The Pneumococcus Blog: 2014

Thursday, December 11, 2014

The impact of glpQ2 gene on virulence in a Streptococcus pneumoniae serotype 19AST320 strain.

Infect Immun. 2014 Nov 24. pii: IAI.02357-14. [Epub ahead of print]

The impact of glpQ2 gene on virulence in a Streptococcus pneumoniae serotype 19AST320 strain.

Chuang YP1, Peng ZR2, Tseng SF3, Lin YC4, Sytwu HK2, Hsieh YC5.

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Abstract

Glycerophosphodiester phosphodiesterase (GlpQ) metabolizes glycerophosphorylcholine from the lung epithelium to produce free choline, which is transformed into phosphorylcholine and presented on the surfaces of many respiratory pathogens. Two orthologs of glpQ genes are found in Streptococcus pneumoniae: glpQ with a membrane motif is widespread in pneumococci whereas glpQ2, which shares high similarity with glpQ in Haemophilus influenzae and Mycoplasma pneumoniae, is only present in S. pneumoniae serotype 3, 6B, 19A, and 19F strains. Recently, serotype 19A has emerged as an epidemiological etiology associated with invasive pneumococcal diseases. Thus, we investigated the pathophysiological role of glpQ2 in a serotype 19AST320 strain, which was the prevalent sequence type in 19A associated with severe pneumonia and invasive pneumococcal disease in pediatric patients. Mutations in glpQ2 reduced phosphorylcholine expression and the anchorage of choline-binding proteins to the pneumococcal surface during the exponential phase, where the mutants exhibited reduced autolysis and lower natural transformation abilities compared with the parent strain. The deletion of glpQ2 also decreased the adherence and cytotoxicity to human lung epithelial cell lines, whereas these functions were indistinguishable from the wild type in complementation strains. In a respiratory infection murine model, glpQ2 was important for nasopharynx and lung colonization. Furthermore, infection with a glpQ2 mutant decreased the severity of pneumonia compared with the parent strain and glpQ2 gene complementation restored the inflammation level. Therefore, glpQ2 enhances surface phosphorylcholine expression in S. pneumoniae 19AST320 during the exponential phase, which contributes to the severity of pneumonia by promoting adherence and host cell cytotoxicity.

PMID: 25422269 [PubMed - as supplied by publisher]

Lethal co-infection of influenza virus and Streptococcus pneumoniae lowers antibody response to influenza virus in lung, and reduces germinal center B cells, T follicular helper cells and plasma cells in mediastinal lymph node.

J Virol. 2014 Nov 26. pii: JVI.02455-14. [Epub ahead of print]

Lethal co-infection of influenza virus and Streptococcus pneumoniae lowers antibody response to influenza virus in lung, and reduces germinal center B cells, T follicular helper cells and plasma cells in mediastinal lymph node.

Wu Y1, Tu W2, Lam KT1, Chow KH3, Ho PL3, Guan Y4, Malik Peiris JS4, Lau YL5.

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Abstract

Secondary Streptococcus pneumoniae infection after influenza is a significant clinical complication resulting in morbidity and sometimes mortality. Prior influenza virus infection has been demonstrated to impair the macrophage and neutrophil response to the subsequent pneumococcal infection. In contrast, how the secondary pneumococcal infection after influenza can affect the adaptive immune response to the initial influenza virus infection is less well understood. Therefore, this study focuses on how secondary pneumococcal infection after influenza may impact on the humoral immune response to the initial influenza virus infection in a lethal co-infection mouse model. When compared to mice infected with influenza virus alone, mice co-infected with influenza virus followed by pneumococcus had significant body weight loss and 100% mortality. In the lung, lethal co-infection significantly increased virus titer, bacterial cell counts and decreased the level of virus specific IgG, IgM and IgA, as well as the number of B cells, CD4 T cells and plasma cells. In spleen, lethal co-infection significantly reduced the size and weight of spleen, as well as the B cells along the follicular developmental lineage. In mediastinal lymph nodes, lethal co-infection significantly decreased germinal center B cells, T follicular helper cells and plasma cells. Adoptive transfer of influenza virus-specific immune serum to co-infected mice improved survival, suggesting the protective functions of anti-influenza virus antibodies. In conclusion, co-infection reduced the B cell response to influenza virus. This study helps us to understand the modulation of B cell response to influenza virus during the lethal co-infection.

IMPORTANCE:

Secondary pneumococcal infection after influenza is an important clinical issue that often results in excess mortality. Since antibodies are key mediator of protection, this study aims to examine the antibody response to influenza virus, and demonstrated that lethal co-infection reduced the B cell response to influenza virus. This study helps to highlight the complexity of the modulation of B cell response in the context of co-infection.

PMID: 25428873 [PubMed - as supplied by publisher]

Prevalence and characteristics of Streptococcus pneumoniae "putative serotype 6E" isolates from Asian countries.

Diagn Microbiol Infect Dis. 2014 Sep 6;80(4):334-337. doi: 10.1016/j.diagmicrobio.2014.08.017. [Epub ahead of print]

Prevalence and characteristics of Streptococcus pneumoniae "putative serotype 6E" isolates from Asian countries.

Baek JY1, Park IH2, So TM3, Lalitha MK4, Shimono N5, Yasin RM6, Carlos CC7, Perera J8, Thamlikitkul V9, Hsueh PR10, Van PH11, Shibl AM12, Song JH13, Ko KS14.

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Abstract

The prevalence, antimicrobial susceptibility, and genotypes of Streptococcus pneumoniae "putative serotype 6E" isolates from Asian countries were investigated. A total of 244 S. pneumoniae serogroup 6 isolates obtained from 11 Asian countries were included in this study. Of the 244 serogroup 6 isolates, 101 (41.4%) were typed as "putative serotype 6E," followed by serotypes 6A, 6B, 6C, and 6D (27.0, 20.1, 5.7, and 5.7%, respectively). Multilocus sequence typing revealed that clonal complex (CC) 90, including ST90 and its variants, was the most prevalent clonal group of "putative serotype 6E" isolates (n = 63; 62.4%). CC146 and CC315 were also found frequently in some of the countries. Most of the "putative serotype 6E" isolates showed very high resistance rates against cefuroxime, erythromycin, azithromycin, clarithromycin, clindamycin, and trimethoprim/sulfamethoxazole, probably due to their highly resistant to antimicrobials clone, CC90. Our results indicate that "putative serotype 6E" is prevalent in Asian countries. The clonal dissemination of "putative serotype 6E" isolates was also identified.

KEYWORDS:

CC90; Pneumococci; Serogroup 6

PMID: 25439447 [PubMed - as supplied by publisher]

Natural transformation and genome evolution in Streptococcus pneumoniae.

Infect Genet Evol. 2014 Nov 4. pii: S1567-1348(14)00391-8. doi: 10.1016/j.meegid.2014.10.020. [Epub ahead of print]

Natural transformation and genome evolution in Streptococcus pneumoniae.

Straume D1, Stamsås GA1, Håvarstein LS2.

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Abstract

Streptococcus pneumoniae is a frequent colonizer of the human nasopharynx that has the potential to cause severe infections such as pneumonia, bacteremia and meningitis. Despite considerable efforts to reduce the burden of pneumococcal disease, it continues to be a major public health problem. After the Second World War, antimicrobial therapy was introduced to fight pneumococcal infections, followed by the first effective vaccines more than half a century later. These clinical interventions generated a selection pressure that drove the evolution of vaccine-escape mutants and strains that were highly resistant against antibiotics. The remarkable ability of S. pneumoniae to acquire drug resistance and evade vaccine pressure is due to its recombination-mediated genetic plasticity. S. pneumoniae is competent for natural genetic transformation, a property that enables the pneumococcus to acquire new traits by taking up naked DNA from the environment and incorporating it into its genome through homologous recombination. In the present paper, we review current knowledge on pneumococcal transformation, and discuss how the pneumococcus uses this mechanism to adapt and survive under adverse and fluctuating conditions.

KEYWORDS:

Fratricide; Genome evolution; Natural genetic transformation; Penicillin resistance; Streptococcus pneumoniae

PMID: 25445643 [PubMed - as supplied by publisher]

Identification of Proteins in Streptococcus pneumoniae by Reverse Vaccinology and Genetic Diversity of These Proteins in Clinical Isolates.

Appl Biochem Biotechnol. 2014 Dec 2. [Epub ahead of print]

Identification of Proteins in Streptococcus pneumoniae by Reverse Vaccinology and Genetic Diversity of These Proteins in Clinical Isolates.

Argondizzo AP1, da Mota FF, Pestana CP, Reis JN, de Miranda AB, Galler R, Medeiros MA.

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Abstract

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. Virulence-associated proteins common and conserved among all capsular types now represent the best strategy to combat pneumococcal infections. Our aim was to identify conserved targets in pneumococci that showed positive prediction for lipoprotein and extracellular subcellular location using bioinformatics programs and verify the distribution and the degree of conservation of these targets in pneumococci. These targets can be considered potential vaccine candidate to be evaluated in the future. A set of 13 targets were analyzed and confirmed the presence in all pneumococci tested. These 13 genes were highly conserved showing around >96 % of amino acid and nucleotide identity, but they were also present and show high identity in the closely related species Streptococcus mitis, Streptococcus oralis, and Streptococcus pseudopneumoniae. S. oralis clusters away from S. pneumoniae, while S. pseudopneumoniae and S. mitis cluster closer. The divergence between the selected targets was too small to be observed consistently in phylogenetic groups between the analyzed genomes of S. pneumoniae. The proteins analyzed fulfill two of the initial criteria of a vaccine candidate: targets are present in a variety of different pneumococci strains including different serotypes and are conserved among the samples evaluated.

PMID: 25448632 [PubMed - as supplied by publisher]

Endocytosis of Streptococcus pneumoniae via the polymeric immunoglobulin receptor of epithelial cells relies on clathrin and caveolin dependent mechanisms.

Int J Med Microbiol. 2014 Nov;304(8):1233-46. doi: 10.1016/j.ijmm.2014.10.001. Epub 2014 Oct 14.

Endocytosis of Streptococcus pneumoniae via the polymeric immunoglobulin receptor of epithelial cells relies on clathrin and caveolin dependent mechanisms.

Asmat TM1, Agarwal V2, Saleh M3, Hammerschmidt S4.

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Abstract

Colonization of Streptococcus pneumoniae (pneumococci) is a prerequisite for bacterial dissemination and their capability to enter the bloodstream. Pneumococci have evolved various successful strategies to colonize the mucosal epithelial barrier of humans. A pivotal mechanism of host cell invasion implicated with invasive diseases is promoted by the interaction of pneumococcal PspC with the polymeric Ig-receptor (pIgR). However, the mechanism(s) of pneumococcal endocytosis and the intracellular route of pneumococci upon uptake by the PspC-pIgR-interaction are not known. Here, we demonstrate by using a combination of pharmacological inhibitors and genetics interference approaches the involvement of active dynamin-dependent caveolae and clathrin-coated vesicles for pneumococcal uptake via the PspC-pIgR mechanism. Depleting cholesterol from host cell membranes and disruption of lipid microdomains impaired pneumococcal internalization. Moreover, chemical inhibition of clathrin or functional inactivation of dynamin, caveolae or clathrin by RNA interference significantly affected pneumococcal internalization suggesting that clathrin-mediated endocytosis (CME) and caveolae are involved in the bacterial uptake process. Confocal fluorescence microscopy of pIgR-expressing epithelial cells infected with pneumococci or heterologous Lactococcus lactis expressing PspC demonstrated bacterial co-localization with fluorescent-tagged clathrin and early as well as recycling or late endosomal markers such as Lamp1, Rab5, Rab4, and Rab7, respectively. In conclusion these data suggest that PspC-promoted uptake is mediated by both CME and caveolae. After endocytosis pneumococci are routed via the endocytic pathway into early endosomes and are then sorted into recycling or late endosomes, which can result in pneumococcal killing in phagolysosomes or transcytosis via recycling endosomes.

KEYWORDS:

Adherence; Caveolin; Clathrin; Dynamin; Endocytosis; Polymeric Ig receptor; PspC; Rab; Streptococcus pneumoniae

PMID: 25455218 [PubMed - in process]

Structural determination of Streptococcus pneumoniae repeat units in serotype 41A and 41F capsular polysaccharides to probe gene functions in the corresponding capsular biosynthetic loci.

Carbohydr Res. 2014 Dec 5;400:26-32. doi: 10.1016/j.carres.2014.08.017. Epub 2014 Sep 16.

Structural determination of Streptococcus pneumoniae repeat units in serotype 41A and 41F capsular polysaccharides to probe gene functions in the corresponding capsular biosynthetic loci.

Petersen BO1, Skovsted IC2, Paulsen BS3, Redondo AR2, Meier S4.

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Abstract

We report the repeating unit structures of the native capsular polysaccharides of Streptococcus pneumoniae serotypes 41A and 41F. Structural determinations yielded six carbohydrate units in the doubly branched repeating unit to give the following structure for serotype 41A: The structure determinations were motivated (1) by an ambition to help close the remaining gaps in S. pneumoniae capsular polysaccharide structures, and (2) by the attempt to derive functional annotations of carbohydrate active enzymes in the biosynthesis of bacterial polysaccharides from the determined structures. An activity present in 41F but not 41A is identified as an acetyltransferase acting on the rhamnopyranosyl sidechain E. The genes encoding the formation of the six glycosidic bonds in serogroup 41 were determined from the capsular polysaccharide structures of serotype 41A, 41F, and genetically related serotypes, in conjunction with corresponding genomic information and computational homology searches. In combination with complementary information, NMR spectroscopy considerably simplifies the functional annotation of carbohydrate active enzymes in the biosynthesis of bacterial polysaccharides.

KEYWORDS:

Biosynthetic loci; Capsular polysaccharide; NMR; Serotype 41A; Streptococcus pneumoniae

PMID: 25457607 [PubMed - in process]

Increase in Fitness of Streptococcus pneumoniae is Associated with the Severity of Necrotizing Pneumonia.

Pediatr Infect Dis J. 2014 Dec 3. [Epub ahead of print]

Increase in Fitness of Streptococcus pneumoniae is Associated with the Severity of Necrotizing Pneumonia.

Hsieh YC1, Chi H, Chang KY, Lai SH, Mu JJ, Wong KS, Liu CC, Huang YC, Lin HC, Chang LY, Huang YC, Huang LM; for The Taiwan Pediatric Infectious Diseases Alliance.

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Abstract

BACKGROUND::

The incidence of necrotizing pneumococcal pneumonia has increased during the past two decades. We hypothothesized that increased pneumococcal load or augmented inflammatory cytokine production might lead to destructive pneumococcal lung disease.

METHODS::

This study enrolled prospectively 0-18 year-old children with a diagnosis of community-acquired pneumonia with pleural effusion admitted to 6 medical centers during March 2010 to April 2012. Children were diagnosed with pneumococcal empyema if the pleural fluid tested positive for quantitative pneumococcal (lytA) detection by real-time polymerase chain reaction (RT-PCR). Pneumococcal empyema cases were further divided into four groups according to necrosis severity: 0) non-necrosis, 1) mild necrosis, 2) cavitation, and 3) bronchopleural fistula (BPF). Nasopharyngeal and pleural pneumococcal load, as well as proinflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8), Th1-(IL-2, IFN-γ), Th2-(IL-4, IL-10), and Th17-cytokines (IL-17) in the pleural fluid were measured.

RESULTS::

Serotypes 19A and 3 accounted for 69.4% and 12.5% (respectively) of 72 cases of pneumococcal empyema. Pleural pneumococcal load was significantly higher in serotypes 19A and 3 infection than for other strains causing infection (P=0.006). There was a correlation between nasopharyngeal and pleural pneumococcal load (ρ=0.35; P=0.05). In multivariate ordinal logistic regression analysis, pleural pneumococcal load (adjusted odds ratio [aOR], 1.79; 95% confidence interval [CI], 1.03-3.06), and IL-8 (aOR, 2.64; 95% CI, 1.21-5.75) were independent factors associated with the severity of lung necrosis.

CONCLUSIONS::

Evolution of S. pneumoniae toward increased fitness in their interaction with host and exaggerated IL-8 expression may be responsible for the increase of necrotizing pneumococcal pneumonia.

PMID: 25461475 [PubMed - as supplied by publisher]

MapZ marks the division sites and positions FtsZ rings in Streptococcus pneumoniae.

Nature. 2014 Nov 26. doi: 10.1038/nature13966. [Epub ahead of print]

MapZ marks the division sites and positions FtsZ rings in Streptococcus pneumoniae.

Fleurie A1, Lesterlin C2, Manuse S1, Zhao C1, Cluzel C3, Lavergne JP1, Franz-Wachtel M4, Macek B4, Combet C1, Kuru E5, VanNieuwenhze MS5, Brun YV5, Sherratt D2, Grangeasse C1.

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Abstract

In every living organism, cell division requires accurate identification of the division site and placement of the division machinery. In bacteria, this process is traditionally considered to begin with the polymerization of the highly conserved tubulin-like protein FtsZ into a ring that locates precisely at mid-cell. Over the past decades, several systems have been reported to regulate the spatiotemporal assembly and placement of the FtsZ ring. However, the human pathogen Streptococcus pneumoniae, in common with many other organisms, is devoid of these canonical systems and the mechanisms of positioning the division machinery remain unknown. Here we characterize a novel factor that locates at the division site before FtsZ and guides septum positioning in pneumococcus. Mid-cell-anchored protein Z (MapZ) forms ring structures at the cell equator and moves apart as the cell elongates, therefore behaving as a permanent beacon of division sites. MapZ then positions the FtsZ ring through direct protein-protein interactions. MapZ-mediated control differs from previously described systems mostly on the basis of negative regulation of FtsZ assembly. Furthermore, MapZ is an endogenous target of the Ser/Thr kinase StkP, which was recently shown to have a central role in cytokinesis and morphogenesis of S. pneumoniae. We show that both phosphorylated and non-phosphorylated forms of MapZ are required for proper Z-ring formation and dynamics. Altogether, this work uncovers a new mechanism for bacterial cell division that is regulated by phosphorylation and illustrates that nature has evolved a diversity of cell division mechanisms adapted to the different bacterial clades.

PMID: 25470041 [PubMed - as supplied by publisher]

The Role of Macrophages in the Innate Immune Response to Streptococcus pneumoniae and Staphylococcus aureus: Mechanisms and Contrasts.

Adv Microb Physiol. 2014;65:125-202. doi: 10.1016/bs.ampbs.2014.08.004. Epub 2014 Nov 4.

The Role of Macrophages in the Innate Immune Response to Streptococcus pneumoniae and Staphylococcus aureus: Mechanisms and Contrasts.

Cole J1, Aberdein J1, Jubrail J1, Dockrell DH2.

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Abstract

Macrophages are critical mediators of innate immune responses against bacteria. The Gram-positive bacteria Streptococcus pneumoniae and Staphylococcus aureus express a range of virulence factors, which challenge macrophages' immune competence. We review how macrophages respond to this challenge. Macrophages employ a range of strategies to phagocytose and kill each pathogen. When the macrophages capacity to clear bacteria is overwhelmed macrophages play important roles in orchestrating the inflammatory response through pattern recognition receptor-mediated responses. Macrophages also ensure the inflammatory response is tightly constrained, to avoid tissue damage, and play an important role in downregulating the inflammatory response once initial bacterial replication is controlled.

KEYWORDS:

Activation; Antimicrobicidal mechanisms; Macrophages; Pattern recognition receptors; Phagocytosis; Phagolysosomes; Staphylococcus aureus; Streptococcus pneumoniae

PMID: 25476766 [PubMed - in process]

Global phylogenomic analysis of nonencapsulated Streptococcus pneumoniae reveals a deep-branching classic lineage that is distinct from multiple sporadic lineages.

Genome Biol Evol. 2014 Dec 4. pii: evu263. [Epub ahead of print]

Global phylogenomic analysis of nonencapsulated Streptococcus pneumoniae reveals a deep-branching classic lineage that is distinct from multiple sporadic lineages.

Hilty M1, Wüthrich D2, Salter SJ3, Engel H4, Campbell S4, Sá-Leão R5, de Lencastre H6, Hermans P7, Sadowy E8, Turner P9, Chewapreecha C10, Diggle M11, Pluschke G12, McGee L13, Eser OK14, Low DE15, Smith-Vaughan H16, Endimiani A4, Küffer M4, Dupasquier M17, Beaudoing E17, Weber J17, Bruggmann R2, Hanage WP18, Parkhill J3, Hathaway LJ4, Mühlemann K19, Bentley SD20.

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Abstract

The surrounding capsule of Streptococcus pneumoniae has been identified as a major virulence factor and is targeted by pneumococcal conjugate vaccines (PCV). However, nonencapsulated Streptococcus pneumoniae (Non-Ec-Sp) have also been isolated globally, mainly in carriage studies. It is unknown if Non-Ec-Sp evolve sporadically, if they have high antibiotic non-susceptiblity rates and a unique, specific gene content. Here, whole genome sequencing of 131 Non-Ec-Sp isolates sourced from 17 different locations around the world was performed. Results revealed a deep-branching classic lineage that is distinct from multiple sporadic lineages. The sporadic lineages clustered with a previously sequenced, global collection of encapsulated S. pneumoniae (Ec-Sp) isolates while the classic lineage is comprised mainly of the frequently identified multi-locus sequences types ST344 (n=39) and ST448 (n=40). All ST344 and nine ST448 isolates had high non-susceptiblity rates to β-lactams and other antimicrobials. Analysis of the accessory genome reveals that the classic Non-Ec-Sp contained an increased number of mobile elements, than Ec-Sp and sporadic Non-Ec-Sp. Performing adherence assays to human epithelial cells for selected classic and sporadic Non-Ec-Sp revealed that the presence of a integrative conjugative element (ICE) results in increased adherence to human epithelial cells (P=0.005). In contrast, sporadic Non-Ec-Sp lacking the ICE had greater growth in vitro possibly resulting in improved fitness. In conclusion, Non-Ec-Sp isolates from the classic lineage have evolved separately. They have spread globally, are well adapted to nasopharyngeal carriage and are able to coexist with Ec-Sp. Due to continued use of pneumococcal conjugate vaccines, Non-Ec-Sp may become more prevalent.

KEYWORDS:

Pneumococcal isolates; antibiotic non-susceptibility; comparative genomics; integrative conjugative elements (ICEs); whole genome sequencing

PMID: 25480686 [PubMed - as supplied by publisher]

Saturday, November 15, 2014

C4 Deficiency Is a Predisposing Factor for Streptococcus pneumoniae-Induced Autoantibody Production.

J Immunol. 2014 Oct 22. pii: 1401462. [Epub ahead of print]

C4 Deficiency Is a Predisposing Factor for Streptococcus pneumoniae-Induced Autoantibody Production.

Yammani RD1, Leyva MA1, Jennings RN1, Haas KM2.

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Abstract

Reductions in C4 levels may predispose individuals to infection with encapsulated bacteria as well as autoimmunity. In this study, we examined the role C4 has in protection against Streptococcus pneumoniae-induced autoimmunity. Mild respiratory infection with serotype 19F pneumococci selectively induced systemic anti-dsDNA IgA production in naive C4-/- mice, but not in C3-/- or wild-type mice. Systemic challenge with virulent serotype 3 pneumococci also induced anti-dsDNA IgA production in immune C4-/- mice. Remarkably, pneumococcal polysaccharide (PPS) vaccination alone induced C4-/- mice to produce increased anti-dsDNA IgA levels that were maintained in some mice for months. These effects were most pronounced in female C4-/- mice. Importantly, immunization-induced increases in anti-dsDNA IgA levels were strongly associated with increased IgA deposition in kidneys. Cross-reactivity between pneumococcal Ags and dsDNA played a partial role in the induction of anti-dsDNA IgA, but a major role for PPS-associated TLR2 agonists was also revealed. Administration of the TLR2/4 antagonist, OxPAPC, at the time of PPS immunization completely blocked the production of anti-dsDNA IgA in C4-/- mice without suppressing PPS-specific Ab production. The TLR2 agonist, Pam3CSK4, similarly induced anti-dsDNA IgA production in C4-/- mice, which OxPAPC also prevented. LPS, a TLR4 agonist, had no effect. Pam3CSK4, but not LPS, also induced dsDNA-specific IgA production by C4-/- splenic IgA+ B cells in vitro, indicating that TLR2 agonists can stimulate autoantibody production via B cell-intrinsic mechanisms. Collectively, our results show an important role for C4 in suppressing autoantibody production elicited by cross-reactive Ags and TLR2 agonists associated with S. pneumoniae.

PMID: 25339671 [PubMed - as supplied by publisher]

Recent advances in our understanding of Streptococcus pneumoniae infection.

F1000Prime Rep. 2014 Sep 4;6:82. doi: 10.12703/P6-82. eCollection 2014.

Recent advances in our understanding of Streptococcus pneumoniae infection.

Feldman C1, Anderson R2.

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Abstract

A number of significant challenges remain with regard to the diagnosis, treatment, and prevention of infections with Streptococcus pneumoniae (pneumococcus), which remains the most common bacterial cause of community-acquired pneumonia. Although this infection is documented to be extremely common in younger children and in older adults, the burden of pneumonia it causes is considerably underestimated, since the incidence statistics are derived largely from bacteremic infections, because they are easy to document, and yet the greater burden of pneumococcal pneumonias is non-invasive. It has been estimated that for every bacteremic pneumonia that is documented, three non-bacteremic infections occur. Management of these infections is potentially complicated by the increasing resistance of the isolates to the commonly used antibiotics. Furthermore, it is well recognized that despite advances in medical care, the mortality of bacteremic pneumococcal pneumonia has remained largely unchanged over the past 50 years and averages approximately 12%. Much recent research interest in the field of pneumococcal infections has focused on important virulence factors of the organism, on improved diagnostic and prognostication tools, on defining risk factors for death, on optimal treatment strategies involving both antibiotics and adjunctive therapies, and on disease prevention. It is hoped that through these endeavors the outlook of pneumococcal infections will be improved.

PMID: 25343039 [PubMed] PMCID: PMC4166932

Protection against Streptococcus pneumoniae lung infection after nasopharyngeal colonization requires both humoral and cellular immune responses.

Mucosal Immunol. 2014 Oct 29. doi: 10.1038/mi.2014.95. [Epub ahead of print]

Protection against Streptococcus pneumoniae lung infection after nasopharyngeal colonization requires both humoral and cellular immune responses.

Wilson R1, Cohen JM2, Jose RJ1, de Vogel C3, Baxendale H4, Brown JS1.

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Abstract

Streptococcus pneumoniae is a common cause of pneumonia and infective exacerbations of chronic lung disease, yet there are few data on how adaptive immunity can specifically prevent S. pneumoniae lung infection. We have used a murine model of nasopharyngeal colonization by the serotype 19F S. pneumoniae strain EF3030 followed by lung infection to investigate whether colonization protects against subsequent lung infection and the mechanisms involved. EF3030 colonization induced systemic and local immunoglobulin G against a limited number of S. pneumoniae protein antigens rather than capsular polysaccharide. During lung infection, previously colonized mice had increased early cytokine responses and neutrophil recruitment and reduced bacterial colony-forming units in the lungs and bronchoalveolar lavage fluid compared with control mice. Colonization-induced protection was lost when experiments were repeated in B-cell- or neutrophil-deficient mice. Furthermore, the improved interleukin (IL)-17 response to infection in previously colonized mice was abolished by depletion of CD4+ cells, and prior colonization did not protect against lung infection in mice depleted of CD4+ cells or IL17. Together these data show that naturally acquired protective immunity to S. pneumoniae lung infection requires both humoral and cell-mediated immune responses, providing a template for the design of improved vaccines that can specifically prevent pneumonia or acute bronchitis.Mucosal Immunology advance online publication, 29 October 2014; doi:10.1038/mi.2014.95.

PMID: 25354319 [PubMed - as supplied by publisher]

UlaR activates the expression of the ula operon in Streptococcus pneumoniae in the presence of ascorbic acid.

Microbiology. 2014 Oct 29. pii: mic.0.083899-0. doi: 10.1099/mic.0.083899-0. [Epub ahead of print]

UlaR activates the expression of the ula operon in Streptococcus pneumoniae in the presence of ascorbic acid.

Afzal M1, Shafeeq S2, Henriques-Normark B2, Kuipers OP3.

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Abstract

In this study, the regulatory mechanism of the ula (utilization of L-ascorbic acid) operon putatively responsible for transport and utilization of ascorbic acid in Streptococcus pneumoniae D39 strain is studied. β-galactosidase assay data demonstrate that the expression of the ula operon is increased in the presence of ascorbic acid, as compared to the effects of other sugar sources, including glucose. The ula operon consists of nine genes, including a BglG-family transcriptional regulator UlaR, and is transcribed as a single transcriptional unit. We demonstrate the role of the BglG-family transcriptional regulator UlaR as a transcriptional activator of the ula operon in the presence of ascorbic acid and show that activation of the ula operon genes by UlaR is CcpA-independent. Furthermore, we predict a 16-bp regulatory site (5'-AACAGTCCGCTGTGTA-3') for UlaR in the promoter region of ulaA. Deletion of the half- or full UlaR regulatory site in the PulaA confirmed that the UlaR regulatory site present in PulaA is functional.

KEYWORDS:

Ascorbic acid; Pneumococcus; UlaR; carbon source; ula operon

PMID: 25355938 [PubMed - as supplied by publisher]

Regional and global antimicrobial susceptibility among isolates of Streptococcus pneumoniae and Haemophilus influenzae collected as part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) from 2009 to 2012 and comparison with previous years of T.E.S.T. (2004-2008).

Ann Clin Microbiol Antimicrob. 2014 Nov 7;13(1):52. [Epub ahead of print]

Regional and global antimicrobial susceptibility among isolates of Streptococcus pneumoniae and Haemophilus influenzae collected as part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) from 2009 to 2012 and comparison with previous years of T.E.S.T. (2004-2008).

Tomic V, Dowzicky MJ.

Abstract

BackgroundWe report here on 14438 Streptococcus pneumoniae and 14770 Haemophilus influenzae isolates collected from 560 centres globally between 2004 and 2012 as a part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.).MethodsMIC testing was performed using broth microdilution methods as described by the Clinical and Laboratory Standards Institute (CLSI) using CLSI-approved breakpoints; US Food and Drug Administration breakpoints were used for tigecycline as CLSI breakpoints are not available.ResultsAt least 99% of S. pneumoniae isolates globally were susceptible to levofloxacin, linezolid, tigecycline or vancomycin. Penicillin resistance was observed among 14.8% of S. pneumoniae and was highest in Asia/Pacific Rim (30.1%) and Africa (27.6%); 23.4% of S. pneumoniae isolates were penicillin-intermediate, which were most common in Africa (37.6%). Minocycline susceptibility among S. pneumoniae decreased by 20% between 2004-2008 and 2009-2012. High (>98.5%) susceptibility was reported among H. influenzae to all antimicrobial agents on the T.E.S.T. panel excluding ampicillin, to which only 78.3% were susceptible. ß-lactamase production was observed among 20.2% of H. influenzae isolates; 1.5% of isolates were ß-lactamase negative, ampicillin-resistant.Conclusions S. pneumoniae remained highly susceptible to levofloxacin, linezolid, tigecycline and vancomycin while H. influenzae was susceptible to most antimicrobial agents in the testing panel (excluding ampicillin).

PMID: 25376749 [PubMed - as supplied by publisher]

Mechanism of β-Lactam Action in Streptococcus pneumoniae: the Piperacillin Paradox.

Antimicrob Agents Chemother. 2014 Nov 10. pii: AAC.04283-14. [Epub ahead of print]

Mechanism of β-Lactam Action in Streptococcus pneumoniae: the Piperacillin Paradox.

Philippe J1, Gallet B1, Morlot C1, Denapaite D2, Hakenbeck R3, Chen Y4, Vernet T1, Zapun A5.

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Abstract

The human pathogen Streptococcus pneumoniae has been fought for decades with β-lactam antibiotics. Resistance is now widespread, mediated by the expression of mosaic variants of the target enzymes, the penicillin-binding proteins or PBPs. Understanding the mode of action of β-lactams, not only in molecular details, but also in their physiological consequences, will be crucial to improve these drugs and counter resistance. In this work, we investigate the piperacillin paradox, by which this β-lactam selects primarily variants of PBP2b, whereas its most reactive target is PBP2x. These PBPs are both essential mono-functional transpeptidases involved in peptidoglycan assembly. PBP2x participates to septal synthesis, while PBP2b functions in peripheral elongation. The formation of "lemon"-shaped cells induced by piperacillin treatment is consistent with the inhibition of PBP2x. Following the examination of treated and untreated cells by electron microscopy, localization of the PBPs by epifluorescence microscopy, and determination of the inhibition time-course of the different PBPs, we propose a model of peptidoglycan assembly that can account for the piperacillin paradox.

PMID: 25385114 [PubMed - as supplied by publisher]

Unencapsulated Streptococcus pneumoniae from conjunctivitis encode variant traits and belong to a distinct phylogenetic cluster.

Nat Commun. 2014 Nov 12;5:5411. doi: 10.1038/ncomms6411.

Unencapsulated Streptococcus pneumoniae from conjunctivitis encode variant traits and belong to a distinct phylogenetic cluster.

Valentino MD1, McGuire AM2, Rosch JW3, Bispo PJ4, Burnham C3, Sanfilippo CM5, Carter RA3, Zegans ME6, Beall B7, Earl AM2, Tuomanen EI3, Morris TW5, Haas W4, Gilmore MS1.

Author information

Abstract

Streptococcus pneumoniae, an inhabitant of the upper respiratory mucosa, causes respiratory and invasive infections as well as conjunctivitis. Strains that lack the capsule, a main virulence factor and the target of current vaccines, are often isolated from conjunctivitis cases. Here we perform a comparative genomic analysis of 271 strains of conjunctivitis-causing S. pneumoniae from 72 postal codes in the United States. We find that the vast majority of conjunctivitis strains are members of a distinct cluster of closely related unencapsulated strains. These strains possess divergent forms of pneumococcal virulence factors (such as CbpA and neuraminidases) that are not shared with other unencapsulated nasopharyngeal S. pneumoniae. They also possess putative adhesins that have not been described in encapsulated pneumococci. These findings suggest that the unencapsulated strains capable of causing conjunctivitis utilize a pathogenesis strategy substantially different from that described for S. pneumoniae at other infection sites.

PMID: 25388376 [PubMed - in process]

Thursday, October 23, 2014

Coinfection with Streptococcus pneumoniae Negatively Modulates the Size and Composition of the Ongoing Influenza-Specific CD8+ T Cell Response.

J Immunol. 2014 Oct 13. pii: 1400529. [Epub ahead of print]

Coinfection with Streptococcus pneumoniae Negatively Modulates the Size and Composition of the Ongoing Influenza-Specific CD8+ T Cell Response.

Blevins LK1, Wren JT1, Holbrook BC1, Hayward SL1, Swords WE1, Parks GD1, Alexander-Miller MA2.

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Abstract

Infection with influenza A virus can lead to increased susceptibility to subsequent bacterial infection, often with Streptococcus pneumoniae. Given the substantial modification of the lung environment that occurs following pathogen infection, there is significant potential for modulation of immune responses. In this study, we show that infection of mice with influenza virus, followed by the noninvasive EF3030 strain of Streptococcus pneumoniae, leads to a significant decrease in the virus-specific CD8+ T cell response in the lung. Adoptive-transfer studies suggest that this reduction contributes to disease in coinfected animals. The reduced number of lung effector cells in coinfected animals was associated with increased death, as well as a reduction in cytokine production in surviving cells. Further, cells that retained the ability to produce IFN-γ exhibited a decreased potential for coproduction of TNF-α. Reduced cytokine production was directly correlated with a decrease in the level of mRNA. Negative regulation of cells in the mediastinal lymph node was minimal compared with that present in the lung, supporting a model of selective regulation in the tissue harboring high pathogen burden. These results show that entry of a coinfecting pathogen can have profound immunoregulatory effects on an ongoing immune response. Together, these findings reveal a novel dynamic interplay between concurrently infecting pathogens and the adaptive immune system.

PMID: 25311807 [PubMed - as supplied by publisher]

Ethanol-induced alcohol dehydrogenase E (AdhE) potentiates pneumolysin in Streptococcus pneumoniae.

Infect Immun. 2014 Oct 13. pii: IAI.02434-14. [Epub ahead of print]

Ethanol-induced alcohol dehydrogenase E (AdhE) potentiates pneumolysin in Streptococcus pneumoniae.

Luong TT1, Kim EH1, Bak JP1, Nguyen CT1, Choi S2, Briles DE3, Pyo S1, Rhee DK4.

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Abstract

Alcohol impairs the host immune system, rendering hosts more vulnerable to infection. Therefore, alcoholics are at increased risk of acquiring serious bacterial infections caused by Streptococcus pneumoniae, including pneumonia. Nevertheless, how alcohol affects pneumococcal virulence remains unclear. Here we showed that S. pneumoniae type 2 D39 is ethanol tolerant, and that alcohol up-regulates alcohol dehydrogenase E (AdhE) and potentiates pneumolysin (Ply). Hemolytic activity, colonization, and virulence of S. pneumoniae, as well as host cell myeloperoxidase activity, pro-inflammatory cytokine secretion, and inflammation, were significantly attenuated in adhE mutant bacteria (ΔadhE) compared to D39 wild-type bacteria. Therefore, AdhE might act as a pneumococcal virulence factor. Moreover, in the presence of ethanol, S. pneumoniae AdhE produced acetaldehyde and NADH, which subsequently led Rex (redox-sensing transcriptional repressor) to dissociate from the adhE promoter. An increase in AdhE in the ethanol condition conferred an increase of Ply and H2O2 levels. Consistently, S. pneumoniae D39 caused higher cytotoxicity to RAW 264.7 cells than ΔadhE during the ethanol stress condition, and alcoholic mice were more susceptible to infection with the D39 wild-type bacteria than the ΔadhE. Taken together, these data indicate that AdhE increases Ply in the ethanol stress condition, thus potentiating pneumococcal virulence.

PMID: 25312953 [PubMed - as supplied by publisher]

Topology of Streptococcus pneumoniae CpsC, a Polysaccharide co-polymerase and BY-kinase adaptor protein.

J Bacteriol. 2014 Oct 13. pii: JB.02106-14. [Epub ahead of print]

Topology of Streptococcus pneumoniae CpsC, a Polysaccharide co-polymerase and BY-kinase adaptor protein.

Whittall JJ1, Morona R1, Standish AJ2.

Author information

Abstract

In Gram-positive bacteria, tyrosine kinases are split into two proteins, the cytoplasmic tyrosine kinase and a transmembrane adaptor protein. In Streptococcus pneumoniae this transmembrane adaptor is CpsC, with the C-terminus of CpsC critical for interaction and subsequent tyrosine kinase activity of CpsD. Topology predictions suggest CpsC has two transmembrane domains, with the N and C-termini present in the cytoplasm. In order to investigate CpsC topology, we used a chromosomal HA-tagged Cps2C protein in D39. Incubation of both protoplasts and membranes with the CP-B resulted in complete degradation of HA-Cps2C in all cases, indicating that the C-terminus of Cps2C was likely extra-cytoplasmic, and hence the protein's topology was not as predicted. Similar results were seen with membranes from TIGR4, indicating Cps4C also showed similar topology. A chromosomally encoded fusion of HA-Cps2C and Cps2D was not degraded by CP-B, suggesting that the fusion fixed the C-terminus within the cytoplasm. However, capsule synthesis was unaltered by this fusion. Detection of the CpsC C-terminus by flow cytometry indicated that it was extra-cytoplasmic in approximately 30% of cells. Interestingly, a mutant in the protein tyrosine phosphatase CpsB had a significantly greater proportion of positive cells, although this affect was independent of its phosphatase activity. Our data indicate that CpsC possesses a varied topology, with the C-terminus flipping across the cytoplasmic membrane where it interacts with CpsD in order to regulate tyrosine kinase activity.

PMID: 25313397 [PubMed - as supplied by publisher]

Mutant prevention concentration of tigecycline for clinical isolates of Streptococcus pneumoniae and Staphylococcus aureus.

J Antimicrob Chemother. 2014 Oct 16. pii: dku389. [Epub ahead of print]

Mutant prevention concentration of tigecycline for clinical isolates of Streptococcus pneumoniae and Staphylococcus aureus.

Hesje CK1, Drlica K2, Blondeau JM3.

Author information

Abstract

BACKGROUND:

The mutant prevention concentration (MPC) reflects the antimicrobial susceptibility of the resistant mutant subpopulations present in large bacterial populations. In principle, combining the MPC with pharmacokinetic measurements can guide treatment to restrict the enrichment of resistant subpopulations, just as the MIC is used with pharmacokinetics to restrict the growth of bulk, susceptible populations. Little is known about the MPC of tigecycline, one of the more recently approved antimicrobials. Tigecycline is particularly interesting because it shows good activity against Gram-positive pathogens.

METHODS:

MPCs were determined using tigecycline-containing agar plates for clinical isolates of Streptococcus pneumoniae (n = 47), MRSA (n = 50) and MSSA (n = 50).

RESULTS:

Trypticase soy agar containing sheep red blood cells, commonly used for the growth of S. pneumoniae, gave tigecycline MPC90 values that were two orders of magnitude higher than expected. The addition of agar to Todd-Hewitt broth (solidified Todd-Hewitt broth) allowed the high-density growth of S. pneumoniae in the absence of red blood cells and lowered the MPC90 of tigecycline by 100-fold to 0.5 mg/L. The addition of red blood cells to solidified Todd-Hewitt broth raised the MPC90 by 100-fold. Thus, red blood cells reduce the efficacy of tigecycline against S. pneumoniae. The growth of Staphylococcus aureus was not sensitive to red blood cells; values of MPC90 were 2 and 4 mg/L for MSSA and MRSA, respectively.

CONCLUSIONS:

Values of MPC constitute a concentration threshold for restricting the emergence of tigecycline resistance that can now be used in animal studies to determine pharmacodynamic thresholds. The off-label treatment of S. pneumoniae blood infections with tigecycline may require caution due to blood-cell-mediated interference with the antimicrobial.

© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

KEYWORDS:

blood agar; mutant selection window; resistance

PMID: 25324419 [PubMed - as supplied by publisher]

Structural Determinants of Host Specificity of Complement Factor H Recruitment by Streptococcus pneumoniae.

Biochem J. 2014 Oct 21. [Epub ahead of print]

Structural Determinants of Host Specificity of Complement Factor H Recruitment by Streptococcus pneumoniae.

Achila D, Liu A, Banerjee R, Li Y, Martinez-Hackert E, Zhang JR, Yan H.

Abstract

Many human pathogens have strict host specificity, which affects not only their epidemiology but also development of animal models and vaccines. Complement factor H (FH) is recruited to pneumococcal cell surface in a human-specific manner via the N-terminal domain of the pneumococcal protein virulence factor CbpA (CbpAN). FH recruitment enables Streptococcus pneumoniae to evade surveillance by human complement system and contributes to pneumococcal host specificity. The molecular determinants of host specificity of complement evasion are unknown. Here we show that a single human FH domain is sufficient for tight binding of CbpAN, present the crystal structure of the complex, and identify the critical structural determinants for host-specific FH recruitment. The results offer new approaches to development of better animal models for pneumococcal infection and redesign of the virulence factor for pneumococcal vaccine development, and reveal how FH recruitment can serve as a mechanism for both pneumococcal complement evasion and adherence.

PMID: 25330773 [PubMed - as supplied by publisher]