PERSISTENCE IN BOVINE MASTITIS OF STAPHYLOCOCCUS-AUREUS CLONES AS ASSESSED BY RANDOM AMPLIFIED POLYMORPHIC DNA ANALYSIS, RIBOTYPING AND BIOTYPING

Staphylococcus aureus isolates (N = 40) from bovine mastitis were char acterized by random amplified polymorphic DNA-PCR (RAPD-PCR), ribotypi ng and biotyping. The isolates were collected in the veterinary survei llance area of the Ambulatory Clinic, Faculty of Veterinary Medicine, University of Helsinki from 20 quarters during the acute phase of infe ction and from the same quarters 3 weeks after cessation of therapy. T he aim of the study was to compare the S. aureus isolates taken from t he same quarter at different times to verify persistence of virulent s trains in infected quarters and to compare the discriminatory power of the diagnostic methods. Using all methods (except for a commercial di agnostic test), the paired isolates of S. aureus were identical. Resul ts suggest that the chronic nature of S. aureus infections was due to the persistence of the original infective strain. More laborious ribot yping and the more convenient RAPD-PCR method produced identical resul ts. The molecular methods differentiated the 40 isolates into 6 distin ct genotypes. Biotyping produced partially identical results to RAPD a nd ribotyping. A commercial diagnostic test system identified only 3 S . aureus biotypes. (C) 1997 Elsevier Science B.V.