beta-lactamase typing by substrate hydrolysis in clinical isolates of methicillin resistant Staphylococcus aureus

ABSTRACT

Staphylococcus aureus is one of the most important causes of nosocomial infections and most clinical isolates are multidrug resistant. Resistance to beta-lactam antibiotics is most often due to bacterial beta-lactamase production. Characterization of beta-lactamases is important for choosing appropriate antibiotic therapy. Thirty methicillin resistant Staphylococcus aureus [MRSA] were identified by standard biochemical methods. Antibacterial susceptibility to 9 beta-lactam antibiotics was determined. Beta-lactamase production was shown in all isolates using the colony iodometric test and nitrocefin discs. Beta-lactamase typing was carried out by measuring the relative substrate hydrolysis rates. The MRSA isolates were resistant to the majority of beta-lactam antibiotics. The results showed that 90% of the isolates displayed type A substrate hydrolysis profile of beta-lactamase. The alarming high level of resistance to beta-lactam antibiotics including methicillin and 3[rd] generation beta-lactams show the need for extensive studies on alternative treatment protocols and use of new drugs