurred two weeks after meningococcus vaccination. There were no history of any infectious diseases preceding his symptoms. He and his family were administered these vaccinations, as the prerequisite for going to Umrah. After coming back of his Umrah, he was diagnosed with GBS based on history, clinical features and test results. Neurological examination revealed absent of knee and ankle reflexes. Nerve conduction studies indicated the decreased of sensory nerve action potential, amplitudes and conduction velocity, also prolongation of distal latency. He had six times therapeutic plasma exchange (TPE) and the symptoms slightly resolved at discharge. One month after plasma exchange, he was readmitted due to dyspnea, worsening of his weakness and severe hyponatremia. He was transferred to intensive care unit with mechanical ventilation. He was diagnosed as GBS-TRF. The treatment was intravenous immunoglobulin (IVIG) with full dose of 400 mg/kg/day. Unfortunately, the patient developed some complications during intensive care. He did not survive, suffering from cardiac arrythmia and septic shock, after IVIG treatment. Conclusion . Meningococcus vaccination may cause GBS as an unexpected abnormal autoimmune response. It is important to note the possibility of neurological complications after vaccine administration.

Transcriptional regulator XtgS is involved in iron transition and attenuates the virulence of Streptococcus agalactiae

Streptococcus agalactiae (GBS) is an important pathogen that has increasingly received attention for its role in invasive infections and its broad host range. Research on the regulation of gene expression could illuminate GBS pathogenesis. We previously identified a novel transcriptional regulator XtgS, which is a negative regulator of GBS pathogenicity. Here, we demonstrate that XtgS overexpression significantly attenuated GBS virulence in zebrafish infection tests, and XtgS indirectly downregulated the transcription of two iron transport systems based on the results of transcriptomic analysis, electrophoretic mobility shift assays (EMSAs) and lacZ fusion assays. Subsequent studies verified that the inactivation of iron transport system 1 resulted in GBS excessive iron accumulation and attenuated virulence. Thus, we infer that the downregulation of iron transport system 1 caused by XtgS overexpression probably attenuates bacterial virulence, which partially clarifies the mechanism by which XtgS alleviates the pathogenesis. These findings provide new insights into the relationship between exogenous transcriptional regulation and bacterial virulence.

The Novel Streptococcal Transcriptional Regulator XtgS Negatively Regulates Bacterial Virulence and Directly Represses PseP Transcription.

Streptococcus agalactiae (group B streptococcus [GBS]) has received continuous attention for its involvement in invasive infections and its broad host range. Transcriptional regulators have an important impact on bacterial adaptation to various environments. Research on transcriptional regulators will shed new light on GBS pathogenesis. In this study, we identified a novel XRE-family transcriptional regulator encoded on the GBS genome, designated XtgS. Our data demonstrate that XtgS inactivation significantly increases bacterial survival in host blood and animal challenge test, suggesting that it is a negative regulator of GBS pathogenicity. Further transcriptomic analysis and quantitative reverse transcription-PCR (qRT-PCR) mainly indicated that XtgS significantly repressed transcription of its upstream gene pseP Based on electrophoretic mobility shift and lacZ fusion assays, we found that an XtgS homodimer directly binds a palindromic sequence in the pseP promoter region. Meanwhile, the PseP and XtgS combination naturally coexists in diverse Streptococcus genomes and has a strong association with sequence type, serotype diversification and host adaptation of GBS. Therefore, this study reveals that XtgS functions as a transcriptional regulator that negatively affects GBS virulence and directly represses PseP expression, and it provides new insights into the relationships between transcriptional regulator and genome evolution.

A Counterselectable Sucrose Sensitivity Marker Permits Efficient and Flexible Mutagenesis in Streptococcus agalactiae.

Streptococcus agalactiae (group B Streptococcus [GBS]) is a cause of severe infections, particularly during the newborn period. While methods exist for generating chromosomal mutations in GBS, they are cumbersome and inefficient and present significant challenges if the goal is to study subtle mutations, such as single-base-pair polymorphisms. To address this problem, we have developed an efficient and flexible GBS mutagenesis protocol based on sucrose counterselection against levansucrase (SacB) expressed from a temperature-selective shuttle vector. GBS containing the SacB expression cassette demonstrates lethal sensitivity to supplemental sucrose whether the plasmid DNA is replicating outside of the chromosome or has been integrated during a crossover event. Transmission electron microscopy shows that SacB-mediated lethal sucrose sensitivity results from the accumulation of inclusion bodies that eventually lead to complete degradation of normal cellular architecture and subsequent lysis. We used this new mutagenesis technique to generate an in-frame, allelic exchange knockout of the GBS sortase gene srtA, demonstrating that >99% of colonies that emerge from our protocol had the expected knockout phenotype and that among a subset tested by sequencing, 100% had the correct genotype. We also generated barcoded nonsense mutations in the cylE gene in two GBS strains, showing that the approach can be used to make small, precise chromosomal mutations.IMPORTANCE The ability to generate chromosomal mutations is fundamental to microbiology. Historically, however, GBS pathogenesis research has been made challenging by the relative genetic intractability of the organism. Generating a single knockout in GBS using traditional techniques can take many months, with highly variable success rates. Furthermore, traditional methods do not offer a straightforward way to generate single-base-pair polymorphisms or other subtle changes, especially to noncoding regions of the chromosome. We have developed a new sucrose counterselection-based method that permits rapid, efficient, and flexible GBS mutagenesis. Our technique requires no additional equipment beyond what is needed for traditional approaches. We believe that it will catalyze rapid advances in GBS genetics research by significantly easing the path to generating mutants.

Characterization of a Two-Component System Transcriptional Regulator, LtdR, That Impacts Group B Streptococcal Colonization and Disease

Streptococcus agalactiae (group B Streptococcus [GBS]) is often a commensal bacterium that colonizes healthy adults asymptomatically and is a frequent inhabitant of the vaginal tract in women. However, in immunocompromised individuals, particularly the newborn, GBS may transition to an invasive pathogen and cause serious disease. Despite the use of the currently recommended intrapartum antibiotic prophylaxis for GBS-positive mothers, GBS remains a leading cause of neonatal septicemia and meningitis. To adapt to the various host environments encountered during its disease cycle, GBS possesses multiple two-component regulatory systems (TCSs). Here we investigated the contribution of a transcriptional regulator containing a LytTR domain, LtdR, to GBS pathogenesis. Disruption of the ltdR gene in the GBS chromosome resulted in a significant increase in bacterial invasion into human cerebral microvascular endothelial cells (hCMEC) in vitro as well as the greater penetration of the blood-brain barrier (BBB) and the development of meningitis in vivo Correspondingly, infection of hCMEC with the ΔltdR mutant resulted in increased secretion of the proinflammatory cytokines interleukin-8 (IL-8), CXCL-1, and IL-6. Further, using a mouse model of GBS vaginal colonization, we observed that the ΔltdR mutant was cleared more readily from the vaginal tract and also that infection with the ΔltdR mutant resulted in increased cytokine production from human vaginal epithelial cells. RNA sequencing revealed global transcriptional differences between the ΔltdR mutant and the parental wild-type GBS strain. These results suggest that LtdR regulates many bacterial processes that can influence GBS-host interactions to promote both bacterial persistence and disease progression.

Human Milk Oligosaccharides Exhibit Antimicrobial and Antibiofilm Properties against Group B Streptococcus.

Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive bacterial pathogen that causes invasive infections in both children and adults. During pregnancy, GBS is a significant cause of infection of the fetal membranes (chorioamnionitis), which can lead to intra-amniotic infection, preterm birth, stillbirth, and neonatal sepsis. Recently, breastfeeding has been thought to represent a potential mode of GBS transmission from mother to newborn, which might increase the risk for late-onset sepsis. Little is known, however, about the molecular components of breast milk that may support or prevent GBS colonization. In this study, we examine how human milk oligosaccharides (HMOs) affect the pathogenesis of GBS. HMOs from discrete donor samples were isolated and profiled by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Growth and biofilm assays show that HMOs from mothers of specific milk groups can modulate the growth and biofilm formation of GBS. High-resolution field-emission gun scanning electron microscopy (SEM) and confocal laser scanning microscopy confirmed the quantitative biofilm assays and demonstrated cell arrangement perturbations in bacterial cultures treated with specific oligosaccharides. These findings demonstrate that HMOs affect the growth and cell biology of GBS. Finally, this study provides the first example of HMOs functioning as antibiofilm agents against GBS.

Alterations of plasma concentrations of lipophilic antioxidants are associated with Guillain-Barre syndrome

BackgroundGuillain-Barré syndrome (GBS) is an acute inflammatory polyneuropathy resulting in demyelination in peripheral nervous system. Myelin enriched in lipids is easily oxidized by reactive oxygen species during inflammation. Oxidative stress and lipophilic anti-oxidative capacities in GBS patients have not been fully explored. To evaluate the redox status of GBS patients, we measured malondialdehyde (MDA), myeloperoxidase (MPO), lipophilic antioxidants, and tocopherols concentrations in plasma from GBS patients and age-matched healthy controls. ResultsConcentrations of γ-tocopherol and δ-tocopherol decreased significantly, and α-carotene significantly increased in GBS patients compared to healthy controls. However, no significant changes in MDA and MPO concentrations were detected. In GBS patients, the γ-tocopherol concentration correlated positively with concentrations of δ-tocopherol, α-tocopherol, lutein, Q10, and γ-CEHC, respectively. Similarly, the δ-tocopherol concentration correlated positively with γ-tocopherol, α-tocopherol, lutein, Q10, δ-CEHC, and γ-CEHC concentrations, respectively. The receiver operating characteristics curve analysis showed that γ-tocopherol may serve as a good predictor for GBS. ConclusionsDiminished lipophilic antioxidant defense, mainly γ-tocopherol and δ-tocopherol, in GBS patients accounting for their lowered resistance to reactive oxygen species is probably associated with pathogenesis of GBS, and potentially useful for the development of therapeutic strategies.

Group B Streptococcus infection induces M1-like activation in human placental and mouse decidual macrophages.

Abstract Group B Streptococcus (GBS), a vaginal colonizing gram-positive bacterium, is a leading cause of neonatal death and sepsis. How GBS evades macrophage defenses in the gravid uterus is not yet known. In response to stimuli, macrophages are activated along a spectrum known as polarization ranging from classically-activated, pro-inflammatory “M1” to alternatively-activated anti-inflammatory “M2” macrophages. These activation states can contribute to disease pathogenesis. This study aims to define changes in macrophage activation in response to GBS infection. Human monocyte derived macrophages (MDMs) were infected with GBS or polarized in vitro with M1 (IFNγ/LPS) or M2 (IL-4 or IL-10) stimuli. Placental macrophages (PMs) were infected with GBS or treated with IFNγ/LPS. To mimic human ascending vaginal infection in vivo, C57BL/6 mice were inoculated vaginally with GBS at day E13.5 for 48h. Subsequently, decidual macrophages were isolated and analyzed for polarization markers via flow cytometry and tissues were used for histology. Resulting phenotypes were characterized using qRT-PCR, ELISA, and flow cytometry. In MDMs, GBS upregulated M1 genes (CCR7, CD80) and downregulated M2 genes (CD209, CD163). GBS increased the release of M1 cytokines (TNFα, IL-1β) in MDMs and PMs. PM surface expression of M1 markers (CCR7, CD80) increased while M2 markers (CD206, CD163, CD209) decreased. Mouse decidual macrophage surface expression of CD206 was downregulated while CD11c exhibited little change. Our results suggest that GBS may induce M1 activation in both human and mouse models. These studies provide new insights into the role of macrophage activation in GBS pathogenesis. Studies supported by NIH NIAID Training Grant 5T32AI007281-27.

Contribution of the RgfD Quorum Sensing Peptide to rgf Regulation and Host Cell Association in Group B Streptococcus.

Streptococcus agalactiae (group B Streptococcus; GBS) is a common inhabitant of the genitourinary and/or gastrointestinal tract in up to 40% of healthy adults; however, this opportunistic pathogen is able to breach restrictive host barriers to cause disease and persist in harsh and changing conditions. This study sought to identify a role for quorum sensing, a form of cell to cell communication, in the regulation of the fibrinogen-binding (rgfBDAC) two-component system and the ability to associate with decidualized endometrial cells in vitro. To do this, we created a deletion in rgfD, which encodes the putative autoinducing peptide, in a GBS strain belonging to multilocus sequence type (ST)-17 and made comparisons to the wild type. Sequence variation in the rgf operon was detected in 40 clinical strains and a non-synonymous single nucleotide polymorphism was detected in rgfD in all of the ST-17 genomes that resulted in a truncation. Using qPCR, expression of rgf operon genes was significantly decreased in the ST-17 ΔrgfD mutant during exponential growth with the biggest difference (3.3-fold) occurring at higher cell densities. Association with decidualized endometrial cells was decreased 1.3-fold in the mutant relative to the wild type and rgfC expression was reduced 22-fold in ΔrgfD following exposure to the endometrial cells. Collectively, these data suggest that this putative quorum sensing molecule is important for attachment to human tissues and demonstrate a role for RgfD in GBS pathogenesis through regulation of rgfC.

Increased serum concentrations of transforming growth factor-β1 (TGF-β1) in patients with Guillain-Barré syndrome

BackgroundGuillain-Barré syndrome (GBS) is an acquired demyelinating peripheral neuropathy. It has shown that macrophage activation contribute to the pathogenesis of GBS. Therefore macrophage-mediated factors could be the potential markers for disease diagnosis and status of GBS. MethodsWe measured serum concentrations of 4 macrophage-mediated factors, including interleukin-6 (IL-6), transforming growth factor-β1 (TGF-β1), vascular cell adhesion protein 1 (VCAM-1) and vascular endothelial growth factor (VEGF), in 23 chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), 28 GBS, 11 Miller-Fisher syndrome (MFS), 40 multiple sclerosis (MS), and 12 Alzheimer's disease (AD) patients, as well as 15 healthy controls. ResultsSerum TGF-β1 concentration of GBS patients (35.94±2.55ng/ml) was significantly higher compared with CIDP (25.46±1.40ng/ml, P<0.001), MFS (25.32±2.31ng/ml, P=0.010), MS (21.35±0.90ng/ml, P<0.001) and AD patients (22.92±1.82ng/ml, P<0.001), as well as healthy controls (23.12±1.67ng/ml, P<0.001). A positive correlation between serum TGF-β1 concentrations and Hughes' functional grading scales was observed in GBS patients. Serum concentrations of IL-6, VCAM-1 and VEGF were similar between the studied groups. ConclusionThe high serum concentrations of TGF-β1 and the correlation between serum TGF-β1 concentration and disease severity highlight the potential of TGF-β1 as a biomarker of GBS.

Evolutionary inactivation of a sialidase in group B Streptococcus.

Group B Streptococcus (GBS) is a leading cause of bacterial sepsis and meningitis in newborns. GBS possesses a protein with homology to the pneumococcal virulence factor, NanA, which has neuraminidase (sialidase) activity and promotes blood-brain barrier penetration. However, phylogenetic sequence and enzymatic analyses indicate the GBS NanA ortholog has lost sialidase function – and for this distinction we designate the gene and encoded protein nonA/NonA. Here we analyze NonA function in GBS pathogenesis, and through heterologous expression of active pneumococcal NanA in GBS, potential costs of maintaining sialidase function. GBS wild-type and ΔnonA strains lack sialidase activity, but forced expression of pneumococcal NanA in GBS induced degradation of the terminal sialic acid on its exopolysaccharide capsule. Deletion of nonA did not change GBS-whole blood survival or brain microvascular cell invasion. However, forced expression of pneumococcal NanA in GBS removed terminal sialic acid residues from the bacterial capsule, restricting bacterial proliferation in human blood and in vivo upon mouse infection. GBS expressing pneumococcal NanA had increased invasion of human brain microvascular endothelial cells. Thus, we hypothesize that nonA lost enzyme activity allowing the preservation of an effective survival factor, the sialylated exopolysaccharide capsule.

Association between genotypic diversity and biofilm production in group B Streptococcus.

BackgroundGroup B Streptococcus (GBS) is a leading cause of sepsis and meningitis and an important factor in premature and stillbirths. Biofilm production has been suggested to be important for GBS pathogenesis alongside many other elements, including phylogenetic lineage and virulence factors, such as pili and capsule type. A complete understanding of the confluence of these components, however, is lacking. To identify associations between biofilm phenotype, pilus profile and lineage, 293 strains from asymptomatic carriers, invasive disease cases, and bovine mastitis cases, were assessed for biofilm production using an in vitro assay.ResultsMultilocus sequence type (ST) profile, pilus island profile, and isolate source were associated with biofilm production. Strains from invasive disease cases and/or belonging to the ST-17 and ST-19 lineages were significantly more likely to form weak biofilms, whereas strains producing strong biofilms were recovered more frequently from individuals with asymptomatic colonization.ConclusionsThese data suggest that biofilm production is a lineage-specific trait in GBS and may promote colonization of strains representing lineages other than STs 17 and 19. The findings herein also demonstrate that biofilms must be considered in the treatment of pregnant women, particularly for women with heavy GBS colonization.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0704-9) contains supplementary material, which is available to authorized users.

Circulating memory T follicular helper subsets, Tfh2 and Tfh17, participate in the pathogenesis of Guillain-Barré syndrome.

Circulating memory T follicular helper subsets, Tfh2 and Tfh17 are found to be aberrantly regulated in many autoimmune diseases. However, their roles in the pathogenesis of GBS are still unclear. This study examined the phenotype, distribution, clinical relevance and potential function of Tfh2 and Tfh17 in 36 GBS patients (including 24 AMAN and 12 AIDP patients). We found that the absolute counts of total memory Tfh cells were significantly increased in AMAN, while no significant difference in AIDP compared with HC. Furthermore, the levels of the three subsets of memory Tfh cells, Tfh1, Tfh2 and Tfh17, were differentially altered in AMAN. The absolute counts of Tfh1, Tfh2 and Tfh17 were all increased to a higher level in AMAN. The ratio of (Tfh2+Tfh17)/Tfh1 and the percentages of ICOS+ cells in Tfh2 and Tfh17 cells were greater in AMAN when compared to AIDP and HC, and the former had a positive correlation with the severity of both AMAN and AIDP. Conversely, the percentages of PD1+ cells in Tfh2 and Tfh17 cells were lower in AMAN than in HC. Therefore, circulating memory Tfh2 and Tfh17 cells might promote the autoantibody-related immune response and serve as useful markers to evaluate the progression of AMAN.

Whole-Genome Comparison Uncovers Genomic Mutations between Group B Streptococci Sampled from Infected Newborns and Their Mothers.

Streptococcus agalactiae (group B Streptococcus or GBS), a commensal of the human gut and genitourinary tract, is a leading cause of neonatal infections, in which vertical transmission from mother to child remains the most frequent route of contamination. Here, we investigated whether the progression of GBS from carriage to disease is associated with genomic adaptation. Whole-genome comparison of 47 GBS samples from 19 mother-child pairs uncovered 21 single nucleotide polymorphisms (SNPs) and seven insertions/deletions. Of the SNPs detected, 16 appear to have been fixed in the population sampled whereas five mutations were found to be polymorphic. In the infant strains, 14 mutations were detected, including two independently fixed variants affecting the covRS locus, which is known to encode a major regulatory system of virulence. A one-nucleotide insertion was also identified in the promoter region of the highly immunogenic surface protein Rib gene. Gene expression analysis after incubation in human blood showed that these mutations influenced the expression of virulence-associated genes. Additional identification of three mutated strains in the mothers' milk raised the possibility of the newborns also being a source of contamination for their mothers. Overall, our work showed that GBS strains in carriage and disease scenarios might undergo adaptive changes following colonization. The types and locations of the mutations found, together with the experimental results showing their phenotypic impact, suggest that those in a context of infection were positively selected during the transition of GBS from commensal to pathogen, contributing to an increased capacity to cause disease. Group B Streptococcus (GBS) is a major pathogen responsible for neonatal infections. Considering that its colonization of healthy adults is mostly asymptomatic, the mechanisms behind its switch from a commensal to an invasive state are largely unknown. In this work, we compared the genomic profile of GBS samples causing infections in newborns with that of the GBS colonizing their mothers. Multiple mutations were detected, namely, within key virulence factors, including the response regulator CovR and surface protein Rib, potentially affecting the pathogenesis of GBS. Their overall impact was supported by differences in the expression of virulence-associated genes in human blood. Our results suggest that during GBS's progression to disease, particular variants are positively selected, contributing to the ability of this bacterium to infect its host.