Penicillin Resistance in Staphylococcus aureus and β-Lactamase Activity

OBJECTIVE To study penicillin resistance in Staphylococcus aureus and the activity of β-lactamase.METHODS The strains of S.aureus both sensitive and resistant to penicillin were inoculated into the media with penicillin and then incubated in 37 ℃.The number of the bacteria and the activities of β-lactamase,were determined respectively at varying times.RESULTS In the media with 64 μg/ml penicillin,the number of the sensitive strain decreased gradually in 24 h of culturing.The number of the resistant strains decreased at first 6 h and then the number increased in subsequent 24 h.The activity of penicillin did not be changed in the media with the sensitive strain.The activitiy of penicillin was decreased obviously with the resistant stains.In the media without penicillin,the β-lactamase activities of the resistant stains were stable until 24 h of culturing,while the β-lactamase activities were increased gradually in the media with penicillin.CONCLUSIONS The growth of early stage of S.aureus can be inhibited obviously by penicillin.β-Lactamase would be induced largely in resistant S.aureus.