Microbiological studies on beta-lactamase activity in staphylococcus aureus

ABSTRACT

The study of susceptibility of 92 Gram - positive bacteria to some antibiotics revealed that 27.2%, 96.0%, 13%, 100%, 7.6%, 31.5% and 17.4% of the total 92 isolates were resistant to methicillin, penicillin, tetracycillin, amoxicillin, chloramphenicol, cephradin and streptomycin respectively and only six isolates had high level of MIC ranging from 1500 to 7000 micro g/ml amoxicillin and had ability to produce beta -lactamase activity but they differ in their activities. Therefore cultural, morphological and physiological characteristic of these isolates were studied and these results indicated that they belong to Staphylococcus aureus. One isolate showed the highest level of resistance [MIC] and this isolate produced highest beta -lactamase activity. beta -lactamase activity can be affected by subminimal inhibitory concentration of some antibiotics, the maximal inhibitory effect was induced by concentration ranging from 1/2 to 1/32 of the minimal inhibitory concentration of streptomycin, clindamycin and chloramphenicol