Online-Only Abstract: This article is available online at wileyonlinelibrary.com

Group B Streptococcus (GBS) was the main causative organism of invasive infections in newborns due to vertical transmission from the colonized mothers. The study was undertaken to determine colonization rate, serotype distribution, genotypic characterization, antibiotic susceptibility profiles and molecular characteristics of erythromycin-resistant strains of GBS in pregnant women in Beijing, China. Vaginal rectal swabs were collected from a total of 2850 pregnant women at 35-37 weeks of gestation, in which 7.1% were GBS positive. Serotypes III, Ia and V predominated. All isolates were penicillin susceptible, whereas the resistance rates for erythromycin and clindamycin were strikingly high.     

Carriage of group B Streptococcus in pregnant women and newborns: a 2-year study at Perugia General Hospital

Objective: To study the prevalence of group B Streptococcus (GBS) colonization in pregnant women and their newborns at Perugia General Hospital.
Method: The number of mother-child pairs examined was 2300. Vaginal swabs were collected from the mothers at delivery, and auricular and pharyngeal swabs and gastric aspirate from the newborns at birth. Maternal risk factors for GBS disease, including premature delivery, intrapartum fever, prolonged rupture of membranes and multiple births, were evaluated.
Results: Maternal and neonatal colonization rates were 11.3% and 4.6%, respectively. GBS was isolated in 41.5% of the neonates born to colonized mothers and in 0.1% of those born to non-colonized mothers. No significant difference was observed in vertical transmission rates in the presence or absence of maternal risk factors. The external auditory canal was the most frequent (93.5%) and heavily colonized body site. Type Ib was the most common serotype among GBS isolates from mothers and babies. C surface protein was not detected in serotype V and VIII isolates, but was frequent in all other serotypes. Early-onset disease was observed in 0.4/1000 live births.
Conclusions: The prevalence of maternal and neonatal colonization at Perugia General Hospital was similar to that obtained in other studies performed in Italy. The external auditory canal was confirmed as the most reliable body site to be sampled for the detection of neonates exposed to maternal GBS colonization.     

Epidemiology of Group B streptococcus isolated from pregnant women in Beijing,China

Group B Streptococcus (GBS) was the main causative organism of invasive infections in newborns due to vertical transmission from the colonized mothers. The study was undertaken to determine colonization rate, serotype distribution, genotypic characterization, antibiotic susceptibility profiles and molecular characteristics of erythromycin-resistant strains of GBS in pregnant women in Beijing, China. Vaginal–rectal swabs were collected from a total of 2850 pregnant women at 35–37 weeks of gestation, in which 7.1% were GBS positive. Serotypes III, Ia and V predominated. All isolates were penicillin susceptible, whereas the resistance rates for erythromycin and clindamycin were strikingly high.     

Comparison of DNA dot blot hybridization and lancefield capillary precipitin methods for group B streptococcal capsular typing

Group B streptococci (GBS) (Streptococcus agalactiae) are a major cause of sepsis and meningitis in neonates and infants and of invasive disease in pregnant women, nonpregnant, presumably immunocompromised adults, and the elderly. Nine GBS serotypes based on capsular polysaccharide antigens have been described. The serotype distributions among invasive and colonizing isolates differ between pediatric and adult populations and have changed over time. Thus, periodic monitoring of GBS serotype distributions is necessary to ensure the proper formulation and application of an appropriate GBS vaccine for human use and to detect the emergence of novel serotypes. Since the mid-1990s, the proportion of GBS isolates that are nontypeable by standard serologic methods has increased, creating a need for more sensitive typing methods. We describe a typing method that uses DNA dot blot hybridization with probes generated by PCR from the GBS capsular genes for serotypes Ia, Ib, and II to VIII. PCR primers were designed to amplify type-specific GBS capsular gene sequences. Gene probes were constructed from the PCR products and used to classify isolates based on hybridization profiles. A total of 306 previously serotyped invasive and colonizing isolates were used to compare our dot blot capsular typing (DBCT) identification method with Lancefield serotyping (LS). A dot blot capsular type was assigned to 99% (303 of 306) of the isolates, whereas 273 of 306 isolates (89%) were assigned a Lancefield serotype. The overall agreement between the methods was 95% (256 of 270 isolates typeable by both methods). We conclude that the DBCT method is a specific and useful alternative to the commonly used LS method.     

Serotype IX, a Proposed New Streptococcus agalactiae Serotype

We identified three isolates of Streptococcus agalactiae (group B streptococcus [GBS]), of human origin, which failed to react with antisera against any of the nine known GBS serotypes. Polyclonal rabbit antisera raised against these isolates and standard GBS typing sera were used in capillary precipitation and Ouchterlony tests to compare the strains with known GBS serotype reference strains. All three previously nontypeable isolates reacted with all three new antisera, producing lines of identity in the Ouchterlony test. Weak cross-reactions with antisera against several GBS serotypes were observed but were removed by absorption with corresponding antigens. The new antisera were used to test 227 GBS isolates that had been nontypeable or difficult to type using standard antisera. Of these, five reacted with the new antisera. These results suggested that all eight isolates belong to the previously unrecognized GBS serotype. They were tested by Western blotting for the Calpha and Cbeta proteins and by PCR to identify molecular serotypes and surface protein antigen genes. Two segments of the cps gene cluster (3' end of cpsE-cpsF and 5' end of cpsG, approximately 700 bp; 3' end of cpsH and 5' end of cpsM, approximately 560 bp) were sequenced. All eight isolates expressed Calpha, and seven expressing the Cbeta protein and the corresponding genes, bca and bac, respectively, were identified. They all share the same, unique partial cps sequence. These results indicate that these eight isolates represent a new S. agalactiae serotype, which we propose should be designated serotype IX.     

Colonization rates and serotypes of group B streptococci isolated from pregnant women in a Korean tertiary hospital

In a study designed to provide data on the rates of maternal carriage of group B streptococci (GBS) in Korean women, vaginal, anorectal, and urethral swab specimens from 459 pregnant women and ear canal and umbilicus swabs from their 288 neonates were cultured with new Granada medium and selective Todd-Hewitt broth. Additionally, the serotypes of 64 isolates of GBS and the minimal inhibitory concentrations of seven antimicrobial agents for these isolates were determined. The rate of colonization by GBS in pregnant women and in their babies was 5.9% (27/459) and 0.7% (2/288), respectively. The rates of resistance of GBS isolated from pregnant women were 13.3% to clindamycin, 5% to erythromycin, and 98.3% to tetracycline. The majority of GBS isolates from pregnant women belonged to serotypes Ib (48.3%), la (24.1 %), and III (20.7%).     

Comparison of scpB gene and cfb gene polymerase chain reaction assays with culture on Islam medium to detect Group B Streptococcus in pregnancy

Purpose: The purpose of the current study was to evaluate two low-costing PCR assays for rapid detection of Group B Streptococcus (GBS) in comparison to a pigment-based culture method. Materials and Methods: One-hundred and fifty vaginal swabs were collected from pregnant women at 35–40 weeks of gestation. Vaginal swabs were inoculated in selective enrichment broth medium, and examined using Islam medium, cfb PCR and scpB PCR assays. The demographic data were analysed to identify independent predictors of GBS colonization (age and gravidity), with GBS status as the dependent variable. Results: There was a significant association of age and gravidity with GBS colonization. GBS was detected in 25.3% of isolates by Islam medium, in 30.6% by using the cfb PCR assay and in 30% by using the scpB PCR assay. Conclusion: older pregnant women (≥30 years) and multigravida (>3 pregnancies) are at higher risk of GBS colonization. Both scpB-gene and cfb-gene-based PCR methods are highly sensitive techniques (100% sensitivity) compared to culture method. However, the specificities of the scpB and cfb PCR assays were 93.75 and 92.85%, respectively.     

Comparison of culture with two different qPCR assays for detection of rectovaginal carriage of Streptococcus agalactiae (group B streptococci) in pregnant women

Development of rapid and sensitive detection methods for group B streptococci (GBS) in pregnant women remains useful in order to adequately identify pregnant women at risk of transferring GBS to their neonate. This study compared the CDC recommended sampling and culture method with two qPCR methods for detecting GBS colonization.For a total of 100 pregnant women at 35-37 weeks of gestation, one rectovaginal ESwab each was collected. Eswab medium was inoculated into Lim broth, incubated for 24 h and plated onto chromID™ Strepto B agar (ChromAgar). DNA was extracted with the bioMérieux easyMAG platform, either directly from the rectovaginal ESwab or from Lim broth enrichment culture. Two different qPCR formats were compared, i.e. the hydrolysis probe format (Taqman, Roche) targeting the sip gene and the hybridization probe format (Hybprobe, Roche) targeting the cfb gene.Both qPCR techniques identified 33% of the women as GBS-positive. Only one culture-positive sample was qPCR-negative. QPCR directly on the sample significantly increased the number of women found to be GBS-positive (27%) compared to culture (22%). Moreover, the sensitivity of qPCR after Lim broth enrichment (33%) was again significantly higher than qPCR after DNA extraction directly from the rectovaginal swabs (27%).In conclusion, for prenatal screening of GBS from rectovaginal samples of pregnant women, our results are in accordance with CDC guidelines, which suggest using qPCR after Lim broth enrichment in addition to conventional (culture-based) detection. qPCR after Lim broth enrichment further increased the percentage of GBS-positive women, as detected by direct qPCR, from 27 to 33%, although the bacterial inoculum was low for these subjects.     

Multilocus sequence typing of Swedish invasive group B streptococcus isolates indicates a neonatally associated genetic lineage and capsule switching

Streptococcus agalactiae, also designated group B streptococcus (GBS), is an important pathogen in neonates, pregnant women, and nonpregnant adults with predisposing conditions. We used multilocus sequence typing (MLST) to characterize 158 GBS isolates that were associated with neonatal and adult invasive disease and that were collected in northern and western Sweden from 1988 to 1997. Five major genetic lineages (sequence type [ST] 19, ST-17, ST-1, ST-23, and ST-9 complexes) were identified among the isolates, including serotype Ia, Ib, and II to V isolates, indicating a highly clonal population structure among invasive GBS isolates. A number of STs were found to contain isolates of different serotypes, which indicates that capsule switching occurred rather frequently. Two distantly related genetic lineages were identified among isolates of serotype III, namely, clonal complex 19 (CC19), and CC17. CC19 was equally common among isolates from adult and neonatal disease (accounting for 10.3% of GBS isolates from adult disease and 18.7% from neonatal disease), whereas CC17 significantly appeared to be associated with neonatal invasive disease (isolated from 21.9% of neonatal isolates but only 2.6% of adult isolates). The distribution of the mobile elements GBSi1 and IS1548 reveals that they can act as genetic markers for lineages CC17 and CC19, respectively.     

妊娠35～37周孕妇携带的B群无乳链球菌血清分型

目的 探讨北京地区妊娠35～37周孕妇携带的无乳链球菌(GBS)血清型的分布特点.方法 按照2010年美国CDC颁布的指南中的推荐对6000名妊娠35 ～ 37周的孕妇进行GBS常规筛查.阴道和直肠分泌物联合取样进行分离培养,用VITEK 2 Compact全自动细菌鉴定系统对疑似B群链球菌进行鉴定,使用多重PCR扩增及基因测序的方法对GBS菌株进行血清分型检测.结果 共检出311株无乳链球菌,分为8个血清型.血清分型为Ⅰa型106例(34.1％),Ⅰb型53例(17.4％),Ⅲ型134例(43.1％),Ⅳ型6例(2.3％),Ⅱ型5例(1.6％),Ⅷ型3例(0.96％),Ⅴ型2例(0.64％),Ⅸ型2例(0.64％).结论 北京地区妊娠35 ～ 37周孕妇携带的无乳链球菌血清分型主要为Ⅲ、Ⅰa型.     

Vaginal colonization of the Streptococcus agalactiae in pregnant woman in Tunisia: risk factors and susceptibility of isolates to antibiotics

Streptococcus agalactiae or Group B Streptococcus (GBS) is one of the main bacterial causes of serious infections in newborns. We have evaluated prospectively GBS vaginal colonization in pregnant women and we have tried to determine the risk factors of the colonization by GBS and the particularities of the different isolated strains. We have screened 300 pregnant women with vaginal and anal sample in a same swab. Thirty nine (13%) pregnant women are colonized by SGB, 0% in the first trimester, 10.2% in the second trimester and 17% in the third trimester. Different factors are associated significantly with GBS colonization: past history of infection in newborns, genital infection during pregnancy and parity The highest rates of resistance are found in tetracycline (97.4%), erythromycin (51.3%) and lincomycin (46.2%). All the strains were susceptible to amoxicilin and pristinamycin.     

Bilan bactériologique de six ans de dépistage du streptocoque de groupe B (SGB) au cours du dernier trimestre de la grossesse

Streptococcus agalactiae (GBS) is a significant cause of morbidity and mortality among newborns. Colonization frequently occurs in pregnant women, nearly all international recommendations suggest that all pregnant women must be screened for vaginal colonization at 34 to 37 weeks of gestation. The microbiological diagnostic modalities used to combat GBS had to be accurate and in short time frame. We reported a 6 years experience of GBS screening, comparing results of culture swab of prenatal vaginal specimens and newborns colonization or infection. The carriage rate of 13 to 14% of GBS in newborn was unchanged during all the study period.     

Correlation of serotypes and genotypes of macrolide-resistant Streptococcus agalactiae

Despite the necessity for studies of group B streptococci (GBS), due to the increase in serious adult infections, the emergence of new serotypes, and the increased resistance to macrolide antibiotics, such studies have been limited in Korea. The primary purpose of the present study was to determine the frequency trends of GBS serotypes, including serotypes VI, VII, and VIII. The final objective was to elucidate the relationship between the genotypes and serotypes of macrolide-resistant GBS isolates from a Korean population. Among 446 isolates of Streptococcus agalactiae, isolated between January 1990 and December 2002 in Korea, the frequency of serotypes were III (36.5%), Ib (22.0%), V (21.1%), Ia (9.6%), VI (4.3%), II (1.8%), VIII (1.3%), IV (1.1%), and VII (0.9%). The resistance rates to erythromycin, by serotype, were 85% (V), 23% (III), 21% (VI), 3% (Ib), and 2% (Ia). Of 135 erythromycin- resistant S. agalactiae, ermB was detected in 105 isolates, mefA in 20 isolates, and ermTR in seven isolates; most type V isolates harbored the ermB gene, Ib type isolates had an equal distribution of resistance genes, type III isolates accounted for 70% of all isolates carrying mefA genes, and one fourth of type VI isolates had mefA genes.     

Serotype Identification of Group B Streptococci by PCR and Sequencing

Group B streptococcus (GBS; Streptococcus agalactiae) is the most common cause of neonatal and obstetric sepsis and is an increasingly important cause of septicemia in elderly individuals and immunocompromised patients. Ongoing surveillance to monitor GBS serotype distribution will be needed to guide the development and use of GBS conjugate vaccines. We designed sequencing primers based on the previously published sequences of the capsular polysaccharide (cps) gene clusters to further define partial cps gene clusters for eight of the nine GBS serotypes (serotypes Ia to VII). Subsequently, we designed and evaluated primers to identify serotypes Ia, Ib, III, IV, V, and VI directly by PCR and all eight serotypes (serotypes Ia to VII) by sequence heterogeneity. A total of 206 clinical GBS isolates were used to compare our molecular serotype (MS) identification method with conventional serotyping (CS). All clinical isolates were assigned an MS, whereas 188 of 206 (91.3%) were assigned a serotype by use of antisera. A small number of isolates (serosubtypes III-3 and III-4) showed different serotype specificities between PCR and sequencing, but the PCR results correlated with those obtained by CS. The overall agreement between the MS identification method and CS for isolates for which results of both tests were available was 100% (188 of 188 isolates). The MS identification method is a specific and practical alternative to conventional GBS serotyping and will facilitate epidemiological studies.     

Phenotypes, genotypes, serotypes and molecular epidemiology of erythromycin-resistant Streptococcus agalactiae in Italy

The purpose of this investigation was to analyse Streptococcus agalactiae (group B Streptococcus, GBS) isolates collected in Italy from vaginal and urine samples in respect to their clonality, distribution of virulence factors and antimicrobial resistance determinants. Three hundred and eighty-eight GBS were recovered from clinical samples. They were analysed for antibiotic resistance profiling. Erythromycin-resistant strains were further characterised by multilocus sequence typing (MLST), serotyping and the detection of alp genes of the alpha-like protein (Alp) family. GBS isolates represented 40 different sequence types (STs), grouped in five clonal complexes (CCs) and belonged to seven serotypes. Most serotype V strains (81%) possessed alp2-3; serotype Ia carried mainly epsilon, while the serotype III mainly rib. All isolates were susceptible to penicillin, whereas resistance to erythromycin was detected in 15% of isolates. Most erythromycin-resistant GBS strains were of serotype V (56.8%) and belonged to the CC-1 group (50%). Macrolide resistance phenotypes were the cMLS(B) (46.5%) and the M phenotypes (46.5%) due to the presence of ermB and mefA/E genes, respectively. These results provide data which establish a baseline for monitoring erythromycin resistance in this region and also provide an insight into the correlation among clonal types, serotypes, surface protein and resistance genes. The increased prevalence of strains that displayed the M phenotype strengthens the importance of the epidemiological surveillance of macrolide resistance in GBS, which may also represent an important reservoir of resistance genes for other species.     

Prevention of group B streptococcal neonatal disease revisited. The DEVANI European project

The purpose of this paper was to present the current knowledge on the prevention of group B streptococcus (GBS) neonatal infections and the status of prevention policies in European countries and to present the DEVANI pan-European program, launched in 2008. The aim of this program was to assess the GBS neonatal infection burden in Europe, to design a new vaccine to immunize neonates against GBS infections, to improve the laboratory performance for the diagnosis of GBS colonization and infection, and to improve the methods for the typing of GBS strains. The current guidelines for GBS prevention in different countries were ascertained and a picture of the burden before and after the instauration of prevention policies has been drawn. After the issue of the Centers for Disease Control and Prevention (CDC) guidelines, many European countries have adopted universal screening for the GBS colonization of pregnant women and intrapartum prophylaxis to colonized mothers. Nevertheless, some European countries continue advocating the risk factor approach to GBS prevention. Most European countries have implemented policies to prevent GBS neonatal infections and the burden of the disease has decreased during the last several years. Nevertheless, further steps are necessary in order to develop new strategies of prevention, to improve microbiological techniques to detect GBS colonization and infection, and to coordinate the prevention policies in the EU.     

Evaluation of Trans-Vag Broth,Colistin-Nalidixic Agar,and CHROMagar StrepB for Detection of Group B Streptococcus in Vaginal and Rectal Swabs from Pregnant Women in South Africa

Maternal vaginal colonization with group B streptococcus (GBS) is a major risk factor for invasive GBS infection in newborns. The CDC-recommended method for detecting GBS colonization is to culture vaginal and rectal swabs in a selective broth followed by subculture on blood agar or a selective medium. A high incidence of antimicrobial resistance in the fecal microflora can compromise the recovery of GBS from the selective broth. Here, we compared CHROMagar StrepB (CA), Columbia colistin-nalidixic agar (CNA), and Trans-Vag selective broth enrichment for the isolation of GBS from 130 vaginal and 130 rectal swabs from pregnant women. The swabs were randomized for plating first on either CA or CNA, and they then were inoculated in Trans-Vag broth. GBS was cultured from 37.7% of the vaginal swabs and 33.1% of the rectal swabs. There were no differences in the detection rates for the vaginal swabs between CA (31.5%), CNA (26.2%), and the selective broth (30.0%). The sensitivities in relation to a composite score were 83.7%, 69.4%, and 79.6%, respectively. However, recovery of GBS from the rectal swabs was significantly higher from CA (29.2%; P < 0.0001) and CNA (23.8%; P = 0.002) than from the selective broth (9.2%). The sensitivities were 88.4%, 72.1%, and 27.9%, respectively. The order of plating on the solid medium was significant (P = 0.003), with GBS detection rates of 30.8% and 24.6% when swabs were plated first and second, respectively. These findings show that a selective broth is not suitable for the recovery of GBS from rectal swabs in settings such as ours, due to masking of the GBS colonies by persistent microflora.     

Detection of colonization by Streptococcus agalactiae: prospective study comparing real-time gene amplification with a new chromogenic medium Strepto B ID

We carried out a prospective study including 554 vaginal swabs simultaneously tested for antenatal screening of Group B Streptococcus (GBS or Streptococcus agalactiae) using culture on the chromogenic medium Strepto B ID (Biomérieux, Marcy l'Etoile, France) and real time gene amplification on LightCycler (Roche Applied Science). We centrifuge the swabs with "SETS" device and separate centrifugates in 2 parts: one for the culture and the other one for molecular biology. First half of the centrifugate is inoculated onto Todd-Hewitt broth enriched with antibiotics. This broth is incubated to 35 degrees C during 24 hours and then subcultured on a Strepto B ID medium. This last one is incubated during 24 hours to 35 degrees C in capnophilic conditions before interpretation. DNA extraction for molecular biology is simply obtained by heating the microtubes to 95 degrees C in a water bath. The cfb gene is amplified, allowing a specific gene amplification of GBS even within a polymorphic flora. The concordance between both methods is 94.8%. The sensitivity and negative predictive values obtained are respectively 88.0 and 97.4% for real time PCR and 83.0 and 96.4% for culture on Strepto B ID. Both methods are thus concordant, with equal sensitivity and valid for detection of GBS colonization in pregnant women. However real time gene amplification allows reducing turn around time since molecular biology process (extraction+amplification) does not exceed 1 hour.     

Analysis of group B streptococcal isolates from infants and pregnant women in Portugal revealing two lineages with enhanced invasiveness

The populations of group B streptococcus (GBS) associated with vaginal carriage in pregnant women and invasive neonatal infections in Portugal were compared. GBS isolates were characterized by serotyping, pulsed-field gel electrophoresis (PFGE) profiling, and multilocus sequence typing (MLST). Serotypes III and V accounted for 44% of all colonization isolates (n = 269), whereas serotypes III and Ia amounted to 69% of all invasive isolates (n = 64). Whereas serotype Ia was associated with early-onset disease (EOD), serotype III was associated with late-onset disease (LOD). Characterization by PFGE and MLST identified very diverse populations in carriage and invasive disease. Serotype Ia was represented mainly by a single PFGE cluster defined by sequence type 23 (ST23) and the infrequent ST24. In contrast, serotype III was found in a large number of PFGE clusters and STs, but a single PFGE cluster defined by ST17 was found to be associated with invasive disease. Although serotype III was associated only with LOD, ST17 showed an enhanced capacity to cause both EOD and LOD. Our data reinforce the evidence for enhanced invasiveness of ST17 and identify a lineage expressing serotype Ia capsule and represented by ST23 and ST24 as having enhanced potential to cause EOD.     

Carriage of group B streptococcus in pregnant women from Oxford, UK

OBJECTIVE: To investigate asymptomatic vagino-rectal carriage of group B streptococcus (GBS) in pregnant women. METHODS: Women in the final trimester of pregnancy were recruited. A single vagino-rectal swab was taken, with consent, for culture of GBS. Two microbiological methods for isolation of GBS from vagino-rectal swabs were compared. The distribution of capsular serotypes of the GBS identified was determined. Epidemiological data for a subset (n = 167) of the pregnant women participating were examined. RESULTS: 21.3% were colonised vagino-rectally with GBS. Risk factors for neonatal GBS disease (maternal fever, prolonged rupture of membranes, and preterm delivery) were present in 34 of 167 women (20.4%), and the presence of these factors correlated poorly with GBS carriage. Capsular serotypes III (26.4%), IA (25.8%), V (18.9%), and IB (15.7%) were prevalent in the GBS isolates. Selective broth culture of vagino-rectal swabs was superior to selective plate culture, but the combination of both methods was associated with increased detection of GBS (7.5%). An algorithm for the identification of GBS from vagino-rectal swabs was developed. CONCLUSIONS: GBS carriage is prevalent in pregnant women in Oxfordshire, UK. The poor correlation between risk factors and GBS carriage requires further investigation in larger groups, given that the identification of these surrogate markers is recommended to guide administration of intrapartum antibiotic prophylaxis by the Royal College of Obstetricians of the UK. A selective broth culture detected more GBS carriers than a selective plate culture.