Quantity and fatty acid composition of lipid synthesized by Streptococcus agalactiae and Streptococcus uberis.
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Animals↗
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Identification of a high-virulence clone of type III Streptococcus agalactiae (group B Streptococcus) causing invasive neonatal disease.
Chromosomal genotypes of 128 isolates of six serotypes (Ia, Ib, Ic, II, Ic/II, and III) of Streptococcus agalactiae (group B Streptococcus) recovered predominantly from human infants in the United States were characterized by an analysis of electrophoretically demonstrable allelic profiles at 11 metabolic enzyme loci. Nineteen distinctive electrophoretic types (ETs), representing multilocus clonal genotypes, were identified. Mean genetic diversity per locus among ETs of isolates of the same serotype was, on average, nearly equal to that in all 19 ETs. Cluster analysis of the ETs revealed two primary phylogenetic divisions at a genetic distance of 0.65. A single clone (ET 1) represented by 40 isolates expressing type III antigen formed division I. Division II was composed of 18 ETs in three major lineages diverging from one another at distances greater than 0.35 and included strains of all six antigenic classes. The type III organisms in division I produce more extracellular neuraminidase and apparently are more virulent than the type III strains in division II, which are related to strains of other serotypes that cause disease much less frequently. The existence of this unusually virulent clone accounts, in major part, for the high morbidity and mortality associated with infection by type III organisms.
Genotype↗
Towards a genotyping system for Streptococcus agalactiae (group B streptococcus): use of mobile genetic elements in Australasian invasive isolates.
This study forms part of the development of an integrated genotyping system for Streptococcus agalactiae (group B streptococcus, GBS) that can be used to study the population genetics of the organism and the pathogenesis and epidemiology of GBS disease. In recent previous studies, two sets of markers, the capsular polysaccharide synthesis (cps) gene cluster and surface protein antigen genes, have been used to assign molecular serotypes (MS) and protein-gene profiles (PGP) to more than 200 isolates. In the present study, five mobile genetic elements (MGE) have been used as a third set of markers, to characterize further 194 invasive isolates, recovered from blood or cerebrospinal fluid (CSF). Of these, 97 % contained one or more of the five MGE, the distribution of which was related to MS and PGP, as illustrated by MS III, which is divisible into four serosubtypes with different combinations of the MGE (or none). Fifty-six different genotypes and eight genetic clusters were identified, each with different combinations of the three sets of molecular markers. Five predominant genotypes (Ia-1, Ib-1, III-1, III-2 and V-1) contained 62 % of the isolates and five of the eight genetic clusters contained 92 % of the isolates. The 17 CSF isolates were relatively widely distributed between 10 genotypes and across seven of the eight clusters. Further study is needed to determine whether these genotypes or clusters share common markers of increased virulence. In future, comparison of invasive with colonizing strains of GBS may elucidate the significance of these findings.
Adolescent↗
Role of fibrinogen-binding adhesin expression in septic arthritis and septicemia caused by Streptococcus agalactiae.
BACKGROUND: Streptococcus agalactiae (group B streptococcus) is an important human pathogen that causes neonatal pneumonia, sepsis, septic arthritis, and meningitis, as well as severe infections in immunocompromised adult patients. The streptococci produce several molecules important for virulence. METHODS: We used a murine model of sepsis and septic arthritis to assess the role of FbsA, a fibrinogen-binding adhesin of S. agalactiae as a virulence determinant. NMRI mice were inoculated intravenously with S. agalactiae strains isogenic for the expression of FbsA. RESULTS: Inoculation with wild-type (wt) streptococci resulted in significantly higher mortality, more-pronounced weight decrease, and more-severe arthritis, compared with inoculation with the FbsA mutant isogenic strain. Neither active nor passive immunization with FbsA or FbsA-specific antibodies, respectively, resulted in any protection against subsequent infection with the S. agalactiae wt strain. CONCLUSION: Our results clearly indicate that the expression of FbsA by Streptococcus agalactiae is a significant virulence determinant in septic arthritis and septicemia. However, because blocking of the fibrinogen binding properties did not protect the host against the action of FbsA-expressing streptococci, we believe that the FbsA molecule has some other presently unknown biological in vivo properties.
Animals↗
Macrorestriction analysis of Streptococcus agalactiae (group B Streptococcus) isolates from Malaysia.
Streptococcus agalactiae or group B streptococci (GBS) often colonize the gastrointestinal and urogenital tracts of women, who may transmit these organisms to their offspring during the birth process. Using PFGE analysis, the genetic diversity of GBS was studied for strains isolated from pregnant women and their newborn infants in a teaching hospital. A total of 48 different PFGE profiles were obtained from 123 strains, with one profile (S1) appearing to be predominant among both groups studied. There was good overall correlation between the profiles obtained for strains from mother-infant pairs and for strains isolated from different body sites in the same individual. Occasional discrepancies seen in related body sites and among mother-infant pairs suggest concurrent carriage of different strains in the same individual as well as the possibility of an environmental source of organism for the neonate. The overall results demonstrated that many variants of GBS strains occur in Malaysia.
Electrophoresis, Gel, Pulsed-Field↗
Comparison of a 3-set genotyping system with multilocus sequence typing for Streptococcus agalactiae (Group B Streptococcus).
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. Epidemiological studies of GBS infections require comprehensive typing systems that provide information about variable characteristics, such as antigenic type, virulence, or antibiotic resistance, as well as the "backbone" structure or the genetic lineage of isolates. We have previously described a 3-set genotyping system that identifies the molecular serotype (MS) or molecular serosubtype (msst), the protein gene profile, and the presence of several mobile genetic elements (F. Kong, D. Martin, G. James, and G. L. Gilbert, J. Med. Microbiol. 52:337-344, 2003). In this study, 83 clinical GBS isolates which had been previously studied by multilocus sequence typing (MLST) (N. Jones, J. F. Bohnsack, S. Takahashi, K. A. Oliver, M. S. Chan, F. Kunst, P. Glaser, C. Rusniok, D. W. Crook, R. M. Harding, N. Bisharat, and B. G. Spratt, J. Clin. Microbiol. 41:2530-2536, 2003) were examined by using the 3-set genotyping system. Genotypes were assigned to five isolates that were nontypeable by conventional serotyping. There were 27 "3-set" genotypes, 24 multilocus sequence types (STs), and 35 unique combinations (or strains), of which the 4 most common, msst III-2 (ST-17), msst III-1 (ST-19), Ia-1 (ST-23), and V-1 (ST-1), accounted for more than 60% of isolates. The 83 isolates were grouped into seven clusters, with a good correlation between the multilocus STs and the genotypes. The combination of 3-set genotyping and MLST adds discriminatory power to strain typing of GBS, which will be useful for future studies of the epidemiology and pathogenesis of GBS disease.
Bacterial Proteins↗
[Serotypes and antimicrobial susceptibility of Streptococcus agalactiae].
BACKGROUND: Streptococcus agalactiae or group B streptococcus, GBS, is the leading cause of neonatal and maternal infections and an opportunistic pathogen in adults with underlying disease. In the last decade, a dramatic increase in the resistance of this microorganism to erythromycin and clindamycin has been observed. AIM: To determine the serotype distribution and antimicrobial susceptibility of isolates of S. agalactiae collected from infections and colonization and to assess the genetic mechanisms of macrolide and clindamycin resistance. MATERIAL AND METHODS: A total of 100 GBS isolates were collected between 1998 and 2002, in Santiago, Chile. They were isolated from the amniotic fluid from patients with premature rupture of membranes (7 isolates), blood from neonatal sepsis (10 isolates), neonate colonizations (2 strains), skin and soft tissue infections (7 isolates), urinary tract infections (5 isolates), genital infections (3 isolates), articular fluid (one isolate), and 65 strains were recovered from vaginal colonization55. RESULTS: Serotypes Ia, II and III were the predominant serotypes identified in our study, accounting for 90 (90%) of the strains. Five isolates belonged to serotypes Ib (5%) and two (2%) to serotype V respectively; no strains belonging to serotype IV were found. All strains were susceptible to penicillin G, ampicillin and cefotaxime, and four isolates (4%) were resistant to both erythromycin (MIC >64 microg/ml) and clindamycin (MIC >64 microg/ml). The strains had a constitutive macrolide-lincosamide-streptogramin (cMLSB) resistance phenotype and the erm(A) gene was present in the four isolates. CONCLUSIONS: Serotypes Ia, II and III were the predominant serotypes in this study. All strains were susceptible to penicillin G, ampicillin and cefotaxime, and four (4%) strains were resistant to both erythromycin and clindamycin. The cMLSB resistance phenotype, and the erm(A) gene was detected in resistant strains.
Adult↗
Duration of protective antibodies and correlation with survival in Nile tilapia Oreochromis niloticus following Streptococcus agalactiae vaccination.
Streptococcus agalactiae is a major piscine pathogen that causes significant morbidity and mortality among numerous species of freshwater, estuarine and marine fishes. Considering the economic importance of fishes susceptible to S. agalactiae throughout the world, an efficacious S. agalactiae vaccine was developed using an extracellular product (ECP) fraction and formalin-killed whole cells of S. agalactiae. A vaccine study was conducted by intraperitoneal (i.p.) injection in Nile tilapia Oreochromis niloticus in order to determine the duration of protection and its correlation to antibodies specific for this pathogen. After 47, 90 or 180 d post-vaccination (DPV), the fish were i.p. challenged with approximately 2.0 x 10(4) S. agalactiae colony-forming units (CFU) fish(-1) to determine the duration of protective immunity. The percent survival in control fish i.p.-injected with sterile TSB was 16,16, and 4% on 47, 90 and 180 DPV, respectively, while the percent survival for the vaccinated fish was 67, 62 and 49%, respectively. The specific mean antibody concentration of the vaccinated fish was significantly higher than that of the control fish, with significant correlation between the ELISA optical density (OD) and protection. These results indicate that the specific antibody has a correlation with protection following immunization with the S. agalactiae vaccine and that the vaccine can confer protection against S. agalactiae up to 180 DPV.
Animals↗
Streptococcus agalactiae endocarditis.
Streptococcus agalactiae (S. agalactiae) is a rare cause of infective endocarditis, which is associated with a high mortality rate. Endocarditis in adults is generally related to immunocompromised states. We hereby report the case of a 35 year old man who presented with fever and delirium in whom aortic valve endocarditis due to S. agalactiae was detected. Though most patients with S. agalactiae endocarditis need surgical intervention along with antibiotics, our patient improved with medical therapy alone.
Adult↗
Molecular subtyping and characterization of bovine and human Streptococcus agalactiae isolates.
Streptococcus agalactiae causes severe invasive disease in humans and mastitis in cattle. Temporally matched bovine milk isolates and clinical human invasive isolates (52 each) collected in New York State over 18 months were characterized by molecular subtyping and phenotypic methods to probe the interspecies transmission potential of this species. EcoRI ribotyping differentiated 17 ribotypes, and DNA sequencing of the housekeeping gene sodA and the putative virulence gene hylB differentiated 7 and 17 allelic types, respectively. Human and bovine isolates were not randomly distributed between ribotypes or hylB and sodA clusters. The combined analysis of all subtyping data allowed the differentiation of 39 clonal groups; 26 groups contained only bovine isolates, and 2 groups contained both human and bovine isolates. The EcoRI ribotype diversity among bovine isolates (Simpson's numerical index of discrimination [mean +/- standard deviation], 0.90 +/- 0.05) being significantly higher than that among human isolates (0.42 +/- 0.15) further supports that these isolates represent distinct populations. Eight human isolates, but no bovine isolates, showed an IS1548 transposon insertion in hylB, which encodes a hyaluronidase. Based on data for 43 representative isolates, human isolates, on average, showed lower hyaluronidase activities than bovine isolates. Isolates with the IS1548 insertion in hylB showed no hyaluronidase activity. Human and bovine isolates did not differ in their abilities to invade HeLa human epithelial cells. Our data show that (i) EcoRI ribotyping, combined with hylB and sodA sequencing, provides a discriminatory subtype analysis of S. agalactiae; (ii) most human invasive and bovine S. agalactiae isolates represent distinct subtypes, suggesting limited interspecies transmission; and (iii) hyaluronidase activity is not required for all human infections.
Alleles↗
Pathogenesis of neonatal Streptococcus agalactiae infections.
Streptococcus agalactiae is an important human pathogen causing severe neonatal infections. During the course of infection, S. agalactiae colonizes and invades a number of different host compartments. Bacterial molecules including the polysaccharide capsule, the hemolysin, the C5a peptidase, the C-proteins, the hyaluronate lyase and a number of unknown bacterial components determine the interaction with host tissues. This review summarizes our current knowledge about these interactions.
Humans↗
New lnu(C) gene conferring resistance to lincomycin by nucleotidylation in Streptococcus agalactiae UCN36.
Streptococcus agalactiae UCN36 was resistant to lincomycin (MIC = 16 microg/ml) but susceptible to clindamycin (MIC = 0.12 microg/ml) and erythromycin (MIC = 0.06 microg/ml). A 4-kb HindIII fragment was cloned from S. agalactiae UCN36 total DNA on plasmid pUC18 and introduced into Escherichia coli AG100A, where it conferred resistance to lincomycin. The sequence analysis of the fragment showed the presence of a 1,724-bp element delineated by imperfect inverted repeats (22 of 25 bp) and inserted in the operon for capsular synthesis of S. agalactiae UCN36. This element carried two open reading frames (ORF). The deduced amino acid sequence of the upstream ORF displayed similarity with transposases from anaerobes and IS1. The downstream ORF, lnu(C), encoded a 164-amino-acid protein with 26% to 27% identity with the LnuA(N2), LnuA, and LnuA' lincosamide nucleotidyltransferases reported for Bacteroides and Staphylococcus, respectively. Crude lysates of E. coli AG100A containing the cloned lnu(C) gene inactivated lincomycin and clindamycin in the presence of ATP and MgCl2. Mass spectrometry experiments demonstrated that the LnuC enzyme catalyzed adenylylation of lincomycin.
Anti-Bacterial Agents↗
Distribution of novel and previously investigated virulence genes in colonizing and invasive isolates of Streptococcus agalactiae.
Although Streptococcus agalactiae has emerged as an important cause of invasive disease, relatively little is known regarding the genetic basis of virulence of this organism. Three novel genes with characteristics suggesting a role in virulence were identified via comparison of sequenced genomes of S. agalactiae. The presence of these genes and of the previously identified genes bac, bca, rib, and spb1 was determined, and isolates were assigned a binary genetic signature. It was found that isolates containing spb1, previously suggested to be limited to serotype III-3, were represented by 18 different genetic signatures and several serotypes, and that the presence of both sbp1 and rib was more predictive of invasive disease than spb1 alone. Additionally, bac-positive isolates, reported to be genetically homogeneous, were represented by 14 different genetic signatures. Finally, the majority of serotype V isolates examined contained zero or only one of the genes tested, suggesting that much remains undiscovered regarding important virulence factors in isolates of this serotype.
Aged↗
Chromosomal gentamicin resistance transposon Tn3706 in Streptococcus agalactiae B128.
Streptococcus agalactiae B128 is the only highly gentamicin-resistant group B streptococcal (GBS) strain described so far. This strain carries a chromosomal gentamicin resistance transposon, designated Tn3706, which is similar, if not identical, to the Tn4001 and Tn5281 transpons detected in Staphylococcus aureus and Enterococcus faecalis, respectively. Transposition of Tn3706 occurred onto the GBS plasmid pIP501 in two different loci of its 7.5-kb AvaII fragment carrying the genes for chloramphenicol and erythromycin resistance. Molecular analysis of pIP501 derivatives showed that Tn3706 is composed of a central fragment containing the aac6'-aph2" gene; this fragment is flanked by two tandemly repeated copies of IS256 at the 5' extremity of the resistance gene and a single inverted copy of IS256 at its 3' extremity. The two tandemly repeated copies of IS256 were separated by a 6-bp segment identical to that found, in the same orientation, in the IS256-aac6'-aph2" junction. The hybrid replicons pIP501::Tn3706 were found to be structurally unstable following conjugative transfer between GBS strains. Numerous individual copies of IS256 were detected in B128, but this insertion sequence was not found in the 11 wild-type, gentamicin-susceptible GBS strains studied.
Anti-Bacterial Agents↗
Typing of human isolates of Streptococcus agalactiae (group B streptococcus, GBS) strains from Zimbabwe.
Serotyping and genotyping are important tools in epidemiological studies of group B streptococcal (GBS) infections, which are important diseases in man, particularly in newborns. In the present study, 241 GBS isolates from Zimbabwe, comprising 124 carrier isolates from pregnant women and 117 isolates from patients hospitalised for various diseases, were serotyped. Antibodies specific for the capsular polysaccharide antigens (CPAs) Ia, Ib and II-V and antibodies specific for the surface-localised proteins, c(alpha), c(beta), R1, R3 and R4 were used for serotyping. Strains of the CPA types Ia (17%), III (47.7%) and V (23.2%) predominated. Of the various protein antigens, c(alpha) and R4 were expressed with highest frequency, c(alpha) by 100% of the CPA type Ia strains and R4 by 92% of the CPA type III strains. The R3 protein occurred frequently (24%), especially in type V strains (84%). A total of 25 serovariants was detected in the strain collection with the variants Ia/c(alpha) (16%), III/R4 (43.5%) and V/c(alpha), R3 (14.1%) occurring with the highest frequency. Serotype and subtype distribution of the carrier isolates were essentially similar to those of the disease-associated isolates. Genomic heterogeneity was demonstrated by pulsed-field gel electrophoresis of type III/R4 and type V/c(alpha), R3 isolates, but to a much lesser extent than recorded with Norwegian strains. These results demonstrate that many variants of GBS occur in the Zimbabwean population. The data obtained may assist in the formulation of a possible future GBS vaccine for Zimbabwe and perhaps for other African countries.
Adult↗
Experimental model of type IV Streptococcus agalactiae (group B streptococcus) infection in mice with early development of septic arthritis.
We have established an experimental murine model to gain insight into the pathogenicity and clinical features of type IV group B streptococcus (GBS) infections. Adult CD-1 mice were challenged intravenously with 10(7) type IV GBS cells, inducing systemic invasion. Most of the animals were able to clear the infection from the blood, brain, and lungs within 2 weeks and from the spleen and liver within 1 month. However, the animals were unable to clear the microorganism from the joints and kidneys during the 60-day observation period. About 80% of the mice challenged intravenously with type IV GBS manifested early septic arthritis, which evolved from an acute exudative synovitis to permanent lesions characterized by irreversible joint damage and ankylosis. Induction of persistent septic arthritis was dependent on the number and viability of microorganisms inoculated and was unrelated to the strain of type IV GBS and the growth phase of the inoculum. Type-specific antibodies of both immunoglobulin M and G classes could be detected by agglutination and enzyme-linked immunosorbent assay from days 7 and 14, respectively; immunoglobulin G antibodies persisted for more than 40 days. Complexes of antibodies and group- and type-specific antigens were detected in mouse sera 24 h after infection and persisted up to day 22. These results were obtained an experimental model of type IV GBS chronic infection with early development of septic arthritis, which could be useful in future studies of pathogenicity and immune mechanisms involved in the host resistance to this microorganism.
Animals↗
Molecular epidemiology of Streptococcus agalactiae (group B Streptococcus).
Group B Streptococcus (GBS) is a common cause of sepsis and meningitis in newborns, and causes disease in pregnant women and non-pregnant adults. The incidence of disease among non-pregnant adults, particularly those with underlying conditions, is increasing. In addition, many individuals are asymptomatically colonized with GBS. When compared to group A Streptococcus and Streptococcus pneumoniae, however, little is known about the pathogenesis, natural history and transmission dynamics of GBS. Various molecular tools have been utilized to study this organism, including both phenotypic techniques, such as serotyping and multilocus enzyme electrophoresis, and genotypic techniques such as plasmid analysis and pulsed-field gel electrophoresis. This review outlines the contributions of these methods to our current understanding of GBS infections.
Animals↗
Susceptibility of Zimbabwean Streptococcus agalactiae (group B Streptococcus; GBS) isolates to four different antibiotics.
OBJECTIVE: To establish the susceptibility of Zimbabwean GBS strains isolated from hospitalised patients to four antibiotics. DESIGN: Cross sectional survey. SETTINGS: Four regions of Zimbabwe (Bindura, Bulawayo, Harare, and Masvingo). SUBJECTS: 113 GBS isolates from hospitalised patients in Bindura, Bulawayo, Harare and Masvingo, of whom most were suffering from infectious diseases. MAIN OUTCOME MEASURES: All isolates were tested for their susceptibility to clindamycin, erythromycin, penicillin and tetracycline. RESULTS: All isolates were 100% sensitive to clindamycin, 98% to penicillin, 86% to erythromycin; 2% of the isolates showed intermediate susceptibility to penicillin and 100% showed resistance to tetracycline. CONCLUSION: Penicillin is still the antibiotic of choice for treatment of GBS infections and for intrapartum chemoprophylaxis in Zimbabwe. For patients who are allergic to penicillin, clindamycin will be the drug of choice for both treatment and/or chemoprophylactic use in Zimbabwe.
Anti-Bacterial Agents↗