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Fernanda Cristina Petersen - One of the best experts on this subject based on the ideXlab platform.
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mouse igg2a antibodies specific for the commensal Streptococcus Mitis show stronger cross reactivity with Streptococcus pneumoniae than igg1 antibodies
2019Co-Authors: Sudhanshu Shekhar, Rabia Khan, Ata Ul Razzaq Khan, Fernanda Cristina PetersenAbstract:Here we show that mouse IgG2a and IgG1 antibodies specific for the commensal Streptococcus Mitis cross-react with pathogen Streptococcus pneumoniae serotypes 2 and 4, although the cross-reactivity conferred by IgG2a is stronger than that by IgG1 antibodies. These findings may be important for understanding the S. Mitis-induced IgG isotype responses and have consequences for the development of an effective pneumococcal vaccine.
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mouse igg2a antibodies specific for the commensal Streptococcus Mitis show stronger cross reactivity with Streptococcus pneumoniae than igg1 antibodies
2019Co-Authors: Sudhanshu Shekhar, Rabia Khan, Ata Ul Razzaq Khan, Fernanda Cristina PetersenAbstract:Abstract Here we show that mouse IgG2a and IgG1 antibodies specific for the commensal Streptococcus Mitis cross-react with the pathogen Streptococcus pneumoniae, although the cross-reactivity conferred by IgG2a is stronger than IgG1 antibodies. These findings may have implications for designing S. Mitis-based vaccines against pneumococcal infections.
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intranasal immunization with the commensal Streptococcus Mitis confers protective immunity against pneumococcal lung infection
2019Co-Authors: Sudhanshu Shekhar, Rabia Khan, Karl Schenck, Fernanda Cristina PetersenAbstract:ABSTRACT Streptococcus pneumoniae is a bacterial pathogen that causes various diseases of public health concern worldwide. Current pneumococcal vaccines target the capsular polysaccharide surrounding the cells. However, only up to 13 of more than 90 pneumococcal capsular serotypes are represented in the current conjugate vaccines. In this study, we used two experimental approaches to evaluate the potential of Streptococcus Mitis, a commensal that exhibits immune cross-reactivity with S. pneumoniae, to confer protective immunity to S. pneumoniae lung infection in mice. First, we assessed the immune response and protective effect of wild-type S. Mitis against lung infection by S. pneumoniae strains D39 (serotype 2) and TIGR4 (serotype 4). Second, we examined the ability of an S. Mitis mutant expressing the S. pneumoniae type 4 capsule (S. Mitis TIGR4cps) to elicit focused protection against S. pneumoniae TIGR4. Our results showed that intranasal immunization of mice with S. Mitis produced significantly higher levels of serum IgG and IgA antibodies reactive to both S. Mitis and S. pneumoniae, as well as enhanced production of interleukin 17A (IL-17A), but not gamma interferon (IFN-γ) and IL-4, compared with control mice. The immunization resulted in a reduced bacterial load in respiratory tissues following lung infection with S. pneumoniae TIGR4 or D39 compared with control mice. With S. Mitis TIGR4cps, protection upon challenge with S. pneumoniae TIGR4 was superior. Thus, these findings show the potential of S. Mitis to elicit natural serotype-independent protection against two pneumococcal serotypes and to provide the benefits of the well-recognized protective effect of capsule-targeting vaccines. IMPORTANCEStreptococcus pneumoniae causes various diseases worldwide. Current pneumococcal vaccines protect against a limited number of more than 90 pneumococcal serotypes, accentuating the urgent need to develop novel prophylactic strategies. S. pneumoniae and the commensal Streptococcus Mitis share immunogenic characteristics that make S. Mitis an attractive vaccine candidate against S. pneumoniae. In this study, we evaluated the potential of S. Mitis and its mutant expressing pneumococcal capsule type 4 (S. Mitis TIGR4cps) to induce protection against S. pneumoniae lung infection in mice. Our findings show that intranasal vaccination with S. Mitis protects against S. pneumoniae strains D39 (serotype 2) and TIGR4 (serotype 4) in a serotype-independent fashion, which is associated with enhanced antibody and T cell responses. Furthermore, S. Mitis TIGR4cps conferred additional protection against S. pneumoniae TIGR4, but not against D39. The findings highlight the potential of S. Mitis to generate protection that combines both serotype-independent and serotype-specific responses.
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characterization of a signaling system in Streptococcus Mitis that mediates interspecies communication with Streptococcus pneumoniae
2019Co-Authors: Roger Junges, Kjersti Sturod, Gabriela Salvadori, Heidi Aaro Amdal, Tsute Chen, Fernanda Cristina PetersenAbstract:Streptococcus Mitis is found in the oral cavity and nasopharynx and forms a significant portion of the human microbiome. In this study, in silico analyses indicated the presence of an Rgg regulator and short hydrophobic peptide (Rgg/SHP) cell-to-cell communication system in S. Mitis Although Rgg presented greater similarity to a repressor in Streptococcus pyogenes, autoinducing assays and genetic mutation analysis revealed that in S. Mitis Rgg acts as an activator. Transcriptome analysis showed that in addition to shp, the system regulates two other downstream genes, comprising a segment of a putative lantibiotic gene cluster that is in a conjugative element locus in different members of the Mitis group. Close comparison to a similar lantibiotic gene cluster in Streptococcus pneumoniae indicated that S. Mitis lacked the full set of genes. Despite the potential of SHP to trigger a futile cycle of autoinduction, growth was not significantly affected for the rgg mutant under normal or antibiotic stress conditions. The S. Mitis SHP was, however, fully functional in promoting cross-species communication and increasing S. pneumoniae surface polysaccharide production, which in this species is regulated by Rgg/SHP. The activity of SHPs produced by both species was detected in cocultures using a S. Mitis reporter strain. In competitive assays, a slight advantage was observed for the rgg mutants. We conclude that the Rgg/SHP system in S. Mitis regulates the expression of its own shp and activates an Rgg/SHP system in S. pneumoniae that regulates surface polysaccharide synthesis. Fundamentally, cross-communication of such systems may have a role during multispecies interactions.IMPORTANCE Bacteria secrete signal molecules into the environment which are sensed by other cells when the density reaches a certain threshold. In this study, we describe a communication system in Streptococcus Mitis, a commensal species from the oral cavity, which we also found in several species and strains of streptococci from the Mitis group. Further, we show that this system can promote cross-communication with S. pneumoniae, a closely related major human pathogen. Importantly, we show that this cross-communication can take place during coculture. While the genes regulated in S. Mitis are likely part of a futile cycle of activation, the target genes in S. pneumoniae are potentially involved in virulence. The understanding of such complex communication networks can provide important insights into the dynamics of bacterial communities.
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high resolution profiles of the Streptococcus Mitis csp signaling pathway reveal core and strain specific regulated genes
2018Co-Authors: Gabriela Salvadori, Roger Junges, Heidi Aaro Amdal, Tsute Chen, Donald A Morrison, Fernanda Cristina PetersenAbstract:In streptococci of the Mitis group, competence for natural transformation is a transient physiological state triggered by competence stimulating peptides (CSPs). Although low transformation yields and the absence of a widespread functional competence system have been reported for Streptococcus Mitis, recent studies revealed that, at least for some strains, high efficiencies can be achieved following optimization protocols. To gain a deeper insight into competence in this species, we used RNA-seq, to map the global CSP response of two transformable strains: the type strain NCTC12261T and SK321. All known genes induced by ComE in Streptococcus pneumoniae, including sigX, were upregulated in the two strains. Likewise, all sets of streptococcal SigX core genes involved in extracellular DNA uptake, recombination, and fratricide were upregulated. No significant differences in the set of induced genes were observed when the type strain was grown in rich or semi-defined media. Five upregulated operons unique to S. Mitis with a SigX-box in the promoter region were identified, including two specific to SK321, and one specific to NCTC12261T. Two of the strain-specific operons coded for different bacteriocins. Deletion of the unique S. Mitis sigX regulated genes had no effect on transformation. Overall, comparison of the global transcriptome in response to CSP shows the conservation of the ComE and SigX-core regulons in competent S. Mitis isolates, as well as species and strain-specific genes. Although some S. Mitis exhibit truncations in key competence genes, this study shows that in transformable strains, competence seems to depend on the same core genes previously identified in S. pneumoniae.
Laurent Gutmann - One of the best experts on this subject based on the ideXlab platform.
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acquisition of five high mr penicillin binding protein variants during transfer of high level beta lactam resistance from Streptococcus Mitis to Streptococcus pneumoniae
1998Co-Authors: Regine Hakenbeck, Andrea Konig, Izabella Kern, Mark Van Der Linden, Wolfgang Keck, Danielle Billotklein, Raymond Legrand, Bernard Schoot, Laurent GutmannAbstract:Penicillin-resistant isolates of Streptococcus pneumoniae generally contain mosaic genes encoding the low-affinity penicillin-binding proteins (PBPs) PBP2x, PBP2b, and PBP1a. We now present evidence that PBP2a and PBP1b also appear to be low-affinity variants and are encoded by distinct alleles in beta-lactam-resistant transformants of S. pneumoniae obtained with chromosomal donor DNA from a Streptococcus Mitis isolate. Different lineages of beta-lactam-resistant pneumococcal transformants were analyzed, and transformants with low-affinity variants of all high-molecular-mass PBPs, PBP2x, -2a, -2b, -1a, and -1b, were isolated. The MICs of benzyl-penicillin, oxacillin, and cefotaxime for these transformants were up to 40, 100, and 50 microg/ml, respectively, close to the MICs for the S. Mitis donor strain. Recruitment of low-affinity PBPs was accompanied by a decrease in cross-linked muropeptides as revealed by high-performance liquid chromatography of muramidase-digested cell walls, but no qualitative changes in muropeptide chemistry were detected. The growth rates of all transformants were identical to that of the parental S. pneumoniae strain. The results stress the potential for the acquisition by S. pneumoniae of high-level beta-lactam resistance by interspecies gene transfer.
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acquisition of five high mr penicillin binding protein variants during transfer of high level beta lactam resistance from Streptococcus Mitis to Streptococcus pneumoniae
1998Co-Authors: Regine Hakenbeck, Andrea Konig, Izabella Kern, Mark Van Der Linden, Wolfgang Keck, Danielle Billotklein, Raymond Legrand, Bernard Schoot, Laurent GutmannAbstract:Penicillin-resistant isolates of Streptococcus pneumoniae generally contain mosaic genes encoding the lowaffinity penicillin-binding proteins (PBPs) PBP2x, PBP2b, and PBP1a. We now present evidence that PBP2a and PBP1b also appear to be low-affinity variants and are encoded by distinct alleles in b-lactam-resistant transformants of S. pneumoniae obtained with chromosomal donor DNA from a Streptococcus Mitis isolate. Different lineages of b-lactam-resistant pneumococcal transformants were analyzed, and transformants with low-affinity variants of all high-molecular-mass PBPs, PBP2x, -2a, -2b, -1a, and -1b, were isolated. The MICs of benzylpenicillin, oxacillin, and cefotaxime for these transformants were up to 40, 100, and 50 mg/ml, respectively, close to the MICs for the S. Mitis donor strain. Recruitment of low-affinity PBPs was accompanied by a decrease in cross-linked muropeptides as revealed by high-performance liquid chromatography of muramidase-digested cell walls, but no qualitative changes in muropeptide chemistry were detected. The growth rates of all transformants were identical to that of the parental S. pneumoniae strain. The results stress the potential for the acquisition by S. pneumoniae of high-level b-lactam resistance by interspecies gene transfer.
Paul M Sullam - One of the best experts on this subject based on the ideXlab platform.
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strain specific adaptations of Streptococcus Mitis oralis to serial in vitro passage in daptomycin dap genotypic and phenotypic characteristics
2020Co-Authors: Nagendra N Mishra, Truc T Tran, Ravin Seepersaud, Paul M Sullam, Cesar A AriasAbstract:Viridans group streptococci (VGS), especially the Streptococcus Mitis-oralis subgroup, are pivotal pathogens in a variety of invasive endovascular infections, including "toxic shock" in neutropenic cancer patients and infective endocarditis (IE). Previously, we showed that the serial in vitro passage of S. Mitis-oralis strains in sublethal daptomycin (DAP) resulted in rapid, high-level and stable DAP-resistance (DAP-R), which is accompanied by distinct changes in several genotypic and phenotypic signatures: (1) the disappearance of two key membrane phospholipids, phosphatidylglycerol (PG) and cardiolipin (CL); (2) increased membrane fluidity; (3) increased positive surface charge; (4) single nucleotide polymorphisms (SNPs) in two loci involved in CL biosynthesis (pgsA; cdsA); and (5) DAP hyperaccumulation. The current study examined these same metrics following in vitro serial DAP passages of a separate well-characterized S. Mitis-oralis bloodstream isolate (SF100). Although some metrics seen in prior DAP post-passage strains were recapitulated with SF100 (e.g., pgsA SNPs, enhanced membrane fluidity), we observed the following major differences (comparing the parental versus post-passage variant): (1) no change in PG content; (2) reduced, but not absent, CL, with enhancement in phosphatidic acid (PA) content; (3) an unusual pattern of CL localization; (4) significantly decreased positive surface charge; (5) no difference in DAP accumulation; and (6) no cdsA SNPs. Thus, S. Mitis-oralis strains are not "pre-programmed" phenotypically and/or genotypically to adapt in an identical manner during the evolution of the DAP-R.
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Characterization of the Fibrinogen Binding Domain of Bacteriophage Lysin from Streptococcus Mitis
2011Co-Authors: Ho Seong Seo, Paul M SullamAbstract:The binding of bacteria to human platelets is a likely central mechanism in the pathogenesis of infective endocarditis. Platelet binding by Streptococcus Mitis SF100 is mediated in part by a lysin encoded by the lysogenic bacteriophage SM1. In addition to its role in the phage life cycle, lysin mediates the binding of S. Mitis to human platelets via its interaction with fibrinogen on the platelet surface. To better define the region of lysin mediating fibrinogen binding, we tested a series of purified lysin truncation variants for their abilities to bind this protein. These studies revealed that the fibrinogen binding domain of lysin is contained within the region spanned by amino acid residues 102 to 198 (lysin102–198). This region has no sequence homology to other known fibrinogen binding proteins. Lysin102–198 bound fibrinogen comparably to full-length lysin and with the same selectivity for the fibrinogen Aα and Bβ chains. Lysin102–198 also inhibited the binding in vitro of S. Mitis to human fibrinogen and platelets. When assessed by platelet aggregometry, the disruption of the lysin gene in SF100 resulted in a significantly longer time to the onset of aggregation of human platelets than that of the parent strain. The preincubation of platelets with purified lysin102–198 also delayed the onset of aggregation by SF100. These results indicate that the binding of lysin to fibrinogen is mediated by a specific domain of the phage protein and that this interaction is important for both platelet binding and aggregation by S. Mitis.
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Bacteriophage lysin mediates the binding of Streptococcus Mitis to human platelets through interaction with fibrinogen.
2010Co-Authors: Ho Seong Seo, Jennifer Mitchell, Arnold S Bayer, Ravin Seepersaud, Yan Q. Xiong, Paul M SullamAbstract:The binding of bacteria to human platelets is a likely central mechanism in the pathogenesis of infective endocarditis. We have previously found that platelet binding by Streptococcus Mitis SF100 is mediated by surface components encoded by a lysogenic bacteriophage, SM1. We now demonstrate that SM1-encoded lysin contributes to platelet binding via its direct interaction with fibrinogen. Far Western blotting of platelets revealed that fibrinogen was the major membrane-associated protein bound by lysin. Analysis of lysin binding with purified fibrinogen in vitro confirmed that these proteins could bind directly, and that this interaction was both saturable and inhibitable. Lysin bound both the Aα and Bβ chains of fibrinogen, but not the γ subunit. Binding of lysin to the Bβ chain was further localized to a region within the fibrinogen D fragment. Disruption of the SF100 lysin gene resulted in an 83±3.1% reduction (mean ± SD) in binding to immobilized fibrinogen by this mutant strain (PS1006). Preincubation of this isogenic mutant with purified lysin restored fibrinogen binding to wild type levels. When tested in a co-infection model of endocarditis, loss of lysin expression resulted in a significant reduction in virulence, as measured by achievable bacterial densities (CFU/g) within vegetations, kidneys, and spleens. These results indicate that bacteriophage-encoded lysin is a multifunctional protein, representing a new class of fibrinogen-binding proteins. Lysin appears to be cell wall-associated through its interaction with choline. Once on the bacterial surface, lysin can bind fibrinogen directly, which appears to be an important interaction for the pathogenesis of endocarditis.
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Streptococcus Mitis phage encoded adhesins mediate attachment to α2 8 linked sialic acid residues on platelet membrane gangliosides
2009Co-Authors: Jennifer Mitchell, Paul M SullamAbstract:The direct binding of bacteria to human platelets contributes to the pathogenesis of infective endocarditis. Platelet binding by Streptococcus Mitis strain SF100 is mediated in part by two bacteriophage-encoded proteins, PblA and PblB. However, the platelet membrane receptor for these adhesins has been unknown. In this study, we demonstrate that these proteins mediate attachment of bacterial cells to sialylated gangliosides on the platelet cell surface. Desialylation of human platelet monolayers reduced adherence of SF100, whereas treatment of the platelets with N- or O-glycanases did not affect platelet binding. Treatment of platelets with sialidases having different linkage specificities showed that removal of α2-8-linked sialic acids resulted in a marked reduction in bacterial binding. Preincubation of SF100 with ganglioside GD3, a glycolipid containing α2-8-linked sialic acids that is present on platelet membranes, blocked subsequent binding of this strain to these cells. In contrast, GD3 had no effect on the residual binding of platelets by strain PS344, an isogenic ΔpblA ΔpblB mutant. Preincubating platelets with specific monoclonal antibodies to ganglioside GD3 also inhibited binding of SF100 to platelets, but again, they had no effect on binding by PS344. When the direct binding of S. Mitis strains SF100 and PS344 to immobilized gangliosides was tested, binding of PS344 to GD3 was reduced by 70% compared to the parent strain. These results indicated that platelet binding by SF100 is mediated by the interaction of PblA and PblB with α2-8-linked sialic acids on ganglioside GD3.
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mechanism of cell surface expression of the Streptococcus Mitis platelet binding proteins pbla and pblb
2007Co-Authors: Jennifer Mitchell, Ian R Siboo, Daisuke Takamatsu, Henry F Chambers, Paul M SullamAbstract:PblA and PblB are prophage-encoded proteins of Streptococcus Mitis strain SF100 that mediate binding to human platelets. The mechanism for surface expression of these proteins has been unknown, as they do not contain signal sequences or cell wall sorting motifs. We therefore assessed whether expression of these proteins was linked the lytic cycle of the prophage. Deletion of either the holin or lysin gene resulted in retention of PblA and PblB in the cytoplasm, and loss of these proteins from the cell wall. Flow cytometric analysis revealed that induction of phage replication in SF100 produced a subpopulation of cells with increased permeability. This effect was abrogated by disruption of the holin and lysin genes. Treatment of these mutants with exogenous PblA and PblB restored surface expression, apparently via binding of the proteins to cell wall choline. Loss of PblA and PblB expression was associated with decreased platelet binding in vitro, and reduced virulence in an animal model of endocarditis. Thus, expression of PblA and PblB occurs via a novel mechanism, whereby phage induction increases bacterial permeability and release of the proteins, followed by their binding to surface of viable cells. This mechanism may be important for endovascular infection.
Regine Hakenbeck - One of the best experts on this subject based on the ideXlab platform.
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acquisition of five high mr penicillin binding protein variants during transfer of high level beta lactam resistance from Streptococcus Mitis to Streptococcus pneumoniae
1998Co-Authors: Regine Hakenbeck, Andrea Konig, Izabella Kern, Mark Van Der Linden, Wolfgang Keck, Danielle Billotklein, Raymond Legrand, Bernard Schoot, Laurent GutmannAbstract:Penicillin-resistant isolates of Streptococcus pneumoniae generally contain mosaic genes encoding the low-affinity penicillin-binding proteins (PBPs) PBP2x, PBP2b, and PBP1a. We now present evidence that PBP2a and PBP1b also appear to be low-affinity variants and are encoded by distinct alleles in beta-lactam-resistant transformants of S. pneumoniae obtained with chromosomal donor DNA from a Streptococcus Mitis isolate. Different lineages of beta-lactam-resistant pneumococcal transformants were analyzed, and transformants with low-affinity variants of all high-molecular-mass PBPs, PBP2x, -2a, -2b, -1a, and -1b, were isolated. The MICs of benzyl-penicillin, oxacillin, and cefotaxime for these transformants were up to 40, 100, and 50 microg/ml, respectively, close to the MICs for the S. Mitis donor strain. Recruitment of low-affinity PBPs was accompanied by a decrease in cross-linked muropeptides as revealed by high-performance liquid chromatography of muramidase-digested cell walls, but no qualitative changes in muropeptide chemistry were detected. The growth rates of all transformants were identical to that of the parental S. pneumoniae strain. The results stress the potential for the acquisition by S. pneumoniae of high-level beta-lactam resistance by interspecies gene transfer.
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acquisition of five high mr penicillin binding protein variants during transfer of high level beta lactam resistance from Streptococcus Mitis to Streptococcus pneumoniae
1998Co-Authors: Regine Hakenbeck, Andrea Konig, Izabella Kern, Mark Van Der Linden, Wolfgang Keck, Danielle Billotklein, Raymond Legrand, Bernard Schoot, Laurent GutmannAbstract:Penicillin-resistant isolates of Streptococcus pneumoniae generally contain mosaic genes encoding the lowaffinity penicillin-binding proteins (PBPs) PBP2x, PBP2b, and PBP1a. We now present evidence that PBP2a and PBP1b also appear to be low-affinity variants and are encoded by distinct alleles in b-lactam-resistant transformants of S. pneumoniae obtained with chromosomal donor DNA from a Streptococcus Mitis isolate. Different lineages of b-lactam-resistant pneumococcal transformants were analyzed, and transformants with low-affinity variants of all high-molecular-mass PBPs, PBP2x, -2a, -2b, -1a, and -1b, were isolated. The MICs of benzylpenicillin, oxacillin, and cefotaxime for these transformants were up to 40, 100, and 50 mg/ml, respectively, close to the MICs for the S. Mitis donor strain. Recruitment of low-affinity PBPs was accompanied by a decrease in cross-linked muropeptides as revealed by high-performance liquid chromatography of muramidase-digested cell walls, but no qualitative changes in muropeptide chemistry were detected. The growth rates of all transformants were identical to that of the parental S. pneumoniae strain. The results stress the potential for the acquisition by S. pneumoniae of high-level b-lactam resistance by interspecies gene transfer.
Mogens Kilian - One of the best experts on this subject based on the ideXlab platform.
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parallel evolution of Streptococcus pneumoniae and Streptococcus Mitis to pathogenic and mutualistic lifestyles
2014Co-Authors: Mogens Kilian, David R Riley, Anders Jensen, Holger Bruggemann, Herve TettelinAbstract:The bacterium Streptococcus pneumoniae is one of the leading causes of fatal infections affecting humans. Intrigu- ingly, phylogenetic analysis shows that the species constitutes one evolutionary lineage in a cluster of the otherwise commensal Streptococcus Mitis strains, with which humans live in harmony. In a comparative analysis of 35 genomes, including phyloge- netic analyses of all predicted genes, we have shown that the pathogenic pneumococcus has evolved into a master of genomic flexibility while lineages that evolved into the nonpathogenic S. Mitis secured harmonious coexistence with their host by stabi- lizing an approximately 15%-reduced genome devoid of many virulence genes. Our data further provide evidence that interspe- cies gene transfer between S. pneumoniae and S. Mitis occurs in a unidirectional manner, i.e., from S. Mitis to S. pneumoniae. Import of genes from S. Mitis and other Mitis, anginosus, and salivarius group streptococci ensured allelic replacements and antigenic diversification and has been driving the evolution of the remarkable structural diversity of capsular polysaccharides of S. pneumoniae. Our study explains how the unique structural diversity of the pneumococcal capsule emerged and conceivably will continue to increase and reveals a striking example of the fragile border between the commensal and pathogenic lifestyles. While genomic plasticity enabling quick adaptation to environmental stress is a necessity for the pathogenic streptococci, the commensal lifestyle benefits from stability. IMPORTANCE One of the leading causes of fatal infections affecting humans, Streptococcus pneumoniae, and the commensal Streptococcus Mitis are closely related obligate symbionts associated with hominids. Faced with a shortage of accessible hosts, the two opposing lifestyles evolved in parallel. We have shown that the nonpathogenic S. Mitis secured harmonious coexistence with its host by stabilizing a reduced genome devoid of many virulence genes. Meanwhile, the pathogenic pneumococcus evolved into a master of genomic flexibility and imports genes from S. Mitis and other related streptococci. This process ensured anti- genic diversification and has been driving the evolution of the remarkable structural diversity of capsular polysaccharides of S. pneumoniae, which conceivably will continue to increase and present a challenge to disease prevention.
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genomes of Streptococcus Mitis Streptococcus oralis and Streptococcus infantis
2011Co-Authors: Herve Tettelin, Mogens KilianAbstract:This chapter talks about the closest relatives of Streptococcus Mitis that are the commensals S. oralis, S. infantis, and, in particular, the important pathogen Streptococcus pneumoniae and the still relatively unknown Streptococcus pseudopneumoniae. The genetic diversity among S. Mitis strains may have important consequences in the oral cavity. Draft genomes display an artificially high total number of genes and number of paralogs due to sequencing errors and gaps leading to gene fragmentation, as well as low-quality redundant sequences at contig ends. The verification results in the conclusion that this observation is not due to the fact that (i) all but one of the non-S. pneumoniae genomes studied are draft genomes, and (ii) gene prediction standards differ among sequencing centers. First, the closed S. Mitis B6 genome displays a higher coding percentage. Second, the coding density was measured in three unpublished draft S. pneumoniae genomes obtained from three different sequencing centers, and the average coding percentage was 84.9%. The previous observation that virtually every independent isolate of S. Mitis represents a distinct species according to traditional taxonomic principles is supported by our multigenome analysis. The significant sharing of core genes between S. Mitis and S. pneumoniae reinforces the conclusion that S. pneumoniae is one lineage of the S. Mitis complex.
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population dynamics of Streptococcus Mitis in its natural habitat
2001Co-Authors: Jesper Hohwy, Jesper Reinholdt, Mogens KilianAbstract:The purpose of this study was to examine the genetic structure of the typical commensal Streptococcus Mitis biovar 1 in its natural habitat in the human oral cavity and pharynx and to investigate the role that selected microbial properties and host, spatial, and temporal factors play in determining the structure of the bacterial population. Consecutive samples were collected from buccal and pharyngeal mucosal surfaces of two infants, their four parents, and two elderly individuals over a period of approximately 1 year. A total of 751 isolates identified as S. Mitis biovar 1 were typed by restriction endonuclease analysis (REA) and representative clones were typed by multilocus enzyme electrophoresis (MLEE). The genetic diversity of the S. Mitis biovar 1 isolates collected from single infant hosts over a period of 9 to 10 months was found to be between 0.69 and 0.76, which is considerably higher than that previously observed for intestinal populations of Escherichia coli. The study provides evidence of the existence of both transient and persistent clones in adult individuals. In the two infants, however, none of 42 demonstrated clones were detected on more than a single occasion. Statistical calculations showed that the ability to persist was not distributed at random in the S. Mitis biovar 1 population. However, neither immunoglobulin A1 protease activity nor the ability to bind α-amylase from saliva was a preferential characteristic of persistent genotypes. In contrast to current concepts of climax ecosystems, the species niche in the habitat appears to be maintained predominantly by a succession of clones rather than by stable strains. Several lines of evidence suggest that the major origin of “new” clones is the many other habitats in the respiratory tract that are occupied by this species.
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structures of two cell wall associated polysaccharides of a Streptococcus Mitis biovar 1 strain
2000Co-Authors: Niklas Bergstrom, Mogens Kilian, Pererik Jansson, Uffe Skov B SorensenAbstract:The cell wall of Streptococcus Mitis biovar 1 strain SK137 contains the C-polysaccharide known as the common antigen of a closely related species Streptococcus pneumoniae, and a teichoic acid-like polysaccharide with a unique structure. The two polysaccharides are different entities and could be partially separated by gel chromatography. The structures of the two polysaccharides were determined by chemical methods and by NMR spectroscopy. The teichoic acid-like polymer has a heptasaccharide phosphate repeating unit with the following structure: The structure neither contains ribitol nor glycerol phosphate as classical teichoic acids do, thus we have used the expression teichoic acid-like for this polysaccharide. The following structure of the C-polysaccharide repeating unit was established: where AAT is 2-acetamido-4-amino-2,4, 6-trideoxy-D-galactose. It has a carbohydrate backbone identical to that of one of the two structures of C-polysaccharide previously identified in S. pneumoniae. C-polysaccharide of S. Mitis is characterized by the presence, in each repeating unit, of two residues of phosphocholine and both galactosamine residues in the N-acetylated form. Immunochemical analysis showed that C-polysaccharide constitutes the Lancefield group O antigen. Studies using mAbs directed against the backbone and against the phosphocholine moiety of the C-polysaccharide revealed several different patterns of these epitopes among 95 S. Mitis and Streptococcus oralis strains tested and the exclusive presence of the group O antigen in the majority of S. Mitis biovar 1 strains.
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clonal diversity of the Streptococcus Mitis biovar 1 population in the human oral cavity and pharynx
1995Co-Authors: J Hohwy, Mogens KilianAbstract:A total of 250 isolates of oral streptococci were recovered from swabs of oropharyngeal surfaces of 3 members of one family. All isolates were examined by biochemical and serological means, and 106 isolates were identified as Streptococcus Mitis biovar 1. These were typed by restriction endonuclease analysis using the enzymes EcoRI and HaeIII and further characterized by their whole-cell polypeptide profile patterns in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In addition, rabbit antisera raised against 8 reference strains of oral streptococci were used to characterize representative isolates both by their carbohydrate and protein antigens by Ouchterlony and Western blot analyses. Very limited biochemical diversity was observed among the 106 S. Mitis biovar 1 isolates. In contrast, 24 different genotypes defined by restriction endonuclease analysis were detected, and each individual carried 6-13 types. Limited sharing of genotypes was observed between the 3 members of the same family and between the pharyngeal and buccal mucosa of single individuals. The antigenic analyses showed remarkable antigenic diversity between the 24 genotypes. The results provide a basis for studying the population dynamics of an oral commensal species and its interaction with the salivary immune system.