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  • 1
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    Production of capsular polysaccharide does not influence Staphylococcus aureusvancomycin susceptibility
    Springer Science and Business Media LLC ; 2013
    In:  BMC Microbiology Vol. 13, No. 1 ( 2013-12)
    Details
    In: BMC Microbiology, Springer Science and Business Media LLC, Vol. 13, No. 1 ( 2013-12)
    Abstract: Diverse mechanisms (increased cell wall thickness, low cross linking, decreased autolysis, etc.) have been reported for Staphylococcus aureus strains with intermediate vancomycin susceptibility (VISA). This study was conducted to identify common mechanisms responsible for decreased vancomycin susceptibility in a VISA strain pair. Results Transcriptional profiling of the clinical heterogeneous VISA isolate SA137/93A and its spontaneous homogeneous mutant strain SA137/93G pointed to an increased capsule production in the strain pair compared to a susceptible control. Furthermore, transcript quantification of the gene cap5E , which is essential for capsule biosynthesis, revealed elevated levels in the VISA strains SA137/93A, SA137/93G and Mu50 in comparison with susceptible strains Reynolds, Newman and SA1450/94. The increased expression was observed in bacteria from exponential as well as stationary growth phase. However, suppression of type 5 capsule formation by expression of antisense RNA did not increase vancomycin susceptibility in the VISA strain SA137/93G. Likewise, construction of inducible mutants of S. aureus Newman or repair of capsule biosynthesis of S. aureus HG001 and S. aureus 1450/94 did not influence resistance to vancomycin. Furthermore, purified type 5 polysaccharide did not protect indicator strains from the action of vancomycin. Conclusions The VISA strain tested in this study displayed an increased production of type 5 capsular polysaccharide. However, the production of capsule material did not protect strain SA137/93G and three vancomycin sensitive strains in the presence of vancomycin and thus is not part of the resistance mechanism; however it may represent a by-product of VISA life style that is often characterized by a high sigma factor B activity.
    Type of Medium: Online Resource
    ISSN: 1471-2180
    URL: Article
    DOI: 10.1186/1471-2180-13-65
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2013
    detail.hit.zdb_id: 2041505-9
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  • 2
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    Insertion of host DNA into PVL-encoding phages of the Staphylococcus aureus lineage ST80 by intra-chromosomal recombination
    Elsevier BV ; 2010
    In:  Virology Vol. 406, No. 2 ( 2010-10), p. 322-327
    Details
    In: Virology, Elsevier BV, Vol. 406, No. 2 ( 2010-10), p. 322-327
    Type of Medium: Online Resource
    ISSN: 0042-6822
    URL: Article
    DOI: 10.1016/j.virol.2010.07.017
    RVK:
    WA 15000
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2010
    detail.hit.zdb_id: 1471925-3
    SSG: 12
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  • 3
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    Transcription of the phage-encoded Panton–Valentine leukocidin of Staphylococcus aureus is dependent on the phage life-cycle and on the host background
    Microbiology Society ; 2009
    In:  Microbiology Vol. 155, No. 11 ( 2009-11-01), p. 3491-3499
    Details
    In: Microbiology, Microbiology Society, Vol. 155, No. 11 ( 2009-11-01), p. 3491-3499
    Abstract: Panton-Valentine leukocidin (PVL) is a pore-forming, bi-component toxin secreted by Staphylococcus aureus strains epidemiologically associated with diseases such as necrotizing pneumonia and skin and soft-tissue infections. Here we demonstrate that transcription of the phage-encoded PVL (encoded in the luk -PV operon) is dependent on two major determinants: the phage life-cycle and the host chromosomal background. Mitomycin C induction of PVL-encoding prophages from different community-acquired MRSA strains led to an increase in the amount of luk -PV mRNA as a result of read-through transcription from latent phage promoters and an increase in phage copy numbers. Failing prophage excision was reflected in a constant expression of luk -PV as in the case of strain USA300, suggesting that φ Sa2USA300 is a replication-defective prophage. Additionally, we could show that luk -PV transcription is influenced by the S. aureus global virulence regulators agr and sae . We found a strong impact of the host background on prophage induction and replication when analysing PVL phages in different S. aureus strains. For example phage φ Sa2mw was greatly induced by mitomycin C in its native host MW2 and in strain Newman but to a considerably lesser extent in strains 8325-4, RN6390 and ISP479c. This discrepancy was not linked to the SOS response of the bacteria since recA transcription did not vary between the strains. These results suggest a fine tuning between certain phages and their host, with major impact on the expression of phage-encoded virulence genes.
    Type of Medium: Online Resource
    ISSN: 1350-0872 , 1465-2080
    URL: Article
    DOI: 10.1099/mic.0.032466-0
    Language: English
    Publisher: Microbiology Society
    Publication Date: 2009
    detail.hit.zdb_id: 2008736-6
    SSG: 12
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  • 4
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    Extensive phage dynamics in Staphylococcus aureus contributes to adaptation to the human host during infection
    Wiley ; 2006
    In:  Molecular Microbiology Vol. 61, No. 6 ( 2006-09), p. 1673-1685
    Details
    In: Molecular Microbiology, Wiley, Vol. 61, No. 6 ( 2006-09), p. 1673-1685
    Abstract: Bacteriophages serve as a driving force in microbial evolution, adaptation to new environments and the pathogenesis of human bacterial infections. In Staphylococcus aureus phages encoding immune evasion molecules (SAK, SCIN, CHIPS), which integrate specifically into the β‐haemolysin (Hlb) gene, are widely distributed. When comparing S. aureus strain collections from infectious and colonizing situations we could detect a translocation of sak ‐encoding phages to atypical genomic integration sites in the bacterium only in the disease‐related isolates. Additionally, significantly more Hlb producing strains were detected in the infectious strain collection. Extensive phage dynamics (intragenomic translocation, duplication, transfer between hosts, recombination events) during infection was shown by analysing cocolonizing and consecutive isolates of patients. This activity leads to the splitting of the strain population into various subfractions exhibiting different virulence potentials (Hlb‐production and/or production of immune evasion molecules). Thus, phage‐inducing conditions and strong selection for survival of the bacterial host after phage movement are typical for the infectious situation. Further in vitro characterization of phages revealed that: (i) SAK is encoded not only on serogroup F phages showing a conserved tropism for hlb but also on serogroup B phages which always integrate in a distinct intergenic region, (ii) the level of sak transcription correlates to phage inducibility but is independent of the phage localization in the chromosome, and (iii) phages can be stabilized extra‐chromosomally during their life cycle.
    Type of Medium: Online Resource
    ISSN: 0950-382X , 1365-2958
    URL: Issue
    URL: Article
    DOI: 10.1111/mmi.2006.61.issue-6
    DOI: 10.1111/j.1365-2958.2006.05354.x
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 1501537-3
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  • 5
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    Transcription of Clumping Factor A in Attached and Unattached Staphylococcus aureus In Vitro and during Device-Related Infection
    American Society for Microbiology ; 2002
    In:  Infection and Immunity Vol. 70, No. 6 ( 2002-06), p. 2758-2762
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 70, No. 6 ( 2002-06), p. 2758-2762
    Abstract: Staphylococcus aureus is one of the pathogens most frequently isolated in device-related infections. S. aureus is equipped with surface-associated proteins promoting specific binding to matrix molecules. Clumping factor A (ClfA, encoded by clfA ) mediates adhesion to fibrinogen. Whereas the contribution of ClfA to pathogenicity is well documented, the influence of different growth and host parameters on gene activity is unclear. To elucidate this question, we investigated clfA transcript levels in an animal model of device-related infection and in planktonic and sessile bacteria grown in vitro. Specific mRNA from the S. aureus strains Newman, Reynolds, and RN6390 was quantified by LightCycler reverse transcription-PCR. In vitro, clfA transcript levels were low in the early logarithmic growth phase, but a clear increase was observed after the late logarithmic phase. Quantities of clfA transcripts were four to six times higher in the planktonic than in the sessile bacterial subpopulations grown to the stationary phase. During infection, in strains Newman and Reynolds levels of clfA transcripts in exudates accumulating in the infected devices were lower than those in the bacteria grown in vitro to stationary phase. clfA mRNA levels in the exudates increased during the initial phase of infection and remained constant after 96 h postinoculation. In contrast to the in vitro results, quantities of clfA transcripts in the unattached bacteria of the exudates never exceeded the level of clfA transcripts in the sessile bacteria attached to glass beads. However, a clear increase in clfA quantities in the sessile bacteria was observed late in infection after 144 h. In conclusion, maximal clfA transcript levels are reached late during growth in vitro and in vivo.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.70.6.2758-2762.2002
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2002
    detail.hit.zdb_id: 1483247-1
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  • 6
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    Staphylococcus aureus CcpA Affects Biofilm Formation
    American Society for Microbiology ; 2008
    In:  Infection and Immunity Vol. 76, No. 5 ( 2008-05), p. 2044-2050
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 76, No. 5 ( 2008-05), p. 2044-2050
    Abstract: Biofilm formation in Staphylococcus aureus under in vitro growth conditions is generally promoted by high concentrations of sugar and/or salts. The addition of glucose to routinely used complex growth media triggered biofilm formation in S. aureus strain SA113. Deletion of ccpA , coding for the catabolite control protein A (CcpA), which regulates gene expression in response to the carbon source, abolished the capacity of SA113 to form a biofilm under static and flow conditions, while still allowing primary attachment to polystyrene surfaces. This suggested that CcpA mainly affects biofilm accumulation and intercellular aggregation. trans -Complementation of the mutant with the wild-type ccpA allele fully restored the biofilm formation. The biofilm produced by SA113 was susceptible to sodium metaperiodate, DNase I, and proteinase K treatment, indicating the presence of polysaccharide intercellular adhesin (PIA), protein factors, and extracellular DNA (eDNA). The investigation of several factors which were reported to influence biofilm formation in S. aureus ( arlRS , mgrA , rbf , sarA , atl , ica , citZ , citB , and cidABC ) showed that CcpA up-regulated the transcription of cidA , which was recently shown to contribute to eDNA production. Moreover, we showed that CcpA increased icaA expression and PIA production, presumably over the down-regulation of the tricarboxylic acid cycle genes citB and citZ .
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00035-08
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2008
    detail.hit.zdb_id: 1483247-1
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  • 7
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    CodY in Staphylococcus aureus : a Regulatory Link between Metabolism and Virulence Gene Expression
    American Society for Microbiology ; 2009
    In:  Journal of Bacteriology Vol. 191, No. 9 ( 2009-05), p. 2953-2963
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 191, No. 9 ( 2009-05), p. 2953-2963
    Abstract: The repressor CodY is reported to inhibit metabolic genes mainly involved in nitrogen metabolism. We analyzed codY mutants from three unrelated Staphylococcus aureus strains (Newman, UAMS-1, and RN1HG). The mutants grew more slowly than their parent strains in a chemically defined medium. However, only codY mutants were able to grow in medium lacking threonine. An excess of isoleucine resulted in growth inhibition in the wild type but not in the codY mutants, indicating that isoleucine plays a role in CodY-dependent repression. Prototypic CodY-repressed genes including the virulence regulator agr are repressed after up-shift with isoleucine. The CodY-dependent repression of agr is consistent with the concomitant influence of CodY on typical agr -regulated genes such as cap , spa , fnbA , and coa . However, some of these virulence genes (e.g., cap , fnbA , and spa ) were also regulated by CodY in an agr- negative background. Microarray analysis revealed that the large majority of CodY-repressed genes were involved in amino acid metabolism; CodY-activated genes were mainly involved in nucleotide metabolism or virulence. In summary, CodY in S. aureus not only acts as a repressor for genes involved in nitrogen metabolism but also contributes to virulence gene regulation by supporting as well as substituting for agr function.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.01492-08
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2009
    detail.hit.zdb_id: 1481988-0
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  • 8
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    Online Resource
    σ B and the σ B -Dependent arlRS and yabJ-spoVG Loci Affect Capsule Formation in Staphylococcus aureus
    American Society for Microbiology ; 2007
    In:  Infection and Immunity Vol. 75, No. 9 ( 2007-09), p. 4562-4571
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 75, No. 9 ( 2007-09), p. 4562-4571
    Abstract: The alternative transcription factor σ B of Staphylococcus aureus affects the transcription of the cap gene cluster, required for the synthesis of capsular polysaccharide (CP), although this operon is lacking an apparent σ B -dependent promoter. Regulation of cap expression and CP production in S. aureus strain Newman was shown here to be influenced by σ B , the two-component signal transduction regulatory system ArlRS, and the yabJ-spoVG locus to different extents. Inactivation of arlR or deletion of the sigB operon strongly suppressed capA (CP synthesis enzyme A) transcription. Deletion of spoVG had a polar effect on yabJ-spoVG transcription and resulted in a two- to threefold decrease in capA transcription. Interestingly, immunofluorescence showed that CP production was strongly impaired in all three mutants, signaling that the yabJ-spoVG inactivation, despite its only partial effect on capA transcription, abolished capsule formation. trans -Complementation of the Δ spoVG mutant with yabJ-spoVG under the control of its native promoter restored CP-5 production and capA expression to levels seen in the wild type. Northern analyses revealed a strong impact of σ B on arlRS and yabJ-spoVG transcription. We hypothesize that ArlR and products of the yabJ-spoVG locus may serve as effectors that modulate σ B control over σ B -dependent genes lacking an apparent σ B promoter.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00392-07
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2007
    detail.hit.zdb_id: 1483247-1
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  • 9
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    Online Resource
    Molecular Architecture of the Regulatory Locus sae of Staphylococcus aureus and Its Impact on Expression of Virulence Factors
    American Society for Microbiology ; 2003
    In:  Journal of Bacteriology Vol. 185, No. 21 ( 2003-11), p. 6278-6286
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 185, No. 21 ( 2003-11), p. 6278-6286
    Abstract: We characterized the sae operon, a global regulator for virulence gene expression in Staphylococcus aureus . A Tn 917 sae mutant was obtained by screening a Tn 917 library of the agr mutant ISP479Mu for clones with altered hemolytic activity. Sequence analysis of the sae operon revealed two additional open reading frames (ORFs) (ORF3 and ORF4) upstream of the two-component regulatory genes saeR and saeS . Four overlapping sae -specific transcripts (T1 to T4) were detected by Northern blot analysis, and the transcriptional initiation points were mapped by primer extension analysis. The T1, T2, and T3 mRNAs are probably terminated at the same stem-loop sequence downstream of saeS . The T1 message (3.1 kb) initiates upstream of ORF4, T2 (2.4 kb) initiates upstream of ORF3, and T3 (2.0 kb) initiates in front of saeR . T4 (0.7 kb) represents a monocistronic mRNA encompassing ORF4 only. sae -specific transcripts were detectable in all of the 40 different clinical S. aureus isolates investigated. Transcript levels were at maximum during the post-exponential growth phase. The sae mutant showed a significantly reduced rate of invasion of human endothelial cells, consistent with diminished transcription and expression of fnbA . The expression of type 5 capsular polysaccharide is activated in the sae mutant of strain Newman, as shown by immunofluorescence and promoter-reporter fusion experiments. In summary, the sae operon constitutes a four-component regulator system which acts on virulence gene expression in S. aureus .
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.185.21.6278-6286.2003
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2003
    detail.hit.zdb_id: 1481988-0
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  • 10
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    Staphylococcus aureus CcpA Affects Virulence Determinant Production and Antibiotic Resistance
    American Society for Microbiology ; 2006
    In:  Antimicrobial Agents and Chemotherapy Vol. 50, No. 4 ( 2006-04), p. 1183-1194
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 50, No. 4 ( 2006-04), p. 1183-1194
    Abstract: Carbon catabolite protein A (CcpA) is known to function as a major regulator of gene expression in different gram-positive organisms. Deletion of the ccpA homologue ( saCOL1786 ) in Staphylococcus aureus was found to affect growth, glucose metabolization, and transcription of selected virulence determinants. In liquid culture, deletion of CcpA decreased the growth rate and yield; however, the effect was only transient during the exponential-growth phase as long as glucose was present in the medium. Depletion of glucose and production of lactate was delayed, while the level of excretion of acetate was less affected and was even higher in the mutant culture. On solid medium, in contrast, growth of the Δ ccpA mutant resulted in smaller colonies containing a lower number of CFU per colony. Deletion of CcpA had an effect on the expression of important virulence factors of S. aureus by down-regulating RNAIII , the effector molecule of the agr locus, and altering the transcription patterns of hla , encoding α-hemolysin, and spa , encoding protein A. CcpA inactivation markedly reduced the oxacillin resistance levels in the highly methicillin-resistant S. aureus strain COLn and the teicoplanin resistance level in a glycopeptide-intermediate-resistant S. aureus strain. The presence of CcpA in the capsular polysaccharide serotype 5 (CP5)-producing strain Newman abolished capsule formation and decreased cap operon transcription in the presence of glucose. The staphylococcal CcpA thus not only is involved in the regulation of carbon metabolism but seems to function as a modulator of virulence gene expression as well.
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.50.4.1183-1194.2006
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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