Molecular profiles of group B streptococcal surface protein antigen genes: relationship to molecular serotypes

The Streptococcus agalactiae R3 surface protein is encoded by sar5

Streptococcus agalactiae (group B streptococcus; GBS) is an important human pathogen causing pneumonia, sepsis and meningitis in neonates, as well as infections in pregnant women, immunocompromised individuals, and the elderly. For the future control of GBS-inflicted disease, GBS surface exposed proteins are particularly relevant as they may act as antigens for vaccine development and/or as serosubtype markers in epidemiological settings. Even so, the genes encoding some of the surface proteins established as serosubtype markers by antibody-based methods, like the R3 surface protein, are still unknown. Here, by examining a Norwegian GBS collection consisting of 140 strains, we find that R3 protein expression correlates with the presence of the gene sar5. By inducible expression of sar5 in an R3-negative bacterial strain we show that the sar5 gene product is specifically recognized by an R3 monoclonal antibody. With this we identify sar5 as the gene encoding the R3 surface protein, a serosubtype marker of hitherto unknown genetic origin.

Molecular Characteristic, Antibiotic Resistance, and Detection of Highly Immunoreactive Proteins of Group B Streptococcus Strains Isolated From Urinary Tract Infections in Polish Adults

Group B streptococcus (GBS) is one of the uropathogens that causes urinary tract infections (UTIs). The aims of this article were molecular characterization, an analysis of antimicrobial susceptibility profiles, adherence to bladder endothelial cells, and the detection of immunoreactive proteins of 94 clinical strains of GBS isolated from adult Polish patients with UTI. Antibiotic susceptibilities were determined by disk diffusion. Serotyping and Alp family genes detection were studied using multiplex PCR. Genetic profiles were determined by pulsed-field gel electrophoresis. The adherence ability of the studied strains was estimated by incubation on human bladder microvascular endothelial cell line. Immunoreactive proteins were studied by immunoblotting. Antibiotic susceptibility investigation revealed that 22% of GBS strains were resistant to erythromycin, whereas 18% demonstrated resistance to clindamycin. cMLS_B was present in 76% of the resistant strains, M phenotype was detected in 14%, whereas iMLS_B was present for 10%. The most common serotype was serotype III (31%), followed by serotype V (27%), and serotype Ia (17%). The genes that dominated among other Alp genes were: epsilon (29%), alp2 (27%), and rib (23%). The most common co-occurring serotypes and Alp genes were: Ia and epsilon, III and rib, III and alp2, V and alp2, and V and alp3 (p < 0.001). The PFGE method showed high clonality for serotype V and cMLS_B (p < 001). The PFGE method showed high clonality for serotype V. Furthermore, this serotype was significantly associated with the cMLS_B phenotype (p < 0.001). The most common immunoreactive proteins demonstrated masses of 50 kDa and 45–47 kDa. Although examined GBS isolates showed high genetic diversity, immunoreactive proteins were common for most of the studied GBS isolates, which may indicate their conservation, and allows to consider them as potential immunodiagnostic markers. Although the examined GBS isolates showed high genetic diversity, immunoreactive proteins were shared by most of the studied GBS isolates. It may indicate their conservation, thus allowing to consider them as potential immunodiagnostic markers.

Identifying large-scale recombination and capsular switching events in Streptococcus agalactiae strains causing disease in adults in the UK between 2014 and 2015

Cases of invasive group B streptococcal infection in the adult UK population have steadily increased over recent years, with the most common serotypes being V, III and Ia, but less is known of the genetic background of these strains. We have carried out in-depth analysis of the whole-genome sequences of 193 clinically important group B Streptococcus (GBS) isolates (184 were from invasive infection, 8 were from non-invasive infection and 1 had no information on isolation site) isolated from adults and submitted to the National Reference Laboratory at the UK Health Security Agency between January 2014 and December 2015. We have determined that capsular serotypes III (26.9%), Ia (26.4%) and V (15.0%) were most commonly identified, with slight differences in gender and age distribution. Most isolates (n=182) grouped to five clonal complexes (CCs), CC1, CC8/CC10, CC17, CC19 and CC23, with common associations between specific serotypes and virulence genes. Additionally, we have identified large recombination events mediating potential capsular switching events between sequence type (ST)1 serotype V and serotypes Ib (n=2 isolates), II (n=2 isolates) and VI (n=2 isolates); between ST19 serotype III and serotype V (n=5 isolates); and between CC17 serotype III and serotype IV (n=1 isolate). The high genetic diversity of disease-causing isolates and multiple recombination events reported in this study highlight the need for routine surveillance of the circulating disease-causing GBS strains. This information is crucial to better understand the global spread of GBS serotypes and genotypes, and will form the baseline information for any future GBS vaccine research in the UK and worldwide.

Emergence of Invasive Serotype Ib Sequence Type 10 Group B Streptococcus Disease in Chinese Infants Is Driven by a Tetracycline-Sensitive Clone

Background

Group B streptococcus (GBS) is a leading cause of serious infections in infants. The extensive use of tetracycline has led to the selection of specific resistant and infectious GBS clones. The sequence type (ST) 10 GBS strain, causing invasive infections in infants, is becoming prevalent in China. We aimed to understand the clinical and microbiological characteristics of this GBS strain.

Methods

We conducted a retrospective study on infants with invasive GBS disease from the largest women’s and children’s medical center in Shanxi and collected data between January 2017 and October 2020. GBS isolates were analyzed by capsule serotyping, genotyping, antibiotic resistance, and surface protein genes.

Results

All ST10 isolates belonged to serotype Ib; type Ib/ST10 strains were responsible for 66.7% (14/21, P < 0.05) of infant invasive GBS infections during the period and all resulted in late-onset (LOD) and late LOD disease (14/14). Infants with type Ib/ST10 GBS disease had significantly higher rates of meningitis (9/14, 64.3%, p < 0.05) and clinical complications (5/14, 35.7%, p < 0.05). The Ib/ST10 GBS isolates had limited genetic diversity, clustered in the CC10/bca/PI-1 + PI-2a genetic lineage, showed resistance to erythromycin, lincomycin, and fluoroquinolones and sensitivity to tetracycline, and possessed genes ermT, ermB, and amino acid changes in gyrA and parC.

Conclusions

The probable clonal expansion can result in severe infections in infants and ongoing emergence of multi-drug resistant isolates. Continued monitoring for type Ib/ST10 GBS infections is warranted.

High prevalence of group B streptococcus ST17 hypervirulent clone among non-pregnant patients from a Hungarian venereology clinic

Background

Although Streptococcus agalactiae is the leading causative agent of neonatal sepsis and meningitis, recently it is increasingly isolated from non-pregnant adults. The relation between its presence in the genitourinary tract and manifested clinical symptoms of STD patients remains an open question. In this study, a complex epidemiological investigation of GBS isolates from a venerology clinic was performed.

Methods

Ninety-six GBS isolates were serotyped and their genetic relatedness determined by PFGE. MLST was also performed for a subset of 20 isolates. The antibiotic susceptibility was tested with agar dilution. Surface proteins and the ST-17 hypervirulent clone was detected by PCR.

Results

The serotype prevalence was the following: V (29.2%), III (27.1%), Ia (22.9%), IV (10.4%), II (5.2%) and Ib (4.2%). A strong association was demonstrated between surface protein genes and serotypes. All isolates were fully susceptible to penicillin, but erythromycin and clindamycin resistance was high (41.7 and 35.4%, respectively), and 8 phenotypically macrolide sensitive isolates carried the ermB gene.

21.9% of all strains belonged to the hypervirulent ST17 clone, most being of serotype III and all were rib +. We found a few serotype IV isolates belonging to several STs and one serotype V/ST110 strain, containing a 44-bp deletion in the atr allele.

Conclusions

The presence of silent ermB genes is of worry, as their expression upon macrolide exposure could lead to unforeseen therapeutic failure, while clindamycin is used for intrapartum antibiotic prophylaxis, in case of penicillin allergy. The other alarming result is the high prevalence of ST17 among these strains from STD patients, who could be sources of further infections.

This is the first report from Hungary providing both serotyping and genotyping data of GBS isolates. These results could be helpful for vaccine production as the major vaccine candidates are capsular antigens or surface proteins.

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.

Determination of surface proteins profile, capsular genotyping, and antibiotic susceptibility patterns of Group B Streptococcus isolated from urinary tract infection of Iranian patients

Objectives

Group B Streptococcus (GBS) is an important opportunistic bacteria that causes a wide range of infections including neonatal sepsis, meningitis, pneumonia, soft tissue and urinary tract infections (UTI). The aim of this study was to evaluate the antimicrobial susceptibility patterns, surface proteins and capsular types of GBS isolates.

Results

100 of UTI isolates were confirmed as GBS. Antimicrobial susceptibility pattern showed that 95% of GBS isolates were resistant to tetracycline, followed by erythromycin (52%), clindamycin (47%), levofloxacin (9%) and penicillin, cefepime, cefotaxime, and ceftriaxone each with (8%), and vancomycin 1%. Common capsular types were III, Ib, V, II, Ia and IV respectively and the distribution of surface protein genes was as follows: rib (40%), alpha-c (22%), alp2/3 (18%) and epsilon (15%), and alp4 gene was not detected in the isolates. Our findings showed the relationship between capsular types with Alpha-like proteins, as well as reduced sensitivity to antibiotics, so the performance of antibiotic surveillance programs is recommended.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4428-4) contains supplementary material, which is available to authorized users.

The N-terminal domain of the R28 protein promotes emm28 group A Streptococcus adhesion to host cells via direct binding to three integrins

Group A Streptococcus (GAS) is a human-specific pathogen responsible for a wide range of diseases, ranging from superficial to life-threatening invasive infections, including endometritis, and autoimmune sequelae. GAS strains express a vast repertoire of virulence factors that varies depending on the strain genotype, and many adhesin proteins that enable GAS to adhere to host cells are restricted to some genotypes. GAS emm28 is the third most prevalent genotype in invasive infections in France and is associated with gyneco-obstetrical infections. emm28 strains harbor R28, a cell wall-anchored surface protein that has previously been reported to promote adhesion to cervical epithelial cells. Here, using cellular and biochemical approaches, we sought to determine whether R28 supports adhesion also to other cells and to characterize its cognate receptor. We show that through its N-terminal domain, R28_Nt, R28 promotes bacterial adhesion to both endometrial-epithelial and endometrial-stromal cells. R28_Nt was further subdivided into two domains, and we found that both are involved in cell binding. R28_Nt and both subdomains interacted directly with the laminin-binding α3β1, α6β1, and α6β4 integrins; interestingly, these bindings events did not require divalent cations. R28 is the first GAS adhesin reported to bind directly to integrins that are expressed in most epithelial cells. Finally, R28_Nt also promoted binding to keratinocytes and pulmonary epithelial cells, suggesting that it may be involved in supporting the prevalence in invasive infections of the emm28 genotype.

Status of group B streptococcal vaccine development

Streptococcus agalactiae (group B streptococcus, GBS) is a leading causal organism of neonatal invasive diseases and severe infections in the elderly. Despite significant advances in the diagnosis and treatment of GBS infections and improvement in personal hygiene standards, this pathogen is still a global health concern. Thus, an effective vaccine against GBS would augment existing strategies to substantially decrease GBS infection. In 2014, World Health Organization convened the first meeting for consultation on GBS vaccine development, focusing on the GBS maternal immunization program, which was aimed at reducing infections in neonates and young infants worldwide. Here, we review the history of GBS infections, the current vaccine candidates, and the current status of immunogenicity assays used to evaluate the clinical efficacy of GBS vaccines.

Potential biomarkers for effective screening of neonatal sepsis infections: An overview

Neonatal sepsis, a clinical disorder developed by bacterial blood stream infections (BSI) in neonates, is one of the serious global public health problems that must be addressed. More than one million of the estimated global newborn deaths per year are occurred due to severe infections. The genesis of the infection is divided into early-onset sepsis (EOS) and late-onset sepsis (LOS) of the disease. The clinical complications of neonatal sepsis may be associated with bronchopulmonary dysplasia, ductus arteriosus and necrotizing enterocolitis. The clinical diagnosis and treatment of neonatal sepsis is highly complicated. Over the past few years distinct biomarkers have been identified. Most widely used biomarkers are C-reactive protein, Procalcitonin (PCT) and Serum amyloid A (SAA). Until recently, many potential biomarkers including Cell Surface antigens and Bacterial surface antigens and genetic biomarkers are being investigated. Protein biomarkers, cytokines and chemokines are getting much interest for identification of neonatal sepsis infection.

Molecular characteristics and antimicrobial resistance in invasive and noninvasive Group B Streptococcus between 2008 and 2015 in China

Group B streptococcus (GBS) is an increasing pathogen threat to newborns and adults with immunodepressive diseases. Here, a total of 193 GBS, including 51 invasive and 142 noninvasive isolates, were collected from the patients with infections in 7 tertiary hospitals from 5 cities in China during the year 2008 to 2015. The strains of GBS were characterized by classical and molecular techniques for capsular polysaccharide serotyping, genes for pilus island (PI) and α-like protein (alp), and antibiotic resistance profiling. Of 193 isolates, the predominant serotypes were III (45.6%) and Ia (18.7%). All strains carried at least 1 PI gene. The combination of PI-2b and PI-1 was present in 46.1% isolates, followed by PI-2a alone (80, 41.5%) and PI-2b alone (23, 11.9%). The most prevalent alp gene was rib (87, 45.1%), followed by α-C (47, 24.4%), ε (33, 17.1%), alp2/3 (7, 3.6%) and alp4 (2, 1.0%), respectively. The clonal relationships between strains were investigated using multilocus sequence typing. The strains were distinguished into 26 individual sequence typing, and further clustered into 6 clonal complexes. A significant association was noted between the distributions of alp genes, serotyping and PI profiles, such as serotype III-rib-PI+PI-2a, Ib-α-C, and Ia-ε-PI-2a. No penicillin-resistant strains were detected, and 74.1%, 64.2%, and 68.9% were resistant to erythromycin, clindamycin, and tetracycline, respectively. The infective GBS isolates in China demonstrated epidemical features.

Characterization of virulence factors, antimicrobial resistance pattern and clonal complexes of group B streptococci isolated from neonates

Between January and December 2013, swab samples were taken for the throat and external ear canals of 1037 newborns for screening of Group B Streptococcus (GBS or S. agalactiae). Isolates were analyzed form Multilocus sequence typing (MLST), capsular type, virulence genes and antibiotic susceptibility. The MLST analysis of 19 GBS isolates showed 8 sequence types (STs). Overall the most common STs were ST19 and ST28. Other STs were ST1, ST4, ST8, ST12, ST335 and ST734 (a new ST). The most common clonal complexes (CCs) were CC19 (68.4%) and CC10 (21%). The scpB, hlyB and bca virulence genes were detected in all ST_S, while the bac gene was predominant in ST12 with capsular type (CT) Ib. The IS1548 and the rib genes were particularly prevalent in CTIII and were detected in isolates belong to ST19, ST335 and ST734 and were grouped in CC19. All isolates were susceptible to penicillin, vancomycin, linezolid and quinupristin-dalfopristin. Resistance to tetracycline was observed in all 19 (100%) strains and was correlated with presence of the tetM gene except for one isolate with ST12. All the ST8 and ST12 isolates were resistant to macrolide carrying two resistance genes; the ermTR and the ermB, respectively. The results of this study showed that the CC19 was a major clone in the neonatal intensive care unit (NICU) of Imam Khomeini hospital which can cause severe infections in susceptible neonates (particularly in premature infants). As a result, an intensive infection control policy is needed to prevent the spread of this clone.

Characterization of a Group B Streptococcus infection based on the demographics, serotypes, antimicrobial susceptibility and genotypes of selected isolates from sterile and non-sterile isolation sites in three major hospitals in Malaysia

BACKGROUND/PURPOSE

The purpose of this study is to characterize GBS isolates that were collected from three major hospitals in a densely populated area of Klang Valley for their demographics, serotypes, antibiotic susceptibility patterns and genetic background.

METHODS

Sixty GBS isolates from sterile and non-sterile samples in three major hospitals in the Klang Valley area of Malaysia were collected by convenience sampling from 2012 until March 2014. These isolates were studied for their antimicrobial susceptibilities, serotypes and genotypes. Patients' demographic data and clinical information were collected from lab request forms.

RESULTS

Diabetes mellitus was the only underlying condition (7 patients, 23.3%); the remaining samples were from patients who were immunocompromised due to medications. Fifty-nine (98%) isolates were sensitive to penicillin, while 78.3% and 88.3% of the isolates were sensitive to erythromycin and clindamycin, respectively. Serotype Ia was the most common serotype (n=27, 45%), followed by serotype III (n=10, 16.7%), V (n=9, 15%), VI (n=8, 13.3%), VIII (n=2, 3.3%) and VII (n=1, 1.7%). Random Amplified Polymorphic DNA (RAPD) typing showed a diverse genetic pedigree for all isolates, including four major groups that clustered according to geographical location.

CONCLUSION

This preliminary study determines the prevalence of limited common serotypes and antimicrobial resistance in distinct GBS isolates. Nonetheless, the RAPD clustering pattern suggests a close genetic lineage of the GBS isolates based on their isolation sites and location of hospitals.

Molecular Characterization of Streptococcus agalactiae Isolates From Pregnant and Non-Pregnant Women at Yazd University Hospital, Iran

Background:

Streptococcus agalactiae (Group B streptococcus, GBS) that colonize the vaginas of pregnant women may occasionally cause neonatal infections. It is one of the most common causes of sepsis and meningitis in neonates and of invasive diseases in pregnant women. It can also cause infectious disease among immunocompromised individuals. The distribution of capsular serotypes and genotypes varies over time and by geographic era. The serotyping and genotyping data of GBS in Iranian pregnant and non-pregnant women seems very limited.

Objectives:

The aim of this study was to investigate the GBS ‎molecular capsular serotype ‎and genotype distribution of pregnant and non-pregnant carrier ‎women at Yazd university hospital, in Iran.‎

Patients and Methods:

In this cross-sectional study, a total of 100 GBS strains isolated from 237 pregnant and 413 non-pregnant women were investigated for molecular capsular serotypes and surface protein genes using the multiplex PCR assay. The Chi-square method was used for statistical analysis.

Results:

Out of 650 samples, 100 (15.4%) were identified as GBS, with a predominance of capsular serotypes III (50%) [III-1 (49), III-3 (1)], followed by II (25%), Ia (12%), V (11%), and Ib (2%), which was similar with another study conducted in Tehran, Iran, but they had no serotype Ia in their report. The surface protein antigen genes distribution was rib (53%), epsilon (38%), alp2/3 (6%), and alpha-c (3%).

Conclusions:

The determination of serotype and surface proteins of GBS strains distribution would ‎be ‎relevant ‎for the future possible formulation of a GBS vaccine.

Genomic comparison of virulent and non-virulent Streptococcus agalactiae in fish

Streptococcus agalactiae infections in fish are predominantly caused by beta-haemolytic strains of clonal complex (CC) 7, notably its namesake sequence type (ST) 7, or by non-haemolytic strains of CC552, including the globally distributed ST260. In contrast, CC23, including its namesake ST23, has been associated with a wide homeothermic and poikilothermic host range, but never with fish. The aim of this study was to determine whether ST23 is virulent in fish and to identify genomic markers of fish adaptation of S. agalactiae. Intraperitoneal challenge of Nile tilapia, Oreochromis niloticus (Linnaeus), showed that ST260 is lethal at doses down to 10(2) cfu per fish, whereas ST23 does not cause disease at 10(7) cfu per fish. Comparison of the genome sequence of ST260 and ST23 with those of strains derived from fish, cattle and humans revealed the presence of genomic elements that are unique to subpopulations of S. agalactiae that have the ability to infect fish (CC7 and CC552). These loci occurred in clusters exhibiting typical signatures of mobile genetic elements. PCR-based screening of a collection of isolates from multiple host species confirmed the association of selected genes with fish-derived strains. Several fish-associated genes encode proteins that potentially provide fitness in the aquatic environment.

Antigenic distribution of Streptococcus agalactiae isolates from pregnant women at Garankuwa hospital - South Africa

INTRODUCTION

Streptococcus agalactiae (group B streptococcus; GBS) is globally recognised as one of the leading causes of neonatal sepsis and meningitis. It also causes adverse pregnancy outcomes such as stillbirth and miscarriages. Incidence of invasive disease is increasing in non-pregnant adults with underlying medical conditions (e.g., diabetes mellitus). Epidemiological studies of GBS infections are based on capsular serotyping. Genotyping of the surface anchored protein genes is also becoming an important tool for GBS studies. Currently ten different GBS serotypes have been identified. This study was performed to determine the prevalence of GBS capsular types (CTs) and surface anchored protein genes in isolates from colonized pregnant women attending antenatal clinic, at Dr George Mukhari Academic Hospital, Garankuwa, Pretoria, South Africa.

METHODS

The samples were collected over 11 months and cultured on selective media. GBS was identified using different morphological and biochemical tests. Capsular typing was done using latex agglutination test and conventional PCR. Multiplex PCR with specific primers was used to detect the surface anchored protein genes.

RESULTS

Of the 413 pregnant women recruited, 128 (30.9%) were colonized with GBS. The capsular polysaccharide (CPS) typing test showed that CPS type III (29.7%) was the most prevalent capsular type followed by CPS type Ia (25.8%), II (15.6%), IV (8.6%), V (10.9%) and Ib (8.6%); 0.7% of the isolates were nontypeable. Multiplex PCR revealed that the surface proteins genes were possessed by all the capsular types: rib (44.5%), bca (24.7%), alp2/3 (17.9%), epsilon (8.6%) and alp4 (4.7%).

CONCLUSION

The common capsular types found in this study are Ia, III, and II. The most common protein genes identified were rib and bca, and the distribution of the surface protein genes among the isolates of different capsular types showed similar trends to the distribution reported from previous studies.

Natural Mutations in Streptococcus agalactiae Resulting in Abrogation of β Antigen Production

Streptococcus agalactiae genome encodes 21 two-component systems (TCS) and a variety of regulatory proteins in order to control gene expression. One of the TCS, BgrRS, comprising the BgrR DNA-binding regulatory protein and BgrS sensor histidine kinase, was discovered within a putative virulence island. BgrRS influences cell metabolism and positively control the expression of bac gene, coding for β antigen at transcriptional level. Inactivation of bgrR abrogated bac gene expression and increased virulence properties of S. agalactiae. In this study, a total of 140 strains were screened for the presence of bac gene, and the TCS bgrR and bgrS genes. A total of 53 strains carried the bac, bgrR and bgrS genes. Most of them (48 strains) expressed β antigen, while five strains did not express β antigen. Three strains, in which bac gene sequence was intact, while bgrR and/or bgrS genes had mutations, and expression of β antigen was absent, were complemented with a constructed plasmid pBgrRS(P) encoding functionally active bgrR and bgrS gene alleles. This procedure restored expression of β antigen indicating the crucial regulatory role of TCS BgrRS. The complemented strain A49V/BgrRS demonstrated attenuated virulence in intraperitoneal mice model of S. agalactiae infection compared to parental strain A49V. In conclusion we showed that disruption of β antigen expression is associated with: i) insertion of ISSa4 upstream the bac gene just after the ribosomal binding site; ii) point mutation G342A resulting a stop codon TGA within the bac gene and a truncated form of β antigen; iii) single deletion (G) in position 439 of the bgrR gene resulting in a frameshift and the loss of DNA-binding domain of the BgrR protein, and iv) single base substitutions in bgrR and bgrS genes causing single amino acid substitutions in BgrR (Arg187Lys) and BgrS (Arg252Gln). The fact that BgrRS negatively controls virulent properties of S. agalactiae gives a novel clue for understanding of S. agalactiae adaptation to the human.

Distribution of pilus islands and alpha-like protein genes of group B Streptococcus colonized in pregnant women in Beijing, China

Group B Streptococcus (GBS) is one of the major pathogens of severe newborn sepsis and meningitis. Understanding its regional molecular epidemiology is helpful for regulating efficient prevention practice. A total of 160 GBS strains were collected from colonized pregnant women in six hospital settings in Beijing, China. Polymerase chain reaction (PCR) assays were used to identify the pilus island (PI), alp genes profiling of the alpha-like protein family, and capsular polysaccharide (cps) serotyping. The clonal relationships between strains were investigated using multilocus sequence typing (MLST). All isolates carried at least one pilus island. The most frequently detected pilus island was PI-2a alone (70 isolates, 43.8 %). The most prevalent alp gene was rib (60 isolates, 37.5 %). Moreover, a strong association was noted between alp genes, serotyping, and pilus island profiles. The GBS isolates under study hinted similar molecular epidemical characteristics in Beijing to those reported worldwide, but having their regional distributional features.

Survey of immunological features of the alpha-like proteins of Streptococcus agalactiae

Nearly all Streptococcus agalactiae (group B streptococcus [GBS]) strains express a protein which belongs to the so-called alpha-like proteins (Alps), of which Cα, Alp1, Alp2, Alp3, Rib, and Alp4 are known to occur in GBS. The Alps are chimeras which form mosaic structures on the GBS surface. Both N- and C-terminal stretches of the Alps possess immunogenic sites of dissimilar immunological specificity. In this review, we have compiled data dealing with the specificity of the N- and C-terminal immunogenic sites of the Alps. The majority of N-terminal sites show protein specificity while the C-terminal sites show broader cross-reactivity. Molecular serotyping has revealed that antibody-based serotyping has often resulted in erroneous Alp identification, due to persistence of cross-reacting antibodies in antisera for serotyping. Retrospectively, this could be expected on the basis of sequence analysis results. Some of the historical R proteins are in fact Alps. The data included in the review may provide a basis for decisions regarding techniques for the preparation of specific antisera for serotyping of GBS, for use in other approaches in GBS research, and for decision making in the context of GBS vaccine developments.

Virulence factors, antimicrobial susceptibility and molecular characterization of Streptococcus agalactiae isolated from pregnant women

Forty-one Streptococcus agalactiae isolates collected from pregnant women at 35-37 weeks of gestation were analysed for their capsular types, antimicrobial resistance determinants, distribution of virulence factors and genetic relatedness using PCR and multiplex PCR. Capsular type III was predominant (65.8%), followed by capsular type II (14.6%), Ib (7.3%), and V(4.9%). All isolates were susceptible to penicillin, vancomycin, linezolid and quinupristin-dalfopristin. Resistance to tetracycline, erythromycin and clindamycin were found in 97.6%, 24.4%, and 14.6% of isolates, respectively. The most common antimicrobial resistance gene was tetM found in 97.6% of the isolates followed by ermTR and ermB found in 12% and 7.3% of isolates, respectively. The most common virulence gene was hly (100%), followed by scpB (97.6%), bca (97.6%), rib (53.65%) and bac (4.9%). The insertion sequence IS1548 was found in 63.4% of isolates. By multi locus variable number of tandem repeat analysis (MLVA) typing, 30 different allelic profiles or MLVA types (MTs) were identified. The most frequent was the MT1 (5/41, 12.2%) and followed by MT2 (4/41, 9.75%). Our data revealed that population structure of these isolates is highly diverse and indicates different MLVA types.

Physiological impact of transposable elements encoding DDE transposases in the environmental adaptation of Streptococcus agalactiae

We have referenced and described Streptococcus agalactiae transposable elements encoding DDE transposases. These elements belonged to nine families of insertion sequences (ISs) and to a family of conjugative transposons (TnGBSs). An overview of the physiological impact of the insertion of all these elements is provided. DDE-transposable elements affect S. agalactiae in a number of aspects of its capability to adapt to various environments and modulate the expression of several virulence genes, the scpB–lmB genomic region and the genes involved in capsule expression and haemolysin transport being the targets of several different mobile elements. The referenced mobile elements modify S. agalactiae behaviour by transferring new gene(s) to its genome, by modifying the expression of neighbouring genes at the integration site or by promoting genomic rearrangements. Transposition of some of these elements occurs in vivo, suggesting that by dynamically regulating some adaptation and/or virulence genes, they improve the ability of S. agalactiae to reach different niches within its host and ensure the ‘success’ of the infectious process.

Genetic diversity and antimicrobial resistance in Streptococcus agalactiae strains recovered from female carriers in the Bucharest area

For the first time, we used multilocus sequence typing (MLST) to understand how Romanian group B streptococcus (GBS) strains fit into the global GBS population structure. Colonising isolates recovered from adult human females were tested for antibiotic resistance, were molecularly serotyped based on the capsular polysaccharide synthesis (cps) gene cluster and further characterised using a set of molecular markers (surface protein genes, pilus-encoded islands and mobile genetic elements inserted in the scpB-lmb intergenic region). Pulsed-field gel electrophoresis was used to complement the MLST clonal distribution pattern of selected strains. Among the 55 strains assigned to six cps types (Ia, Ib, II-V), 18 sequence types (STs) were identified by MLST. Five STs represented new entries to the MLST database. The prevalent STs were ST-1, ST-17, ST-19 and ST-28. Twenty molecular marker profiles were identified. The most common profiles (rib+GBSi1+PI-1, rib+GBSi1+PI-1, PI-2b and alp2/3+PI-1, PI-2a) were associated with the cps III/ST-17 and cps V/ST-1 strains. A cluster of fluoroquinolone-resistant strains was detected among the cps V/ST-19 members; these strains shared alp1 and IS1548 and carried PI-1, PI-2a or both. Our results support the usefulness of implementing an integrated genotyping system at the reference laboratory level to obtain the reliable data required to make comparisons between countries.

Molecular epidemiology of group B streptococci in Ireland reveals a diverse population with evidence of capsular switching

The molecular epidemiology of group B Streptococcus (GBS) in Ireland was investigated. Invasive (n = 132) and non-invasive (n = 45) isolates, collected in 2007-2011, were analysed by multilocus locus sequence typing, capsular polysaccharide (CPS) serotyping, profiling of surface proteins, pilus islands (PI), and antimicrobial susceptibility. Isolates grouped into 45 sequence types and five main clonal complexes (CC). CC1, CC17 and CC23 represented 67.2 % of isolates and the most prevalent serotypes Ia, III and V. Serotype and surface protein genes were largely predictive of CC. Accordingly, CPS V/alp3, CPS Ib/CPS II/bca + bac, and CPS Ia/eps predominated in CC1, CC12 and CC23, respectively, and CPS III/rib in CC17 and CC19. Supporting their vaccine potential, all isolates harboured at least one PI, of which the PI-1 + PI-2a combination was most prevalent. Macrolide resistance was found in 18.6 % of isolates. erm(B) and the globally disseminated CC1/CPS V were the most common resistance mechanism and CC/CPS type, respectively. CC17, significantly associated with neonatal disease, was also prevalent in pregnant adults, but was underrepresented among non-pregnant adults. Two of 46 CC17 isolates (typically CPS III) were CPS IV. Sequence analysis confirmed capsular switching and their relatedness to CC17/CPS IV strains recently characterized in France. CPS IV, detected only in invasive isolates (6.8 %), was most prevalent in adults (12 %) and showed an increase in prevalence to that reported (1.4 %) for invasive isolates in Ireland 1997-1999. Increases in serotype IV and evidence of capsular switching in CC17 highlights the importance of ongoing surveillance of GBS and may have implications for vaccine development strategies.

Comparison of Z and R3 antigen expression and of genes encoding other antigenic markers in invasive human and bovine Streptococcus agalactiae strains from Norway

Streptococcus agalactiae (GBS) may cause a variety of infectious diseases in humans caused by human GBS and mastitis in cattle caused by bovine GBS. Over the last few years molecular testing has provided evidence that human and bovine GBS have evolved along diverse phylogenetic lines. In the present study 173 invasive human GBS strains and 52 invasive bovine strains were tested for altogether 18 strain-variable and surface-localized antigenic markers including all 10 capsular polysaccharides (CPS) and proteins including Cβ, the alpha-like proteins, R3 and the recently described Z1 and Z2 antigens. PCR was used to detect encoding genes and antibody-based methods to detect expression of antigens. Thirteen of the 18 markers were detected in isolates of both strain categories. Seven of the ten CPS antigens were detected in both groups with types III and V predominating in the human GBS strains, types IV and V in the bovine isolates. Z1, Z2 and/or R3 expression and the genes encoding Cβ, Cα, Alp1, Alp2/3 or R4 (Rib) were detected in both groups. Protein antigen-CPS associations well known for human strains were essentially the same in the bovine isolates. The results show that in spite of evolution along different lines, human and bovine GBS share a variety of surface-exposed antigenic markers, substantiating close relationship between the two GBS subpopulations.

Serotype and surface protein gene distribution of colonizing group B streptococcus in women in Egypt

Group B streptococcus (GBS) is a leading cause of neonatal sepsis and meningitis. We determined the distribution of serotypes and surface protein encoding genes of GBS strains from pregnant and non-pregnant women in Egypt. Vaginal swabs from 364 women were screened by culture and 100 (27·4%) yielded GBS. Serotype V was the most predominant (33%), followed by serotypes II (17%), III (15%), Ia (14%), VI (12%), Ib (8%) and IV (1%). The most common surface protein genes were epsilon (27%), alp3 (26%), bca (18%), rib (16%) and alp2 (10%). Two isolates were negative for surface protein genes. The distribution of serotypes and surface proteins was similar to reports from other parts of the world but the relatively high frequency of serotype VI was a notable feature of the strains from women in Egypt.

Novel aspects of the Z and R3 antigens of Streptococcus agalactiae revealed by immunological testing

Group B streptococci (GBS) are important human and bovine pathogens which can be classified by a variety of phenotype- and gene-based techniques. The capsular polysaccharide and strain-variable, surface-anchored proteins are particularly important phenotypic markers. In an earlier study, a previously unrecognized protein antigen called Z was described. It was expressed by 27.2% of GBS strains from Zimbabwe, usually in combination with R3 protein expression. In this study, a putative Z-specific antiserum actually contained antibodies against two different antigens named Z1 and Z2; Z1 was >250 kDa in molecular mass. Z1, Z2, and R3 generated multiple stained bands on Western blots and showed similar chromatographic characteristics with respect to molecular mass, aggregate formation, and charge. Of 28 reference and prototype GBS strains examined, 8/28 (28.5%) isolates expressed one, two, or all three of the Z1, Z2, and R3 antigens; 4/28 expressed all three antigens; 2/28 expressed Z2 and R3; 1/28 expressed Z1 only; and 1/28 expressed R3 only. Twenty (71.5%) of the 28 isolates expressed none of the three antigens. Expression of one or more of these antigens was shown by isolates of the capsular polysaccharide types Ia, Ib, V, and IX and NT strains and occurred in combination with expression of various other strain-variable and surface-localized protein antigens. When used as serosubtype markers, Z1, Z2, and R3 affected existing GBS serotype designations for some of the isolates. For instance, the R3 reference strain Prague 10/84 (ATCC 49447) changed serotype markers from V/R3 to V/R3, Z1, and Z2. Other isolates may change correspondingly, implying consequences for GBS serotyping and research.

Natural outbreak of Streptococcus agalactiae (GBS) infection in wild giant Queensland grouper, Epinephelus lanceolatus (Bloch), and other wild fish in northern Queensland, Australia

Ninety-three giant Queensland grouper, Epinephelus lanceolatus (Bloch), were found dead in Queensland, Australia, from 2007 to 2011. Most dead fish occurred in northern Queensland, with a peak of mortalities in Cairns in June 2008. In 2009, sick wild fish including giant sea catfish, Arius thalassinus (Rüppell), and javelin grunter, Pomadasys kaakan (Cuvier), also occurred in Cairns. In 2009 and 2010, two disease epizootics involving wild stingrays occurred at Sea World marine aquarium. Necropsy, histopathology, bacteriology and PCR determined that the cause of deaths of 12 giant Queensland grouper, three wild fish, six estuary rays, Dasyatis fluviorum (Ogilby), one mangrove whipray, Himantura granulata (Macleay), and one eastern shovelnose ray, Aptychotrema rostrata (Shaw), was Streptococcus agalactiae septicaemia. Biochemical testing of 34 S. agalactiae isolates from giant Queensland grouper, wild fish and stingrays showed all had identical biochemical profiles. The 16S rRNA gene sequences of isolates confirmed all isolates were S. agalactiae; genotyping of selected S. agalactiae isolates showed the isolates from giant Queensland grouper were serotype Ib, whereas isolates from wild fish and stingrays closely resembled serotype II. This is the first report of S. agalactiae from wild giant Queensland grouper and other wild tropical fish and stingray species in Queensland, Australia.

Genetic differences between invasive and noninvasive neonatal group B streptococcal isolates

BACKGROUND

Streptococcus agalactiae, also known as group B streptococcus (GBS), is the most common cause of neonatal sepsis and meningitis. To improve our understanding of the pathogenesis of neonatal GBS sepsis, better knowledge of clonal relatedness and diversity among invasive and noninvasive GBS isolates is critical.

METHODS

In a Germany-based study, invasive neonatal GBS isolates were compared with noninvasive isolates from neonates in whom sepsis was suspected, but whose blood cultures were sterile. The comparison was conducted by means of pulsed-field gel electrophoresis and surface protein gene profiling. In addition, multilocus sequence typing was performed on invasive and noninvasive isolates of the most frequent invasive serotype III.

RESULTS

Pulsed-field gel electrophoresis analysis of noninvasive GBS showed a remarkably more diverse fingerprinting pattern than that of invasive isolates. In contrast to invasive strains, noninvasive isolates did not show any clustering. Surface protein gene profiling also showed significantly different distribution patterns between the 2 panels of isolates. Multilocus sequence typing of invasive and noninvasive serotype III isolates revealed the same clonal complexes, but displayed different sequence types (ST); ST-17 was most common (68.6%) among invasive strains, whereas ST-389 (clonal complex-19) was predominant among noninvasive strains (47.8%).

CONCLUSIONS

Our results illustrate a large molecular diversity among neonatal noninvasive GBS strains. Invasive strains, however, represent only a small proportion of the noninvasive GBS population. These findings suggest a selection process that prefers more virulent strains during invasion.

Streptococcus agalactiae alpha-like protein 1 possesses both cross-reacting and Alp1-specific epitopes

Most isolates of group B streptococci (GBS) express an alpha-like protein (Alp), Cα (encoded by bca), Alp1 (also called epsilon; alp1), Alp2 (alp2), Alp3 (alp3), Alp4 (alp4), or R4/Rib (rib). These proteins are chimeras with a mosaic structure and with antigenic determinants with variable immunological cross-reactivities between the Alps, including Alp1 and Cα cross-reactivity. This study focused on antigenic domains of Alp1, studied by using rabbit antisera in immunofluorescence, Western blotting, and enzyme-linked immunosorbent assay (ELISA)-based tests and whole cells of GBS or trypsin-extracted and partially purified antigens from the strains A909 (serotype Ia/Cα, Cβ) and 335 (Ia/Alp1). Alp1 and Cα shared an antigenic determinant, Alp1/Cα common, not harbored by other Alps, probably located in the Alp1 and Cα repeat units, as these units are nearly identical in genomic sequence. An antigenic Alp1 determinant was Alp1 specific and was most likely located in the N-terminal unit of Alp1 in which an Alp1-specific primer site for PCR is also located. In addition, Alp1 possessed a domain with low immunogenicity which cross-reacted immunologically with Alp2 and Alp3, with unknown location in Alp1. Alp1 was partially degraded by trypsin during antigen extraction but with the antigenic domains preserved. The results indicate that Cα and Alp1 are immunologically related in the same manner that R4 (Rib) and Alp3 are related. The domain called Alp1 specific should be important in GBS serotyping as a surface-anchored serosubtype marker. The Alp1/Cα common determinant may be of prime interest as an immunogenic domain in a GBS vaccine.

Molecular characterization of capsular polysaccharides and surface protein genes in relation to genetic similarity of group B streptococci isolated from Polish pregnant women

Serotyping, subtyping and genotyping are important tools for epidemiological studies of group B streptococci (GBS). We investigated the genotype distribution of 353 GBS isolates originating from vaginal or rectal carriage to identify capsular serotypes and subtypes based on the surface protein genes of the alpha-like protein (Alp) family. GBS were recovered from 30% of 1176 pregnant women during the period 2007-2009, with a predominance of capsular genotypes III (35%), Ia (20%), V (17%), II (15%), Ib (8%) and IV (5%). The most common Alp gene was epsilon (26%), followed by rib (22%), alp2 (21%), bca (17%) and alp3 (14%). Several protein genes were significantly associated (G(2)=249·635, P<0·0001) with particular serotypes: epsilon with Ia, Ib, IV; bca with Ib, II; rib with II, III; alp3 with V; alp2 with III. High genetic diversity within GBS strains was observed using DNA macrorestriction. Serotypes Ib, II and III demonstrated the greatest genetic heterogeneity and serotype V the lowest heterogeneity (relative frequency coefficient ≥0·03 vs. -0·46, respectively). Macrolide-resistant strains with serotype V and alp3 gene, showed higher uniformity in genetic profile. The distribution of serotypes and surface proteins of GBS strains are necessary data to inform the design and formulation of new GBS vaccines for use in Poland and other countries.

Serotypes, surface proteins, and clinical syndromes of invasive Group B streptococcal infections in northern Taiwan, 1998-2009

BACKGROUND

The incidence of invasive Group B streptococcal (GBS) infections is increasing in the elderly and immunocompromised adults in many countries worldwide. There are, however, few reports regarding the current status of the infection in northern Taiwan. This study investigated retrospectively the molecular epidemiology and clinical syndromes of the invasive GBS diseases in a tertiary care hospital in northern Taiwan over the past decade.

METHODS

One hundred twenty episodes of invasive GBS disease were recorded at Cathay General Hospital, a tertiary care, teaching hospital in northern Taiwan, from January 1998 to June 2009. Clinical information was acquired from medical records. Capsular serotypes and alpha family of surface proteins were genotyped with multiplex and specific polymerase chain reaction.

RESULTS

Of all episodes, 58.3% was found in the elderly (age ≥ 65), 36.1% in nonpregnant women and young adults (age 18-64), and 5.9% in the neonates (0-90 days). Case-fatality rate was 6.7%. Eighty-three (69%) of the invasive isolates were available for genotyping. In sharp contrast to the studies in southern Taiwan (1991-2004), Type Ib (26.5%) was the most frequent invasive isolate, followed by V (22.9%), III (18.1%), VI (12%), Ia (10.8%), II (6%), VIII (2.4%), and nontypable strain (1.2%). In particular, Serotype VI, which had been rarely implicated in invasive infection, emerged as a significant pathogen. A significant trend of increase in incidence was observed for the infection (p<0.0001), with concurrent increase of cases in the elderly and of Serotype Ib and VI. There was significant association with young adults of Type II and III and chronic skin conditions and older adults with Type Ia and V and chronic cardiovascular diseases. Type V was closely associated with skin and soft tissue infection. Recurrent episodes (10%) occurred most often in patients with concomitant malignancy, with an average of 314 days for recurrence.

CONCLUSIONS

The incidence of GBS invasive infection among nonpregnant women and adults is rising in northern Taiwan, particularly in the elderly caused by Serotype Ib and VI. Population-based surveillance program should be implanted for assessment of the disease burden to the susceptible adult population.

Phenotypic and genotypic characterization of group B streptococcal isolates in southern Brazil

One-hundred sixty-eight group B streptococcal (GBS) isolates from a Brazilian hospital were phenotypically and genotypically characterized. Isolates were recovered from human sources from April 2006 to May 2008 and classified as either invasive, noninvasive, or colonizing isolates. Classical methods for serotyping and antibiotic resistance profiling were employed. Clonal groups were also defined by pulsed-field gel electrophoresis (PFGE). Results showed that susceptibility to beta-lactam antimicrobials was predominant among the isolates. Only 4.7% were resistant to erythromycin and clindamycin. The erm(B) gene was widely detected in our GBS isolates, according to our phenotypic results (constitutive macrolide-lincosamide-streptogramin B [cMLSB] resistance phenotype), and the erm(A) gene was also detected in some isolates. MLSB resistance was restricted to strains isolated from patients with noninvasive infections and carriers. Serotype Ia was predominant (38.1%), serotype IV isolates were found at a high frequency (13.1%), and few isolates of serotype III were identified (3%). Pulsed-field gel electrophoresis results revealed a variety of types, reflecting the substantial genetic diversity among GBS strains, although a great number of isolates could be clustered into two major groups with a high degree of genetic relatedness. Three main PFGE clonal groups were found, and isolates sharing the same PFGE type were grouped into different serotypes. Furthermore, in a few cases, isolates from the same patients and possessing the same PFGE type were of different serotypes. These findings could be related to the occurrence of capsular switching by horizontal transfer of capsular genes.

Population structure, virulence factors and resistance determinants of invasive, non-invasive and colonizing Streptococcus agalactiae in Poland

OBJECTIVES

To analyse Streptococcus agalactiae (group B Streptococcus; GBS) isolates collected in Poland from various human infections and carriage in respect of their clonality, distribution of virulence factors and antimicrobial resistance determinants, including the detection of transposons involved in the dissemination of antimicrobial resistance.

METHODS

One hundred and fourteen GBS isolates were analysed by multilocus sequence typing (MLST), serotyping and detection of alp genes of the alpha-like-protein (Alp) family. Determinants of resistance to macrolides and tetracycline, and associated transposons, were detected by PCR and analysed by sequencing.

RESULTS

GBS isolates represented 30 different sequence types (STs), grouped in four clonal complexes (CCs), and belonged to seven serotypes. Serotype III was predominant (36.0%), followed by Ia, V, Ib, II, IV and VI. The most common alp genes were rib (26.3%) and alp1/alp5 (23.7%). The bac gene encoding the beta-compound of the surface C-protein was present in 17.5% of isolates. Erythromycin resistance (18.4% of isolates) was found in all CCs, but was associated with serotype V and ST1. The most prevalent determinant of resistance was erm(B), usually located on the Tn3872-like transposon. Several changes were observed in the regulatory region of erm(B), some of them resulting in elevated ketolide MICs. Resistance to tetracycline was ubiquitous (91.2%) and its most common determinant was tet(M), occurring in several variants that were typically carried on Tn916-family transposons.

CONCLUSIONS

Analysis of bacterial serotypes, alp genes and antimicrobial resistance determinants in the background of MLST-based population structure strengthened evidence of the importance of horizontal gene transfer in GBS evolution.

Correlation between Group B Streptococcal Genotypes, Their Antimicrobial Resistance Profiles, and Virulence Genes among Pregnant Women in Lebanon

The antimicrobial susceptibility profiles of 76 Streptococcus agalactiae (Group B Streptococci [GBS]) isolates from vaginal specimens of pregnant women near term were correlated to their genotypes generated by Random Amplified Polymorphic DNA analysis and their virulence factors encoding genes cylE, lmb, scpB, rib, and bca by PCR. Based on the distribution of the susceptibility patterns, six profiles were generated. RAPD analysis detected 7 clusters of genotypes. The cylE gene was present in 99% of the isolates, the lmb in 96%, scpB in 94.7%, rib in 33%, and bca in 56.5% of isolates. The isolates demonstrated a significant correlation between antimicrobial resistance and genotype clusters denoting the distribution of particular clones with different antimicrobial resistance profiles, entailing the practice of caution in therapeutic options. All virulence factors encoding genes were detected in all seven genotypic clusters with rib and bca not coexisting in the same genome.

Putative novel surface-exposed Streptococcus agalactiae protein frequently expressed by the group B streptococcus from Zimbabwe

Group B streptococci (GBS) express a variety of surface-exposed and strain-variable proteins which function as phenotypic markers and as antigens which are able to induce protective immunity in experimental settings. Among these proteins, the chimeric and immunologically cross-reacting alpha-like proteins are particularly important. Another protein, R3, which has been less well studied, occurred at a frequency of 21.5% in GBS from Zimbabwe and, notably, occurred in serotype V strains at a frequency of 75.9%. Working with rabbit antiserum raised against the R3 reference strain ATCC 49447 (strain 10/84; serotype V/R3) to detect the expression of the R3 protein, we recorded findings which suggested that strain 10/84 expressed a strain-variable protein antigen, in addition to R3. The antigen was detected by various enzyme-linked immunosorbent assay-based tests by using acid extract antigens or GBS whole-cell coats and by whole-cell-based Western blotting. We named the putative novel antigen the Z antigen. The Z antigen was a high-molecular-mass antigen that was susceptible to degradation by pepsin and trypsin but that was resistant to m-periodate oxidation and failed to show immunological cross-reactivity with any of a variety of other GBS protein antigens. The Z antigen was expressed by 33/121 (27.2%) of strains of a Zimbabwean GBS strain collection and by 64.2% and 72.4% of the type Ib and type V strains, respectively, and was occasionally expressed by GBS of other capsular serotypes. Thus, the putative novel GBS protein named Z showed distinct capsular antigen associations and presented as an important phenotypic marker in GBS from Zimbabwe. It may be an important antigen in GBS from larger areas of southern Africa. Its prevalence in GBS from Western countries is not known.

Identification of surface proteins of group B streptococci: serotyping versus genotyping

We compared serotyping to genotyping of group B streptococcal (GBS) surface proteins in 147 Australasian isolates. Results were concordant for the two methods in 73.8% of 122 isolates, discordant for three and partially discordant for 29 isolates. For the purpose of epidemiological typing of GBS, genotyping is superior to serotyping.

Distinctive features of surface-anchored proteins of Streptococcus agalactiae strains from Zimbabwe revealed by PCR and dot blotting

The distribution of capsular polysaccharide (CPS) types and subtypes (serovariants) among 121 group B streptococcus (GBS) strains from Zimbabwe was examined. PCR was used for the detection of both CPS types and the surface-anchored and strain-variable proteins Calpha, Cbeta, Alp1, Alp2, Alp3, R4/Rib, and Alp4. The R3 protein was detected by an antibody-based method using monoclonal anti-R3 antibody in dot blotting. The CPS types detected, Ia (15.7% of strains), Ib (11.6%), II (8.3%), III (38.8%), V (24.0%), and nontypeable (1.7%), were essentially as expected on the basis of data from Western countries. The type V strains showed distinctive features with respect to protein markers in that Alp3 was detected in only 6.9% of the isolates while R3 occurred in 75.9% and R4/Rib occurred in 37.9% of the isolates. R3 occurred nearly always in combination with one of the alpha-like (Alp) proteins, and it was the third most common of the proteins studied. These results show that type V GBS strains from Zimbabwe differed from type V strains from other geographical areas and also emphasize the importance of the R3 protein in GBS serotyping and its potential importance in the immunobiology of GBS, including a potential role in a future GBS vaccine.

Recombinant group B Streptococcus alpha-like protein 3 is an effective immunogen and carrier protein

Conjugate vaccines against pathogens of multiple serotypes are optimized when all components induce functional antibody, resulting in broadened coverage. While most clinical studies of vaccines against group B Streptococcus (GBS) have evaluated conjugates composed of capsular polysaccharide (CPS) coupled to tetanus toxoid, conjugates prepared with GBS proteins as carriers have also been efficacious in animals. Here, we report that recombinant GBS alpha-like protein 3 (rAlp3) is both a strong immunogen and a viable carrier protein for type III CPS. The type III CPS-specific immunoglobulin G (IgG) titer rose from <100 to 64,000 among mice that received type III CPS coupled to rAlp3 (III-rAlp3) compared with an absence of a specific response among mice that received an uncoupled mixture. Most (94%) newborn pups born to III-rAlp-vaccinated dams survived challenge with viable type III GBS, compared with 43% survival among those born to dams that received the uncoupled mixture (P < 0.0001). A tricomponent conjugate of type III CPS, rAlp3, and a GBS recombinant beta C protein lacking its IgA binding site (III-rAlp3-rBCP(DeltaIgA)) provided protection against a serotype III strain and a serotype Ia strain bearing beta C protein. High-titered anti-rAlp3 rabbit serum opsonized Alp3-containing strains of two GBS serotypes (types V and VIII) and invasive type III strains bearing the cross-reactive Rib protein for in vitro killing by human peripheral blood leukocytes. Thus, the potential exists for the inclusion of rAlp3 in a GBS vaccine formulated to provide multiserotype coverage.

Characterisation of invasive group B streptococci based on investigation of surface proteins and genes encoding surface proteins

The joint distributions of the six genes bca, bac, epsilon/alp1, alp2, alp3 and rib (encoding alpha-C-protein, beta-C-protein, epsilon/Alp1, Alp2, Alp3, and Rib, respectively) and the proteins alpha-C-protein, beta-C-protein and Rib were investigated in invasive isolates of group B streptococcus (GBS). In total, 297 invasive isolates (123 from neonates, 174 from adults) from south-west Sweden were collected during a 13-year period. Genes were detected using multiplex and specific PCRs, and expression of the surface proteins was demonstrated using monoclonal antibodies. The genes studied were found alone or in combinations in 294 (99%) of the invasive isolates. The most common genes were rib (n = 127 isolates, 43%), alp3 (n = 78, 26%) and epsilon/alp1 (n = 42, 14%). The bac gene was never found alone, but was found in combination with one other gene in 36 isolates. The surface proteins studied were detected alone or in combinations in 152 (51%) isolates, with the most common being Rib (n = 80, 27%), alpha-C-protein (n = 68, 23%) and beta-C-protein (n = 24, 8%). Several genes were associated significantly with particular serotypes (e.g., epsilon/alp1 with serotype Ia; bca and bac with serotypes Ib and II; rib with serotype III; alp3 with serotype V). Overall, it was concluded that demonstration of different genes and surface proteins of GBS strains can be useful in epidemiological studies and in formulation of vaccines, but disappointingly, no single gene or surface protein included in the study was sufficiently common for it to be considered as the basis for a successful GBS vaccine.

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.

Comparison of single- and multilocus sequence typing and toxin gene profiling for characterization of methicillin-resistant Staphylococcus aureus

We compared three novel methicillin-resistant Staphylococcus aureus (MRSA) genotyping methods with multilocus sequence typing (MLST) and spa typing to assess their utility for routine strain typing. The new methods were femA and nuc sequence typing and toxin gene profiling (TGP), using a multiplex-PCR-based reverse line blot assay to detect 13 pyrogenic superantigen and exfoliative toxin genes. Forty-two well-characterized MRSA strains, representing 15 MLSTs or 9 clonal clusters (CCs), were genotyped by all methods. Twenty-two spa, nine femA, and seven nuc sequence types were identified. The femA sequence types correlated exactly with CCs; nuc sequences types were less discriminatory but generally correlated well with femA types and CCs. Ten isolates contained none of 13 toxin genes; TGPs of the remainder comprised 1 to 5 toxin genes. The combination of spa typing and TGPs identified 26 genotypes among the 42 strains studied. A combination of two or three rapid, inexpensive genotyping methods could potentially provide rapid MRSA strain typing as well as useful information about clonal origin and virulence.