Some investigations on chronic mastitis in dairy cattle in Kyungnam Province during the year 1982 were conducted with the special reference to the causative agents and their drug resistance. Milk samples from 46 isolated cases of chronic mastitis cattle were investigated bacteriologically and the organisms recovered were examined for their drug susceptibility against the major antibiotics used in this country by the rose of disk diffusion susceptibility test.
Four major causative agents involved in chronic mastitis were in order of prevalence Staphylococcus aureus (32.6%), Escherichia coli (28.3%), Streptoccus agalactiae (8.7%) and Candida albicans (8.7%). Staph. Epidermidis, Streptococcus uberis, Klebsiella pneumoniae and Candida subtropicalis were found to be one of the minor agents.
The majority of staphylococcal isolated were highly resistant to the most of antibiotics employed while 8% of them were resistant to gentdmicin and 32% to chloramphenicol. The percentages of stoaphylococcal cultures resistant to penicillin, lincomycin. streptomycin, methicillin, oleandomrcin, tetracycline, cephalothin, ampicillin and erythromycin were 100%, 96%, 96%, 92%, 84%, 84%, 80%, 76%, and 64% respectively.
Streptococcal isolates were also highly resistant to the majority of the drugs used although 85.7% of them were susceptible to gentamicin.
All Escherichia coli isolates were found to be resistant to erythromycin, lincomycin and penicillin while the majority of them were resistant to ampicillin (92.9%), carbenicillin (85.7%), oleandomycin (85.7%), streptomycin(85.7%), kanamycin (78.6%), methicillin (78.6%) and tetracycline (71.4%). The percentages of E. coli cultures resistant to gentamicin, nitrofurantoin, cephalothin and chloramphenicol were 21.4%, 21.4%, 35.7% and 50.0% respectively.
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