Sixty-three Staphylococcus aureus isolates recovered
from bovine sources in the USA and the
Republic of Ireland were characterized by multilocus enzyme electrophoresis
(MLEE),
ribotyping, and random amplified polymorphic DNA polymerase chain reaction
(RAPD–PCR)
typing at two separate laboratories. The S. aureus isolates were
assigned by MLEE to 10
electrophoretic types (ETs) (Index of Discrimination, D=0·779).
In contrast, the same isolates
were assigned to 13 ribotypes (D=0·888), and to 12 RAPD
types
(D=0·898). A common
clone, ET3, of worldwide distribution, was represented by six distinct
combinations of
ribotypes and RAPD types. S. aureus clones recovered from cows
in
Ireland were also associated with mastitis in dairy cows in the USA. These
findings are consistent with the
hypothesis that only a few specialized clones of S. aureus are
responsible for the majority of
cases of bovine mastitis, and that these clones have a broad geographic
distribution.