Abstract
During the period from November1988to May1989, causative bacteria in a total of172 clinical mastitis cases observed in 66 farms in5districts with6areas in Japan were examined and frequencies of their occurrences were determined.
Susceptibilities (in MICs) of the isolates to 6β-lactam antibacterial agents were also determined.
As a result, coagulase-negative staphylococci (CNS) was identified in94out of172cases (54.7%) and were the most prevalent.Corynebacterium spp., Gram-negative bacteria and Staphylococcus aureus were found in52 (30.2%), 49 (28.5%) and43 (25.0%) cases, respectively.Four species of Streptococcus family (S.agalactiae, S.dysgalactiae, S.uberis and S.bovis) were identified in a total of58cases (33.7%).
Susceptibility testing of CNS to cefoperazone (CPZ), cefazolin (CEZ), benzylpenicillin (PCG), ampicillin (ABPC), methicillin (DMPPC) and cloxacillin (MCIPC) showed that all MIC80's (inhibiting bacterial growth of80%of all isolates) were within a range from0.10to3.13μg/ml and that there was no marked difference in antibacterial effects among the antibiotics used.The highest antibacterial effect on S.aureus was exhibited by MCIPC, which inhibited the growth of all isolates at0.39μg/ml.The MICs of DMPPC against all isolates of S.aureus were3.13μg/ml or less and no methicillin-resistant S.aureus (MRSA) was detected.
There was no difference in antibacterial activities against Streptococccus family between penicillin antibiotics (DMPPC, MCIPC, ABPC and PCG) and cephem antibiotics (CPZ and CEZ), both of which showed excellent antibacterial activities.
Cephem antibiotics exhibited higher activities against Gram-negaive bacteria than penicillin antibiotics.Especially CPZ, the third generation cephem, showed excellent antibacterial activity against Escherichia coli, Klebsiella spp., Enterobacter spp., as well as against other Enterobacteriaceae.
