Modulation of the activity of moxifloxacin and solithromycin in an in vitro pharmacodynamic model of Streptococcus pneumoniae naive and induced biofilms.

J Antimicrob Chemother. 2015 Feb 23. pii: dkv032. [Epub ahead of print]

Modulation of the activity of moxifloxacin and solithromycin in an in vitro pharmacodynamic model of Streptococcus pneumoniae naive and induced biofilms.

Vandevelde NM1, Tulkens PM1, Muccioli GG2, Van Bambeke F3.

Author information

Abstract

OBJECTIVES:

Bacterial biofilms developing in the bronchial tree of patients experiencing acute exacerbations of chronic bronchitis (AECBs) are suggested to cause relapses and recurrences of the disease because the matrix barrier impairs antibiotic access to the offending organisms. We examined whether bronchodilators could modulate pneumococcal biofilm development and antibiotic action using an in vitro model.

METHODS:

Streptococcus pneumoniae strains from patients hospitalized for AECBs and two reference strains (ATCC 49619 and R6) were screened for biofilm formation (multi-well plates; 2-11 days of growth). Ipratropium and salbutamol (alone or in combination) were added at concentrations of 1.45 and 7.25 mg/L, respectively (mimicking those in the bronchial tree), and their effects were measured on biofilm formation and modulation of the activity of antibiotics [full antibiotic concentration-dependent effects (pharmacodynamic model)] with a focus on moxifloxacin and solithromycin. Bacterial viability and biomass were measured by the reduction of resazurin and crystal violet staining, respectively. Release of sialic acid (from biofilm) and neuraminidase activity were measured using enzymatic and HPLC-MS detection of sialic acid.

RESULTS:

All clinical isolates produced biofilms, but with fast disassembly if from patients who had received muscarinic antagonists. Ipratropium caused: (i) reduced biomass formation and faster biofilm disassembly with free sialic acid release; and (ii) a marked improvement of antibiotic activity (bacterial killing and biomass reduction). Salbutamol stimulated neuraminidase activity associated with improved antibiotic killing activity (reversed by zanamivir) but modest biomass reduction.

CONCLUSIONS:

Ipratropium and, to a lesser extent, salbutamol may cooperate with antibiotics for bacterial clearance and disassembly of pneumococcal biofilms.

© The Author 2015. 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:

biomass; crystal violet; neuraminidase; resazurin; sialic acid; viability; zanamivir

PMID: 25712316 [PubMed - as supplied by publisher]

Ascorbic acid-dependent gene expression in Streptococcus pneumoniae and the activator function of the transcriptional regulator UlaR2.

Front Microbiol. 2015 Feb 11;6:72. doi: 10.3389/fmicb.2015.00072. eCollection 2015.

Ascorbic acid-dependent gene expression in Streptococcus pneumoniae and the activator function of the transcriptional regulator UlaR2.

Afzal M1, Shafeeq S2, Kuipers OP3.

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Abstract

In this study, we have explored the impact of ascorbic acid on the transcriptome of Streptococcus pneumoniae D39. The expression of several genes and operons, including the ula operon (which has been previously shown to be involved in ascorbic acid utilization), the AdcR regulon (which has been previously shown to be involved in zinc transport and virulence) and a PTS operon (which we denote here as ula2 operon) were altered in the presence of ascorbic acid. The ula2 operon consists of five genes, including the transcriptional activator ulaR2. Our β-galactosidase assay data and transcriptome comparison of the ulaR2 mutant with the wild-type demonstrated that the transcriptional activator UlaR2 in the presence of ascorbic acid activates the expression of the ula2 operon. We further predict a 16-bp regulatory site (5'-ATATTGTGCTCAAATA-3') for UlaR2 in the Pula2. Furthermore, we have explored the effect of ascorbic acid on the expression of the AdcR regulon. Our ICP-MS analysis showed that addition of ascorbic acid to the medium causes zinc starvation in the cell which leads to the activation of the AdcR regulon.

KEYWORDS:

AdcR; UlaR2; Zinc; ascorbic acid; pneumococcus; ula2 operon

PMID: 25717320 [PubMed] PMCID: PMC4324149 

Sialic acid-mediated gene expression in Streptococcus pneumoniae and the role of NanR as a transcriptional activator of the nan gene cluster.

Appl Environ Microbiol. 2015 Feb 27. pii: AEM.00499-15. [Epub ahead of print]

Sialic acid-mediated gene expression in Streptococcus pneumoniae and the role of NanR as a transcriptional activator of the nan gene cluster.

Afzal M1, Shafeeq S2, Ahmed H3, Kuipers OP4.

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Abstract

In this study, we investigated the transcriptomic response of Streptococcus pneumoniae D39 to sialic acid (N-acetylneuraminic acid: Neu5Ac). Transcriptome comparison of the D39 wild-type grown in M17 medium with and without sialic acid revealed the elevated expression of various genes and operons including the nan gene cluster (nan operon-I and nanA gene). Our microarray analysis and promoter-lacZ fusion studies showed that the transcriptional regulator NanR, acts as a transcriptional activator of nan operon-I and the nanA gene in the presence of sialic acid. The putative regulatory site of NanR in the promoter region of nan operon-I is predicted and confirmed by promoter truncation experiments. Furthermore, the role of CcpA in the regulation of the nan gene cluster is demonstrated through microarray analysis and promoter-lacZ fusion studies, suggesting that in the presence of sialic acid and glucose, CcpA represses the expression of nan operon-I while the expression of the nanA gene is CcpA-independent.

Copyright © 2015, American Society for Microbiology. All Rights Reserved.

PMID: 25724955 [PubMed - as supplied by publisher]

Copper intoxication inhibits aerobic nucleotide synthesis in Streptococcus pneumoniae.

Metallomics. 2015 Mar 2. [Epub ahead of print]

Copper intoxication inhibits aerobic nucleotide synthesis in Streptococcus pneumoniae.

Johnson MD1, Kehl-Fie TE, Rosch JW.

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Abstract

Copper is universally toxic in excess, a feature exploited by the human immune system to facilitate bacterial clearance. The mechanism of copper intoxication remains unknown for many bacterial species. Here, we demonstrate that copper toxicity in Streptococcus pneumoniae is independent from oxidative stress but, rather, is the result of copper inhibiting the aerobic dNTP biosynthetic pathway. Furthermore, we show that copper-intoxicated S. pneumoniae is rescued by manganese, which is an essential metal in the aerobic nucleotide synthesis pathway. These data provide insight into new targets to enhance copper-mediated toxicity during bacterial clearance.

PMID: 25730343 [PubMed - as supplied by publisher]

Dysregulation of transition metal ion homeostasis is the molecular basis for cadmium toxicity in Streptococcus pneumoniae.

Nat Commun. 2015 Mar 3;6:6418. doi: 10.1038/ncomms7418.

Dysregulation of transition metal ion homeostasis is the molecular basis for cadmium toxicity in Streptococcus pneumoniae.

Begg SL1, Eijkelkamp BA1, Luo Z2, Couñago RM2, Morey JR1, Maher MJ3, Ong CL4, McEwan AG4, Kobe B2, O'Mara ML5, Paton JC1, McDevitt CA1.

Author information

Abstract

Cadmium is a transition metal ion that is highly toxic in biological systems. Although relatively rare in the Earth's crust, anthropogenic release of cadmium since industrialization has increased biogeochemical cycling and the abundance of the ion in the biosphere. Despite this, the molecular basis of its toxicity remains unclear. Here we combine metal-accumulation assays, high-resolution structural data and biochemical analyses to show that cadmium toxicity, in Streptococcus pneumoniae, occurs via perturbation of first row transition metal ion homeostasis. We show that cadmium uptake reduces the millimolar cellular accumulation of manganese and zinc, and thereby increases sensitivity to oxidative stress. Despite this, high cellular concentrations of cadmium (~17 mM) are tolerated, with negligible impact on growth or sensitivity to oxidative stress, when manganese and glutathione are abundant. Collectively, this work provides insight into the molecular basis of cadmium toxicity in prokaryotes, and the connection between cadmium accumulation and oxidative stress.

PMID: 25731976 [PubMed - in process]

The sequence elements upstream of the core promoter are necessary for the full transcription of the capsule gene operon in Streptococcus pneumoniae strain D39.

Infect Immun. 2015 Mar 2. pii: IAI.02944-14. [Epub ahead of print]

The sequence elements upstream of the core promoter are necessary for the full transcription of the capsule gene operon in Streptococcus pneumoniae strain D39.

Wen Z1, Sertil O2, Cheng Y1, Zhang S1, Liu X1, Wang WC3, Zhang JR4.

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Abstract

Streptococcus pneumoniae is a major bacterial pathogen in humans. Its polysaccharide capsule is a key virulence factor, which promotes bacterial evasion of human phagocytic killing. While S. pneumoniae produces at least 94 antigenically different types of capsule, the genes for biosynthesis of almost all capsular types are arranged in the same locus. The transcription of the capsular polysaccharide (cps) locus is not well understood. This study determined the transcriptional features of the cps locus in the type-2 virulent strain D39. The initial analysis revealed that the cps genes are co-transcribed from a major transcription start site at the -25th nucleotide G upstream of cps2A, the first gene in the locus. Using unmarked chromosomal truncations and a luciferase-based transcriptional reporter, we showed that the full transcription of the cps genes not only depends on the core promoter immediately upstream of cps2A, but also requires additional elements upstream of the core promoter, particularly a 59-base pair sequence immediately upstream of the core promoter. Unmarked deletion of these promoter elements in the D39 genome also led to significant reduction in CPS production and virulence in mice. Lastly, the mutants of the common cps genes cps2ABCD did not show significant abnormality in the cps transcription although they produced significantly less CPS, indicating that the CpsABCD proteins are involved in the encapsulation of S. pneumoniae in a post-transcriptional manner. This study has yielded important information on the transcriptional characteristics of the cps locus in S. pneumoniae.

Copyright © 2015, American Society for Microbiology. All Rights Reserved.

PMID: 25733517 [PubMed - as supplied by publisher]

A novel chimeric phage lysin with high in vitro and in vivo bactericidal activity against Streptococcus pneumoniae.

J Antimicrob Chemother. 2015 Mar 1. pii: dkv038. [Epub ahead of print]

A novel chimeric phage lysin with high in vitro and in vivo bactericidal activity against Streptococcus pneumoniae.

Díez-Martínez R1, De Paz HD2, García-Fernández E3, Bustamante N4, Euler CW5, Fischetti VA6, Menendez M4, García P7.

Author information

Abstract

OBJECTIVES:

Streptococcus pneumoniae is becoming increasingly antibiotic resistant worldwide and new antimicrobials are urgently needed. Our aim was new chimeric phage endolysins, or lysins, with improved bactericidal activity by swapping the structural components of two pneumococcal phage lysozymes: Cpl-1 (the best lysin tested to date) and Cpl-7S.

METHODS:

The bactericidal effects of four new chimeric lysins were checked against several bacteria. The purified enzymes were added at different concentrations to resuspended bacteria and viable cells were measured after 1 h. Killing capacity of the most active lysin, Cpl-711, was tested in a mouse bacteraemia model, following mouse survival after injecting different amounts (25-500 μg) of enzyme. The capacity of Cpl-711 to reduce pneumococcal biofilm formation was also studied.

RESULTS:

The chimera Cpl-711 substantially improved the killing activity of the parental phage lysozymes, Cpl-1 and Cpl-7S, against pneumococcal bacteria, including multiresistant strains. Specifically, 5 μg/mL Cpl-711 killed ≥7.5 log of pneumococcal R6 strain. Cpl-711 also reduced pneumococcal biofilm formation and killed 4 log of the bacterial population at 1 μg/mL. Mice challenged intraperitoneally with D39_IU pneumococcal strain were protected by treatment with a single intraperitoneal injection of Cpl-711 1 h later, resulting in about 50% greater protection than with Cpl-1.

CONCLUSIONS:

Domain swapping among phage lysins allows the construction of new chimeric enzymes with high bactericidal activity and a different substrate range. Cpl-711, the most powerful endolysin against pneumococci, offers a promising therapeutic perspective for the treatment of multiresistant pneumococcal infections.

© The Author 2015. 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:

S. pneumoniae; animal infections; antimicrobial therapy; bacterial biofilm; bacteriophages

PMID: 25733585 [PubMed - as supplied by publisher]

Nonencapsulated Streptococcus pneumoniae Cause Acute Otitis Media in the Chinchilla That Is Enhanced by Pneumococcal Surface Protein K.

Open Forum Infect Dis. 2014 Jul 1;1(2):ofu037. doi: 10.1093/ofid/ofu037. eCollection 2014.

Nonencapsulated Streptococcus pneumoniae Cause Acute Otitis Media in the Chinchilla That Is Enhanced by Pneumococcal Surface Protein K.

Keller LE1, Friley J1, Dixit C1, Nahm MH2, McDaniel LS3.

Author information

Abstract

BACKGROUND:

Use of the pneumococcal conjugate vaccine has led to serotype replacement of carriage and acute otitis media (AOM) pneumococcal isolates. Increases in nonencapsulated Streptococcus pneumoniae (NESp) isolates have also occurred, and there are increasing reports of NESp-associated disease. Disease prevalence and virulence factors of NESp isolates have not been studied.

METHODS:

A chinchilla model of pneumococcal AOM was utilized, and disease was assessed through bacterial enumeration along with scoring visible signs of pathology. An adhesion-invasion assay using a human epithelial cell line was performed.

RESULTS:

Nonencapsulated Streptococcus pneumoniae strains containing pneumococcal surface protein K (PspK) were more likely to cause AOM and pathology upon infection. Deletion of PspK from an isolate significantly reduced bacterial loads. Increased epithelial cell adhesion correlated with increased virulence of NESp isolates naturally lacking PspK. Furthermore, expression of PspK by an avirulent NESp resulted in virulence.

CONCLUSIONS:

The presence of PspK increased the disease potential of NESp. Pneumococcal surface protein K is not the only virulence factor of NESp in AOM. Expression of PspK in an avirulent NESp mediated the progression to pneumococcal disease. Genetic exchange between pneumococci may allow dissemination of PspK, increasing the potential of NESp disease. The current study is the first report of a NESp-specific virulence factor.

KEYWORDS:

AOM; NESp; PspK; acute otitis media; nonencapsulated Streptococcus pneumoniae; pneumococcal surface protein K

PMID: 25734113 [PubMed] PMCID: PMC4281809 Free PMC Article

Comparison of the clinical characteristics and outcomes of Klebsiella pneumoniae and Streptococcus pneumoniae meningitis.

Diagn Microbiol Infect Dis. 2015 Feb 20. pii: S0732-8893(15)00040-1. doi: 10.1016/j.diagmicrobio.2015.02.006. [Epub ahead of print]

Comparison of the clinical characteristics and outcomes of Klebsiella pneumoniae and Streptococcus pneumoniae meningitis.

Jung J1, Park KH2, Park SY3, Song EH4, Lee EJ5, Choi SH6, Choo EJ7, Kwak YG8, Sung H9, Kim SH1, Lee SO1, Kim MN9, Kim YS1, Woo JH1, Choi SH10.

Author information

Abstract

This multicenter, retrospective cohort study compared the clinical characteristics and outcomes of community-acquired Klebsiella pneumoniae meningitis (CA-KPM) with those of community-acquired Streptococcus pneumoniae meningitis (CA-SPM). Eighty-three adult patients, 27 with CA-KPM and 56 with CA-SPM, were included. Diabetes mellitus (48.1% versus 21.4%; P=0.01) and liver cirrhosis (22.2% versus 5.4%; P=0.05) were more commonly associated with CA-KPM. Comatose mental status (40.7% versus 12.5%; P=0.01), septic shock (44.4% versus 8.9%; P<0.001), and concomitant extrameningeal infections (40.7% versus 7.1%; P=0.001) were also more common in the CA-KPM group. The 28-day mortality (44.4% versus 10.7%; P<0.001) and inhospital mortality (51.9% versus 14.3%; P<0.001) were higher in the CA-KPM group. In conclusion, diabetes mellitus and liver cirrhosis are more common in the CA-KPM patients who were also more likely to present with severe manifestations and poor outcomes.

Copyright © 2015. Published by Elsevier Inc.

KEYWORDS:

Klebsiella pneumoniae; Meningitis; Streptococcus pneumoniae

PMID: 25752203 [PubMed - as supplied by publisher]

Killing of Streptococcus pneumoniae by azithromycin, clarithromycin, erythromycin, telithromycin and gemifloxacin using drug minimum inhibitory concentrations and mutant prevention concentrations.

Int J Antimicrob Agents. 2015 Feb 16. pii: S0924-8579(15)00063-1. doi: 10.1016/j.ijantimicag.2014.12.034. [Epub ahead of print]

Killing of Streptococcus pneumoniae by azithromycin, clarithromycin, erythromycin, telithromycin and gemifloxacin using drug minimum inhibitory concentrations and mutant prevention concentrations.

Blondeau JM1, Shebelski SD2, Hesje CK3.

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Abstract

Streptococcus pneumoniae continues to be a significant respiratory pathogen, and increasing antimicrobial resistance compromises the use of β-lactam and macrolide antibiotics. Bacterial eradication impacts clinical outcome, and bacterial loads at the site of infection may fluctuate. Killing of two macrolide- and quinolone-susceptible clinical S. pneumoniae isolates by azithromycin, clarithromycin, erythromycin, telithromycin and gemifloxacin against varying bacterial densities was determined using the measured minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC). For kill experiments, 106-109 CFU/mL were exposed to the drug and were sampled at 0, 0.5, 1, 2, 3, 4, 6, 12 and 24h following drug exposure. The log10 reduction and percent reduction (kill) of viable cells was recorded. MICs and MPCs (mg/L) for azithromycin, clarithromycin, erythromycin, telithromycin and gemifloxacin were 0.063-0.125/0.5-1, 0.031-0.063/0.25-0.5, 0.063/0.25-0.5, 0.008/0.016 and 0.031/0.25, respectively. Killing 106-109 CFU/mL of bacteria by the drug MIC yielded incomplete killing, however log10 reductions occurred by 12h and 24h for all drugs. Exposure of 106-109 CFU/mL to MPC drug concentrations resulted in the following log10 reduction by 6h of drug exposure: azithromycin, 1.3-3.9; clarithromycin, 1.9-5.8; erythromycin, 0.8-4.7; telithromycin, 0.3-1.7; and gemifloxacin, 1.8-4.2. Bacterial loads at the site of infection may range from 106 to 109, and kill experiments utilising a higher bacterial inoculum provided a more accurate measure of antibiotic performance in high biomass situations. Killing was slower with telithromycin. Kill was greater and fastest with MPC versus MIC drug concentrations.

Copyright © 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

KEYWORDS:

Killing activity; Macrolides; Mutant prevention concentration; Quinolones; Streptococcus pneumoniae

PMID: 25752567 [PubMed - as supplied by publisher]

Ethanol Impairs Mucosal Immunity Against Streptococcus pneumoniae Infection by Disrupting IL-17 Gene Expression.

Infect Immun. 2015 Mar 9. pii: IAI.02869-14. [Epub ahead of print]

Ethanol Impairs Mucosal Immunity Against Streptococcus pneumoniae Infection by Disrupting IL-17 Gene Expression.

Trevejo-Nunez G1, Chen K1, Dufour JP2, Bagby GJ3, Horne WT1, Nelson S3, Kolls JK4.

Author information

Abstract

Acute ethanol intoxication suppresses the host immune responses against Streptococcus pneumoniae. As IL-17 is a critical cytokine in host defense against extracellular pathogens including S. pneumoniae, we hypothesized that ethanol impairs mucosal immunity against this pathogen by disrupting IL-17 production or IL-17R signaling. A chronic ethanol feeding model in SIV-infected Rhesus macaques and acute ethanol in a murine model were used. Transcriptome analysis of bronchial brushes in the non-human primate model showed downregulation of the expression of IL-17 regulated chemokines in ethanol fed animals, a finding also replicated in the murine model. Surprisingly, recombinant CXCL1 and CXCL5 but not IL-17 or IL-23 + IL1β rescued bacterial burden in the ethanol group to control levels. Taken together, this study suggests that ethanol impairs IL-17 mediated chemokine production in the lung. Thus, exogenous luminal restoration of IL-17 related chemokines, CXCL1 and CXCL5, improves host defenses against S. pneumoniae.

Copyright © 2015, American Society for Microbiology. All Rights Reserved.

PMID: 25754201 [PubMed - as supplied by publisher]

Phenotypes and genotypes of macrolide-resistant streptococcus pneumoniae.

Balkan Med J. 2015 Jan;32(1):84-8. doi: 10.5152/balkanmedj.2015.15169. Epub 2015 Jan 1.

Phenotypes and genotypes of macrolide-resistant streptococcus pneumoniae.

Sirekbasan L1, Gönüllü N1, Sirekbasan S1, Kuşkucu M1, Midilli K1.

Abstract

BACKGROUND:

Macrolide resistance in Streptococcus pneumoniae (S. pneumoniae) is a worldwide problem.

AIMS:

The aim of this work was to analyze the phenotypes, genotypes, and clonal relatedness among macrolide-resistant S. pneumoniae strains isolated from various clinical specimens in our hospital.

STUDY DESIGN:

Cross-sectional study.

METHODS:

80 non-duplicate S. pneumoniae strains were analyzed by polymerase chain reaction for both the erm (B) and mef (A) genes.

RESULTS:

Macrolide resistance was observed in 22.5% (18 strains) of strains. Two (11.2%) isolates possessed mef (A), eight possessed erm (B) (44.4%) and eight strains (44.4%) were positive for both erm (B) and mef (A) genes. Although BOX-PCR of 18 macrolide-resistant strains revealed 11 band patterns, they clustered as seven clones with a genetic distance >10% to each other. Eight isolates possessed both erm (B) and mef (A) genes and belonged to a single clone (44.44% of all macrolide-resistant strains).

CONCLUSION:

Increased positivity rates for both resistance genes have also been reported from other hospitals in Turkey, but this is the first study from Turkey showing the clonal dissemination of both resistance genes.

KEYWORDS:

BOX-PCR; Macrolide resistance; Streptococcus pneumoniae; erm (B); mef (A)

PMID: 25759777 [PubMed] PMCID: PMC4342144

A Novel Gene Amplification Causes Up-regulation of the PatAB ABC Transporter and Fluoroquinolone Resistance in Streptococcus pneumoniae.

Antimicrob Agents Chemother. 2015 Mar 16. pii: AAC.04858-14. [Epub ahead of print]

A Novel Gene Amplification Causes Up-regulation of the PatAB ABC Transporter and Fluoroquinolone Resistance in Streptococcus pneumoniae.

Baylay AJ1, Ivens A2, Piddock LJ3.

Author information

Abstract

Over-expression of the ABC transporter genes patA and patB confers efflux-mediated fluoroquinolone resistance in Streptococcus pneumoniae, and is also linked to pneumococcal stress responses. Although up-regulation of patAB has been observed in many laboratory mutants and clinical isolates, regulatory mechanisms controlling expression of these genes are unknown. In this study, we aimed to identify the cause of high-level constitutive over-expression of patAB in M184, a multidrug resistant mutant of S. pneumoniae R6. Using a whole genome transformation and sequencing approach, we identified a novel duplication of a 9.2 kb region of the M184 genome, which included the patAB genes. This duplication did not affect growth and was semi-stable with a low segregation rate. Expression levels of patAB in M184 were much higher than could be fully explained by doubling of gene dosage alone, and inactivation of the first copy of patA had no effect on multidrug resistance. Using a GFP reporter system, increased patAB expression was ascribed to transcriptional read-through from a tRNA gene upstream of the second copy of patAB. This is the first report of a large genomic duplication causing antibiotic resistance in S. pneumoniae, and also of a genomic duplication causing antibiotic resistance by a promoter switching mechanism.

Copyright © 2015, American Society for Microbiology. All Rights Reserved.

PMID: 25779578 [PubMed - as supplied by publisher]

Structural and Enzymatic Characterization of the Choline Kinase LicA from Streptococcus pneumoniae.

PLoS One. 2015 Mar 17;10(3):e0120467. doi: 10.1371/journal.pone.0120467. eCollection 2015.

Structural and Enzymatic Characterization of the Choline Kinase LicA from Streptococcus pneumoniae.

Wang L1, Jiang YL1, Zhang JR2, Zhou CZ1, Chen Y1.

Author information

Abstract

LicA plays a key role in the cell-wall phosphorylcholine biosynthesis of Streptococcus pneumonia. Here we determined the crystal structures of apo-form LicA at 1.94 Å and two complex forms LicA-choline and LicA-AMP-MES, at 2.01 and 1.45 Å resolution, respectively. The overall structure adopts a canonical protein kinase-like fold, with the active site located in the crevice of the N- and C- terminal domains. The three structures present distinct poses of the active site, which undergoes an open-closed-open conformational change upon substrate binding and product release. The structure analyses combined with mutageneses and enzymatic assays enabled us to figure out the key residues for the choline kinase activity of LicA. In addition, structural comparison revealed the loop between helices α7 and α8 might modulate the substrate specificity and catalytic activity. These findings shed light on the structure and mechanism of the prokaryotic choline kinase LicA, and might direct the rational design of novel anti-pneumococcal drugs.

PMID: 25781969 [PubMed - in process] 

Arginase 1 activity worsens lung protective immunity against Streptococcus pneumoniae infection.

Eur J Immunol. 2015 Mar 18. doi: 10.1002/eji.201445419. [Epub ahead of print]

Arginase 1 activity worsens lung protective immunity against Streptococcus pneumoniae infection.

Knippenberg S1, Brumshagen C, Aschenbrenner F, Welte T, Maus UA.

Abstract

Type 2 helper cell (Th2) dominated chronic lung diseases like asthma are characterized by an increased risk for bacterial lung infections. However, the underlying mechanisms are poorly defined. Arginase 1 (Arg1) has been suggested to play an important role in the pathophysiology of asthma, and is rapidly induced in lung macrophages by Th2 cytokines, thereby limiting macrophage-derived antimicrobial nitric oxide (NO) production. Here we examined the effect of Th2 cytokine-induced upregulation or lung myeloid cell-specific conditional knockdown of Arg1 on lung resistance against Streptococcus pneumoniae (Spn) in mice. Lung macrophages responded with a profound induction of Arg1 mRNA and protein to treatment with IL-13 both in vitro and in vivo. Interleukin 13-induced Arg1 activity in the lungs of mice led to significantly attenuated lung protective immunity against Spn, while conditional Arg1 knock-down had no effect on lung protective immunity against Spn. Collectively, the data show that Th2 cytokine-induced increased Arg1 activity worsens lung protective immunity against Spn, and interventions to block Th2 cytokine-induced lung Arg1 activity may thus be a novel immunomodulatory strategy to lower the risk of bacterial infections in asthmatic patients. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

KEYWORDS:

Alternative macrophage activation; Arg1; IL-13; Inflammation; Lung

PMID: 25789453 [PubMed - as supplied by publisher]

Carriage of Streptococcus pneumoniae in Aged Adults with Influenza-Like-Illness.

PLoS One. 2015 Mar 19;10(3):e0119875. doi: 10.1371/journal.pone.0119875. eCollection 2015.

Carriage of Streptococcus pneumoniae in Aged Adults with Influenza-Like-Illness.

Krone CL1, Wyllie AL1, van Beek J2, Rots NY2, Oja AE1, Chu ML1, Bruin JP3, Bogaert D1, Sanders EA1, Trzciński K1.

Author information

Abstract

Incidence of pneumococcal disease is disproportionally high in infants and elderly. Nasopharyngeal colonisation by Streptococcus pneumoniae is considered a prerequisite for disease but unlike in children, carriage in elderly is rarely detected. Here, we tested for S. pneumoniae in nasopharyngeal and saliva samples collected from community-dwelling elderly with influenza-like-illness (ILI). Trans-nasal nasopharyngeal, trans-oral nasopharyngeal and saliva samples (n = 270 per sample type) were collected during winter/spring 2011/2012 from 135 persons aged 60-89 at onset of ILI and 7-9 weeks later following recovery. After samples were tested for pneumococci by conventional culture, all plate growth was collected. DNA extracted from plate harvests was tested by quantitative-PCRs (qPCR) specific for S. pneumoniae and serotypes included in the 13-valent pneumococcal conjugated vaccine (PCV13). Pneumococci were cultured from 14 of 135 (10%) elderly with none of the sampled niches showing superiority in carriage detection. With 76/270 (28%) saliva, 31/270 (11%) trans-oral and 13/270 (5%) trans-nasal samples positive by qPCR, saliva was superior to nasopharyngeal swabs (p<0.001) in qPCR-based carriage detection. Overall, from all methods used in the study, 65 of 135 (48%) elderly carried pneumococci at least once and 26 (19%) at both study time points. The difference between carriage prevalence at ILI (n = 49 or 36%) versus recovery (n = 42 or 31%) was not significant (p = 0.38). At least 23 of 91 (25%) carriage events in 19 of 65 (29%) carriers were associated with PCV13-serotypes. We detected a large reservoir of pneumococci in saliva of elderly, with PCV13-serotype distribution closely resembling the contemporary carriage of serotypes reported in the Netherlands for PCV-vaccinated infants.

PMID: 25789854 [PubMed - in process]