title: Enterotoxin production, enterotoxin gene distribution, and genetic diversity of Staphylococcus aureus recovered from milk of cows with subclinical mastitis.
abstract: OBJECTIVE
  To evaluate enterotoxin production, enterotoxin gene distribution, and genetic diversity of Staphylococcus aureus in milk obtained from cows with subclinical mastitis.
  
  
  METHODS
  Milk samples obtained from 350 cows (1,354 mammary glands) on 11 Wisconsin dairy farms.
  
  
  METHODS
  Of 252 S aureus isolates obtained from 146 cows, 83 isolates (from 66 cows with subclinical mastitis) were compared genotypically by use of pulsed-field gel electrophoresis and via PCR identification of toxic shock syndrome toxin 1 (TSST-1) and classical S aureus enterotoxin genes (sea, seb, sec, sed, and see).
  
  
  RESULTS
  Among the 83 S aureus isolates, ≥ 1 enterotoxin genes were identified in 8 (9.6%). Enterotoxin gene distribution was as follows: TSST-1, 7 isolates (8.4%); sec, 5 isolates (6.0%); and sed, 2 isolates (2.4%). Enterotoxin genes sea, seb, and see were not identified. Twelve pulsotypes and 5 subtypes were identified among the 83 isolates; 5 of the 12 pulsotypes were represented by only 1 isolate. In cows of 1 herd, only a single S aureus pulsotype was detected; in cows on most other farms, a variety of pulsotypes were identified. One pulsotype was recovered from 4 farms (n = 23 cows) and another from 5 other farms (16). Isolates with an enterotoxin gene were represented by 6 pulsotypes.
  
  
  CONCLUSIONS
  S aureus classical enterotoxins and TSST-1 were rarely recovered from milk samples obtained from cows with subclinical mastitis in Wisconsin. Diverse pulsotypes of S aureus were detected within and among farms, indicating that different strains of S aureus cause subclinical mastitis in dairy cows.
authors.affiliation: Department of Dairy Science, College of Agriculture and Life Sciences, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: Leane
authors.initials: L
authors.lastname: Oliveira
authors.forename: Ana C
authors.initials: AC
authors.lastname: Rodrigues
authors.forename: Carol
authors.initials: C
authors.lastname: Hulland
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Ruegg
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics*; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D004768:Enterotoxins / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D008413:Mastitis / Q000382:microbiology / Q000662:veterinary*; D008892:Milk / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D013045:Species Specificity; D013211:Staphylococcus aureus / Q000235:genetics* / Q000378:metabolism; D018089:Superantigens / Q000235:genetics*; D014922:Wisconsin
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D018089:Superantigens; C030107:enterotoxin F, Staphylococcal