家畜 및 原乳에서 分離한 satphylococcus aureus의 β-lactamase 産生과 藥劑 感受性

Antimicrobial Susceptibilities and β-lactamase production of staphylococcus aureus isolated from bulk milk and domestic animals

The present study was carried out for the purpose of investigating the β-lactamase production and drug resistance of Staphylococcus aureus isolated from bulk milk and domestic animals. Frequency of β-lactamase producing strains was 94.4% of bulk milk isolates, 35.4% of chicken isolates, 26.9% of cattle isolates and 5.9% of pig isolates in 280 S. aureus isolates. The 90% MIC of kanamycin was more than 100㎍/ml but was 6.29㎍/ml to methicillin and 1.56㎍/ml to oxacillin. Most of 280 isolates were sensitive to cephalexin, methicillin and oxacillin but 23.9%-55.4% of the strains were resistant to kanamycin, ampicillin and penicillin. The β-lactamase nonproducers were more sensitive than producers to penicillin and ampicillin on the basis of MICs in arithmetic mean, but there were no differences in sensitivity of these groups to cephalexin, methicillin, oxacillin and kanamycin. The most frequently encountered drug resistant patterns were AmPc in double patterns and AmKmPc in triple patterns. The 87.1% of β-lactamase producing strains were ampicillin resistant but no β-lactamase nonproducing strains were resistant. The resistant rates of β-lactamase producers generally were higher than those of β-lactamase nonproducers to all antibiotics. Most of β-lactamase producing strains harborred plasmids of 25kb or 48kb. The 48kb plasmid was suspected as the penicillin-resistant plasmid after plasmid curing experiment.