Group B streptococcal disease and genotypes in Australian infants

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.

Multicenter Performance Evaluation of the Revogene® GBS DS Real-Time PCR Assay for Group B Streptococcus Detection During Labor

PURPOSE

This study aimed to evaluate the performance and ease of use of the Revogene® GBS DS PCR assay for the intrapartum detection of Group B Streptococcus (GBS) colonization, as compared with intrapartum culture and antenatal culture-based screening.

METHODS

Between April and August 2019, 398 women who gave birth in one of the three maternities participating in this study agreed to the collection of a vaginal swab when they arrived in the labor ward. The samples were immediately sent to the adjacent laboratory where they were discharged into the buffer provided with the Revogene® GBS DS assay. Part of the buffer was used to perform the Revogene® GBS DS test, and part of the same buffer was used for GBS culture.

RESULTS

The Revogene® GBS DS assay provided a valid result in less than 70 min for 356 (89%) women. The sensitivity of the test was 85.7% (66.4-95.3%). The specificity of the test was 99.1% (97.3-99.8%). The positive predictive value was 88.9% (69.7-97.1%). The negative predictive value was 98.9% (96.9-99.6%).

CONCLUSION

The easy-to-use Revogene® GBS DS assay provides a valuable tool for the detection of GBS colonization at the beginning of labor. The sensitivity and turn-around time are adequate. The high number of invalid results needs to be addressed before the Revogene® GBS DS test can be expected to replace the current screening-based approach.

Neonatal Group B Streptococcal Infection in Australia: A Case-control Study

BACKGROUND

To determine maternal and neonatal risk factors for, and incidence of, neonatal early-onset group B streptococcus (EOGBS) and late-onset (LOGBS) infection in South Australia (SA) and the Northern Territory (NT).

METHODS

A case-control study with 2:1 matched controls to cases. The study included tertiary hospitals in South Australia and the Northern Territory, Australia. Retrospective data were collected from a 16-year epoch (2000-2015).

RESULTS

Of a total of 188 clinically suspected or confirmed cases, 139 were confirmed, of which 56.1% (n = 78) were EOGBS and 43.9% (n = 61) were LOGBS. The incidence of clinically suspected and confirmed cases of EOGBS was 0.26/1000 live births in SA and 0.73/1000 live births in the NT, and the incidence of confirmed cases was 0.19/1000 for SA and 0.36/1000 for the NT. The incidence of clinically suspected or confirmed LOGBS was 0.18/1000 live births in SA and 0.16/1000 for the NT. The majority of infants with GBS presented with sepsis, pneumonia, or meningitis. Developmental delay was the most commonly recorded long-term complication at 1 year old. Risk factors for EOGBS included maternal GBS carriage, previous fetal death, identifying as Aboriginal and/or Torres Strait Islander, and maternal fever in labor/chorioamnionitis.

CONCLUSIONS

GBS remains a leading cause of neonatal morbidity and mortality. Adding previous fetal death to GBS screening guidelines would improve GBS prevention. The introduction of maternal GBS vaccination programs should be guided by country-specific disease epidemiology.

Analysis of Factors Related to Neonatal Infection and Monitoring of Bacterial Drug Resistance

OBJECTIVE

To study the factors related to neonatal infection, as well as bacterial distribution and drug resistance in neonatal infections, in an obstetrics and gynecology hospital in Shanghai.

METHODS

The bacterial culture and drug resistance monitoring results from neonates treated at the hospital from January 2020 to June 2021 were analyzed and compared with the data for children and newborns from the national bacterial resistance surveillance report.

RESULTS

Among the 209 bacterial strains isolated from infected neonates, 90 were gram-positive, including the four most common isolates: coagulase-negative Staphylococcus, Staphylococcus aureus, Enterococcus, and Streptococcus agalactiae. The remaining 119 strains were gram-negative and included Klebsiella pneumoniae, Acinetobacter baumannii, and Enterobacter aerogenes. The drug sensitivity results showed that the methicillin-resistant Staphylococcus aureus isolates were sensitive to linezolid, vancomycin, rifampicin, levofloxacin, and gentamicin. All Klebsiella pneumoniaisolates were sensitive to amikacin, ertapenem, imipenem, and gentamicin. These two strains were resistant to other antibiotics to varying degrees.

CONCLUSIONS

Understanding the distribution and drug resistance of bacterial pathogens is vital for guiding the rational selection of antibiotics and reducing neonatal mortality and nosocomial infections.

Clinical Risk Factors Associated with Late-Onset Invasive Group B Streptococcal Disease: Systematic Review and Meta-analyses

Background

Group B streptococcal (GBS) infection remains one of the most significant causes of late-onset sepsis and meningitis (LOGBS) among young infants. However, transmission routes and risk factors for LOGBS are not yet fully understood.

Methods

We conducted systematic reviews on clinical risk factors previously reported in the literature (prematurity, low birth weight [<2500 g], antenatal colonization, multiple-gestation pregnancy, maternal age <20 years, male infant sex, intrapartum fever, prolonged rupture of membranes) and meta-analyses to determine pooled estimates of risk.

Results

We included 27 articles, reporting 5315 cases. Prematurity (odds ratio [OR] 5.66; 95% confidence interval [CI]: 4.43–7.22), low birth weight (OR 6.73; 95% CI: 4.68–9.67), maternal colonization (2.67; [2.07–3.45]), and multiple-gestation pregnancies (OR 8.01; 95% CI: 5.19–12.38) were associated with an increased risk of LOGBS.

Conclusions

Prematurity/low birth weight and maternal colonization are major risk factors for LOGBS. Future GBS vaccine studies should try to establish the optimal time for vaccination during pregnancy to protect preterm infants.

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.

Early-onset neonatal infections in Australia and New Zealand, 2002-2012

BACKGROUND

The epidemiology of early-onset neonatal sepsis (EONS) varies over time, and requires regular surveillance.

OBJECTIVE

To analyse data on EONS in Australia and New Zealand.

METHODS

Retrospective analysis of data collected longitudinally from multiple neonatal units from 2002 to 2012.

RESULTS

Of 386 423 live births, 454 infants had EONS. The incidence rate of EONS was 1.20 per 1000 live births in 2002 and 0.83 in 2012, decreasing by 4% per year (95% CI 1% to 7%, p=0.007). Group B streptococcus (GBS) (37%) and Escherichia coli (25%) were the most prevalent organisms. The early-onset GBS (EOGBS) incidence rate was 0.43/1000 live births, with no evidence of change over time (p=0.3). Of EOGBS-infected babies, 62% were born at term compared with 8% with early-onset E. coli sepsis, p<0.0001. The mortality of E. coli early-onset sepsis (EOS) (25%) was higher than GBS (11%), but this difference in mortality was no longer significant after adjusting for gestation and birth weight. Mortality from EOS fell significantly over the study period (17% per year, 95% CI 10 to 24, p<0.0001).

CONCLUSIONS

GBS was the most common cause of early sepsis, but the incidence was lower than prior to the introduction of intrapartum antibiotic prophylaxis, and remained steady over time. The mortality of early-onset E. coli sepsis was significantly higher than GBS sepsis, but this may have been because almost all babies with E. coli were born preterm, rather than a difference in virulence.

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

PURPOSE

Streptococcus agalactiae, or group B streptococcus (GBS), is a leading neonatal pathogen that causes sepsis, meningitis and pneumonia. Globally, strategies have been implemented to address vertical transmission, and in Western Australia (WA), culture-based screening at 35-37 weeks' gestation is part of routine care and guides antibiotic administration. Previous Australian studies have focused on other regions or included low sample-size representatives; we aimed to describe antenatal GBS colonization in WA.

METHODOLOGY

A cohort of 814 pregnant women attending antenatal clinics (2015-2017) self-collected vaginal and rectal swabs at ≤22 weeks (n=814) and ≥33 weeks' (n=567) gestation. These were assessed for GBS presence using culture and PCR, and serotyping was conducted using molecular methods. Lifestyle questionnaires and medical data were collected.

RESULTS

We observed an overall GBS colonization rate of 24%, with 10.6  % of positive participants transiently colonized. Ethnicity (Aboriginal, Torres Strait Islander and African), maternal age ≥25 years, vitamin use, frequent sexual intercourse (≥5 times/week) and use of sex toys were associated with GBS colonization. The dominant serotypes identified were Ia (27.9%), III (20.9%), II (16.3%), V (15.8%), Ib (8.4%), VI (5.1%), IV (2.8%), NT (1.9), VIII (0.5%) and IX (0.5%) at visit one, with V (18.9%) preceding serotype II (18.2%) at visit two. Serotype VII was not detected.

CONCLUSION

This is the first cohort study to assess GBS colonization in Western Australian pregnant women and will be highly beneficial for guiding clinical practice and future therapeutic options, in particular, the selection of suitable vaccine candidates.

Long-term outcomes after group B streptococcus infection: a cohort study

OBJECTIVE

To describe the risk of death and hospitalisation until adolescence of children after group B streptococcus (GBS) infection during infancy.

DESIGN

Population-based cohort study.

SETTING

New South Wales, Australia.

PATIENTS

All registered live births from 2000 to 2011.

INTERVENTIONS

Comparison of long-term outcomes in children with the International Statistical Classification of Diseases and Related Health Problems-10th Revision discharge codes corresponding to GBS infections and those without.

MAIN OUTCOME MEASURES

Death and hospitalisation.

RESULTS

A total of 1206 (0.1%) children (936 (77.6%)≥37 weeks' gestation) were diagnosed with GBS infection. Over the study period, infection rates decreased from 2.1 (95% CI 1.8 to 2.4) to 0.7 (95% CI 0.5 to 0.9) per 1000 live births. Infants with GBS infection were born at lower gestation (mean 37.6 vs 39.0 weeks), were more likely very low birth weight (<1500 g, OR 9.1(95% CI 7.4 to 11.3)), born premature (OR 3.9(95% CI 3.4 to 4.5)) and have 5 min Apgar scores ≤5 (OR 6.7(95% CI 5.1 to 8.8)). Children with GBS had three times the adjusted odds of death (adjusted OR (AOR) 3.0(95% CI 2.1 to 4.3)) or rehospitalisations (AOR 3.1(95% CI 2.7 to 3.5)). Thirty-six (3.0%) with GBS died, with >50% of deaths occurring <28 days. Children with GBS were hospitalised more frequently (median 2 vs 1), for longer duration (mean 3.7 vs 2.2 days) and were at higher risk for problems with genitourinary (OR 3.1(95% CI 2.8 to 3.5)) and nervous (OR 2.0 (95% CI1.7 to 2.3)) systems.

CONCLUSIONS

Despite decreasing GBS rates, the risk of poor health outcomes for GBS-infected children remains elevated, especially during the first 5 years. Survivors continue to be at increased risk of death and chronic conditions requiring hospitalisations, such as cerebral palsy and epilepsy.

Early-onset group B streptococcal disease in a risk factor-based prevention setting: A 15-year population-based study

BACKGROUND

Intrapartum chemoprophylaxis reduces early-onset group B streptococcal disease (EOGBSD) in newborns. Some guidelines advise that intrapartum antibiotics should be offered following universal antenatal screening for GBS carriage and others recommend intrapartum antibiotics based on clinical risk factors alone. Since 1999, Queensland guidelines have recommended a risk factor-based approach. We examined trends in EOGBSD rates over time in Queensland in the setting of these guidelines and whether management of cases reflected the recommendations.

METHODS

A state-wide retrospective search of pathology databases, allowing near-complete, population-based case identification, was conducted to detect live-born infants from January 2000 to December 2014 with GBS cultured from blood or cerebrospinal fluid within seven days of age. A nested audit of EOGBSD cases comparing two epochs, 2000-2010 and 2011-2014, was performed to determine patient characteristics and guideline adherence for each case.

RESULTS

Mean incidence of EOGBSD in Queensland from 2000 to 2014 was 0.33 per 1000 live births (SD± 0.08) with no changing trend over time. The case-mortality rate in the 2011-2014 epoch was 1.2% compared to 11.9% in 2000-2004 (odds ratio (OR) 0.09, 95% confidence interval (CI) 0.002-0.67). The proportion of EOGBSD cases who were preterm infants decreased from 29.8% to 13.3% (OR 0.36, 95% CI 0.14-0.84). Of cases with risk factors in the 2011-2014 epoch, 46% received intrapartum antibiotics compared to 25% in 2000-2004 (OR 2.49, 95% CI 0.86-7.58, P = 0.09).

CONCLUSIONS

EOGBSD incidence rate in Queensland remained low during 2000-2014. However, both the 2011-2014 case-mortality rate and the proportion of preterm cases significantly decreased. Missed opportunities for intrapartum chemoprophylaxis remain.

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

Background

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

Methods

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

Results

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

Conclusions

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

Maternal Group B Streptococcus colonisation

Streptococcus agalactiae, commonly known as Group B Streptococcus (GBS), is an important neonatal pathogen known to cause sepsis, meningitis and pneumonia. Australian pregnant women undergo screening during pregnancy in an effort to eradicate GBS before delivery where transmission to the neonate can occur. Preventative treatment includes intrapartum antibiotic prophylaxis and results in widespread treatment of the 10–40% of pregnant women colonised. GBS are separated into ten different capsular polysaccharide serotypes and previous studies have suggested associations between specific serotypes and disease. At present, however, minimal data exist on serotype distribution within Western Australian-pregnant women, information that may play an important role in future prophylactic treatment regimens. Our preliminary data, obtained from GBS isolated from vaginal swabs from 191 pregnant women, suggests that GBS serotype distributions in Western Australia are different to other parts of Australasia. In particular, compared to the eastern Australian states and New Zealand, in our cohort, serotype Ib prevalence was 7–17 times lower, II was 2–6 times greater and VI was 2–12 times greater. In addition, serotype IX represented 6.3% of all serotypes. Understanding which serotypes are present in our population will provide valuable data for future targeted treatment regimens such as vaccination and bacteriophage therapy.

Epidemiology of Late and Very Late Onset Group B Streptococcal Disease: Fifteen-Year Experience From Two Australian Tertiary Pediatric Facilities

BACKGROUND

Group B Streptococcus (GBS) is a recognized cause of sepsis and meningitis, particularly in infants. Early onset (<7 days) GBS disease has been well characterized, whereas the epidemiology of late onset disease (LOD, 7-89 days) and very late onset disease (VLOD, ≥90 days) is less well understood. The aims of this study were to assess risk factors, presentation, management and outcome for GBS LOD and VLOD.

METHODS

Microbiology laboratory databases and hospital diagnostic coding for Sydney Children's Hospital and the Children's Hospital at Westmead were investigated for patients ≥7 days of age diagnosed with GBS bloodstream infection or meningitis from January 1, 2000 to December 31, 2014 (15 years). Subjects' medical records were reviewed to confirm diagnosis and analyze risk factors, presentation, management and outcome.

RESULTS

Eighty-seven cases of LOD and 28 cases of VLOD were identified, including 49 cases of bloodstream infection and 66 cases of meningitis. No significant differences in risk factors or presentation were identified between LOD and VLOD. Patients with LOD were more likely to develop sequelae compared with VLOD [odds ratio (OR): 3, 95% confidence interval (CI): 1.03-8.77]. Female sex was the only significant risk factor identified for GBS meningitis (OR: 3.5, 95% CI: 1.5-8.1). GBS meningitis was significantly associated with neurodevelopmental impairment or death compared with bloodstream infection (OR: 30, 95% CI: 6.4-140.6).

CONCLUSIONS

GBS LOD and VLOD are encountered in similar at-risk populations, with LOD associated with higher morbidity. Infants presenting with meningitis are at significantly higher risk of sequelae compared with bloodstream infection.