title: spa typing method for discriminating among Staphylococcus aureus isolates: implications for use of a single marker to detect genetic micro- and macrovariation.
abstract: Strain typing of microbial pathogens has two major aims: (i). to index genetic microvariation for use in outbreak investigations and (ii). to index genetic macrovariation for use in phylogenetic and population-based analyses. Until now, there has been no clear indication that one genetic marker can efficiently be used for both purposes. Previously, we had shown that DNA sequence analysis of the protein A gene variable repeat region (spa typing) provides a rapid and accurate method to discriminate Staphylococcus aureus outbreak isolates from those deemed epidemiologically unrelated. Here, using the hypothesis that the genetic macrovariation within a low-level recombinogenic species would accurately be characterized by a single-locus marker, we tested whether spa typing could congruently index the extensive genetic variation detected by a whole-genome DNA microarray in a collection of 36 isolates, which was recovered from 10 countries on four continents over a period of four decades, that is representative of the breadth of diversity within S. aureus. Using spa and coa typing, pulsed-field gel electrophoresis (PFGE), and microarray and multilocus enzyme electrophoresis (MLEE) data in molecular epidemiologic and evolutionary analyses, we determined that S. aureus likely has a primarily clonal population structure and that spa typing can singly index genetic variation with 88% direct concordance with the microarray and can correctly assign isolates to phylogenetic lineages. spa typing performed better than MLEE, PFGE, and coa typing in discriminatory power and in the degree of agreement with the microarray at various phylogenetic depths. This study showed that genetic analysis of the repeat region of protein A comprehensively characterizes both micro- and macrovariation in the primarily clonal population structure of S. aureus.
authors.affiliation: Public Health Research Institute, International Center for Public Health, Graduate School of Biomedical Sciences and New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA.
authors.forename: Larry
authors.initials: L
authors.lastname: Koreen
authors.forename: Srinivas V
authors.initials: SV
authors.lastname: Ramaswamy
authors.forename: Edward A
authors.initials: EA
authors.lastname: Graviss
authors.forename: Steven
authors.initials: S
authors.lastname: Naidich
authors.forename: James M
authors.initials: JM
authors.lastname: Musser
authors.forename: Barry N
authors.initials: BN
authors.lastname: Kreiswirth
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics*; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005819:Genetic Markers; D014644:Genetic Variation; D005838:Genotype; D005843:Geography; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000942:Antigens, Bacterial; D017931:DNA Primers; D004269:DNA, Bacterial; D005819:Genetic Markers; C119204:streptococcal protective antigen