Wednesday, July 16, 2014

The responsiveness of TrkB to exogenous BDNF in frontal cortex during antibiotic treatment of Streptococcus pneumoniae meningitis.

Neurol Sci. 2014 Jul 11. [Epub ahead of print]
The responsiveness of TrkB to exogenous BDNF in frontal cortex during antibiotic treatment of Streptococcus pneumoniae meningitis.
Author information


Abstract
Our previous studies suggested that the expression of TrkB and BDNF decreased concomitantly in brain during Streptococcus pneumoniae meningitis after antibiotic treatment, and that adjuvant administration of exogenous BDNF could rescue neurons from S. pneumoniae meningitis. In this study, we investigated the responsiveness of TrkB to exogenous BDNF treatment in frontal cortex during antibiotic treatment of S. pneumoniae meningitis. We found that adjuvant administration of exogenous BDNF led to increased number of survived neurons, improved the conduction of central auditory pathway and neurological disfunction, and up-regulated TrkB expression at the mRNA level in the frontal cortex of rats under S. pneumonia meningitis (P < 0.01). When treated with placebo, on the contrary, neurons in the frontal cortex of control rats were seriously damaged and the TrkB expression was remarkably decreased. These findings indicated that exogenous BDNF could up-regulate TrkB expression and thus played a neuroprotective role in frontal cortex injury from S. pneumoniae meningitis. They further confirmed our previous report that the decrease of intrinsic BDNF and TrkB expression is involved in the pathogenesis of neurological brain damage during S. pneumoniae meningitis after antibiotic treatment.

PMID: 25012754 [PubMed - as supplied by publisher]

Role of Global and Local Topology in the Regulation of Gene Expression in Streptococcus pneumoniae.

PLoS One. 2014 Jul 14;9(7):e101574. doi: 10.1371/journal.pone.0101574. eCollection 2014.
Role of Global and Local Topology in the Regulation of Gene Expression in Streptococcus pneumoniae.
Author information


Abstract
The most basic level of transcription regulation in Streptococcus pneumoniae is the organization of its chromosome in topological domains. In response to drugs that caused DNA-relaxation, a global transcriptional response was observed. Several chromosomal domains were identified based on the transcriptional response of their genes: up-regulated (U), down-regulated (D), non-regulated (N), and flanking (F). We show that these distinct domains have different expression and conservation characteristics. Microarray fluorescence units under non-relaxation conditions were used as a measure of gene transcriptional level. Fluorescence units were significantly lower in F genes than in the other domains with a similar AT content. The transcriptional level of the domains categorized them was D>U>F. In addition, a comparison of 12 S. pneumoniae genome sequences showed a conservation of gene composition within U and D domains, and an extensive gene interchange in F domains. We tested the organization of chromosomal domains by measuring the relaxation-mediated transcription of eight insertions of a heterologous Ptccat cassette, two in each type of domain, showing that transcription depended on their chromosomal location. Moreover, transcription from the four promoters directing the five genes involved in supercoiling homeostasis, located either in U (gyrB), D (topA), or N (gyrA and parEC) domains was analyzed both in their chromosomal locations and in a replicating plasmid. Although expression from the chromosomal PgyrB and PtopA showed the expected domain regulation, their expression was down-regulated in the plasmid, which behaved as a D domain. However, both PparE and PgyrA carried their own regulatory signals, their topology-dependent expression being equivalent in the plasmid or in the chromosome. In PgyrA a DNA bend acted as a DNA supercoiling sensor. These results revealed that DNA topology functions as a general transcriptional regulator, superimposed upon other more specific regulatory mechanisms.

PMID: 25019515 [PubMed - in process]

Friday, July 11, 2014

The Proteasome-Ubiquitin System Is Required for Efficient Killing of Intracellular Streptococcus pneumoniae by Brain Endothelial Cells.

MBio. 2014 Jul 1;5(4). pii: e00984-14. doi: 10.1128/mBio.00984-14.
The Proteasome-Ubiquitin System Is Required for Efficient Killing of Intracellular Streptococcus pneumoniae by Brain Endothelial Cells.
Author information


Abstract
Streptococcus pneumoniae (pneumococcus) is a Gram-positive bacterium that causes serious invasive diseases, such as pneumonia, bacteremia, and meningitis, with high morbidity and mortality throughout the world. Before causing invasive disease, S. pneumoniae encounters cellular barriers, which are often composed of endothelial cells, like the alveolar-capillary barrier and the blood-brain barrier. S. pneumoniae adheres to endothelial cells and may invade them, which requires an efficient host response to the intracellular bacteria. The precise intracellular fate of S. pneumoniae during infection still remains a subject of debate. The proteasome-ubiquitin system is largely responsible for the degradation of misfolded, damaged, or no-longer-useful proteins. Recently, the role of the proteasome-ubiquitin system in the clearing of invading bacteria and viruses has been more closely studied. In this study, we show that inhibition of the proteasome-ubiquitin system leads to a marked increase in S. pneumoniae survival inside host cells. Immunofluorescence analysis showed that intracellular pneumococci colocalized with proteasome and ubiquitin in human endothelial cells in vitro. Confocal imaging analysis demonstrated that in the brains of mice intravenously infected with S. pneumoniae, the bacteria were inside endothelial cells, where they colocalized with proteasome and ubiquitin signals. In conclusion, our data indicate that a fully functional proteasome-ubiquitin system in endothelial cells is crucial for efficient killing of intracellular S. pneumoniae.
IMPORTANCE:
Bacterial meningitis is a serious invasive disease with high morbidity and mortality. How bacteria traverse the blood-brain barrier in vivo and what mechanisms are employed by the host to prevent invasion are still unclear. Our data show that inhibition of the proteasome-ubiquitin system in vitro leads to a significant increase in S. pneumoniae survival inside brain endothelial cells. Confocal imaging analysis of brain tissue from mice intravenously infected with pneumococci demonstrated that the bacteria are inside brain microvascular endothelial cells, where they associate with the proteasome and ubiquitin. This is, as far as we know, the first report that demonstrates that Streptococcus pneumoniae invades endothelial cells of the blood-brain barrier in vivo. The host requires the proteasome-ubiquitin system for an efficient decimation of intracellular S. pneumoniae.
Copyright © 2014 Iovino et al.

PMID: 24987087 [PubMed - in process] 

GHIP in Streptococcus pneumoniae is involved in antibacterial resistance and elicits a strong innate immune response through TLR2 and JNK/p38MAPK.

FEBS J. 2014 Jul 2. doi: 10.1111/febs.12903. [Epub ahead of print]
GHIP in Streptococcus pneumoniae is involved in antibacterial resistance and elicits a strong innate immune response through TLR2 and JNK/p38MAPK.
Author information


Abstract
Interaction between pneumococcal virulence factors and innate immune receptors triggers host responses via specific signaling pathways after infection. By generating deficient mutant, we showed here that, compared with wild-type parent strain, glycosyl hydrolase 25 relating to invasion protein mutant strain was impaired in rapid dissemination into vessel and caused less severe inflammation in mice lungs. Further study demonstrated that the lack of this protein in Streptococcus pneumoniae caused an increased susceptibility to the whole blood or neutrophils, while this impairment could be recovered by supplementing recombinant GHIP (rGHIP). Additionally, secreted glycosyl hydrolase 25 relating to invasion protein could be detected in culture medium, and purified protein was capable to induce the release of tumor necrosis factor alpha and interleukin 6 from peritoneal macrophage. Further investigations revealed that the induction of interleukin 6 by this virulence factor depended on the phosphorylation of c-Jun N- terminal kinase and p38 mitogen activated protein kinase and Toll-like receptor 2. Taken together, glycosyl hydrolase 25 relating to invasion protein, a novel pneumococcal virulence factor, appeared to play a critical role in bacterial survival and the induction of host innate immune response during pneumococcal infection. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
KEYWORDS:
Streptococcus pneumoniae ; antibacterial resistance; glycosyl hydrolase 25; leukocytes recruitment; toll-like receptor 2

PMID: 24989111 [PubMed - as supplied by publisher]

The roles of epithelial cell contact, respiratory bacterial interactions and phosphorylcholine in promoting biofilm formation by Streptococcus pneumoniae and nontypeable Haemophilus influenzae.

Microbes Infect. 2014 Jul 3. pii: S1286-4579(14)00082-3. doi: 10.1016/j.micinf.2014.06.008. [Epub ahead of print]
The roles of epithelial cell contact, respiratory bacterial interactions and phosphorylcholine in promoting biofilm formation by Streptococcus pneumoniae and nontypeable Haemophilus influenzae.
Author information


Abstract
Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) often share a common niche within the nasopharynx, both associated with infections such as bronchitis and otitis media. This study investigated how the association between NTHi and S. pneumoniae and the host affects their propensity to form biofilms. We investigated a selection of bacterial strain and serotype combinations on biofilm formation, and the effect of contact with respiratory epithelial cells. Measurement of biofilm showed that co-infection with NTHi and S. pneumoniae increased biofilm formation following contact with epithelial cells compared to no contact demonstrating the role of epithelial cells in biofilm formation. Additionally, the influence of phosphorylcholine (ChoP) on biofilm production was investigated using the licD mutant strain of NTHi 2019 and found that ChoP had a role in mixed biofilm formation but was not the only requirement. The study highlights the complex interactions between microbes and the host epithelium during biofilm production, suggesting the importance of understanding why certain strains and serotypes differentially influence biofilm formation. A key contributor to increased biofilm formation was the upregulation of biofilm formation by epithelial cell factors.
Copyright © 2014. Published by Elsevier Masson SAS.
KEYWORDS:
differential biofilm formation; epithelial cells; mixed-species biofilm; phosphorylcholine

PMID: 24998491 [PubMed - as supplied by publisher]

Pneumolysin expression by streptococcus pneumoniae protects colonized mice from influenza virus-induced disease.

Virology. 2014 Jul 3;462-463C:254-265. doi: 10.1016/j.virol.2014.06.019. [Epub ahead of print]
Pneumolysin expression by streptococcus pneumoniae protects colonized mice from influenza virus-induced disease.


Abstract
The response to influenza virus (IAV) infection and severity of disease is highly variable in humans. We hypothesized that one factor contributing to this variability is the presence of specific respiratory tract (RT) microbes. One such microbe is Streptococcus pneumoniae (Sp) that is carried asymptomatically in the RT of many humans. In a mouse co-infection model we found that in contrast to secondary bacterial infection that exacerbates disease, Sp colonization 10 days prior to IAV protects from virus-induced morbidity and lung pathology. Using mutant Sp strains, we identified a critical role for the bacterial virulence factor pneumolysin (PLY) in mediating this protection. Colonization with the PLY-sufficient Sp strain induces expression of the immune-suppressive enzyme arginase 1 in alveolar macrophages (aMø) and correlates with attenuated recruitment and function of pulmonary inflammatory cells. Our study demonstrates a novel role for PLY in Sp-mediated protection by maintaining aMø as "gatekeepers" against virus-induced immunopathology.
Copyright © 2014. Published by Elsevier Inc.
KEYWORDS:
Alveolar macrophages; Arginase I; Immunopathology; Inflammatory monocytes; Influenza virus; Pneumolysin; Protection; Respiratory tract co-infection; Streptococcus pneumoniae; iNOS
PMID: 24999050 [PubMed - as supplied by publisher]

An Ahemolytic Pneumolysin of Streptococcus Pneumoniae Manipulates Human Innate and CD4+ T-Cell Responses and Reduces Resistance to Colonization in Mice in a Serotype-Independent Manner.

J Infect Dis. 2014 Jun 13. pii: jiu321. [Epub ahead of print]
An Ahemolytic Pneumolysin of Streptococcus Pneumoniae Manipulates Human Innate and CD4+ T-Cell Responses and Reduces Resistance to Colonization in Mice in a Serotype-Independent Manner.
Author information


Abstract
BACKGROUND:
 Some Streptococcus pneumoniae serotypes express an ahemolytic pneumolysin (PLYa). Serotypes that commonly express PLYa, including serotype 8 (ST8) and ST1, are often associated with a low prevalence during colonization but a higher propensity to cause invasive disease. We sought to study the host response to ST8 PLYa in a homologous and heterologous capsular background.
METHODS:
 We genetically exchanged the PLYa of ST8 strain 6308 with the hemolytic PLY (PLYh) of ST3 A66.1 and vice versa and determined the impact of the exchange on nasopharyngeal colonization in mice. Then, to compare the response of human cells to PLYa-expressing and PLYh-expressing strains, we infected human peripheral blood mononuclear cells (PBMCs) with PLY-switched strains and assessed dendritic cell and CD4+ T-cell responses by intracellular cytokine staining.
RESULT:
 Mice colonized with PLYa-expressing strains had significantly higher colonization densities than those colonized with PLYh-expressing strains, irrespective of capsular background. Compared with infection of PBMCs with PLYh-expressing strains, infection with PLYa-expressing strains induced diminished innate (dendritic cell cytokines, costimulatory receptor, and apoptotic) and adaptive (CD4+ T-cell proliferative and memory interleukin 17A) responses.
CONCLUSION:
 Our findings demonstrate that PLYa has the potential to manipulate host immunity irrespective of capsule type. PLY exchange between STs expressing PLYa and PLYh could lead to unexpected colonization or invasion phenotypes.
© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
KEYWORDS:
Streptococcus pneumoniae; T cell; apoptosis; colonization; dendritic cell; invasion; mice; pneumolysin; serotype
PMID: 25001458 [PubMed - as supplied by publisher]

Chemical Structure of the Capsular Polysaccharides (CPS) of Streptococcus pneumoniae Types 39, 47F and 34 by NMR Spectroscopy and their Relation to CPS10A.

J Bacteriol. 2014 Jul 7. pii: JB.01731-14. [Epub ahead of print]
Chemical Structure of the Capsular Polysaccharides (CPS) of Streptococcus pneumoniae Types 39, 47F and 34 by NMR Spectroscopy and their Relation to CPS10A.
Author information


Abstract
Structural characterization of Streptococcus pneumoniae capsular polysaccharides (CPS) is a prerequisite for unraveling antigenic as well as genetic relationships that exist between different serotypes. In the current study, comparative structural studies of S. pneumoniae CPS serogroup 10 were extended to include genetically related S. pneumoniae CPS34, 39 and 47F. High-resolution hetero-nuclear NMR spectroscopy confirmed the published structure of CPS34 and in conjunction with glycosyl composition analyses, revealed repeat unit structures of the other serotypes, which have not been previously characterized: jb;JB.01731-14v1/FU1F1FU1 Common and unique structural features of these polysaccharides, including different positions of O-acetylation, were unambiguously associated with specific genes in each corresponding cps locus. The only exception involved the gene designated wcrC, which is associated with the α1-2 transfer of Galp to ribitol-5-phosphate in synthesis of CPS10A, CPS47F and CPS34 but α1-1 transfer of Gal to ribitol-5-phosphate in CPS39. The corresponding gene in the cps39 locus, although related to wcrC, more closely resembled a previously identified gene (i.e. wefM) of S. oralis associated with α1-1 transfer of Galp to ribitol-5-phosphate. These and other recent findings identify linkages from α-Galp to ribitol-5-phosphate and from this residue to adjacent Galf as important sites of CPS structural and genetic diversity.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.

PMID: 25002537 [PubMed - as supplied by publisher]

A novel protein RafX is important for common cell wall polysaccharide biosynthesis in Streptococcus pneumoniae: implications for bacterial virulence.

J Bacteriol. 2014 Jul 7. pii: JB.01696-14. [Epub ahead of print]
A novel protein RafX is important for common cell wall polysaccharide biosynthesis in Streptococcus pneumoniae: implications for bacterial virulence.
Author information


Abstract
Teichoic acid (TA), together with peptidoglycan (PG), represents a highly complex glycopolymer to ensure cell wall integrity and has several crucial physiological activities. Through insertion-deletion mutation strategy, we show that ΔrafX mutants were impaired in WTA-PG biosynthesis as evidenced by the abnormal banding pattern and reduced amount of wall teichoic acid in comparison with wild type strains. Site-directed mutagenesis revealed an essential role for the external loop 4 and some highly conserved amino acid residues for the function of RafX protein. rafX gene was highly conserved in closely related streptococcal species, suggesting an important physiological function in the lifestyle of streptococci. Moreover, D39 ΔrafX mutant was impaired in bacterial growth, autolysis as well as bacterial division and morphology. We observed that R6 ΔrafX mutant was reduced in adhesion relative to the wild type R6 strain, which was supported by the inhibition assay and a reduced amount of CbpA protein on the bacterial surface of ΔrafX mutants shown by flow cytometric analysis. Finally, ΔrafX mutants were significantly attenuated in virulence in murine sepsis model. Together these findings suggest that RafX contributes to the biosynthesis of wall teichoic acid which is essential for full pneumococcal virulence.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
PMID: 25002545 [PubMed - as supplied by publisher]



In Vitro Bactericidal and Bacteriolytic Activity of Ceragenin CSA-13 against Planktonic Cultures and Biofilms of Streptococcus pneumoniae and Other Pathogenic Streptococci.

PLoS One. 2014 Jul 9;9(7):e101037. doi: 10.1371/journal.pone.0101037. eCollection 2014.
In Vitro Bactericidal and Bacteriolytic Activity of Ceragenin CSA-13 against Planktonic Cultures and Biofilms of Streptococcus pneumoniae and Other Pathogenic Streptococci.
Author information


Abstract
Ceragenin CSA-13, a cationic steroid, is here reported to show a concentration-dependent bactericidal/bacteriolytic activity against pathogenic streptococci, including multidrug-resistant Streptococcus pneumoniae. The autolysis promoted by CSA-13 in pneumococcal cultures appears to be due to the triggering of the major S. pneumoniae autolysin LytA, an N-acetylmuramoyl-L-alanine amidase. CSA-13 also disintegrated pneumococcal biofilms in a very efficient manner, although at concentrations slightly higher than those required for bactericidal activity on planktonic bacteria. CSA-13 has little hemolytic activity which should allow testing its antibacterial efficacy in animal models.

PMID: 25006964 [PubMed - in process] 

Thursday, July 3, 2014

Streptococcus pneumoniae secretes a glyceraldehyde-3-phosphate dehydrogenase, which binds haemoglobin and haem.

Biometals. 2014 Jun 18. [Epub ahead of print]
Streptococcus pneumoniae secretes a glyceraldehyde-3-phosphate dehydrogenase, which binds haemoglobin and haem.
Author information


Abstract
Streptococcus pneumoniae is a gram positive encapsulated bacterium responsible of septicaemia and upper respiratory infections in children. This pathogen requires iron to survive in the host, which it can obtain of haemoglobin (Hb) or haem. Only two Hb-binding membrane proteins have been identified up to now. However it is unknown whether this pathogen secretes proteins in order to scavenge iron from the Hb or haem. Therefore, in order to explore these possibilities, cellular growth of S. pneumoniae was tested with several alternative iron supplies. The bacterial growth was supported with iron, Hb and haem. Additionally, S. pneumoniae expressed and secreted a protein of 38 kDa which was purified and characterized as Hb and haem-binding protein. This protein was also identified by mass spectrometry as glyceraldehyde-3-phosphate dehydrogenase. Our overall results suggest that S. pneumoniae secretes a protein capable of binding two usefull iron sources for this bacterium (Hb and haem). This protein could be playing a dynamic role in the success of the invasive and infective processes of this pathogen.

PMID: 24938797 [PubMed - as supplied by publisher]

Serotype distribution and antimicrobial susceptibility of USA Streptococcus pneumoniae isolates collected prior to and post introduction of 13-valent pneumococcal conjugate vaccine

 2014 May 24. pii: S0732-8893(14)00214-4. doi: 10.1016/j.diagmicrobio.2014.05.020. [Epub ahead of print]

Serotype distribution and antimicrobial susceptibility of USA Streptococcus pneumoniae isolates collected prior to and post introduction of 13-valent pneumococcal conjugate vaccine.

Abstract

This study evaluated pneumococci cultured from blood or lower respiratory tract specimens from hospitalized patients in the USA (all age groups) during 2011-2012 (N = 1190) and compared findings with those from a similar study performed in 2008 (N = 694). Isolates were tested for susceptibility by broth microdilution and serotypes determined by cpsB sequencing, supplemented with multiplex PCR and capsular swelling assays. Relative percentages of 7-valent pneumococcal conjugate vaccine (PCV7) types were 6.3 and 4.9% in 2008 and 2011-2012, respectively, and the most common PCV7 serotypes (19F and 6B) comprised only 3.7% and 4.0% of all isolates from both periods, respectively. Thirteen-valent pneumococcal conjugate vaccine (PCV13) serotypes represented 42.9% of isolates in 2008 and 30.1% in the second period, and this decrease was driven by 19A and 7F. Non-PCV13 serogroups/serotypes 23A, 15B/15C, 7C, 8, and 31 increased. Penicillin non-susceptibility rates were 9.6-10.0% and 38.9-42.7% when applying the parenteral (i.e. ≥4μg/mL) and oral breakpoints (i.e. ≥0.12μg/mL), respectively. Ceftaroline was the most potent agent tested based on MIC50 and MIC90 values (≤0.015 and 0.12μg/mL, respectively) for both time periods.
Copyright © 2014 Elsevier Inc. All rights reserved.

KEYWORDS:

Pneumococci; Serotype; Vaccine
PMID:
 
24974272
 
[PubMed - as supplied by publisher]

Streptococcus pneumoniae antigen in urine: Diagnostic usefulness and impact on outcome of bacteraemic pneumococcal pneumonia in a large series of adult patients.

Respirology. 2014 Jun 26. doi: 10.1111/resp.12341. [Epub ahead of print]
Streptococcus pneumoniae antigen in urine: Diagnostic usefulness and impact on outcome of bacteraemic pneumococcal pneumonia in a large series of adult patients.
Author information


Abstract
BACKGROUND AND OBJECTIVE:
Urinary pneumococcal antigen detection provides good results in the diagnosis of pneumococcal pneumonia but has rarely been used in bacteraemic pneumococcal pneumonia and it is not known whether it is associated with outcome in this type of pneumonia. Our objectives were to assess the usefulness of an immunochromatographic technique for detecting the pneumococcal antigen in urine in a large prospective study of patients with bacteraemic pneumococcal pneumonia and explore any potential association with outcomes.
METHODS:
This study, carried out over 8 years, included all adult immunocompetent patients admitted for bacteraemic pneumococcal pneumonia. An immunochromatographic test for the Streptococcus pneumoniae antigen in urine was performed in the first 24 h. The sensitivity of test was assessed and patients were divided into two groups according to test results to explore differences on admission and during the course of the illness using logistic regression models.
RESULTS:
Of the 350 patients with bacteraemic pneumococcal pneumonia included, 261 (74.6%) were positive for the antigen. Patient characteristics were very similar on admission and differences in severity (Pneumonia Severity Index) were not statistically significant. In the adjusted analysis, antigen-positive patients had a higher risk of intensive care unit admission, treatment failure and adverse outcome.
CONCLUSIONS:
The sensitivity of the immunochromatographic urinary antigen test was 74.6% and positive results were associated with poorer clinical outcome. We therefore recommend systematic use of this test when pneumonia is diagnosed in the emergency department.
© 2014 Asian Pacific Society of Respirology.
KEYWORDS:
bacteraemic pneumococcal pneumonia; community-acquired pneumonia; outcome; sensitivity; urinary pneumococcal antigen

PMID: 24976113 [PubMed - as supplied by publisher]