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.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

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.

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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]

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.

Copyright © 2014 by The American Association of Immunologists, Inc.

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.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

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.

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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.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

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.

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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] 

Pronounced metabolic changes in adaptation to biofilm growth by Streptococcus pneumoniae.

PLoS One. 2014 Sep 4;9(9):e107015. doi: 10.1371/journal.pone.0107015. eCollection 2014.

Pronounced metabolic changes in adaptation to biofilm growth by Streptococcus pneumoniae.

Allan RN1, Skipp P2, Jefferies J3, Clarke SC4, Faust SN5, Hall-Stoodley L6, Webb J7.

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Abstract

Streptococcus pneumoniae accounts for a significant global burden of morbidity and mortality and biofilm development is increasingly recognised as important for colonization and infection. Analysis of protein expression patterns during biofilm development may therefore provide valuable insights to the understanding of pneumococcal persistence strategies and to improve vaccines. iTRAQ (isobaric tagging for relative and absolute quantification), a high-throughput gel-free proteomic approach which allows high resolution quantitative comparisons of protein profiles between multiple phenotypes, was used to interrogate planktonic and biofilm growth in a clinical serotype 14 strain. Comparative analyses of protein expression between log-phase planktonic and 1-day and 7-day biofilm cultures representing nascent and late phase biofilm growth were carried out. Overall, 244 proteins were identified, of which >80% were differentially expressed during biofilm development. Quantitatively and qualitatively, metabolic regulation appeared to play a central role in the adaptation from the planktonic to biofilm phenotype. Pneumococci adapted to biofilm growth by decreasing enzymes involved in the glycolytic pathway, as well as proteins involved in translation, transcription, and virulence. In contrast, proteins with a role in pyruvate, carbohydrate, and arginine metabolism were significantly increased during biofilm development. Downregulation of glycolytic and translational proteins suggests that pneumococcus adopts a covert phenotype whilst adapting to an adherent lifestyle, while utilization of alternative metabolic pathways highlights the resourcefulness of pneumococcus to facilitate survival in diverse environmental conditions. These metabolic proteins, conserved across both the planktonic and biofilm phenotypes, may also represent target candidates for future vaccine development and treatment strategies. Data are available via ProteomeXchange with identifier PXD001182.

PMID: 25188255 [PubMed - in process] PMCID: PMC4154835 

Streptococcus pneumoniae Translocates into the Myocardium and Forms Unique Microlesions That Disrupt Cardiac Function.

PLoS Pathog. 2014 Sep 18;10(9):e1004383. doi: 10.1371/journal.ppat.1004383. eCollection 2014.

Streptococcus pneumoniae Translocates into the Myocardium and Forms Unique Microlesions That Disrupt Cardiac Function.

Brown AO1, Mann B2, Gao G2, Hankins JS3, Humann J2, Giardina J2, Faverio P4, Restrepo MI5, Halade GV6, Mortensen EM7, Lindsey ML8, Hanes M9, Happel KI10, Nelson S10, Bagby GJ10, Lorent JA11, Cardinal P11, Granados R11, Esteban A11, LeSaux CJ12, Tuomanen EI2, Orihuela CJ1.

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Abstract

Hospitalization of the elderly for invasive pneumococcal disease is frequently accompanied by the occurrence of an adverse cardiac event; these are primarily new or worsened heart failure and cardiac arrhythmia. Herein, we describe previously unrecognized microscopic lesions (microlesions) formed within the myocardium of mice, rhesus macaques, and humans during bacteremic Streptococcus pneumoniae infection. In mice, invasive pneumococcal disease (IPD) severity correlated with levels of serum troponin, a marker for cardiac damage, the development of aberrant cardiac electrophysiology, and the number and size of cardiac microlesions. Microlesions were prominent in the ventricles, vacuolar in appearance with extracellular pneumococci, and remarkable due to the absence of infiltrating immune cells. The pore-forming toxin pneumolysin was required for microlesion formation but Interleukin-1β was not detected at the microlesion site ruling out pneumolysin-mediated pyroptosis as a cause of cell death. Antibiotic treatment resulted in maturing of the lesions over one week with robust immune cell infiltration and collagen deposition suggestive of long-term cardiac scarring. Bacterial translocation into the heart tissue required the pneumococcal adhesin CbpA and the host ligands Laminin receptor (LR) and Platelet-activating factor receptor. Immunization of mice with a fusion construct of CbpA or the LR binding domain of CbpA with the pneumolysin toxoid L460D protected against microlesion formation. We conclude that microlesion formation may contribute to the acute and long-term adverse cardiac events seen in humans with IPD.

PMID: 25232870 [PubMed - in process] 

The Impact of Pneumolysin on the Macrophage Response to Streptococcus pneumoniae is Strain-Dependent.

PLoS One. 2014 Aug 8;9(8):e103625. doi: 10.1371/journal.pone.0103625. eCollection 2014.

The Impact of Pneumolysin on the Macrophage Response to Streptococcus pneumoniae is Strain-Dependent.

Harvey RM1, Hughes CE1, Paton AW1, Trappetti C1, Tweten RK2, Paton JC1.

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Abstract

Streptococcus pneumoniae is the world's leading cause of pneumonia, bacteremia, meningitis and otitis media. A major pneumococcal virulence factor is the cholesterol-dependent cytolysin, which has the defining property of forming pores in cholesterol-containing membranes. In recent times a clinically significant and internationally successful serotype 1 ST306 clone has been found to express a non-cytolytic variant of Ply (Ply306). However, while the pneumococcus is a naturally transformable organism, strains of the ST306 clonal group have to date been virtually impossible to transform, severely restricting efforts to understand the role of non-cytolytic Ply in the success of this clone. In this study isogenic Ply mutants were constructed in the D39 background and for the first time in the ST306 background (A0229467) to enable direct comparisons between Ply variants for their impact on the immune response in a macrophage-like cell line. Strains that expressed cytolytic Ply were found to induce a significant increase in IL-1β release from macrophage-like cells compared to the non-cytolytic and Ply-deficient strains in a background-independent manner, confirming the requirement for pore formation in the Ply-dependent activation of the NLRP3 inflammasome. However, cytolytic activity in the D39 background was found to induce increased expression of the genes encoding GM-CSF (CSF2), p19 subunit of IL-23 (IL23A) and IFNβ (IFNB1) compared to non-cytolytic and Ply-deficient D39 mutants, but had no effect in the A0229467 background. The impact of Ply on the immune response to the pneumococcus is highly dependent on the strain background, thus emphasising the importance of the interaction between specific virulence factors and other components of the genetic background of this organism.

PMID: 25105894 [PubMed - in process] PMCID: PMC4126675 

Competence for Genetic Transformation in Streptococcus pneumoniae: Mutations in σA Bypass the comW Requirement.

J Bacteriol. 2014 Aug 11. pii: JB.01933-14. [Epub ahead of print]

Competence for Genetic Transformation in Streptococcus pneumoniae: Mutations in σA Bypass the comW Requirement.

Tovpeko Y1, Morrison DA2.

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Abstract

Competence for genetic transformation in the genus streptococcus depends on an alternative sigma factor, σX, for coordinated synthesis of 23 proteins, which together establish the X state by permitting lysis of incompetent streptococci, uptake of DNA fragments, and integration of strands of that DNA into the resident genome. Initiation of transient accumulation of high levels of σX is coordinated between cells by transcription factors linked to peptide pheromone signals. In S. pneumoniae, elevated σX is insufficient for development of full competence without co-expression of a second competence-specific protein, ComW. ComW, shared by six species in the mitis and anginosus groups, is regulated by the same pheromone circuit that controls σX, but its role in expression of the σX regulon is unknown. Using the strong, but not absolute, dependence of transformation on comW as a selective tool, we collected 27 independent comW bypass mutations and mapped them to ten single-base transitions, all within rpoD, encoding the primary sigma factor subunit of RNA polymerase, σA. Eight mapped to sites in rpoD region 4 that are implicated in interaction with the core β subunit, indicating that ComW may act to facilitate competition of the alternative sigma factor σX for access to core polymerase.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

PMID: 25112479 [PubMed - as supplied by publisher]

The Oral Commensal Streptococcus mitis Shows a Mixed Memory Th Cell Signature That Is Similar to and Cross-Reactive with Streptococcus pneumoniae.

PLoS One. 2014 Aug 13;9(8):e104306. doi: 10.1371/journal.pone.0104306. eCollection 2014.

The Oral Commensal Streptococcus mitis Shows a Mixed Memory Th Cell Signature That Is Similar to and Cross-Reactive with Streptococcus pneumoniae.

Engen SA1, Valen Rukke H1, Becattini S2, Jarrossay D2, Blix IJ3, Petersen FC1, Sallusto F2, Schenck K1.

Author information

Abstract

BACKGROUND:

Carriage of and infection with Streptococcus pneumoniae is known to predominantly induce T helper 17 (Th17) responses in humans, but the types of Th cells showing reactivity towards commensal streptococci with low pathogenic potential, such as the oral commensals S. mitis and S. salivarius, remain uncharacterized.

METHODS:

Memory CD4+ T helper (Th) cell subsets were isolated from healthy human blood donors according to differential expression of chemokine receptors, expanded in vitro using polyclonal stimuli and characterized for reactivity against different streptococcal strains.

RESULTS:

Th cells responding to S. mitis, S. salivarius and S. pneumoniae were predominantly in a CCR6+CXCR3+ subset and produced IFN-γ, and in a CCR6+CCR4+ subset and produced IL-17 and IL-22. Frequencies of S. pneumoniae-reactive Th cells were higher than frequencies of S. mitis- and S. salivarius-specific Th cells. S. mitis and S. pneumoniae isogenic capsule knock-out mutants and a S. mitis mutant expressing the serotype 4 capsule of S. pneumoniae showed no different Th cell responses as compared to wild type strains. S. mitis-specific Th17 cells showed cross-reactivity with S. pneumoniae.

CONCLUSIONS:

As Th17 cells partly control clearance of S. pneumoniae, cross-reactive Th17 cells that may be induced by commensal bacterial species may influence the immune response, independent of capsule expression.

PMID: 25119879 [PubMed - in process] PMCID: PMC4131883 

Characterisation of a collection of Streptococcus pneumoniae isolates from patients suffering from acute exacerbations of chronic bronchitis: In vitro susceptibility to antibiotics and biofilm formation in relation to antibiotic efflux and serotypes/serogroups.

Int J Antimicrob Agents. 2014 Sep;44(3):209-17. doi: 10.1016/j.ijantimicag.2014.05.016. Epub 2014 Jul 7.

Characterisation of a collection of Streptococcus pneumoniae isolates from patients suffering from acute exacerbations of chronic bronchitis: In vitro susceptibility to antibiotics and biofilm formation in relation to antibiotic efflux and serotypes/serogroups.

Vandevelde NM1, Tulkens PM2, Diaz Iglesias Y1, Verhaegen J3, Rodriguez-Villalobos H4, Philippart I5, Cadrobbi J6, Coppens N7, Boel A8, Van Vaerenbergh K8, Francart H9, Vanhoof R10, Liistro G11, Jordens P12, d'Odemont JP13, Valcke Y14, Verschuren F15, Van Bambeke F1.

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Abstract

The correlation between Streptococcus pneumoniae serotypes, biofilm production, antibiotic susceptibility and drug efflux in isolates from patients suffering from acute exacerbations of chronic bronchitis (AECB) remains largely unexplored. Using 101 isolates collected from AECB patients for whom partial (n=51) or full (n=50) medical details were available, we determined serotypes (ST)/serogroups (SG) (Quellung reaction), antibiotic susceptibility patterns [MIC (microdilution) using EUCAST and CLSI criteria] and ability to produce biofilm in vitro (10-day model; crystal violet staining). The majority of patients were 55-75 years old and <5% were vaccinated against S. pneumoniae. Moreover, 54% showed high severity scores (GOLD 3-4), and comorbidities were frequent including hypertension (60%), cancer (24%) and diabetes (20%). Alcohol and/or tobacco dependence was >30%. Isolates of SG6-11-15-23, known for large biofilm production and causing chronic infections, were the most prevalent (>15% each), but other isolates also produced biofilm (SG9-18-22-27 and ST8-20 being most productive), except SG7, SG29 and ST5 (<2% of isolates each). Resistance (EUCAST breakpoints) was 8-13% for amoxicillin and cefuroxime, 35-39% for macrolides, 2-8% for fluoroquinolones and 2% for telithromycin. ST19A isolates showed resistance to all antibiotics, ST14 to all except moxifloxacin, and SG9 and SG19 to all except telithromycin, moxifloxacin and ceftriaxone (SG19 only). Solithromycin and telithromycin MICs were similar. No correlation was observed between biofilm production and MIC or efflux (macrolides, fluoroquinolones). S. pneumoniae serotyping may improve AECB treatment by avoiding antibiotics with predictable low activity, but it is not predictive of biofilm production.

Copyright © 2014 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

KEYWORDS:

Acute exacerbations of chronic bronchitis (AECB); Biofilm; Efflux; Serotype; Streptococcus pneumoniae; Susceptibility

PMID: 25123808 [PubMed - in process]

Streptococcus pneumoniae and influenza: dynamic changes in the pneumococcal transcriptome during transition from biofilm formation to invasive disease.

Infect Immun. 2014 Aug 18. pii: IAI.02225-14. [Epub ahead of print]

Streptococcus pneumoniae and influenza: dynamic changes in the pneumococcal transcriptome during transition from biofilm formation to invasive disease.

Pettigrew MM1, Marks LR2, Kong Y3, Gent JF4, Roche-Hakansson H2, Hakansson AP5.

Author information

Abstract

Streptococcus pneumoniae is a leading cause of infectious disease globally. Nasopharyngeal colonization occurs in biofilms and precedes infection. Prior studies indicate that biofilm derived pneumococci are avirulent. However, influenza A virus (IAV) infection releases virulent pneumococci from biofilms in vitro and in vivo. Triggers of dispersal include IAV-induced changes in the nasopharynx such as increased temperature (fever) and extracellular ATP (tissue damage). We used RNA-seq to compare the S. pneumoniae transcriptome in biofilms, bacteria dispersed from biofilms after exposure to IAV, febrile-range temperature, or ATP, and planktonic cells grown at 37°C. Compared with biofilm bacteria, actively dispersed S. pneumoniae, which were more virulent in invasive disease, up-regulated genes involved in carbohydrate metabolism. Enzymatic assays for ATP and lactate production confirmed that dispersed pneumococci exhibited increased metabolism compared to those in biofilms. Dispersed pneumococci also up-regulated genes associated with production of bacteriocins and down-regulated colonization-associated genes related to competence, fratricide, and the transparent colony phenotype. IAV had the largest impact on the pneumococcal transcriptome. Similar transcriptional differences were also observed when actively dispersed bacteria were compared with avirulent planktonic bacteria. Our data demonstrate complex changes in the pneumococcal transcriptome in response to IAV-induced changes in the environment. Our data suggest that disease is caused by pneumococci that are primed to move to tissue sites with altered nutrient availability and to protect themselves from the nasopharyngeal microflora and host immune response. These data help explain pneumococcal virulence after IAV infection and have important implications for studies of S. pneumoniae pathogenesis.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

PMID: 25135685 [PubMed - as supplied by publisher]

MicroRNA-155 is required for the clearance of Streptococcus pneumoniae from the nasopharynx.

Infect Immun. 2014 Aug 25. pii: IAI.02251-14. [Epub ahead of print]

MicroRNA-155 is required for the clearance of Streptococcus pneumoniae from the nasopharynx.

Verschoor CP1, Dorrington MG1, Novakowski KE1, Kaiser J2, Radford K3, Nair P3, Anipindi V1, Kaushic C1, Surette MG2, Bowdish DM4.

Author information

Abstract

Pneumonia caused by Streptococcus pneumoniae is a major cause of death and economic burden worldwide. S. pneumoniae is an intermittent colonizer of the human upper respiratory tract and the ability to control asymptomatic colonization determines the likelihood of developing invasive disease. Recognition of S. pneumoniae by resident macrophages via TLR-2 and MARCO and the presence of IL-17 secreting CD4+ T-cells are required for macrophage recruitment and bacterial clearance. Despite the fact that the primary cellular effectors needed for bacterial clearance have been identified, much of the underlying regulatory mechanisms are unknown. Herein we demonstrate that the small, non-coding RNA, microRNA-155 (mir-155) is critical for the effective clearance of S. pneumoniae. Our studies show that mir-155 deficient mice maintain the ability to prevent acute, invasive pneumococcal infection, but have significantly higher bacterial burdens following colonization, independent of macrophage recognition by TLR-2, MARCO expression, or bactericidal capacity. The observed defects in bacterial clearance parallel reduced IL-17A and IFN-gamma CD4+ T-cell responses in vivo, lower IL-17A mRNA in the nasopharynx and a reduced capacity to induce Th17 cell polarization. Given that knockout mice are also limited in their capacity to generate high titre S. pneumoniae specific antibodies, we conclude that mir-155 is a critical mediator of the cellular effectors needed to clear primary and secondary S. pneumoniae colonization.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

PMID: 25156727 [PubMed - as supplied by publisher]