title: Comparison of Virulence Gene Identification, Ribosomal Spacer PCR, and Pulsed-Field Gel Electrophoresis for Typing of Staphylococcus aureus Strains Isolated from Cases of Subclinical Bovine Mastitis in the United States.
abstract: Staphylococcus aureus is one of the most important pathogens causing contagious mastitis in dairy cattle worldwide. The objectives of this study were to determine if recently described S. aureus genotype B was present among previously characterized isolates from cases of bovine intramammary infection in the United States and to compare pulsed-field gel electrophoresis (PFGE) to the combination of ribosomal spacer PCR (RS-PCR) and virulence gene identification for typing of S. aureus strains. The hypothesis was that isolates that were previously characterized as contagious would be identified as genotype B and that the results of the two strain-typing methods would be comparable. Isolates were selected from a collection of S. aureus isolates from eight dairy farms. Mammary quarter milk somatic cell count (SCC) and N-acetyl-β-d-gluconaminidase (NAGase) activity data were known and used to evaluate strain pathogenicity. RS-PCR was performed with conventional gel electrophoresis, and PCR was used for toxin gene identification. RS-PCR patterns were associated with a specific virulence gene pattern, as previously reported. Five RS-PCR banding patterns were identified. None of the isolates were characterized as genotype B. No association between RS-PCR types and milk SCC was found; however, NAGase activity was significantly higher in milk from mammary glands infected with RS-PCR banding type 1 (RSP type 1) than in milk from those infected with RSP type 2. The discriminatory power values were 1.0 and 0.46 for PFGE and RS-PCR, respectively. These data suggest that genotype B may have a limited geographic distribution and that PFGE is more discriminatory than RS-PCR performed with conventional gel electrophoresis for typing of S. aureus isolates of bovine origin.
authors.affiliation: Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, Missouri, USA adkinsp@missouri.edu.
authors.forename: Pamela R F
authors.initials: PRF
authors.lastname: Adkins
authors.affiliation: Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, Missouri, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Middleton
authors.affiliation: Department of Veterinary Clinical Sciences, Washington State University, Pullman, Washington, USA.
authors.forename: Lawrence K
authors.initials: LK
authors.lastname: Fox
mesh_terms: D000818:Animals; D058345:Asymptomatic Infections; D002417:Cattle; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods; D005260:Female; D005838:Genotype; D008414:Mastitis, Bovine / Q000382:microbiology* / Q000473:pathology; D058889:Molecular Typing / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods; D013203:Staphylococcal Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D014481:United States; D014774:Virulence; D037521:Virulence Factors / Q000032:analysis / Q000235:genetics
chemical_list: D037521:Virulence Factors