Severe sepsis in women with group B Streptococcus in pregnancy: an exploratory UK national case-control study

Group B Streptococcus Infection and Obstetric Hemorrhage Risk

OBJECTIVE

To elucidate the association between GBS infection and maternal risk for obstetric hemorrhage (OBH) and OBH-related morbidities (OBH-M).

METHODS

This was a retrospective cohort study of all deliveries with a documented GBS status at a single large academic medical center from 2018 to 2019. GBS status was determined by either urine culture or rectovaginal culture collected during the antepartum period. The primary outcomes were quantitative blood loss (QBL), OBH, and a composite of OBH-M. Secondary outcomes were individual components of the OBH-M composite and frequency of hemorrhage-related interventions utilized intrapartum and postpartum. A stratified analysis was conducted examining only patients who were diagnosed intrapartum with an intrapartum intraamniotic infection (III).

RESULTS

Of 4679 pregnant individuals who delivered a live infant between January 1, 2018 and January 1,2019 with a documented GBS status, 1,487 were identified as GBS positive (+) and 3192 were identified as GBS negative (-). The GBS + group did not have significantly higher QBL (p = 0.29) or rate of OBH (p = 0.35). There were no significant differences by GBS status in OBH morbidity (p = 0.79) or its individual components or frequency of individual pharmacologic or non-pharmacologic OBHrelated interventions. There were also no significant differences by GBS status among patients with an III.

CONCLUSIONS FOR PRACTICE

GBS infection at the time of delivery was not associated with increased risk for OBH or OBH-M. Further research is needed to further explore the relationship between peripartum infections and OBH risk.

Rapid systematic review on risks and outcomes of sepsis: the influence of risk factors associated with health inequalities

BACKGROUND AND AIMS

Sepsis is a serious and life-threatening condition caused by a dysregulated immune response to an infection. Recent guidance issued in the UK gave recommendations around recognition and antibiotic treatment of sepsis, but did not consider factors relating to health inequalities. The aim of this study was to summarise the literature investigating associations between health inequalities and sepsis.

METHODS

Searches were conducted in Embase for peer-reviewed articles published since 2010 that included sepsis in combination with one of the following five areas: socioeconomic status, race/ethnicity, community factors, medical needs and pregnancy/maternity.

RESULTS

Five searches identified 1,402 studies, with 50 unique studies included in the review after screening (13 sociodemographic, 14 race/ethnicity, 3 community, 3 care/medical needs and 20 pregnancy/maternity; 3 papers examined multiple health inequalities). Most of the studies were conducted in the USA (31/50), with only four studies using UK data (all pregnancy related). Socioeconomic factors associated with increased sepsis incidence included lower socioeconomic status, unemployment and lower education level, although findings were not consistent across studies. For ethnicity, mixed results were reported. Living in a medically underserved area or being resident in a nursing home increased risk of sepsis. Mortality rates after sepsis were found to be higher in people living in rural areas or in those discharged to skilled nursing facilities while associations with ethnicity were mixed. Complications during delivery, caesarean-section delivery, increased deprivation and black and other ethnic minority race were associated with post-partum sepsis.

CONCLUSION

There are clear correlations between sepsis morbidity and mortality and the presence of factors associated with health inequalities. To inform local guidance and drive public health measures, there is a need for studies conducted across more diverse setting and countries.

Maternal sepsis and factors associated with poor maternal outcomes in a tertiary hospital in Tigray, Ethiopia: a retrospective chart review

BACKGROUND

Maternal sepsis is the third leading cause of maternal death in the world. Women in resource-limited countries shoulder most of the burdens related to sepsis. Despite the growing risk associated with maternal sepsis, there are limited studies that have tried to assess the impact of maternal sepsis in resource-limited countries. The current study determined the outcomes of maternal sepsis and factors associated with having poor maternal outcomes.

METHODS

A facility-based retrospective cross-sectional study design was employed to assess the clinical presentation, maternal outcomes, and factors associated with maternal sepsis. The study was conducted in Ayder Comprehensive Specialized Hospital, Tigray, Ethiopia, from January 1, 2017, to December 31, 2021. Sociodemographic characteristics, clinical characteristics and outcomes of women with maternal sepsis were analyzed using a descriptive statistic. The association between dependent and independent variables was determined using multivariate logistic regression.

RESULTS

Among 27,350 live births, 298 mothers developed sepsis, giving a rate of 109 maternal sepsis for every 10,000 live births. There were 22 maternal deaths, giving rise to a case fatality rate of 7.4% and a maternal mortality ratio of 75 per 100,000 live births. Admission to the intensive care unit and use of mechanical ventilator were observed in 23.5% and 14.1% of the study participants, respectively. A fourth (24.2%) of the mothers were complicated with septic shock. Overall, 24.2% of women with maternal sepsis had severe maternal outcomes (SMO). Prolonged hospital stay, having parity of two and above, having the lung as the focus of infection, switchof antibiotics, and developing septic shock were significantly associated with SMO.

CONCLUSIONS

This study revealed that maternal sepsis continues to cause significant morbidity and mortality in resource-limited settings; with a significant number of women experiencing death, intensive care unit admission, and intubation attributable to sepsis. The unavailability of recommended diagnostic modalities and management options has led to the grave outcomes observed in this study. To ward off the effects of infection during pregnancy, labor and postpartum period and to prevent progression to sepsis and septic shock in low-income countries, we recommend that concerted and meticulous efforts should be applied to build the diagnostic capacity of health facilities, to have effective infection prevention and control practice, and to avail recommended diagnostic and management options.

Functional Insights into the High-Molecular-Mass Penicillin-Binding Proteins of Streptococcus agalactiae Revealed by Gene Deletion and Transposon Mutagenesis Analysis

High-molecular-mass penicillin-binding proteins (PBPs) are enzymes that catalyze the biosynthesis of bacterial cell wall peptidoglycan. The Gram-positive bacterial pathogen Streptococcus agalactiae (group B streptococcus [GBS]) produces five high-molecular-mass PBPs, namely, PBP1A, PBP1B, PBP2A, PBP2B, and PBP2X. Among these, only PBP2X is essential for cell viability, whereas the other four PBPs are individually dispensable. The biological function of the four nonessential PBPs is poorly characterized in GBS. We deleted the pbp1a, pbp1b, pbp2a, and pbp2b genes individually from a genetically well-characterized serotype V GBS strain and studied the phenotypes of the four isogenic mutant strains. Compared to the wild-type parental strain, (i) none of the pbp isogenic mutant strains had a significant growth defect in Todd-Hewitt broth supplemented with 0.2% yeast extract (THY) rich medium, (ii) isogenic mutant Δpbp1a and Δpbp1b strains had significantly increased susceptibility to penicillin and ampicillin, and (iii) isogenic mutant Δpbp1a and Δpbp2b strains had significantly longer chain lengths. Using saturated transposon mutagenesis and transposon insertion site sequencing, we determined the genes essential for the viability of the wild-type GBS strain and each of the four isogenic pbp deletion mutant strains in THY rich medium. The pbp1a gene is essential for cell viability in the pbp2b deletion background. Reciprocally, pbp2b is essential in the pbp1a deletion background. Moreover, the gene encoding RodA, a peptidoglycan polymerase that works in conjunction with PBP2B, is also essential in the pbp1a deletion background. Together, our results suggest functional overlap between PBP1A and the PBP2B-RodA complex in GBS cell wall peptidoglycan biosynthesis. IMPORTANCE High-molecular-mass penicillin-binding proteins (HMM PBPs) are enzymes required for bacterial cell wall biosynthesis. Bacterial pathogen group B streptococcus (GBS) produces five distinct HMM PBPs. The biological functions of these proteins are not well characterized in GBS. In this study, we performed a comprehensive deletion analysis of genes encoding HMM PBPs in GBS. We found that deleting certain PBP-encoding genes altered bacterial susceptibility to beta-lactam antibiotics, cell morphology, and the essentiality of other enzymes involved in cell wall peptidoglycan synthesis. The results of our study shed new light on the biological functions of PBPs in GBS.

Assessing the added value of group B Streptococcus maternal immunisation in preventing maternal infection and fetal harm: population surveillance study

OBJECTIVE

To assess the incidence of maternal group B Streptococcus (GBS) infection in England.

DESIGN

Population surveillance augmented through data linkage.

SETTING

England.

POPULATION

All pregnant women accessing the National Health Service (NHS) in England.

METHODS

Invasive GBS (iGBS) infections during pregnancy or within 6 weeks of childbirth were identified by linking Public Health England (PHE) national microbiology surveillance data for 2014 to NHS hospital admission records. Capsular serotypes of GBS were determined by reference laboratory typing of clinical isolates from women aged 15-44 years. Post-caesarean section surgical site infection (SSI) caused by GBS was identified in 21 hospitals participating in PHE SSI surveillance (2009-2015).

MAIN OUTCOME MEASURES

iGBS rate per 1000 maternities; risk of GBS SSI per 1000 caesarean sections.

RESULTS

Of 1601 patients diagnosed with iGBS infections in England in 2014, 185 (12%) were identified as maternal infections, a rate of 0.29 (95% CI 0.25-0.33) per 1000 maternities and representing 83% of all iGBS cases in women aged 18-44 years. Seven (3.8%) were associated with miscarriage. Fetal outcome identified excess rates of stillbirth (3.4 versus 0.5%) and extreme prematurity (<28 weeks of gestation, 3.7 versus 0.5%) compared with national averages (P < 0.001). Caesarean section surveillance in 27 860 women (21 hospitals) identified 47 cases of GBS SSI, with an estimated 4.24 (3.51-5.07) per 1000 caesarean sections, a median time-to-onset of 10 days (IQR 7-13 days) and ten infections that required readmission. Capsular serotype analysis identified a diverse array of strains with serotype III as the most common (43%).

CONCLUSIONS

Our assessment of maternal GBS infection in England indicates the potential additional benefit of GBS vaccination in preventing adverse maternal and fetal outcomes.

Manejo de la sepsis en el embarazo. Revisión de la literatura

La sepsis se reconoce como una enfermedad común y mortal, cuya epidemiología obliga al médico tratante a realizar un diagnóstico oportuno por el alto riesgo de complicaciones o muerte. En las gestantes hay una gran vulnerabilidad debido a los cambios físicos y hormonales que están afrontado. Es indispensable iniciar el tratamiento tan pronto se tenga el diagnóstico, para evitar que sea mortal tanto para la madre como para el feto. Es por esto que el objetivo es una revisión sobre la intervención en las pacientes con diagnóstico de sepsis en estado de embarazo al ingreso a la UCI, bajo los siguientes ejes temáticos: definición clara de sepsis en el embarazo, factores de riesgo, intervención terapéutica en UCI y consecuencias para el feto durante su intervención. Se concluye que el manejo de la sepsis en las embarazadas es muy similar a las que no lo están. Hacen falta investigaciones con evidencia científica, velando siempre por la vida ya que no solo se trata un ser humano sino de dos.

Genetic Basis Underlying the Hyperhemolytic Phenotype of Streptococcus agalactiae Strain CNCTC10/84

Streptococcus agalactiae (group B streptococcus [GBS]) is a major cause of infections in newborns, pregnant women, and immunocompromised patients. GBS strain CNCTC10/84 is a clinical isolate that has high virulence in animal models of infection and has been used extensively to study GBS pathogenesis. Two unusual features of this strain are hyperhemolytic activity and hypo-CAMP factor activity. These two phenotypes are typical of GBS strains that are functionally deficient in the CovR-CovS two-component regulatory system. A previous whole-genome sequencing study found that strain CNCTC10/84 has intact covR and covS regulatory genes. We investigated CovR-CovS regulation in CNCTC10/84 and discovered that a single-nucleotide insertion in a homopolymeric tract in the covR promoter region underlies the strong hemolytic activity and weak CAMP activity of this strain. Using isogenic mutant strains, we demonstrate that this single-nucleotide insertion confers significantly decreased expression of covR and covS and altered expression of CovR-CovS-regulated genes, including that of genes encoding β-hemolysin and CAMP factor. This single-nucleotide insertion also confers significantly increased GBS survival in human whole blood ex vivo IMPORTANCE Group B streptococcus (GBS) is the leading cause of neonatal sepsis, pneumonia, and meningitis. GBS strain CNCTC10/84 is a highly virulent blood isolate that has been used extensively to study GBS pathogenesis for over 20 years. Strain CNCTC10/84 has an unusually strong hemolytic activity, but the genetic basis is unknown. In this study, we discovered that a single-nucleotide insertion in an intergenic homopolymeric tract is responsible for the elevated hemolytic activity of CNCTC10/84.

Genome-Wide Assessment of Streptococcus agalactiae Genes Required for Survival in Human Whole Blood and Plasma

Streptococcus agalactiae (group B streptococcus, or GBS) is a common cause of bacteremia and sepsis in newborns, pregnant women, and immunocompromised patients. The molecular mechanisms used by GBS to survive and proliferate in blood are not well understood. Here, using a highly virulent GBS strain and transposon-directed insertion site sequencing (TraDIS), we performed genome-wide screens to discover novel GBS genes required for bacterial survival in human whole blood and plasma. The screen identified 85 and 41 genes that are required for GBS growth in whole blood and plasma, respectively. A common set of 29 genes was required in both whole blood and plasma. Targeted gene deletion confirmed that (i) genes encoding methionine transporter (metP) and manganese transporter (mtsA) are crucial for GBS survival in whole blood and plasma, (ii) gene W903_1820, encoding a small multidrug export family protein, contributes significantly to GBS survival in whole blood, (iii) the shikimate pathway gene aroA is essential for GBS growth in whole blood and plasma, and (iv) deletion of srr1, encoding a fibrinogen-binding adhesin, increases GBS survival in whole blood. Our findings provide new insight into the GBS-host interactions in human blood.

Operative vaginal delivery and post-partum infection

During the past decade, there has been an increase in the awareness of infections associated with pregnancy and delivery. The most significant cause of post-partum infection is caesarean section; 20-25% of operations are followed by wound infections, endometritis or urinary tract infections. Approximately 13% of women in the UK undergo operative vaginal delivery (OVD) with forceps or vacuum, which is also associated with an increased risk of infection, estimated at 0.7%-16% of these deliveries. Despite this, previous reviews have identified only one small trial of antibiotic prophylaxis in 393 women and concluded that there was insufficient evidence to support the routine use of prophylactic antibiotics after OVD. The ANODE trial, a multicentre, blinded, placebo-controlled trial from the UK, is due to report findings from more than 3400 women in 2019 and will be the largest study to date of antibiotic prophylaxis following OVD.

Systematic review of the clinical development of group B streptococcus serotype-specific capsular polysaccharide-based vaccines

INTRODUCTION

Vaccination against group B Streptococcus (GBS) during pregnancy could provide protection against disease in the mother, fetus, and newborn. Immunity through transplacental acquired antibodies in the newborns could persist through early infancy, reducing the risk of early-onset (<7 days age) and late-onset (7-89 days age) disease. We conducted a systematic review of clinical trials on GBS capsular polysaccharide (CPS) vaccine to assess its safety and immunogenicity in pregnant and nonpregnant adults.

AREAS COVERED

We searched literature databases PubMed (Medline), Scopus, and the Cochrane library and identified 25 unique records on GBS CPS vaccines with or without conjugant protein.

EXPERT COMMENTARY

GBS vaccines were well tolerated, with mild local reactogenicity being the main solicited adverse event and no difference in reporting of other serious adverse events compared to placebo recipients. CPS vaccines conjugated to immunogenic proteins induced ≥fourfold increase of serotype-specific antibodies with high longevity (1-2 years); and capable of promoting homotypic GBS opsonophagocytic killing. Feto-maternal transplacental antibody ratio of serotype-specific IgG ranged between 0.49 and 0.81. The clinical relevance of these immunogenicity studies, however, need to be weighed against a correlate of protection against invasive GBS disease in infants, which is yet to be established using a universally accepted standardized assay.

Maternal Disease With Group B Streptococcus and Serotype Distribution Worldwide: Systematic Review and Meta-analyses

BACKGROUND

Infections such as group B Streptococcus (GBS) are an important cause of maternal sepsis, yet limited data on epidemiology exist. This article, the third of 11, estimates the incidence of maternal GBS disease worldwide.

METHODS

We conducted systematic literature reviews (PubMed/Medline, Embase, Latin American and Caribbean Health Sciences Literature [LILACS], World Health Organization Library Information System [WHOLIS], and Scopus) and sought unpublished data on invasive GBS disease in women pregnant or within 42 days postpartum. We undertook meta-analyses to derive pooled estimates of the incidence of maternal GBS disease. We examined maternal and perinatal outcomes and GBS serotypes.

RESULTS

Fifteen studies and 1 unpublished dataset were identified, all from United Nations-defined developed regions. From a single study with pregnancies as the denominator, the incidence of maternal GBS disease was 0.38 (95% confidence interval [CI], .28-.48) per 1000 pregnancies. From 3 studies reporting cases by the number of maternities (pregnancies resulting in live/still birth), the incidence was 0.23 (95% CI, .09-.37). Five studies reported serotypes, with Ia being the most common (31%). Most maternal GBS disease was detected at or after delivery.

CONCLUSIONS

Incidence data on maternal GBS disease in developing regions are lacking. In developed regions the incidence is low, as are the sequelae for the mother, but the risk to the fetus and newborn is substantial. The timing of GBS disease suggests that a maternal vaccine given in the late second or early third trimester of pregnancy would prevent most maternal cases.

Group B streptococcus (GBS) is an important pathogen in human disease- but what about in cystic fibrosis?

BACKGROUND

Group B Streptococcus (GBS) is a common commensal capable of causing severe invasive infections. Most GBS infections occur in neonates (often as pneumonia). GBS can also cause infection in adults with diabetes and other immunological impairments but rarely leads to pneumonia in adults. GBS has occasionally been found in the sputum of Cystic Fibrosis (CF) patients, an inherited condition known for progressive lung disease. However, the epidemiology and clinical significance of GBS in CF are not understood.

METHODS

We retrospectively reviewed a large single-centre adult CF population with an associated comprehensive, prospectively collected bacterial biobank beginning in 1978. We identified all individuals with GBS isolated from their sputum on at least one occasion. The primary outcome was risk of pulmonary exacerbation (PEx) at the time of the first GBS isolate compared to the preceding visit. Secondary outcomes included determining: prevalence of GBS infection in a CF population, whether GBS infections where transient or persistent, whether GBS strains were shared among patients, change in % predicted FEV₁ at the time of GBS isolate compared to the preceding visit, PEx frequency after the first GBS isolate, change in % predicted FEV₁ after the first GBS isolate, and complications of GBS infection.

RESULTS

GBS was uncommon, infecting 3.5% (11/318) adults within our cohort. Only three individuals developed persistent GBS infection, all lasting > 12 months. There were no shared GBS strains among patients. PEx risk was not increased at initial GBS isolation (RR 5.0, CI 0.69-36.1, p=0.10). In the two years preceding initial GBS isolation compared to the two following years, there was no difference in PEx frequency (median 2, range 0-4 vs 1, range 0 to 5, respectively, p=0.42) or lung function decline, as measured by % predicted FEV₁, (median -1.0%, range -19 to 7% vs median -6.0%, range -18 to 22%, p=0.86). There were no invasive GBS infections.

CONCLUSION

In adults with CF, GBS is uncommon and is generally a transient colonizer of the lower airways. Despite the presence of structural lung disease and impaired innate immunity in CF, incident GBS infection did not increase PEx risk, PEx frequency, rate of lung function decline, or other adverse clinical outcomes.

Mast cell chymase decreases the severity of group B Streptococcus infections

BACKGROUND

Group B Streptococcus (GBS) or Streptococcus agalactiae are β-hemolytic gram-positive bacteria that colonize the lower genital tracts of women and are frequently associated with infections during pregnancy. Innate immune defenses are critical for controlling GBS dissemination and systemic infection. Mast cells are resident sentinel cells that come into contact with pathogens early during colonization and infection.

OBJECTIVE

We aimed to investigate the contribution of chymase to systemic GBS infection and rates of preterm birth.

METHODS

Pharmacologic and genetic approaches using mice deficient in mast cell protease (MCPT) 4, the mouse functional homologue of human chymase, were used.

RESULTS

Our studies show that mast cells release a protease with chymotrypsin-like cleavage specificity in response to GBS. Additionally, increased GBS systemic infection and preterm births were observed in MCPT4-deficient mice versus MCPT4-sufficient mice. Furthermore, we observed that proteolytic cleavage of the host extracellular matrix protein fibronectin by peritoneal cell-derived mast cell lysates diminished GBS adherence. Consistent with this observation, the increase in GBS dissemination and preterm births observed in MCPT4-deficient mice was abolished when GBS was deficient in expression of the fibronectin-binding protein SfbA.

CONCLUSIONS

Taken together, our results suggest that the protective effect of MCPT4 against GBS dissemination and preterm labor can be attributed in part to MCPT4-mediated proteolysis of fibronectin. Our studies reveal a novel role of mast cells in defense against bacterial infections.

Group B Streptococcus circumvents neutrophils and neutrophil extracellular traps during amniotic cavity invasion and preterm labor

Preterm birth is a leading cause of neonatal morbidity and mortality. Although microbial invasion of the amniotic cavity (MIAC) is associated with the majority of early preterm births, the temporal events that occur during MIAC and preterm labor are not known. Group B Streptococci (GBS) are β-hemolytic, gram-positive bacteria, which commonly colonize the vagina but have been recovered from the amniotic fluid in preterm birth cases. To understand temporal events that occur during MIAC, we utilized a unique chronically catheterized nonhuman primate model that closely emulates human pregnancy. This model allows monitoring of uterine contractions, timing of MIAC and immune responses during pregnancy-associated infections. Here, we show that adverse outcomes such as preterm labor, MIAC, and fetal sepsis were observed more frequently during infection with hemolytic GBS when compared to nonhemolytic GBS. Although MIAC was associated with systematic progression in chorioamnionitis beginning with chorionic vasculitis and progressing to neutrophilic infiltration, the ability of the GBS hemolytic pigment toxin to induce neutrophil cell death and subvert killing by neutrophil extracellular traps (NETs) in placental membranes in vivo facilitated MIAC and fetal injury. Furthermore, compared to maternal neutrophils, fetal neutrophils exhibit decreased neutrophil elastase activity and impaired phagocytic functions to GBS. Collectively, our studies demonstrate how a unique bacterial hemolytic lipid toxin enables GBS to circumvent neutrophils and NETs in placental membranes to induce fetal injury and preterm labor.