title: Genotypic and Phenotypic Characterization of Methicillin-Resistant Staphylococcus aureus Isolated from Bovine Mastitic Milk in Korea.
abstract: Staphylococcus aureus is a major etiological pathogen for bovine mastitis, foodborne illness, and various clinical infections. Methicillin-resistant S. aureus (MRSA) has been isolated from bovine mastitic milk, and the presence of MRSA in milk is a major public health concern. We investigated the frequency of MRSA isolation from mastitic raw milk in Korea and characterized the patterns of antimicrobial resistance, virulence, and genotypes of the MRSA isolates. A total of 1,222 raw milk samples were collected from 47 dairy farms in Gyeonggi province from 2011 to 2012. Of these samples, 649 were considered mastitic milk based on somatic cell counts of more than 200,000 cells per ml, and 165 S. aureus isolates (from 25.4% of samples) were obtained from these samples. Of these isolates, 23 (13.9%) collected from five farms were confirmed as MRSA by detection of the mecA gene. Disk diffusion and MIC tests for antibiotic resistance revealed that all MRSA isolates were resistant to four or more antimicrobial agents. All MRSA isolates had staphylococcal enterotoxin genes, and two clusters of these genes were identified: seg-sei-sek-sem-sen-seo (20 isolates, 87%) and sed-seg-sei-sej-sem-sen-seo (3 isolates, 13%). Each MRSA-positive farm had only one spa-SCCmec type. Nine MRSA isolates (39.1%) with the t324-IVa genotype, which is related to community-acquired MRSA infection, were isolated from three dairy farms. Additional genotypes of t148-IVa and t002-II were detected and related to human MRSA strains. Most MRSA isolates had distinct pulsed-field gel electrophoresis subtypes, indicating they were not the same clones. Only two isolates collected from the same farm during different years had an identical electrophoresis type, indicating persistence of the clone at this farm. Taken together, these findings may indicate an increased virulence and risk of MRSA strains on dairy farms. Therefore, an efficient surveillance and control program is needed to prevent the transmission of MRSA from animals to humans.
authors.affiliation: Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Jae Won
authors.initials: JW
authors.lastname: Song
authors.affiliation: Department of Animal Science and Technology, College of Biotechnology and Natural Resource, Chung-Ang University, Anseong 456-756, Gyeonggi-do, Republic of Korea.
authors.forename: Soo Jin
authors.initials: SJ
authors.lastname: Yang
authors.affiliation: Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Sook
authors.initials: S
authors.lastname: Shin
authors.affiliation: Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39762, USA.
authors.forename: Keun Seok
authors.initials: KS
authors.lastname: Seo
authors.affiliation: Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Yong Ho
authors.initials: YH
authors.lastname: Park
authors.affiliation: Department of Veterinary Microbiology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Kun Taek
authors.initials: KT
authors.lastname: Park
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents; D002417:Cattle; D005260:Female; D006801:Humans; D008414:Mastitis, Bovine; D008712:Methicillin; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D008892:Milk / Q000382:microbiology*; D056910:Republic of Korea; D013203:Staphylococcal Infections / Q000662:veterinary; D013211:Staphylococcus aureus / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D008712:Methicillin
keywords: Antimicrobial resistance; Bovine mastitic milk; Methicillin-resistant Staphylococcus aureus