title: Analysis of the matrix-assisted laser desorption ionization-time of flight mass spectrum of Staphylococcus aureus identifies mutations that allow differentiation of the main clonal lineages.
abstract: Nosocomial infections involving epidemic methicillin-resistant Staphylococcus aureus (MRSA) strains are a serious problem in many countries. In order to analyze outbreaks, the infectious isolates have to be typed; however, most molecular methods are expensive or labor-intensive. Here, we evaluated matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) of cell extracts for the molecular characterization of S. aureus strains. The peak patterns of 401 MRSA and methicillin-susceptible S. aureus (MSSA) strains, including clinical and laboratory strains, were analyzed. Database searches indicated the peptides that were represented by the corresponding peaks in the spectra. The identities of the peptides were confirmed by the sequencing of mutants, the expression of antisense RNA fragments that resulted in the knockdown of the peptide of interest and the concomitant loss of the signal, or tandem MALDI-TOF MS (MALDI-TOF/TOF MS). It was shown that the signals derive mainly from stress proteins and ribosomal proteins. Peak shifts that differentiate the main S. aureus clonal complexes CC5, CC22, CC8, CC45, CC30, and CC1 correlate to point mutations in the respective genes. Retrospective typing of an MRSA outbreak showed that it is possible to differentiate unrelated MSSA, MRSA, and borderline resistant S. aureus (BORSA) strains isolated from health care workers. In conclusion, this method allows for the detection of the epidemic lineages of S. aureus during species identification by MALDI-TOF MS analysis.
authors.affiliation: University of Bonn, Institute of Medical Microbiology, Immunology, and Parasitology, Bonn, Germany.
authors.forename: Michaele
authors.initials: M
authors.lastname: Josten
authors.forename: Marion
authors.initials: M
authors.lastname: Reif
authors.forename: Christiane
authors.initials: C
authors.lastname: Szekat
authors.forename: Nahed
authors.initials: N
authors.lastname: Al-Sabti
authors.forename: Terry
authors.initials: T
authors.lastname: Roemer
authors.forename: Katrin
authors.initials: K
authors.lastname: Sparbier
authors.forename: Markus
authors.initials: M
authors.lastname: Kostrzewa
authors.forename: Holger
authors.initials: H
authors.lastname: Rohde
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Sahl
authors.forename: Gabriele
authors.initials: G
authors.lastname: Bierbaum
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis*; D015373:Bacterial Typing Techniques / Q000379:methods*; D006801:Humans; D050505:Mutant Proteins / Q000032:analysis; D009154:Mutation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013211:Staphylococcus aureus / Q000737:chemistry* / Q000145:classification* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D050505:Mutant Proteins
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