Untersuchungen zur Virulenz- und Resistenz-Genexpression in Biofilm-bildendenden und persistierenden Staphylokokken zur Entwicklung eines diagnostischen Mikroarrays

BMBF PTJ-BIO/0313134 im Rahmen der BMBF-Fördermaßnahme "Kompetenznetz Genomforschung an pathogenen Bakterien – PathoGenoMik
G. Peters, K. Becker, C. von Eiff
Past studies have addressed the problem of staphylococcal antibiotic resistance from the standpoint of classic forms of resistance, e.g. altered penicillin-binding proteins and enzymatic degradation. However, Staphylococcus aureus as well as coagulase-negative staphylococci (CoNS) may have additional mechanisms for resisting therapy that extend beyond these classical mechanisms. In patients infected with susceptible microorganisms, some demonstrate poor clinical and bacteriologic response to antimicrobial regimens. Both, biofilm formation on surfaces of medical devices in foreign body associated infections as well as the formation of small colony variants (SCVs) in various species of staphylococci have been associated with chronic, recurrent and/or antibiotic refractory infections often designated as phenotypic resistance. Furthermore, the ability of staphylococci to adapt to different conditions is complicated by difficulties to detect, to identify and to differentiate the staphylococcal species and their variants. Thus, the versatility of staphylococci pose a challenge to develop more sophisticated approaches for diagnosis and susceptibility testing. The main goals of our project are:
  1. to develop and evaluate quality-controlled sequence databases of the genus Staphylococcus and related taxa to overcome the drawbacks of the currently available databases such as the presence of faulty and/or redundant sequence entries, ragged sequence ends, outdated nomenclature, and unavailable quality assurance;
  2. to analyze the global gene expression in SCVs of S. aureus and of Staphylococcus epidermidis versus their normal phenotypes using clinical isolates, laboratory-generated SCVs (induced/selected by gentamicin), and genetically defined mutants mimicking the SCV phenotype (mutants with defects in electron transport)
  3. to develop and evaluate new methods (e.g. FTIR spectroscopy) for susceptibilty testing of fastidious and/or intracelluar phenotypic variants of S. aureus and CoNS;
  4. to compare sessile staphylococcal cells (isolated from foreign-body infections) versus planctonic cells of SCVs and of
  5. strains with normal phenotype in particular applying different stress and starvation conditions;
  6. to detect and characterize new virulence factors with special regard to toxins in S. aureus and non-S. aureus coagulase-positive/-variable staphylococcal species;
  7. to compare the results of different “-omic” approaches, i.e. transcriptomics, proteomics (in collaboration with the group of Hecker/Engelmann), and metabolomics (phenotypic microarrays).

Staphylococcal phenotypes: Normal and small colony variant (SCV) phenotype