Group B streptococcus prevalence, serotype distribution and colonization dynamics in Western Australian pregnant women

Group B streptococcal infections in pregnancy and early life

SUMMARYBacterial infections with Group B Streptococcus (GBS) are an important cause of adverse outcomes in pregnant individuals, neonates, and infants. GBS is a common commensal in the genitourinary and gastrointestinal tracts and can be detected in the vagina of approximately 20% of women globally. GBS can infect the fetus either during pregnancy or vaginal delivery resulting in preterm birth, stillbirth, or early-onset neonatal disease (EOD) in the first week of life. The mother can also become infected with GBS leading to postpartum endometritis, and rarely, maternal sepsis. An invasive GBS infection of the neonate may present after the first week of life (late-onset disease, LOD) through transmission from caregivers, breast milk, and other sources. Invasive GBS infections in neonates can result in sepsis, pneumonia, meningitis, neurodevelopmental impairment, death, and lifelong disability. A policy of routine screening for GBS rectovaginal colonization in well-resourced countries can trigger the administration of intrapartum antibiotic prophylaxis (IAP) when prenatal testing is positive, which drastically reduces rates of EOD. However, many countries do not routinely screen pregnant women for GBS colonization but may administer IAP in cases with a high risk of EOD. IAP does not reduce rates of LOD. A global vaccination campaign is needed to reduce the significant burden of invasive GBS disease that remains among infants and pregnant individuals. In this narrative review, we provide a comprehensive overview of the global impact of GBS colonization and infection, virulence factors and pathogenesis, and current and future prophylactics and therapeutics.

Distribution of group B streptococci serotypes on women nasopharynx

Group B Streptococcus (GBS) is a significant pathogen responsible for neonatal infections, primarily transmitted through maternal carriage. However, current preventive strategies, such as intrapartum antibiotic prophylaxis, present limitations and are ineffective in preventing late-onset neonatal infections. This study aimed to assess the prevalence and serotype distribution of GBS in the nasopharynx of women of reproductive age, providing data to the potential implementation of a novel hexavalent capsular vaccine (GBS6). Nasopharyngeal swabs were collected from 500 women and analyzed using a qPCR assay targeting the cfb gene to detect GBS and the cps locus. GBS was identified in 7.4 % of patients, with serotype Ia being the most prevalent. Other serotypes detected included II, V, Ib, III, and IV. These findings suggest that the nasopharynx may act as a reservoir for GBS in women of reproductive age. The results also highlight the importance of developing preventive strategies focused on upper respiratory tract colonization. Additionally, the potential introduction of the GBS6 vaccine could provide significant coverage against circulating GBS serotypes.

Gestational diabetes as a risk factor for GBS maternal rectovaginal colonization: a systematic review and meta-analysis

BACKGROUND

Maternal rectovaginal colonization by group B Streptococcus (GBS) increases the risk of perinatal GBS disease that can lead to death or long-term neurological impairment. Factors that increase the risk of rectovaginal GBS carriage are incompletely understood resulting in missed opportunities for detecting GBS in risk-based clinical approaches. There is a lacking consensus on whether gestational diabetes mellitus (GDM) is a risk factor for rectovaginal GBS. This systematic review and meta-analysis aims to address current conflicting findings and determine whether GDM should be clinically considered as a risk factor for maternal GBS colonization.

METHODS

Peer-reviewed studies that provided GDM prevalence and documented GBS vaginal and/or rectal colonization in women with and without GDM were included in this analysis. From study inception to October 30, 2023, we identified 6,275 relevant studies from EMBASE and PUBMED of which 19 were eligible for inclusion. Eligible studies were analyzed and thoroughly assessed for risk of bias with a modified Newcastle-Ottawa Scale that interrogated representativeness and comparability of cohorts, quality of reporting for GDM and GBS status, and potential bias from other metabolic diseases. Results were synthesized using STATA 18 and analyzed using random-effects meta-analyses.

RESULTS

Studies encompassed 266,706 women from 10 different countries, with study periods spanning from 1981 to 2020. Meta-analysis revealed that gestational diabetes is associated with a 16% increased risk of rectovaginal GBS carriage (OR 1.16, CI 1.07-1.26, P = 0.003). We also performed subgroup analyses to assess independent effects of pregestational vs. gestational diabetes on risk of maternal GBS carriage. Pregestational diabetes (Type 1 or Type 2 diabetes mellitus) was also associated with an increased risk of 76% (pooled OR 1.76, CI 1.27-2.45, P = 0.0008).

CONCLUSIONS

This study achieved a consensus among previously discrepant observations and demonstrated that gestational diabetes and pregestational diabetes are significant risk factors for maternal rectovaginal carriage of GBS. Recognition of GDM as a risk factor during clinical decisions about GBS screening and intrapartum antibiotic prophylaxis may decrease the global burden of GBS on maternal-perinatal health.

Characterization of invasive Group B Streptococcus isolates from Western Australian infants, 2004-2020

Background. Invasive Group B Streptococcus (GBS; Streptococcus agalactiae) remains a leading cause of infant morbidity and mortality. Intrapartum antibiotic prophylaxis (IAP) has been implemented in many countries with a reduction in early-onset disease, but an effective vaccine may further reduce the disease burden. Candidate vaccines targeting capsular polysaccharides and surface proteins are now in clinical trials.Methods. Using whole-genome sequencing and phenotypic antimicrobial susceptibility testing, we characterized sterile-site GBS isolates recovered from Western Australian infants between 2004 and 2020. Characteristics were compared between three time periods: 2004-2008, 2009-2015 and 2016-2020.Results. A total of 135 isolates were identified. The proportion of serotype III (22.7 % in Period 1 to 47.9 % in Period 3, P=0.04) and clonal complex 17 (13.6-39.6 %, P=0.01) isolates increased over time. Overall coverage of vaccines currently being trialled was >95 %. No isolates were penicillin resistant (MIC>0.25 mg l-1), but 21.5 % of isolates had reduced penicillin susceptibility (MIC>0.12 mg l-1) and penicillin MIC increased significantly over time (P=0.04). Clindamycin resistance increased over time to 45.8 % in the latest period.Conclusions. Based on comprehensive characterization of invasive infant GBS in Western Australia, we found that coverage for leading capsular polysaccharide and surface protein vaccine candidates was high. The demonstrated changes in serotype and molecular type highlight the need for ongoing surveillance, particularly with regard to future GBS vaccination programmes. The reduced susceptibility to IAP agents over time should inform changes to antibiotic guidelines.

Clinical Characteristics and Treatment Strategies for Group B Streptococcus (GBS) Infection in Pediatrics: A Systematic Review

Background and Objectives: Group B streptococcus (GBS) is the leading cause of infections in neonates with high fatality rates. GBS is caused by the streptococcus bacterium known as streptococcus agalactiae, which is highly contagious and can be transmitted from pregnant women to infants. GBS infection can occur as an early onset or late-onset infection and has different treatment strategies. Antibiotics are effective in treating GBS infections at early stages. The aim of this systematic review was to summarize the clinical characteristics and treatment strategies for GBS, with a focus on antibiotics. Material and Methods: The findings of this review were reported in accordance with the PRISMA 2020 guidelines and a flow diagram of the study selection process, a summary of the included studies, a description of the study characteristics, a summary of the results, a discussion of the implications of the findings, and a conclusion are included. Overall, the authors followed a rigorous methodology to ensure that this review is comprehensive and inclusive of relevant studies on GBS infection and its treatment. Results: Overall, 940 studies were reviewed and only the most relevant 22 studies were included in the systematic review. This review describes the characteristics of patients in different studies related to early onset GBS disease and presents various treatment strategies and outcomes for GBS infection in pediatrics. The studies suggest that preventive measures, risk-based intrapartum antibiotic prophylaxis, and maternal vaccination can significantly reduce the burden of GBS disease, but late-onset GBS disease remains a concern, and more strategies are required to decrease its rate. Improvement is needed in the management of the risk factors of GBS. A conjugate vaccine with a serotype (Ia, Ib, II, III, and V) has been proven effective in the prevention of GBS in neonates. Moreover, penicillin is an important core antibiotic for treating early onset GBS (EOD). Conclusions: This systematic review summarizes the treatment comparison for GBS infections in neonates, with a primary focus on antibiotics. IAP (intrapartum antibiotic prophylaxis) according to guidelines, antenatal screening, and the development of a conjugate vaccine may be effective and could lower the incidence of the disease.

Distribution and Prevalence of Serotypes of Group B Streptococcus Isolated from Pregnant Women in 30 Countries: A Systematic Review

Objective

This review aimed to compile scientific data on the distribution and prevalence of group B Streptococcus (GBS) serotypes isolated from pregnant women across 30 countries from 2010 to 2019.

Methods

This was a systematic review that addresses the distribution and prevalence of GBS in pregnant women. The search included studies published between January 2010 and December 2019 in PubMed, Virtual Health Library (BVS), ScienceDirect, Scientific Electronic Library Online (SciELO), and LILACS databases. We also surveyed relevant articles published in English, Spanish, and Portuguese between February and April 2020. Original articles, communication, short report, theses, and dissertations were included. The prevalence of GBS colonization, method for capsular serotyping, antimicrobial resistance, distribution and prevalence of serotypes were extracted from each study.

Results

In all, 795 publications were identified. After applying the eligibility criteria, 48 articles were included for the final systematic analysis; most articles were from Asia and were published during the years 2014 to 2017. For the identification of serotypes, most studies used the polymerase chain reaction technique. There were records of all 10 GBS serotypes, namely, Ia, Ib, and II-IX, among the countries analyzed. GBS susceptibility and resistance to antibiotics were addressed in 37.5% of the publications analysed.

Conclusion

This review showed that GBS serotypes are distributed differently in the 30 analyzed countries, with serotypes Ia, Ib, and II to V being the most prevalent. Furthermore, our results highlighted the relationship of GBS with maternal colonization, implications for neonates, and antibiotic resistance.

Simultaneous carriage of multiple serotypes of Group B Streptococcus: Systematic review and meta-analysis

BACKGROUND

Epidemiological studies evaluating the distribution of Group B Streptococcus (GBS) serotypes are crucial for serotype-specific vaccine development and post-licensure surveillance. However, there is a paucity of data about the prevalence of simultaneous carriage of multiple serotypes.

METHODS

We conducted a systematic review of three databases (Medline, Embase, PubMed) to identify studies reporting GBS serotype co-carriage at the same anatomical site (multiple serotypes in one sample) or different anatomical sites (paired samples from one individual with different serotypes). We conducted a random-effects meta-analysis to evaluate the prevalence of co-carriage.

RESULTS

18 articles met the inclusion criteria, representing at least 12,968 samples from 14 countries. In a random-effects meta-analysis, we identified that 10 % (95 % CI: 4-19) of the positive samples taken from one anatomical site have more than one serotype, and 11 % (95 % CI: 5-20) of positive participants with samples taken from two anatomical sites carried different serotypes. When reported, the number of serotypes simultaneously carried ranged from 1 to 4. The serotypes most often associated with co-carriage are III (20.3 %), V (20.3 %) and Ia (19.5 %).

CONCLUSION

This systematic review demonstrates that co-carriage is a minor but definite phenomenon, but the data are too limited to give a precise picture of the current epidemiology. Co-colonisation detection needs to be taken into consideration in the design and methods of future GBS carriage surveillance studies to estimate and evaluate the potential for serotype replacement once vaccines are introduced.

Epidemiology, Antimicrobial Resistance, and Virulence Determinants of Group B Streptococcus in an Australian Setting

Streptococcus agalactiae [group B Streptococcus (GBS)] is a major neonatal pathogen and also causes invasive disease in non-pregnant adults. One hundred GBS isolates (n = 50 invasive disease and n = 50 colonizing pregnant women) were characterized using capsular serotyping by latex agglutination, antimicrobial susceptibility testing, and whole genome sequencing (WGS). All isolates were susceptible to penicillin, 32% were resistant to clindamycin. Of these, two isolates had reduced susceptibility to ceftriaxone (MIC 0.75 mg/L) and were found to have unique alleles at pbp2X and pbp1A. Capsular serotypes Ia (18%), III (18%), Ib (14%), V (12%), and VI (11%) were most common and comparison of latex agglutination and capsular genotyping by WGS showed 71% agreement. Less common capsular genotypes VI-VIII represented 15% of isolates, indicating that a significant proportion may not be targeted by the proposed pentavalent or hexavalent vaccines under development. WGS is a useful aid in GBS surveillance and shows correlation to phenotypic serotyping and antimicrobial susceptibility data.

Colonization of Streptococcus agalactiae among pregnant patients in Trinidad and Tobago

Objective

To assess colonization of Streptococcus agalactiae [group B streptococcus (GBS)], and delineate capsular serotype distribution and antibiotic susceptibility profiles among pregnant women in Trinidad and Tobago.

Methods

Vaginal swabs were collected from 248 pregnant women attending antenatal clinics in northern Trinidad, and processed using standard microbiological laboratory tests to confirm GBS. Polymerase chain reaction detected atr and cps serotype genes. Antimicrobial susceptibility tests were performed using the Kirby-Bauer method, and SPSS Version 25 was used for statistical analysis. Prevalence ratio measured the risk, and P≤0.05 was considered to indicate significance.

Results

The GBS carriage rate was 29% (72/248, 95% confidence interval 23.3-34.8), and carriage was significantly associated with variables including gestational diabetes (P=0.042), age 25-35 years (P=0.006), multiparity (P=0.035) and marital status (P=0.006). The most common serotype was type II [47.2% (34/72)], and serotypes V, VI, VII and VIII were not encountered. GBS showed high resistance to amoxicillin-clavulanic acid (37.5%), erythromycin (30.6%), trimethoprim-sulphamethoxazole (58.3%) and tetracycline (97.2%).

Conclusion

GBS colonization among pregnant women and resistance to commonly used antibiotics are high in Trinidad and Tobago. A population-based study is required to obtain accurate figures in order to improve maternal healthcare services.

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.

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

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

Establishment of the early-life microbiome: a DOHaD perspective

The human microbiome plays a number of critical roles in host physiology. Evidence from longitudinal cohort studies and animal models strongly supports the theory that maldevelopment of the microbiome in early life can programme later-life disease. The early-life microbiome develops in a clear stepwise manner over the first 3 years of life. During this highly dynamic time, insults such as antibiotic use and formula feeding can adversely affect the composition and temporal development of the microbiome. Such experiences predispose infants for the development of chronic health conditions later in life. This review highlights key factors that disrupt the early-life microbiome and highlights major non-communicable diseases which are underpinned by early-life dysbiosis.

Genomic characterisation of perinatal Western Australian Streptococcus agalactiae isolates

As a leading cause of neonatal sepsis, Streptococcus agalactiae, commonly known as Group B Streptococcus, is a major neonatal pathogen. Current global screening practices employ risk- or culture-based protocols for detection of these organisms. In Western Australia (WA), universal culture-based screening is provided, with subsequent intrapartum antibiotic prophylaxis for all S. agalactiae-positive women during labour. Widespread antibiotic exposure is not ideal and this is one of the factors driving development of vaccines against S. agalactiae. Vaccine candidates have focused on the capsule, surface proteins and pilus types, however, capsule serotypes are known to vary geographically. The aim of this study was to use genome sequencing to gain an understanding of the circulating genotypes in WA, and to assess variations in the associated gene pools. We sequenced 141 antenatal carriage (vaginal/rectal) isolates and 10 neonatal invasive disease isolates from WA. Based on the global PubMLST database, the 151 strains were characterised into 30 sequence types, with clustering of these mainly into clonal complexes 1, 12, 17, 19 and 23. Of the genes encoding eleven surface proteins that were analysed, the most prevalent were fbp, lmb and scpB which were present in ≥ 98% of isolates. A cluster of non-haemolytic isolates, one of which was a neonatal invasive disease isolate, appeared to lack the entire cyl locus. Admixture analysis of population structure revealed evidence of genetic transfer among the WA isolates across structural groups. When compared against the PubMLST S. agalactiae data, WA isolates showed high levels of strain diversity with minimal apparent clustering. This is the first whole genome sequence study of WA S. agalactiae isolates and also represents the first addition of Australian isolate data to PubMLST. This report provides insight into the distribution and diversity of vaccine targets of S. agalactiae within Western Australia, indicating that the most appropriate capsular vaccine for this population would be the proposed pentavalent (Cps Ia, Ib, II, III and V) preparation, whilst vaccines targeting surface proteins should ideally utilise Fbp, Lmb and/or ScpB.