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


Katayoun Borhani 1 , Fereshteh Eftekhar 1 , * , Somayeh Danesh Monfared 1

1 Department of Microbiology, Faculty of Biological Science, Shahid Beheshti University, G.C., Tehran, IR Iran

How to Cite: Borhani K, Eftekhar F, Danesh Monfared S. ?-Lactamase Typing by Substrate Hydrolysis in Clinical Isolates of Methicillin Resistant Staphylococcus Aureus, Arch Clin Infect Dis. Online ahead of Print ; 4(4):202-6.


Archives of Clinical Infectious Diseases: 4 (4); 202-6
Article Type: Research Article


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

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