Vol. 7(16), pp. 1598-1604, 16 April, 2013 DOI: 10.5897/AJMR12.2333 ISSN 1996-0808 ©2013 Academic Journals http://www.academicjournals.org/AJMR African Journal of Microbiology Research Full Length Research Paper Detection of high levels of methicillin and multi-drug resistance among clinical isolates of Staphylococcus aureus Iman Moneer El Karamany 1 , Yasser Musa Ibrahim 1,2 *, Ahmed Megahed Abouwarda 3 , Tamer Mohammed Essam 4 , and Magdy Ali Amin 4 1 Department of Microbiology, General Division of Basic Medical Sciences, National Organization for Drug Control and Research (NODCAR), Giza, Egypt. 2 Department of Pharmaceutics, College of Pharmacy, King Khalid University, Abha, Kingdom of Saudi Arabia. 3 Biology Department, Faculty of Science and Arts-Khulais, King Abdulaziz University, Kingdom of Saudi Arabia. 4 Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, Egypt. Accepted 29 March, 2013 Methicillin-resistant Staphylococcus aureus (MRSA) has become a frequent cause of serious infections worldwide. We identified clinical isolates of S. aureus using conventional methods based on morphological and biochemical characteristics. Resistance of isolates to oxacillin was tested by growth on Oxacillin Resistance Screening Agar Base (ORSAB) and disc diffusion method. Oxacillin MICs were determined by agar dilution method. Sensitivity of isolates to a range of antibiotics was also tested by disc diffusion method. We further confirmed methicillin resistance using a PCR-based molecular approach. Data revealed that among 120 clinical bacterial samples tested 81 were confirmed as S. aureus. Out of these 81 isolates, 72 were MRSA (88.9%). The distribution of resistance among MRSA isolates was alarming. Twenty (20) MRSA isolates (27.8%) showed the highest level of resistance detected in this study with oxacillin MIC >6400 μg/ml. Most isolates were also resistant to multiple antibiotics. PCR results revealed the detection of mecA gene responsible for resistance in all tested isolates and therefore confirmed the conventional identification of MRSA isolates. The present study provides additional evidence that the rate of emergence of MRSA is in a continuous increase. Key words: Staphylococcus aureus, MRSA, mecA gene, methicillin resistance, multi-drug resistance. INTRODUCTION Methicillin-resistant Staphylococcus aureus (MRSA) is a Gram-positive bacterium that has developed antibiotic resistance to all penicillins and has become a major health problem since it was first identified (Barrett et al., 1968). Emergence of new MRSA strains as public health threat has also recently been reported (Grundmann et al., 2006; Yamamoto et al., 2010). This bacterium can cause nosocomial and community-acquired infections ranging from minor skin infections to serious life-threatening diseases such as bacteraemia and invasive endocarditis (Chambers, 2001; Enright et al., 2002; Wisplinghoff et al., 2004). Methicillin was the first penicillinase-resistant penicillin to be used in the treatment of S. aureus infections. It was recognized as the most reliable agent for routine sus- ceptibility testing and hence resistant strains were termed methicillin-resistant S. aureus (MRSA). Methicillin was then replaced by oxacillin and the term oxacillin- resistant S. *Corresponding author. E-mail: yasser_musa@yahoo.com. Tel: +966545084590.