Population-based active surveillance for neonatal group B streptococcal infections in Alberta, Canada: implications for vaccine formulation

Naturally occurring antibodies for the group B streptococcal surface immunogenic protein (Sip) in pregnant women and newborn babies

Sip is a surface-exposed protein of GBS, which causes severe neonatal disease. Because Sip elicits a protective immune response in mice, we assessed whether pregnant women and newborns have Sip antibodies. Sera were collected from 644 pregnant women and 176 of their healthy newborns, and 10 newborns with GBS disease and their mothers. Using ELISA, most (99%) women and newborns (97%) had serum Sip antibodies, as did most newborns followed through 6 months. This suggests that naturally occurring Sip antibodies cross the placenta and persist into infancy, which underscores the need to study Sip further as a potential vaccine candidate.

The efficacy of 2002 CDC guidelines in preventing perinatal group B Streptococcal vertical transmission: a prospective study

OBJECTIVES

The aim of the current study is to evaluate the differences in the rate of perinatal group B streptococcal vertical transmission between women who correctly underwent the CDC 2002 guidelines and women who did not.

METHODS

Two study groups: women who correctly underwent the CDC 2002 guidelines (study group 1) and women who did not (study group 2). Intrapartum chemoprophylaxis (IC) was administered to all pregnant women identified as GBS carrier. All newborns received, in the first hour of life, a culture based screening for GBS colonization.

RESULTS

One thousand six hundred and sixty nine women were enrolled in the study. The 2002 CDC guidelines were correctly applied in 1273 (76.3%) subjects. There was no early-onset GBS disease. No statistically significant difference in the total number of colonized newborns between study group 1 (4.1%) and study group 2 (3.3%) was found. When the analysis was limited to women with positive GBS screening, a significant difference (P < 0.001) was observed in the number of colonized newborns between mothers who received IC during at least 4 h (group 1; 3.7%) and those who received an IC during less than 4 h (group 1; 12.3%).

CONCLUSION

The accurate application of the 2002 CDC guidelines is strongly supported but, to furthermore reduce the risk for GBS colonization and sepsis in the newborns, it appears desirable to identify additional and new prevention strategies.

Dose-response to type V group B streptococcal polysaccharide-tetanus toxoid conjugate vaccine in healthy adults

A phase 1, dose-escalating trial was conducted in healthy adults to evaluate immunogenicity and reactogenicity of a type V group B streptococcal (GBS) capsular polysaccharide (CPS)-tetanus toxoid (TT) conjugate vaccine. Participants received one dose of unconjugated V CPS (37 microg), V-TT (2.4 microg CPS/1.1 microg TT), V-TT (9.6 microg CPS/4.3 microg TT) or V-TT (38.5 microg CPS/17.0 microg TT). Each vaccine and all doses of V-TT were well-tolerated. V CPS-specific antibodies reached a peak 4-8 weeks after immunization and were significantly higher through 52 weeks post-immunization in recipients of V-TT at each dose than in uncoupled CPS vaccinees. V-TT vaccine-induced antibodies promoted opsonophagocytic killing of type V GBS and avidity maturation of V CPS-specific IgG.

The frequency of genes encoding three putative group B streptococcal virulence factors among invasive and colonizing isolates

BACKGROUND

Group B Streptococcus (GBS) causes severe infections in very young infants and invasive disease in pregnant women and adults with underlying medical conditions. GBS pathogenicity varies between and within serotypes, with considerable variation in genetic content between strains. Three proteins, Rib encoded by rib, and alpha and beta C proteins encoded by bca and bac, respectively, have been suggested as potential vaccine candidates for GBS. It is not known, however, whether these genes occur more frequently in invasive versus colonizing GBS strains.

METHODS

We screened 162 invasive and 338 colonizing GBS strains from different collections using dot blot hybridization to assess the frequency of bca, bac and rib. All strains were defined by serotyping for capsular type, and frequency differences were tested using the Chi square test.

RESULTS

Genes encoding the beta C protein (bac) and Rib (rib) occurred at similar frequencies among invasive and colonizing isolates, bac (20% vs. 23%), and rib (28% vs. 20%), while the alpha (bca) C protein was more frequently found in colonizing strains (46%) vs, invasive (29%). Invasive strains were associated with specific serotype/gene combinations.

CONCLUSION

Novel virulence factors must be identified to better understand GBS disease.

Biochemistry testing associated with pregnancy and the newborn period -- a lot has changed since you were a baby!

Everyone has been a newborn, and everyone's mother has been pregnant. Despite the commonality of these events, medical care and the clinical chemistry laboratory's role in it have changed remarkably over the last 50 years. This review is a historical overview of clinical chemistry testing that is related to pregnancy and the newborn period.

Post-genomic vaccine development

For over a century, vaccines were developed according to Pasteur's principles of isolating, inactivating and injecting the causative agent of an infectious disease. The availability of a complete microbial genome sequence in 1995 marked the beginning of a genomic era that has allowed scientists to change the paradigm and approach vaccine development starting from genomic information, a process named reverse vaccinology. This can be considered as one of the most powerful examples of how genomic information can be used to develop therapeutic interventions, which were difficult or impossible to tackle with conventional approaches. As the genomic era progressed, it became apparent that multi-strain genome analysis is fundamental to the design of universal vaccines. In the post-genomic era, the next challenge of the vaccine biologist will be the merging of the vaccinology with structural biology.

Vaccination for Group B Streptococcus during pregnancy: attitudes and concerns of women and health care providers

Group B Streptococcus (GBS) is the leading infectious cause of neonatal morbidity and mortality. Although intrapartum antibiotic prophylaxis (IAP) strategies are effective in preventing GBS transmission from mothers to newborns, there are growing concerns about adverse effects, and the development of antibiotic resistance. GBS vaccines targeting the most virulent neonatal disease serotypes are currently under development and may be used during pregnancy. The objective of this study was to explore the key issues and concerns that would be associated with GBS vaccination during pregnancy from the perspectives of pregnant women and health care providers. Twenty-two women and 25 health care professionals in Alberta, Canada participated in 10 focus groups, each group ranging from 2 to 20 participants. Valuable information emerged from the focus groups about the factors that would affect acceptance of a maternal GBS vaccine. This information will be essential for health systems to consider in the introduction, promotion and delivery of such a vaccine. The data may help optimize education about GBS and a putative vaccine to pregnant women.

Incidence and duration of group B Streptococcus by serotype among male and female college students living in a single dormitory

Group B Streptococcus causes a variety of morbid and sometimes fatal conditions affecting individuals of all age groups. There are nine known serotypes of this Gram-positive coccus but few estimates of the incidence and duration of its colonization and none by serotype in the literature. In 2001, the authors conducted a prospective cohort study among 257 men and women living in a single dormitory in Ann Arbor, Michigan. The 3-week incidence with any serotype was 11.3% (+/-3.9%) among women and 8.8% (+/-3.0%) among men; 3-week incidence rates were highest for serotype V (4.7% for women and 3.5% for men) and type Ia (2.3% for women and 2.4% for men), with no significant differences by gender. The estimated average duration of any group B Streptococcus colonization was longer for women (13.7 weeks) than men (8.5 weeks); serotype Ia was carried an average of 6.5 weeks longer in women, and serotype III was carried 4.9 weeks longer. Colonization with more than one serotype occurred significantly less than would be expected by chance (p <<< 0.001). Based on the overall incidence, transmission occurred between roommate pairs at the rate expected. Group B Streptococcus colonization is frequent and dynamic, but it is not transmitted by casual contact.

Population-based surveillance of invasive pyogenic streptococcal infection in a large Canadian region

Pyogenic streptococci are a major cause of invasive infection. This study presents the results of a population-based laboratory surveillance for invasive pyogenic streptococcal infections among residents of the Calgary Health Region (population 1 million) between 1 July 1999 and 30 June 2004. The overall annual incidence rate was 18.65/100,000 population, with isolates belonging to the Streptococcus milleri group forming the most important aetiology (incidence of 8.65/100,000 population). Invasive infection with groups A, B, G and C streptococci occurred at annual rates of 4.27, 3.13, 1.83 and 0.41/100,000 population, respectively. There was a close relationship between increasing age and development of an invasive pyogenic streptococcal infection, and the incidence of infection was higher among males than among females. Differences in the seasonal occurrence and focus of infection occurred between the different groups.

DNA polymorphism and molecular subtyping of the capsular gene cluster of group B streptococcus

Serotyping and other phenotypic methods are often used to characterize the capsular polysaccharide of group B streptococci (GBS). We describe a capsular genotyping method that utilizes PCR of capsular polysaccharide synthesis genes (cps) and restriction enzyme digestion. This method facilitates the detection of DNA polymorphism in cps genes and correlates well with serotyping.

Group B Streptococcal Testing During Pregnancy: Survey of Postpartum Women and Audit of Current Prenatal Screening Practices

OBJECTIVE

Group B Streptococcus (GBS) can be transmitted from mother to child during delivery. At the time of the study, Nova Scotia guidelines for screening pregnant women for the presence of GBS recommended using one of two testing methods. The objective of this study was to determine the level of compliance with GBS testing recommendations and to determine women's knowledge of, attitudes towards, and beliefs about prenatal screening for this infection.

METHODS

All women who gave birth at a single tertiary care unit during a seven-week period were approached to participate in the study. Study participants were interviewed using a questionnaire to determine their knowledge of, attitudes towards, and beliefs about prenatal screening. Medical and laboratory records were reviewed in order to audit the prenatal screening practices.

RESULTS

A total of 24.5% of study participants were screened for the presence of GBS by culture of a vaginal-rectal swab taken at 35 37 weeks' gestation, and 75.5% were assessed using the risk factor approach. Of the women screened by culture, 19% were identified as needing antibiotic treatment compared with 25% of those screened by assessment of risk factors. Women were significantly less knowledgeable about GBS than about other specific infections, and they felt that the threat of GBS infection for their baby was lower than the threat of the other infections. However, many of these women were uncertain about the threat that GBS poses during pregnancy.

CONCLUSION

Screening for GBS by culture rather than by assessing risk factors would have reduced antibiotic usage in our study population by 23%. These results indicate that all women should be counselled regarding GBS infection and should be tested using the culture-based approach at 35 to 37 weeks' gestation.

Characterization of a novel leucine-rich repeat protein antigen from group B streptococci that elicits protective immunity

Group B streptococci (GBS) usually behave as commensal organisms that asymptomatically colonize the gastrointestinal and urogenital tracts of adults. However, GBS are also pathogens and the leading bacterial cause of life-threatening invasive disease in neonates. While the events leading to transmission and disease in neonates remain unclear, GBS carriage and level of colonization in the mother have been shown to be significant risk factors associated with invasive infection. Surface antigens represent ideal vaccine targets for eliciting antibodies that can act as opsonins and/or inhibit colonization and invasion. Using a genetic screen for exported proteins in GBS, we identified a gene, designated lrrG, that encodes a novel LPXTG anchored surface antigen containing leucine-rich repeat (LRR) motifs found in bacterial invasins and other members of the LRR protein family. Southern blotting showed that lrrG was present in all GBS strains tested, representing the nine serotypes, and revealed the presence of an lrrG homologue in Streptococcus pyogenes. Recombinant LrrG protein was shown in vitro to adhere to epithelial cells in a dose-dependent manner, suggesting that it may function as an adhesion factor in GBS. More importantly, immunization with recombinant LrrG elicited a strong immunoglobulin G response in CBA/ca mice and protected against lethal challenge with virulent GBS. The data presented in this report suggest that this conserved protein is a highly promising candidate antigen for use in a GBS vaccine.

Serotype Distribution of Invasive Group B Streptococcal Isolates in Infants: Results from a Nationwide Active Laboratory Surveillance Study over 2 Years in Germany

We report the serotype distribution of invasive group B streptococci (GBS) isolated from 296 infants in Germany. Serotype distribution was as follows: serotype Ia, 15%; Ib, 5%; II, 5%; III, 65%; IV, 1%; and V, 8%. Analysis of serotype according to the source of isolation highlighted the considerable role of serotype III in meningitis in early-onset infection (82%) and late-onset infection (84%). Use of a trivalent GBS vaccine in Germany could theoretically provide protection against 84% and 94% of invasive early-onset and late-onset infections, respectively.

Serotypes and clinical manifestations of invasive group B streptococcal infections in western Sweden 1998-2001

This study monitored the serotypes of Streptococcus agalactiae (group B streptococcus; GBS) isolated from invasive infections in western Sweden and investigated possible relationships between serotype, age and clinical manifestations. Invasive GBS isolates were collected prospectively during 1998-2001 at six laboratories, covering two counties with a population of 1.8 million, and were serotyped by coagglutination. Clinical data were obtained from hospital notes. In total, 161 invasive strains (50 from neonates and infants aged < 3 months, and 111 from adults) were serotyped. The commonest serotypes from neonates and infants were serotypes III (60%), V (22%) and Ia (10%), and from adults were serotypes V (42%) and III (25%). Serotype V had doubled in frequency among both children and adults compared to a previous study from the same area in 1988-1997. Most (80%) of the adults had an underlying medical condition. No relationship was found between serotype and clinical manifestations. However, the study demonstrated the importance of active surveillance of GBS serotypes and the difficulties of formulating a multivalent polysaccharide conjugate vaccine against GBS.

Prevention of neonatal group B streptococcal disease: progress, challenges and dilemmas

Significant advances in the prevention of neonatal group B streptococcal (GBS) disease have occurred in the last decade. In Australia, as well as in centres overseas, intrapartum penicillin given to carrier mothers has been shown to unequivocally decrease early onset neonatal GBS sepsis. In choosing which women should receive intrapartum chemoprophylaxis, recent data suggest that screening programmes for the detection of GBS carriage may be more effective than risk-based strategies to prevent early onset neonatal GBS sepsis. Combined vaginal and rectal swabs, collected between 35 and 37 weeks gestation, either by a health care worker or by the patient herself and inoculated onto selective media after enrichment provide the optimum conditions to detect carriage. Increasingly erythromycin and clindamycin resistance is being described overseas, which may influence the choice of antibiotics used in those allergic to penicillin. Widespread antibiotic use, particularly with broad-spectrum agents, may lead to increasing neonatal sepsis with ampicillin resistant organisms. Whilst rates of non-GBS neonatal sepsis are generally stable there is evidence suggesting that Escherichia coli sepsis in premature infants is increasing. Novel vaccination strategies for GBS are being developed that may ultimately provide broader protection for mothers and babies and eliminate the need for intrapartum antibiotics.

Multicenter Study of a Rapid Molecular-Based Assay for the Diagnosis of Group B Streptococcus Colonization in Pregnant Women

BACKGROUND

Current prevention of infection due to group B Streptococcus (GBS) involves giving intrapartum antibiotics to women on the basis of either antenatal culture colonization status or presence of risk factors.

METHODS

We prospectively compared the performance characteristics of a rapid molecular diagnostic test (IDI-Strep B; Infectio Diagnostic) with culture for intrapartum GBS detection after 36 weeks' gestation in 5 North American centers during the period September 2001-May 2002. Antenatal GBS screening was done according to the usual practice of participating hospitals. Two combined vaginal/anal specimens were obtained from participants during labor by use of standard techniques and processed by the same laboratories that processed the antenatal specimens. Each swab sample was processed simultaneously by culture and with IDI-Strep B. The collected specimens were randomized for order of testing of the swab samples by culture or the rapid test.

RESULTS

Of enrolled women, 803 (91.1%) were eligible for analysis. The overall intrapartum GBS colonization rate by culture was 18.6% (range, 9.1%-28.7%). Compared with intrapartum culture, the molecular test had a sensitivity of 94.0% (range, 90.1%-97.8%), specificity of 95.9% (range, 94.3%-97.4%), positive predictive value of 83.8% (range, 78.2%-89.4%), and negative predictive value of 98.6% (range, 97.7%-99.5%). The molecular test was superior to antenatal cultures (sensitivity, 94% vs. 54%; P<.0001) and prediction of intrapartum status on the basis of risk factors (sensitivity, 94% vs. 42%; P<.0001).

CONCLUSION

Use of this test for determination of GBS colonization during labor is highly sensitive and specific and may lead to a further reduction in rates of neonatal GBS disease.

The Prevention of Early-Onset Neonatal Group B Streptococcal Disease

This document has been archived because it contains outdated information. It should not be consulted for clinical use, but for historical research only. Please visit the journal website for the most recent guidelines.

[Group B Streptococcus late-onset disease presenting as cellulitis-adenitis syndrome]

Cellulitis-adenitis syndrome is a rare clinical manifestation of group B Streptococcus (GBS) late-onset disease. Its significance lies in the fact that local infection may be the only initial sign of systemic infection that is often concurrent with meningitis. Soft tissue involvement (cellulitis-adenitis) can sometimes be the only initial manifestation of GBS infection. We report four cases of GBS cellulitis-adenitis syndrome from different hospitals in Barcelona and Tarragona. We emphasize that early diagnosis and treatment may improve the potentially poor prognosis of these patients, and stress the need to rule out central nervous system involvement by studying cerebrospinal fluid.

Characterization of Group B Streptococci Recovered from Infants with Invasive Disease in England and Wales

Group B streptococci (GBS) are a major cause of invasive disease in infants, with enhanced surveillance in England and Wales showing an incidence of 0.74 cases per 1000 live births and a mortality rate of 8%. Among 353 isolates obtained during enhanced surveillance, the predominant serotypes were III (48%), Ia (27%), and V (10%), and the remainder comprised Ib, II, IV, VI, and VII; 3% were not typable. Isolates from patients with early-onset disease had serotypes III (38%), Ia (32%), and V (13%), with late-onset disease having a higher incidence of type III (67%) strains. Patients infected with serotype III strains had a higher rate of meningitis, and those with type V strains had a higher mortality rate. Isolates were susceptible to penicillin and ampicillin, but 4% were resistant to erythromycin, and 91% were resistant to tetracycline. A trivalent vaccine containing capsular polysaccharides III, Ia, and V could theoretically provide coverage against 85% of the cases of GBS disease among infants in England and Wales.

Hyperinvasive neonatal group B streptococcus has arisen from a bovine ancestor

The genetic relatedness and evolutionary relationships between group B streptococcus (GBS) isolates from humans and those from bovines were investigated by phylogenetic analysis of multilocus sequence typing data. The collection of isolates consisted of 111 GBS isolates from cows with mastitis and a diverse global collection of GBS isolates from patients with invasive disease (n = 83) and carriers (n = 69). Cluster analysis showed that the majority of the bovine isolates (93%) grouped into one phylogenetic cluster. The human isolates showed greater diversity and clustered separately from the bovine population. However, the homogeneous human sequence type 17 (ST-17) complex, known to be significantly associated with invasive neonatal disease, was the only human lineage found to be clustered within the bovine population and was distinct from all the other human lineages. Split decomposition analysis revealed that the human isolate ST-17 complex, the major hyperinvasive neonatal clone, has recently arisen from a bovine lineage.

Telithromycin susceptibility and genomic diversity of macrolide-resistant serotype III group B streptococci isolated in perinatal infections

We studied the telithromycin, erythromycin, azithromycin, and clindamycin susceptibilities of serotype III macrolide-resistant group B streptococci, together with genetic mechanisms of resistance and genomic diversity. ermB, ermA, and mefA were found in, respectively, 57, 32, and 9% of isolates. The telithromycin MIC at which 90% of isolates were inhibited was 0.5 micro g/ml. Macrolide resistance was associated with dissemination of resistance determinants among isolates of different genetic backgrounds.

Vaccine development for capsulate bacteria causing pneumonia

Pneumonia strikes the extremes of the age spectrum, causing maximal death and disability in children and the elderly. Despite its worldwide impact, there is a paucity of epidemiologic data regarding its incidence and the causative organisms. The two leading causes of bacterial pneumonia in childhood are Streptococcus pneumoniae (SP) and Haemophilus influenzae type b (Hib). SP is the major cause of pneumonia beyond the newborn period. In neonates, Group B Streptococcus (GBS) remains a major cause of sepsis and pneumonia despite recent reductions due to targeted perinatal antibiotic prophylaxis. Hib vaccine can prevent pneumonia in developing countries. SP conjugate vaccine prevents X-ray confirmed pneumonia in low incident populations, but protection appears more marginal in high incident populations. Non-vaccine SP serotypes have demonstrated increased carriage and mucosal disease, but not invasive disease following vaccination. GBS vaccines are in the early stages of clinical development as prenatal or antenatal vaccines.

Group B streptococci during pregnancy and infancy

Group B streptococcus (Streptococcus agalactiae) is still of great relevance in the perinatal period, although maternal antimicrobial prophylaxis has significantly reduced the rate of culture-confirmed invasive infection in neonates. This strategy, however, raises considerable concern because preterm delivery or late-onset sepsis cannot be prevented, and antibiotic resistance is increasing worldwide. Several advances in the development of conjugate vaccines and in research on virulence factors and pathways involved in the immune response to group B streptococcus have been accomplished, some of which might reach clinical practice in the near future.