title: Genotypic and phenotypic analysis of clinical isolates of Staphylococcus aureus revealed production patterns and hemolytic potentials unlinked to gene profiles and source.
abstract: BACKGROUND
  Nosocomial infections caused by the bacterial pathogen Staphylococcus aureus can lead to serious complications due to the varying presence of secreted toxins. Comparative studies of genomic information and production rates are needed to assess the pathogenic potential of isolated strains. Genotypic and phenotypic profiling of clinical and colonising isolates of S. aureus was used to characterise the release of exotoxins. Blood isolates were compared with colonisation strains to determine similarities and differences of single strains and clusters.
  
  
  RESULTS
  Fifty-one fresh isolates obtained from colonised individuals (n = 29) and S. aureus bacteremia (SAB) patients (n = 22) were investigated. The prevalence of genes encoding for three cytolysins (alpha/beta/gamma toxin) and twenty-four superantigens (SEA-SElX) was determined. Isolates exhibited eighteen distinct combinations of superantigens. Sequence analysis identified mutated open reading frames in hla in 13.7% of all strains, in selw (92.2%) and in selx (15.7%). All corrupted genes were associated with specific clonal complexes. Functional assessment of alpha toxin activity by a rabbit erythrocyte lysis assay revealed that supernatants lacking alpha toxin still displayed hemolysis. This was due to the presence of gamma toxin, as proven by inhibition experiments using antisera raised against the respective recombinant proteins. Alpha toxin, SEC, and TSST1 production was quantified by enzyme-linked immunosorbent assays on supernatants of all hla, sec, and tst positive isolates. Blood isolates and colonising strains showed comparable amounts of secreted proteins within a wide range. Agr types I to IV were identified, but did not allow a prediction of high or low production rates. In contrast, alpha toxin production rates between distinct clonal complexes clearly differed. Spa typing was performed and revealed thirty-two unique spa gene patterns and eight small clusters comprising nineteen isolates. Recognised spa-typing clusters displayed highly similar production rates.
  
  
  CONCLUSIONS
  Production rates of the three most prevalent exotoxins varied within both groups of blood isolates and colonising strains. By comparing genotypes and secretion, we found that identical complex gene patterns did not allow predictions of toxin production and function. However, identification of spa typing clusters was suitable to predict similar quantities of released exotoxins.
authors.affiliation: Biomedizinische ForschungsgmbH, Lazarettgasse 19/2, Vienna, A-1090, Austria. andreas.roetzer@biomed-research.at.
authors.forename: Andreas
authors.initials: A
authors.lastname: Roetzer
authors.affiliation: Biomedizinische ForschungsgmbH, Lazarettgasse 19/2, Vienna, A-1090, Austria. guenter.haller@biomed-research.at.
authors.forename: Guenter
authors.initials: G
authors.lastname: Haller
authors.affiliation: Biomedizinische ForschungsgmbH, Lazarettgasse 19/2, Vienna, A-1090, Austria. jbeyerly@gmx.at.
authors.forename: John
authors.initials: J
authors.lastname: Beyerly
authors.affiliation: Immunology Outpatient Clinic, Schwarzspanierstraße 15, Vienna, A-1090, Austria. christoph.geier@itk.at.
authors.forename: Christoph B
authors.initials: CB
authors.lastname: Geier
authors.affiliation: Immunology Outpatient Clinic, Schwarzspanierstraße 15, Vienna, A-1090, Austria. hermann.wolf@itk.at.
authors.forename: Hermann M
authors.initials: HM
authors.lastname: Wolf
authors.affiliation: Biomedizinische ForschungsgmbH, Lazarettgasse 19/2, Vienna, A-1090, Austria. corina.gr@gmx.at.
authors.forename: Corina S
authors.initials: CS
authors.lastname: Gruener
authors.affiliation: Biomedizinische ForschungsgmbH, Lazarettgasse 19/2, Vienna, A-1090, Austria. nina.model@biomed-research.at.
authors.forename: Nina
authors.initials: N
authors.lastname: Model
authors.affiliation: Biomedizinische ForschungsgmbH, Lazarettgasse 19/2, Vienna, A-1090, Austria. office@biomed-research.at.|Immunology Outpatient Clinic, Schwarzspanierstraße 15, Vienna, A-1090, Austria. office@biomed-research.at.
authors.forename: Martha M
authors.initials: MM
authors.lastname: Eibl
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001427:Bacterial Toxins / Q000378:metabolism* / Q000633:toxicity; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects; D005838:Genotype; D053878:Hemolytic Agents / Q000378:metabolism* / Q000633:toxicity; D006801:Humans; D010641:Phenotype; D011817:Rabbits; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D053878:Hemolytic Agents
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