One hundred and fifty-nine cases of clinical Staphylococcus aureus mastitis
were analyzed to detect factors associated with bacteriological cure after
therapy. On 100 Dutch dairy farms, data were collected from four clinical
trials with five intramammary treatment regimes designed to treat beta-lact
amase-positive pathogens. Infected quarters were treated three times, with
a 12-h interval between treatments. Treatment was extended for 2 d if resul
ts of the trial treatment were, according to the owner, not satisfactory. T
he overall bacteriological cure rate was 52%. The bacteriological cure rate
of clinical beta-lactamase-negative S. aureus mastitis was significantly h
igher than that of clinical P-lactamase-positive S. aureus mastitis. Bacter
iological cure was also significantly higher if somatic cell count of the c
ow was low at the milk recording prior to the onset of the clinical mastiti
s. The bacteriological cure rate of clinical beta-lactamase-negative S. aur
eus mastitis was also significantly higher after an extended treatment comp
ared with no extended treatment. The seriousness of the various clinical sy
mptoms and the bacteriological cure rate of clinical S. aureus mastitis wer
e not associated.