Microbiological and clinical characteristics of Group B Streptococcus isolates causing materno-neonatal infections: high prevalence of CC17/PI-1 and PI-2b sublineage in neonatal infections

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.

Molecular epidemiology and virulence factors of group B Streptococcus in South Korea according to the invasiveness

BACKGROUND

Group B Streptococcus (GBS) causes invasive infections in newborns and elderly individuals, but is a noninvasive commensal bacterium in most immunocompetent people. Recently, the incidence of invasive GBS infections has increased worldwide, and there is growing interest in the molecular genetic characteristics of invasive GBS strains. Vaccines against GBS are expected in the near future. Here, we aimed to analyze the molecular epidemiology of GBS according to the invasiveness in South Korea.

METHODS

We analyzed GBS isolates collected and stored in two hospitals in South Korea between January 2015 and December 2020. The invasiveness of these isolates was determined via a retrospective review of clinical episodes. Totally, 120 GBS isolates from 55 children and 65 adults were analyzed. Serotype and sequence type (ST) were determined using multiplex polymerase chain reaction (PCR) and multilocus sequence typing, respectively. Fourteen virulence factor-encoding genes of GBS were analyzed using multiplex PCR.

RESULTS

Forty one (34.2%) were invasive infection-related GBS isolates (iGBS). The most frequently detected serotype was III (39/120, 32.5%), and it accounted for a high proportion of iGBS (21/41, 51.2%). The most frequent ST was ST19 (18/120, 15.0%), followed by ST2 (17/120, 14.2%). Serotype III/ST17 was predominant in iGBS (12/41, 29.3%), and all 17 ST2 strains were noninvasive. The distribution of most of the investigated virulence factors was not significantly related to invasiveness; noteworthily, most of the serotype III/ST17 iGBS carried pilus island (PI) 2b (10/12, 83.3%), and the prevalence of fbsB was significantly low compared with noninvasive GBS isolates (P = 0.004). Characteristically, the combination of bca(+)-cspA(+)-pavA(+)-fbsB(-)-rib(+)-bac(-) was predominant in iGBS (24.4%, 10/41).

CONCLUSIONS

Serotype III/ST17 GBS carrying PI-2b was frequently detected in iGBS. There was no significant association between invasiveness and the pattern of virulence factors; however, a specific combination of virulence factors was predominant in iGBS.

Genomic insights into the diversity, virulence, and antimicrobial resistance of group B Streptococcus clinical isolates from Saudi Arabia

Introduction

Detailed assessment of the population structure of group B Streptococcus (GBS) among adults is still lacking in Saudi Arabia. Here we characterized a representative collection of isolates from colonized and infected adults.

Methods

GBS isolates (n=89) were sequenced by Illumina and screened for virulence and antimicrobial resistance determinants. Genetic diversity was assessed by single nucleotide polymorphisms and core-genome MLST analyses.

Results

Genome sequences revealed 28 sequence types (STs) and nine distinct serotypes, including uncommon serotypes VII and VIII. Majority of these STs (n=76) belonged to the human-associated clonal complexes (CCs) CC1 (33.71%), CC19 (25.84%), CC17 (11.24%), CC10/CC12 (7.87%), and CC452 (6.74%). Major CCs exhibited intra-lineage serotype diversity, except for the hypervirulent CC17, which exclusively expressed serotype III. Virulence profiling revealed that nearly all isolates (94.38%) carried at least one of the four alpha family protein genes (i.e., alphaC, alp1, alp2/3, and rib), and 92.13% expressed one of the two serine-rich repeat surface proteins Srr1 or Srr2. In addition, most isolates harbored the pilus island (PI)-2a alone (15.73%) or in combination with PI-1 (62.92%), and those carrying PI-2b alone (10.11%) belonged to CC17. Phylogenetic analysis grouped the sequenced isolates according to CCs and further subdivided them along with their serotypes. Overall, isolates across all CC1 phylogenetic clusters expressed Srr1 and carried the PI-1 and PI-2a loci, but differed in genes encoding the alpha-like proteins. CC19 clusters were dominated by the III/rib/srr1/PI-1+PI-2a (43.48%, 10/23) and V/alp1/srr1/PI-1+PI-2a (34.78%, 8/23) lineages, whereas most CC17 isolates (90%, 9/10) had the same III/rib/srr2/P1-2b genetic background. Interestingly, genes encoding the CC17-specific adhesins HvgA and Srr2 were detected in phylogenetically distant isolates belonging to ST1212, suggesting that other highly virulent strains might be circulating within the species. Resistance to macrolides and/or lincosamides across all major CCs (n=48) was associated with the acquisition of erm(B) (62.5%, 30/48), erm(A) (27.1%, 13/48), lsa(C) (8.3%, 4/48), and mef(A) (2.1%, 1/48) genes, whereas resistance to tetracycline was mainly mediated by presence of tet(M) (64.18%, 43/67) and tet(O) (20.9%, 14/67) alone or in combination (13.43%, 9/67).

Discussion

These findings underscore the necessity for more rigorous characterization of GBS isolates causing infections.

The Clinical and Genetic Characteristics of Streptococcus agalactiae Meningitis in Neonates

Streptococcus agalactiae (Group B Streptococcus, GBS) is an important pathogen of bacterial meningitis in neonates. We aimed to investigate the clinical and genetic characteristics of neonatal GBS meningitis. All neonates with GBS meningitis at a tertiary level medical center in Taiwan between 2003 and 2020 were analyzed. Capsule serotyping, multilocus sequence typing, antimicrobial resistance, and whole-genome sequencing (WGS) were performed on the GBS isolates. We identified 48 neonates with GBS meningitis and 140 neonates with GBS sepsis. Neonates with GBS meningitis had significantly more severe clinical symptoms; thirty-seven neonates (77.8%) had neurological complications; seven (14.6%) neonates died; and 17 (41.5%) survivors had neurological sequelae at discharge. The most common serotypes that caused meningitis in neonates were type III (68.8%), Ia (20.8%), and Ib (8.3%). Sequence type (ST) is highly correlated with serotypes, and ST17/III GBS accounted for more than half of GBS meningitis cases (56.3%, n = 27), followed by ST19/Ia, ST23/Ia, and ST12/Ib. All GBS isolates were sensitive to ampicillin, but a high resistance rates of 72.3% and 70.7% to erythromycin and clindamycin, respectively, were noted in the cohort. The virulence and pilus genes varied greatly between different GBS serotypes. WGS analyses showed that the presence of PezT; BspC; and ICESag37 was likely associated with the occurrence of meningitis and was documented in 60.4%, 77.1%, and 52.1% of the GBS isolates that caused neonatal meningitis. We concluded that GBS meningitis can cause serious morbidity in neonates. Further experimental models are warranted to investigate the clinical and genetic relevance of GBS meningitis. Specific GBS strains that likely cause meningitis requires further investigation and clinical attention.

Sex-Specific Dysconnective Brain Injuries and Neuropsychiatric Conditions such as Autism Spectrum Disorder Caused by Group B Streptococcus-Induced Chorioamnionitis

Global health efforts have increased against infectious diseases, but issues persist with pathogens like Group B Streptococcus (GBS). Preclinical studies have elaborated on the mechanistic process of GBS-induced chorioamnionitis and its impact on the fetal programming of chronic neuropsychiatric diseases. GBS inoculation in rodents demonstrated the following: (i) silent and self-limited placental infection, similar to human chorioamnionitis; (ii) placental expression of chemokines attracting polymorphonuclear (PMN) cells; (iii) in vitro cytokine production; (iv) PMN infiltration in the placenta (histologic hallmark of human chorioamnionitis), linked to neurobehavioral impairments like cerebral palsy and autism spectrum disorders (ASD); (v) upregulation of interleukin-1β (IL-1β) in the placenta and fetal blood, associated with higher ASD risk in humans; (vi) sex-specific effects, with higher IL-1β release and PMN recruitment in male placenta; (vii) male offspring exhibiting ASD-like traits, while female offspring displayed attention deficit and hyperactivity disorder (ADHD)-like traits; (viii) IL-1 and/or NF-kB blockade alleviate placental and fetal inflammation, as well as subsequent neurobehavioral impairments. These findings offer potential therapeutic avenues, including sex-adapted anti-inflammatory treatment (e.g., blocking IL-1; repurposing of FDA-approved IL-1 receptor antagonist (IL-1Ra) treatment). Blocking the IL-1 pathway offers therapeutic potential to alleviate chorioamnionitis-related disabilities, presenting an opportunity for a human phase II RCT that uses IL-1 blockade added to the classic antibiotic treatment of chorioamnionitis.

Clonal Complex 12 Serotype Ib Streptococcus agalactiae Strain Causing Complicated Sepsis in Neonates: Clinical Features and Genetic Characteristics

Streptococcus agalactiae (group B Streptococcus [GBS]) is well known to cause serious diseases in infants. A serotype Ib GBS strain has recently emerged and become prevalent in Southeast Asia. We aimed to investigate the clinical and genetic characteristics of this strain. All neonates with invasive GBS diseases from a tertiary-level medical center in Taiwan between 2003 and 2020 were analyzed. The capsule serotyping, multilocus sequence typing, and antimicrobial resistance analyses were performed on all the invasive GBS isolates, and whole-genome sequencing (WGS) was performed specifically on the type Ib GBS strain. A total of 188 neonates with invasive GBS disease during the study period were identified. The type Ib GBS strain accounted for 7.4% (n = 14) of neonatal GBS invasive diseases. Almost all type Ib GBS isolates belonged to sequence type 12 (13/14, 92.9%) and clonal complex 12. Neonates with type Ib GBS disease had a significantly higher rate of complicated sepsis (10/14, 71.4%; P < 0.05) and sepsis-attributable mortality (6/14, 42.9%; P < 0.05). Additionally, type Ib GBS isolates had significantly higher rates of resistance to erythromycin and clindamycin (both 100%; P < 0.05) than other GBS serotypes. WGS revealed the presence of an ~75-kb integrative and conjugative element, ICESag37, comprising multiple antibiotic resistance and virulence genes, and PI-1 plus PI-2a were noted in all type Ib serotype 12 (ST12) GBS isolates; these isolates may be responsible for its high invasiveness and antimicrobial resistance rates. The genomic characteristics of the type Ib clonal complex 12 (CC12) GBS strain may account for the high illness severity associated with this strain and its antibiotic resistance. Continuous monitoring and advanced strategies to control the spread of type Ib CC12 GBS should be considered. IMPORTANCE A type Ib ST12 GBS strain is not a common isolate in neonatal invasive diseases and has been ignored for a long time. However, the recent literature and our data showed that such a GBS strain is associated with a significantly higher risk of severe sepsis, higher illness severity, and a significantly higher rate of sepsis-attributable mortality. This study found a novel gene cluster, including the presence of ICESag37 and specific pilus genes, carrying multiple antimicrobial resistance and virulence genes, which may be responsible for the clinical characteristics. Because of the higher mortality and severity of illness, we concluded that continuous monitoring of the type Ib ST12 GBS strain is warranted in the future.

Genomic Analysis of Group B Streptococcus from Neonatal Sepsis Reveals Clonal CC17 Expansion and Virulence- and Resistance-Associated Traits After Intrapartum Antibiotic Prophylaxis

BACKGROUND

Group B Streptococcus (GBS) is a leading cause of invasive neonatal infections. This study aimed to investigate the trend of GBS serotype and genotype change and their correlation with antimicrobial resistance before and after implementation of intrapartum antibiotic prophylaxis (IAP).

METHODS

We performed serotyping, whole-genome sequencing, antimicrobial susceptibility testing, and single-nucleotide polymorphism (SNP)-based phylogenetic analysis on 238 invasive GBS isolates collected from October 1998 to February 2020 in Taiwan.

RESULTS

There were 7 serotypes and 6 clonal complexes (CCs) among the 238 GBS isolates, and more than half of the isolates carried multiple antimicrobial resistance genes. The expansion of CC17 strains and the increase in late-onset disease occurred synchronously after the implementation of IAP. Analysis of the carriage isolates from pregnant women showed diverse serotype distribution in the IAP era. The antimicrobial susceptibility testing showed that all 238 strains were susceptible to ampicillin and penicillin, while the number of various resistance genes in GBS genomes was found increased with the expansion of CC17. Compared with reference genomes, 697 nonsynonymous SNPs in 443 protein-coding genes were CC17 specific.

CONCLUSIONS

The study revealed the expansion of GBS CC17 and the increase of late-onset disease that occurred simultaneously with the implementation of IAP. Although the susceptibility of CC17 to antimicrobial agents is not different from that of other sequence types at present, GBS with phenotypic resistance to antimicrobials may emerge in the future, given the environmental selection pressure and the continued accumulation of SNP mutations.

Serotype Distribution, Virulence Determinants and Antimicrobial Susceptibility of Streptococcus agalactiae Isolated from Young Infants

Background: Streptococcus agalactiae (Group B Streptococcus, GBS) is the most common cause of serious infections in the first 3 months of life worldwide. The pathogenicity of GBS is closely related to serotypes, surface proteins and virulence factors, and the distribution of them may vary temporally and geographically. However, data related to GBS surface proteins and virulence determinants in China are very few. The aim of this study is to investigate the genetic characteristics of clinical GBS isolates from infected infants. Methods: We recovered GBS isolates from infected infants younger than 3 months during 2017−2021 at Maternal and Child Health Hospital of Hubei Province in China. We assessed the GBS serotypes, surface proteins, virulence determinants and antibiotic resistance genes distribution, by Multilocus sequence typing (MLST) and whole-genome sequencing analysis. Results: Among 97 isolates (81 EOD and 16 LOD), 5 serotypes were detected. Serotype III was the most represented (49.5%), followed by type Ib (20.6%). The isolates belonged to 17 different sequence types (STs) that grouped into the 8 clonal complexes (CCs). The most frequently identified ST was ST17 (23.7%). The most predominant surface protein of alpha-protein-like (alp) family (one of the protein components of the GBS surface antigen, resistant to trypsin) present was Rib (41.2%), which was mainly detected in serotype III. The srr1, which encodes Srr1 protein, was identified in 54.6% of isolates. The hvgA encoding for hypervirulent GBS adhesin can be detected in all 24 serotype III GBS. Among the pilus islands genes, 50% and 58.8% of the isolates were positive for pi-1 and pi-2a genes, respectively. The presence of pi-2b was mainly associated with serotype III/CC17 strains; 56.7% of isolates carried tetM, tetO/tetL, ermB antibiotic resistant genes. Among all the virulence genes detected, the cfb-cylE-lmb-pavA pattern was the main virulence gene profile (81.4%), mainly in serotype III/CC17. Conclusions: The whole genomic sequencing data revealed the high variation in surface proteins, determining virulence and antibiotic resistance in clinical isolates from 97 GBS infected infants. These data provide insightful characteristics of genetic features of GBS. Constant epidemiological surveillance is warranted to provide information on the GBS pathogenic dynamics and antibiotic resistance profiles in the surveyed areas for improving therapeutic outcomes.

Genomic Characterization of Serotype III/ST-17 Group B Streptococcus Strains with Antimicrobial Resistance Using Whole Genome Sequencing

Background: Antibiotic-resistant type III/ST-17 Streptococcus agalactiae (group B Streptococcus, GBS) strain is predominant in neonatal invasive GBS diseases. We aimed to investigate the antibiotic resistance profiles and genetic characteristics of type III/ST-17 GBS strains. Methods: A total of 681 non-duplicate GBS isolates were typed (MLST, capsular types) and their antibiotic resistances were performed. Several molecular methods (WGS, PCR, sequencing and sequence analysis) were used to determine the genetic context of antibiotic resistant genes and pili genes. Results: The antibiotic resistant rates were significantly higher in type Ib (90.1%) and type III (71.1%) GBS isolates. WGS revealed that the loss of PI-1 genes and absence of ISSag5 was found in antibiotic-resistant III/ST-17 GBS isolates, which is replaced by a ~75-kb integrative and conjugative element, ICESag37, comprising multiple antibiotic resistance and virulence genes. Among 190 serotype III GBS isolates, the most common pilus island was PI-2b (58.4%) alone, which was found in 81.3% of the III/ST-17 GBS isolates. Loss of PI-1 and ISSag5 was significantly associated with antibiotic resistance (95.5% vs. 27.8%, p < 0.001). The presence of ICESag37 was found in 83.6% of all III/ST-17 GBS isolates and 99.1% (105/106) of the antibiotic-resistant III/ST-17 GBS isolates. Conclusions: Loss of PI-1 and ISSag5, which is replaced by ICESag37 carrying multiple antibiotic resistance genes, accounts for the high antibiotic resistance rate in III/ST-17 GBS isolates. The emerging clonal expansion of this hypervirulent strain with antibiotic resistance after acquisition of ICESag37 highlights the urgent need for continuous surveillance of GBS infections.

Genomic insights on DNase production in Streptococcus agalactiae ST17 and ST19 strains

Streptococcus agalactiae evasion from the human defense mechanisms has been linked to the production of DNases. These were proposed to contribute to the hypervirulence of S. agalactiae ST17/capsular-type III strains, mostly associated with neonatal meningitis. We performed a comparative genomic analysis between ST17 and ST19 human strains with different cell tropism and distinct DNase production phenotypes. All S. agalactiae ST17 strains, with the exception of 2211-04, were found to display DNase activity, while the opposite scenario was observed for ST19, where 1203-05 was the only DNase(+) strain. The analysis of the genetic variability of the seven genes putatively encoding secreted DNases in S. agalactiae revealed an exclusive amino acid change in the predicted signal peptide of GBS0661 (NucA) of the ST17 DNase(-), and an exclusive amino acid change alteration in GBS0609 of the ST19 DNase(+) strain. Further core-genome analysis identified some specificities (SNVs or indels) differentiating the DNase(-) ST17 2211-04 and the DNase(+) ST19 1203-05 from the remaining strains of each ST. The pan-genomic analysis evidenced an intact phage without homology in S. agalactiae and a transposon homologous to TnGBS2.3 in ST17 DNase(-) 2211-04; the transposon was also found in one ST17 DNase(+) strain, yet with a different site of insertion. A group of nine accessory genes were identified among all ST17 DNase(+) strains, including the Eco47II family restriction endonuclease and the C-5 cytosine-specific DNA methylase. None of these loci was found in any DNase(-) strain, which may suggest that these proteins might contribute to the lack of DNase activity. In summary, we provide novel insights on the genetic diversity between DNase(+) and DNase(-) strains, and identified genetic traits, namely specific mutations affecting predicted DNases (NucA and GBS0609) and differences in the accessory genome, that need further investigation as they may justify distinct DNase-related virulence phenotypes in S. agalactiae.

Pathogenic mechanism, detection methods and clinical significance of group B Streptococcus

Group B Streptococcus (GBS) is the main pathogen of perinatal infection. It can lead to adverse pregnancy, maternal infection, premature delivery, abortion, stillbirth and a series of adverse maternal and infant outcomes such as neonatal sepsis, meningitis or pneumonia during delivery. In order to reduce the infection of perinatal pregnant and the adverse pregnancy outcome, more attention should be paid in the clinical practice, screening efforts, universal detection of GBS infection for pregnant women and preventive treatment for the possible mother infant infection. In this study, the biological characteristics, immunophenotype, major pathogenic mechanism, laboratory test methods and clinical significance of GBS are summarized.

Prevalence, population structure, distribution of serotypes, pilus islands and resistance genes among erythromycin-resistant colonizing and invasive Streptococcus agalactiae isolates recovered from pregnant and non-pregnant women in Isfahan, Iran

Background

The information on antibiotic resistance and molecular features of Group B Streptococcus (GBS) are essential for epidemiological purposes as well as vaccine development. Therefore, we aimed to assess the antimicrobial resistance profiles and molecular characteristics of GBS isolates in Isfahan, Iran. A total number of 72 colonizing and invasive GBS were collected from pregnant and non-pregnant women. The GBS isolates were analyzed for resistance profiles, capsular genotyping, and detection of PI-1, PI-2a, PI-2b, hvgA, ermB, ermTR, lnuB and, mefA genes. Besides, erythromycin-resistant strains were subjected to multilocus sequence typing (MLST).

Results

The prevalence of colonizing and invasive GBS were 11 and 0.05%, respectively. The frequency of capsular serotypes was as follows: III (26.3%), Ia (20.83%), Ib and V (each 15.2%), IV (9.7%), II (8.3%), VII (2.7%), and VI (1.3%). Overall frequencies of PIs were as follows: PI-1, 37.5%, PI-1 + PI-2a, 30.5%, PI-1 + PI-2b, 29.1% and PI-2b, 2.7%. Two maternal colonizing GBS (2.6%) were hvgA positive and were belonged to ST-17/CPS-III/PI-1 + PI-2b lineage. Among 30(41.6%) erythromycin resistant GBS, 21 isolates (70%) harbored ermB gene, followed by ermTR (23.3%) and mefA (10%). One clindamycin-resistant isolate harbored the lnuB gene. MLST analysis revealed the following five clonal complexes (CCs) and nine STs: (CC-19/ST-335, ST-19, and ST-197), (CC-12/ST-43, ST-12), (CC-23/ST-163, ST-23), (CC-17/ST-17) and (CC-4/ST-16).

Conclusion

The study shows an alarmingly high prevalence of erythromycin-resistant GBS in Iran. In addition, we report dissemination of ST-335/CPS-III clone associated with tetracycline and erythromycin resistance in our region. The distribution of capsular and pilus genotypes varies between invasive and colonizing GBS that could be helpful for vaccine development.

Streptococcus agalactiae strains isolated from cancer patients in Rio de Janeiro, Brazil

Streptococcus agalactiae is a recognized pathogen associated with infections in neonates, elderly, and immunocompromised adults, particularly those with cancer. In the present investigation, clinical-epidemiological features, multidrug resistance profiles, and virulence genes of S. agalactiae strains isolated from cancer patients were investigated. S. agalactiae capsular distribution assays demonstrated that Ia (43.6%) and V (23.6%) types were predominantly detected among 55 clinical isolates tested; only one strain (GBS1428) was capsular type III/ST-17. The fbsB and hylB genes were detected in all isolates, while the iag, lmb, and fbsA genes were detected in 94.5%, 91%, and 91% of oncological isolates, respectively. The combination of PI-1 and PI-2a was the most common (60%) among S. agalactiae strains isolated from oncologic patients. S. agalactiae strains were resistant to tetracycline (85.5%), erythromycin (9%), and clindamycin (5.5%). Norfloxacin non-susceptible was detected in 7.3% of S. agalactiae strains. Our findings reinforce the need for S. agalactiae control measures in Brazil, including cancer patients.

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

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Most comprehensive review of Group B Streptococcal serotypes through 2018.

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

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

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

Background

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

Methods

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

Results

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

Discussion

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

Molecular characterization of pathogenic group B streptococcus from a tertiary hospital in Shanxi, China: High incidence of sequence type 10 strains in infants/pregnant women

BACKGROUND

Group B streptococcus (GBS) is a leading cause of serious infection in infants. Understanding its regional molecular epidemiology is helpful for regulating efficient prevention practice.

METHODS

A retrospective study was conducted to collected data from infants and pregnant women with culture-proven GBS disease in the largest women and children's medical center in Shanxi between January 2017 and September 2019. All GBS isolates were analyzed by multi-locus sequence typing (MLST) as well as distribution of pilus island (PI) genes.

RESULTS

A total of 54 GBS isolates were obtained from 36 (66.7%) pregnant women and 18 (33.3%) infants with invasive disease. Among invasive GBS strains, the most common sequence type was ST10 (72.2%, P < 0.05), followed by ST23 and ST19. The ST10 strain was also the leading sequence type in colonizing pregnant women (44.4%, P < 0.05). All of the isolates carried at least one pilus island. The most frequently detected pilus island was PI-1+PI-2a (85.2%, P < 0.05), followed in turn by PI-2a and PI-2b.

CONCLUSIONS

Our study demonstrates that one hypervirulent clone, sequence type 10, accounts for a large proportion of invasive GBS disease in infants and colonizing pregnant women, and the PI-1+PI-2a sub-lineages should be noted in infant infections.

Epidemiology of group B streptococcal infection in pregnant women and diseased infants in mainland China

Group B Streptococcus (GBS) is a leading cause of neonatal sepsis and an important cause of maternal disease in many countries; however, no accurate population-based epidemiological data on GBS is yet available in mainland China. In this systematic literature review, we obtained published data regarding the maternal GBS colonization rate, incidence of invasive GBS disease in infants, clinical screening, and the associated GBS typing and clinical outcomes in China. The maternal GBS colonization rate in mainland China ranged from 3.7 to 14.52%, and the incidence of invasive GBS disease in infants was 0.55-1.79 per 1000 live births, with a case fatality risk ranging from 6.45 to 7.1%. Serotype III was the dominant serotype that was observed in GBS isolates. GBS detection and identification has become more commonplace, due to the availability of polymerase chain reaction and DNA microarray technologies. Immunizing pregnant women against GBS is an emerging approach through which newborns are protected from GBS. The available data suggest that five GBS serotypes (Ia, Ib, II, III, and V) account for the majority of the cases of GBS disease in mainland China. Furthermore, conjugate vaccines comprising some or all of these serotypes are of potential value in the prevention of GBS infection.

Sex-specific maternofetal innate immune responses triggered by group B Streptococci

Group B Streptococcus (GBS) is one of the most common bacteria isolated in human chorioamnionitis, which is a major risk factor for premature birth and brain injuries. Males are at greater risk than females for developing lifelong neurobehavioural disorders, although the origins of this sex bias remain poorly understood. We previously showed that end-gestational inflammation triggered by GBS led to early neurodevelopmental impairments mainly in the male rat progeny. Identifying key inflammatory players involved in maternofetal immune activation by specific pathogens is critical to develop appropriate novel therapeutic interventions. We aimed to map out the GBS-induced profile of innate immune biomarkers in the maternal-placental-fetal axis, and to compare this immune profile between male and female tissues. We describe here that the GBS-induced immune signalling involved significantly higher levels of interleukin (IL)-1β, cytokine-induced neutrophil chemoattractant-1 (CINC-1/CXCL1) and polymorphonuclear cells (PMNs) infiltration in male compared to female maternofetal tissues. Although male - but not female - fetuses presented increased levels of IL-1β, fetuses from both sexes in-utero exposed to GBS had increased levels of TNF-α in their circulation. Levels of IL-1β detected in fetal sera correlated positively with the levels found in maternal circulation. Here, we report for the first time that the maternofetal innate immune signalling induced by GBS presents a sexually dichotomous profile, with more prominent inflammation in males than females. These sex-specific placental and fetal pro-inflammatory responses are in keeping with the higher susceptibility of the male population for preterm birth, brain injuries and neurodevelopmental disorders such as cerebral palsy and autism spectrum disorders.

Causal role of group B Streptococcus-induced acute chorioamnionitis in intrauterine growth retardation and cerebral palsy-like impairments

Chorioamnionitis and intrauterine growth retardation (IUGR) are risk factors for cerebral palsy (CP). Common bacteria isolated in chorioamnionitis include group B Streptococcus (GBS) serotypes Ia and III. Little is known about the impact of placental inflammation induced by different bacteria, including different GBS strains. We aimed to test the impact of chorioamnionitis induced by two common GBS serotypes (GBSIa and GBSIII) on growth and neuromotor outcomes in the progeny. Dams were exposed at the end of gestation to either saline, inactivated GBSIa or GBSIII. Inactivated GBS bacteria invaded placentas and triggered a chorioamnionitis featured by massive polymorphonuclear cell infiltrations. Offspring exposed to GBSIII - but not to GBSIa - developed IUGR, persisting beyond adolescent age. Male rats in utero exposed to GBSIII traveled a lower distance in the Open Field test, which was correlating with their level of IUGR. GBSIII-exposed rats presented decreased startle responses to acoustic stimuli beyond adolescent age. GBS-exposed rats displayed a dysmyelinated white matter in the corpus callosum adjacent to thinner primary motor cortices. A decreased density of microglial cells was detected in the mature corpus callosum of GBSIII-exposed males - but not females - which was correlating positively with the primary motor cortex thickness. Altogether, our results demonstrate a causal link between pathogen-induced acute chorioamnionitis and (1) IUGR, (2) serotype- and sex-specific neuromotor impairments and (3) abnormal development of primary motor cortices, dysmyelinated white matter and decreased density of microglial cells.