Abstract

Forty-five Staphylococci spp comprising 33 (73.3%) Staphylococcus aureus and 12 (26.7%) Staphylococcus epidermidis isolated from both non-surgical and post-surgical septic wounds were evaluated for penicillinase activity. Thirty (90.9%) of the S. aureusisolates produced beta-lactamases. Beta-lactamase production accounted for the high level resistance (70-90%) to the penicillins. Five (16.7%) of the penicillinase-producing S. aureus (PPSA) were resistant to methicillin, while 25 (83.3%) PPSA were sensitive. Resistance to the cephalosporins by the PPSA was between 7 and 30% indicating that the beta-lactamase produced was mostly penicillinase. Ciprofloxacin, vancomycin and rifampicin were the most active of the antibiotics against methicillin-resistant S. aureus(MRSA) with activity of between 90 and 100%. They also gave low minimum inhibitory concentration (MIC) values (0.125-8 µg/ml for ciprofloxacin, 0.125-2 µg/ml for vancomycin and 2-32 µg/ml for rifampicin). Methicillin activity of 83.3% was comparable with those of erythromycin, ofloxacin and pefloxacin (range 73.3-86.7%). Azithromycin activity against the PPSA was 90%. S. aureus is the specie of Staphylococci most frequently isolated from septic wound and have shown high rate of resistance to beta-lactam antibiotics which could be attributed to their production of beta–lactamase enzyme especially, penicillinase.

Key words: Antibiotic, susceptibility patterns, penicillinase activity, Staphylococci.