Matthias A Horstkotte

University Medical Center Hamburg - Eppendorf, Hamburg, Hamburg, Germany

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Publications (44)154.2 Total impact

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    ABSTRACT: We report the exceptional case of a severe intraocular Abiotrophia defectiva infection which developed after cataract surgery. Retinal involvement as a complication of A. defectiva endophthalmitis or the combination of acute-onset endophthalmitis with infiltrative keratitis caused by this pathogen has not been described. Moreover, our report represents the first documented ocular A. defectiva infection in Germany. A. defectiva was identified using biotyping and 16S ribosomal RNA gene sequence analysis. Despite vigorous antimicrobial therapy and repeated ocular surgery, visual outcome was poor.
    European Journal of Clinical Microbiology 06/2010; 29(6):727-31. DOI:10.1007/s10096-010-0901-7 · 2.54 Impact Factor
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    ABSTRACT: Biofilm formation is a major pathogenetic factor of Staphylococcus epidermidis. In S. epidermidis the alternative sigma factor sigma B was identified to regulate biofilm formation in S. epidermidis 1457. In S. aureus sigma B dependent regulation plays a minor role, whereas sarA (Staphylococcus accessory regulator) is an essential regulator. Therefore, we investigated the impact of sigma B on sarA transcription and biofilm formation in three independent S. epidermidis isolates. Mutants with dysfunctional sigma B displayed a strongly reduced biofilm formation, whereas in mutants with constitutive sigma B activity biofilm formation was increased. Transcriptional analysis revealed that icaA transcription was down-regulated in all sigma B negative mutants while icaR transcription was up-regulated. However, transcriptional differences varied between individual strains, indicating that additional sigma B-dependent regulators are involved in biofilm expression. Interestingly, despite the presence of a sigma B promoter beside two sigma A promoters no differences, or only minor ones, were observed in sarA transcription, indicating that sigma B-dependent sarA transcript has no influence on the phenotypic changes. The data observed in independent clinical S. epidermidis isolates suggests that, in contrast to S. aureus, regulation of biofilm formation by sigma B is a general feature in S. epidermidis. Additionally, we were able to demonstrate that the sarA- dependent regulation is not involved in this regulatory pathway.
    The International journal of artificial organs 09/2009; 32(9):584-91. · 1.45 Impact Factor
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    ABSTRACT: Staphylococcus epidermidis is a common pathogen in device-associated infections which is able to attach onto polymeric surfaces and develop multilayered biofilms. Attached S. epidermidis displays reduced susceptibility to antimicrobial agents. In this study we investigated the influence of ciprofloxacin and the group IV quinolones gatifloxacin, gemifloxacin, and moxifloxacin with the minimal attachment killing (MAK) assay. MAK concentrations were determined for three biofilm-positive wild-type strains and their isogenic biofilm-negative mutants Depending on strain and investigated quinolone, it was possible to distinguish between a heterogeneous MAK (MAKhetero), and a homogeneous resistance (MAKhomo) which corresponds to the model of a few persisting cells under antibiotic treatment. A lower MAKhomo was detected for the biofilm-negative mutants as well as for the corresponding wild-types for some of the tested quinolones, which seems to be a result of higher bacterial inocula, whereas the MAKhetero concentrations were comparable for mutants and wild-types for nearly all of the tested antibiotics and strains. These data indicate that biofilm formation is not necessary for persistence of attached S. epidermidis cells under treatment with quinolones and could explain therapeutic failure in foreign body-associated infections due to biofilm-negative S. epidermidis isolates. The individual resistance phenotypes of investigated strains indicate that the determination of MAK concentrations might help to predict the therapy outcome of foreign body-associated infections with both biofilm-positive and biofilm-negative S. epidermidis. Thus, the relatively high activity displayed by group IV quinolones against individual attached staphylococcal isolates indicates a possible treatment option with the respective quinolones for foreign body-associated infections due to these isolates.
    The International journal of artificial organs 10/2008; 31(9):752-60. · 1.45 Impact Factor
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    ABSTRACT: In this paper, we describe the phenotypic and molecular characteristics of two clinically relevant, vancomycin-resistant (VanB), linezolid-resistant Enterococcus faecium isolates. Pyrosequencing showed the G to T single nucleotide polymorphism at bp 2576 in the genes coding for 23S rRNA and was used to quantify the proportion of G to T mutations among six different 23S rRNA genes in E. faecium as a marker for the molecular level of resistance to linezolid. In both isolates, the G to T mutation was found in two of six alleles, and no further mutations in the genes coding for 23S rRNA were found. The dynamic process of linezolid resistance could be demonstrated by the complete reversion of resistant alleles back to only wild type alleles in consecutive isolates of one isolate. Pyrosequencing being used to detect and quantify resistance to linezolid has been proven as a fast and reliable molecular screening method for monitoring linezolid resistance.
    European Journal of Clinical Microbiology 05/2008; 27(9):873-8. DOI:10.1007/s10096-008-0514-6 · 2.54 Impact Factor
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    ABSTRACT: Tight Junction (TJ) proteins have been shown to exert a barrier function within the skin. Here, we study the fate of TJ proteins during the challenge of the skin by bacterial colonization and infection. We investigated the influence of various exfoliative toxin-negative Staphylococcus strains on TJ, adherens junction (AJ), desmosomal proteins, and actin in a human keratinocyte infection culture and in a porcine skin infection model. We found that the pathogen Staphylococcus aureus downregulates TJ and subsequently AJ and desmosomal proteins, including atypical protein kinase C, an essential player in TJ formation, at the cell-cell borders of keratinocytes in a time and concentration dependent manner. Little changes in protein and RNA levels were seen, indicating redistribution of proteins. In cultured keratinocytes, a reduction of transepithelial resistance was observed. Staphylococcus epidermidis shows only minor effects. All strains induced enhanced expression of occludin and ZO-1 at the beginning of colonization/infection. Thus, we demonstrate that TJ are likely to be involved in skin infection of exfoliative toxin-negative S. aureus. As we did not find a change in actin, and as changes of TJ preceded alterations of AJs and desmosomes, we suggest that S. aureus targets TJ.
    Journal of Investigative Dermatology 05/2008; 128(4):906-16. DOI:10.1038/sj.jid.5701070 · 6.37 Impact Factor
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    ABSTRACT: Der 51-jährige, männliche Patient wird nach einer Synkope unklarer Genese in der Klinik aufgenommen. Er berichtet über seit etwa 14 Tagen bestehende Beschwerden in Form von allgemeiner körperlicher Abgeschlagenheit, Fieber und Kälteschauern. Er deutet dies am ehesten als Zeichen eines grippalen Infekts. Weitere Beschwerden werden nicht angegeben. Anamnestisch werden weder Auslandsaufenthalte noch Kontakt zu Haustieren angegeben. Des Weiteren gibt es keinen Anhalt für Nikotin-, Alkohol- oder Drogenabusus. Bei dem Patienten sind seit mehreren Jahren ein arterieller Hypertonus sowie eine Hyperlipoproteinämie bekannt, die zum Zeitpunkt der Aufnahme mit einem β-Blocker, einem ACE-Inhibitor, einem Thiazid-Diuretikum und einem HMG-CoA-Reduktase-Inhibitor behandelt werden. Sechs Monate vor Aufnahme war aufgrund einer Aortendissektion vom Typ Stanford A eine Aoarta-ascendens-Prothese implantiert worden.
    04/2008: pages 9-13;
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    ABSTRACT: Eine 34 Jahre alte Patientin wird mit starken Schmerzen im Bereich der rechten Hüfte in der Klinik aufgenommen. Diese rühren von einem Sturz in der häuslichen Umgebung her und waren zunächst nur unter Belastung aufgetreten, schließlich jedoch auch in Ruhe. Bei der Patientin ist seit 1989 eine chronische Polyarthritis bekannt, die 1990 die Implantation einer Hüftendoprothese rechts erforderte. Des Weiteren leidet sie unter einer Psoriasis, und es besteht der Verdacht auf einen unkontrollierten Morphingebrauch. Zum Zeitpunkt der Aufnahme wird die Patientin u.a. mit Decortin H behandelt.
    04/2008: pages 79-82;
  • International Journal of Colorectal Disease 03/2008; 23(2):225-6. DOI:10.1007/s00384-007-0328-5 · 2.42 Impact Factor
  • Infection 03/2008; 36(1):85-7. DOI:10.1007/s15010-007-7220-7 · 2.86 Impact Factor
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    ABSTRACT: Although Nystatin has been used since 1950s as a non-absorbable antifungal agent, there is still no reliable in-vivo data available stating a dose-effect relationship of Nystatin-suspension in the treatment of oropharyngeal infection with Candida albicans. Here, we studied the efficacy of a commercially available topical Nystatin suspension in a new ex-vivo model of candidiasis using porcine oral mucosa. After 48 and 96 h of C. albicans infection, 230 IU Nystatin (standard dosage), 100 IU and 20 IU proved to be equally efficacious. Multiple applications of Nystatin were not superior compared with single application. In dosages of 10 and 0.1 IU the activity of Nystatin suspension against C. albicans was no longer confirmed. In an agar diffusion model, the minimal biocidal concentration of Nystatin proved to be 0.25 IU. Our results suggest that the proposed porcine ex-vivo model is much closer to the in-vivo situation compared with other established in-vitro models of the treatment of muco-cutaneous candidiasis and may provide a substitute for animal models in the investigation of antifungal agents. Additionally, it seems to be a valuable tool for further investigations of the pathogenesis of C. albicans infections.
    Mycoses 01/2008; 51(1):21-9. DOI:10.1111/j.1439-0507.2007.01445.x · 1.81 Impact Factor
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    ABSTRACT: Reporter gene systems are an invaluable tool for investigation of gene transcription activity in eukaryotes and prokaryotes. In order to analyze the temporal and spatial resolution of gene expression patterns in situ and for quantitatively investigating gene expression, the green fluorescent protein (GFP) appears to be especially useful. GFP has been broadly used in various bacterial species, however, there is only limited knowledge about key biological properties in S. epidermidis. Here, the crucial influence of different ribosomal binding sites (RBS) on gfpmut3.1 translation initiation in S. epidermidis 1457 is demonstrated. Only by using the RBS of the delta-hemolysin promoter, after 24 hours a strong fluorescence signal was obtained. The half-life of GFPmut3.1 in S. epidermidis 1457 was significantly shorter than in E. coli (7 h vs. 24 h). GFPmut3.1 derivatives with shorter half-lives (GFP(AAV) and GFP(ASV)) did not reach sufficient quantitative protein levels, and the resulting low fluorescence limits their use as reporter genes in S. epidermidis. This work provides fundamental insights into gfpmut3.1 expression in S. epidermidis and describes the crucial determinants of its biological behavior in this species. In general, this study underlines the need to accurately characterize key biological properties of this transcription marker in gram-positive hosts.
    Journal of Microbiological Methods 12/2007; 71(2):123-32. DOI:10.1016/j.mimet.2007.08.015 · 2.10 Impact Factor
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    ABSTRACT: Nosocomial staphylococcal foreign-body infections related to biofilm formation are a serious threat, demanding new therapeutic and preventive strategies. As the use of biofilm-associated factors as vaccines is critically restricted by their prevalence in natural staphylococcal populations we studied the distribution of genes involved in biofilm formation, the biofilm phenotype and production of polysaccharide intercellular adhesin (PIA) in clonally independent Staphylococcus aureus and Staphylococcus epidermidis strains isolated from prosthetic joint infections after total hip or total knee arthroplasty. Biofilm formation was detected in all S. aureus and 69.2% of S. epidermidis strains. Importantly, 27% of biofilm-positive S. epidermidis produced PIA-independent biofilms, in part mediated by the accumulation associated protein (Aap). Protein-dependent biofilms were exclusively found in S. epidermidis strains from total hip arthroplasty (THA). In S. aureus PIA and proteins act cooperatively in biofilm formation regardless of the infection site. PIA and protein factors like Aap are of differential importance for the pathogenesis of S. epidermidis in prosthetic joint infections (PJI) after THA and total knee arthroplasty (TKA), implicating that icaADBC cannot serve as a general virulence marker in this species. In S. aureus biofilm formation proteins are of overall importance and future work should focus on the identification of functionally active molecules.
    Biomaterials 04/2007; 28(9):1711-20. DOI:10.1016/j.biomaterials.2006.11.046 · 8.31 Impact Factor
  • International Journal of Antimicrobial Agents 03/2007; 29. DOI:10.1016/S0924-8579(07)70627-1 · 4.26 Impact Factor
  • International Journal of Antimicrobial Agents 03/2007; 29. DOI:10.1016/S0924-8579(07)70626-X · 4.26 Impact Factor
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    ABSTRACT: Medical device-associated infections, most frequently caused by coagulase-negative staphylococci, especially Staphylococcus epidermidis, are of increasing importance in modern medicine. The formation of adherent, multilayered bacterial biofilms is the most important factor in the pathogenesis of these infections, which regularly fail to respond to appropriate antimicrobial therapy. Progress in elucidating the factors functional in elaboration of S. epidermidis biofilms and the regulation of their expression with a special emphasis on the role of quorum sensing are reviewed. Significant progress has been made in recent years, which provides the rationale for developing better preventive, therapeutic and diagnostic measures.
    Analytical and Bioanalytical Chemistry 02/2007; 387(2):399-408. DOI:10.1007/s00216-006-0745-2 · 3.58 Impact Factor
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    ABSTRACT: Medical device-associated infections, most frequently caused by coagulase-negative staphylococci, especially Staphylococcus epidermidis, are of increasing importance in modern medicine. Regularly, antimicrobial therapy fails without removal of the implanted device. The most important factor in the pathogenesis of medical device-associated staphylococcal infections is the formation of adherent, multilayered bacterial biofilms. There is urgent need for an increased understanding of the functional factors involved in biofilm formation, the regulation of their expression, and the interaction of those potential virulence factors in device related infection with the host. Significant progress has been made in recent years which may ultimately lead to new rational approaches for better preventive, therapeutic, and diagnostic measures.
    The International journal of artificial organs 05/2006; 29(4):343-59. · 1.45 Impact Factor
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    ABSTRACT: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) after base-specific cleavage of PCR-amplified and in vitro-transcribed bla(SHV) genes was used for the identification and genotyping of SHV beta-lactamases. For evaluation, bla(SHV) stretches of 21 clinical Enterobacteriaceae isolates were PCR amplified using T7 promoter-tagged forward and reverse primers, respectively. In vitro transcripts were generated with T7 RNA and DNA polymerase in the presence of modified analogues replacing either CTP or UTP. Using RNase A, the in vitro transcripts were base-specifically cleaved at every "T" or "C" position. Resulting cleavage products were analyzed by MALDI-TOF MS, generating a characteristic signal pattern based on the fragment masses. All 21 individual SHV genes were identified unambiguously using reference sequences, and the results were in perfect concordance with those obtained by fluorescent dideoxy sequencing, which represents the current standard method. As multiple point mutations can be detected in a single assay and newly emerged mutations which are not yet described in public databases can be identified too, MALDI-TOF MS appears to be an ideal tool for analysis of sequence polymorphisms in resistance-associated gene loci.
    Journal of Clinical Microbiology 04/2006; 44(3):909-15. DOI:10.1128/JCM.44.3.909-915.2006 · 4.23 Impact Factor
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    ABSTRACT: To evaluate the role of the polysaccharide intercellular adhesin as an energy-storage molecule, we investigated the effect of nutrient limitation on S. epidermidis biofilms. The stability of established biofilms depends on sigma(B) activity; however, the slow decay of biofilms under conditions of nutrient limitation reveal its use as an energy-storage molecule to be unlikely.
    Applied and Environmental Microbiology 10/2005; 71(9):5577-81. DOI:10.1128/AEM.71.9.5577-5581.2005 · 3.95 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate phenotypic detection of beta-lactamase-mediated resistance to oxyimino-cephalosporins in Enterobacteriaceae using the Mastascan Elite Expert System challenged with a battery of genotypically characterized organisms. Isolates (n = 120) were identified to species level and antimicrobial susceptibilities were determined using agar incorporation methods and Mastascan Elite. Phenotypes were examined using an Expert System (ES) and putative genotypes were suggested using interpretative reading. Identification was correct in 119 of 120 isolates. The ES was able to identify the correct beta-lactam phenotype (as deduced from molecular methods) in a single choice in 98 of 120 (81.7%) isolates. In an additional 15 (12.5%) cases, the ES identified the correct beta-lactam phenotype within two or more choices. The detected phenotype was incorrect in seven (5.8%) isolates, but three of these were not inherent to the ES. The Mastascan Elite ES is relatively inexpensive and flexible and can identify the mechanism of resistance to oxyimino-cephalosporins in the majority of Enterobacteriaceae without recourse to molecular methods.
    Journal of Antimicrobial Chemotherapy 09/2005; 56(2):292-6. DOI:10.1093/jac/dki203 · 5.44 Impact Factor
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    ABSTRACT: A lack of sigma(B) activity reduces methicillin resistance in heterogeneous Staphylococcus epidermidis 1057, whereas inactivation of the anti-sigma factor RsbW switched the phenotype to homogeneous expression of resistance. Oxacillin induction of mecA transcription is reduced in a sigma(B)-negative strain. However, mecA is not involved in the switch of expression phenotype.
    Antimicrobial Agents and Chemotherapy 04/2005; 49(3):1216-9. DOI:10.1128/AAC.49.3.1216-1219.2005 · 4.45 Impact Factor

Publication Stats

1k Citations
154.20 Total Impact Points


  • 2001–2010
    • University Medical Center Hamburg - Eppendorf
      • Department of Medical Microbiology, Virology and Hygiene
      Hamburg, Hamburg, Germany
  • 2009
    • Charité Universitätsmedizin Berlin
      Berlín, Berlin, Germany
  • 2008
    • Universität zu Lübeck
      Lübeck Hansestadt, Schleswig-Holstein, Germany
  • 2007–2008
    • Bioscientia - Institut für Medizinische Diagnostik GmbH
      Frankfurt, Hesse, Germany
  • 2004
    • Swansea University
      • Institute of Life Science "ILS"
      Swansea, Wales, United Kingdom