title: Analysis of genomic diversity within the Xr-region of the protein A gene in clinical isolates of Staphylococcus aureus.
abstract: Protein A of Staphylococcus aureus contains a polymorphic Xr-region characterized by a tandem repeat of eight amino acid units. In this study, the diversity of genes encoding the repeat regions and their relatedness among S. aureus strains was analyzed. Ten different protein-A types characterized by repeat numbers 4-13 were identified in a total of 293 clinical isolates. The protein-A type with 10 repeat units (10 repeats) in the Xr-region was most frequently detected in methicillin-resistant S. aureus, whereas the majority of methicillin-susceptible strains were distributed almost evenly into protein-A types with 7-11 repeats. Strains that belonged to a single coagulase type were classified into multiple protein-A types, e.g. strains with the common coagulase types II and VII were differentiated into 7 and 8 protein-A types, respectively. Nucleotide sequence analysis of the Xr-region of 42 representative strains revealed the presence of 37 different genotypes (spa types), which were constituted by a combination of several of 24 different repeat unit genotypes. Based on the similarity in arrangement of repeat unit genotypes, 34 strains with different repeat numbers were classified into 5 genetic clusters (C1-C5). The clusters C1, C2 and C3 consisted exclusively of strains with identical coagulase types II, III, and IV, respectively. These findings suggested that the protein-A gene of S. aureus has evolved from a common ancestral clone in individual clusters independently.
authors.affiliation: Department of Hygiene, Sapporo Medical University School of Medicine, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Urasawa
authors.forename: N
authors.initials: N
authors.lastname: Uehara
authors.forename: N
authors.initials: N
authors.lastname: Watanabe
mesh_terms: D000595:Amino Acid Sequence; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D003030:Coagulase / Q000235:genetics; D005798:Genes, Bacterial; D014644:Genetic Variation; D006801:Humans; D008712:Methicillin / Q000494:pharmacology; D016106:Methicillin Resistance; D010406:Penicillins / Q000494:pharmacology; D016133:Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000382:microbiology*; D013205:Staphylococcal Protein A / Q000737:chemistry / Q000235:genetics*; D013211:Staphylococcus aureus / Q000145:classification* / Q000187:drug effects / Q000235:genetics*
chemical_list: D003030:Coagulase; D010406:Penicillins; D013205:Staphylococcal Protein A; D008712:Methicillin