GENOTYPING BY PCR, OF STAPHYLOCOCCUS-AUREUS STRAINS, ISOLATED FROM MAMMARY-GLANDS OF COWS

A total of 71 Staphylococcus aureus strains isolated from bovine mamma ry glands were identified and subtyped. The methods used to differenti ate between the S. aureus isolates were the DNA polymorphism pattern a fter amplification with a Polymerase Chain reaction using several prim er combinations and phage typing. The DNA fingerprinting technique usi ng RAPD, ERIC1R and ERIC primers proved to be useful in differentiatin g isolates of S. aureus. Differentiation of isolates using phage typin g gave no additional information compared to the DNA technique. The ou tbreak of S. aureus in the herd studied was mainly caused by one S. au reus strain. Other strains were only found on three occasions, twice i n subclinical infections and once from a case of clinical mastitis. In the latter case the dominant strain was isolated from a different qua rter of the same cow. Four of the ten cows studied suffered from clini cal mastitis. From those four cows, three remained infected with the s ame S. aureus strain despite antibiotic treatment.