?-Lactamase Typing by Substrate Hydrolysis in Clinical Isolates of Methicillin Resistant Staphylococcus Aureus

Abstract

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