الفهرس 
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Abstract
Methicillin-Resistant Staphylococcus aureus (MRSA) is one of the most important causes of hospital acquired infections all over the world. A new mecA homologue (mecC), was first reported in the United Kingdom and Denmark. The mecC mediated MRSA is resistant only to Β-lactams antibiotics and is sensitive to various classes of antibiotics. So, detection of the prevalence of mecC MRSA is important to provide more options in the treatment of MRSA infections.
This study aimed to detect the prevalence of mecC gene in clinical isolates of MRSA in Ain-Shams University Hospitals and to correlate MIC of Oxacillin with the mecC gene expression in MRSA isolates. Fifty MRSA isolates were recovered from different clinical samples collected from intensive care units of Ain-Shams University Hospitals from April 2018 to December 2018. Methicillin resistance was detected by Cefoxitin disc (30μg) and antimicrobial susceptibility testing was done for all isolates and the results were interpreted according to CLSI 2018. Minimal Inhibitory concentration of Oxacillin were determined using Oxacillin E-test and the results were interpreted according to manufacturer’s instructions, then Polymerase Chain Reaction was done to detect mecA and mecC genes among MRSA isolates.
Fifty isolates were identified as MRSA by Cefoxitin disc out of 163 samples. Twenty-five (50%) were isolated from males and twenty-five (50%) were isolated from females. Their age ranged
from 18 to 75. The most of MRSA were isolated from blood samples 25 isolates (50%) while least were isolated from pus 7 isolates (14%) and other isolates were from sputum and wound 9 isolates (18%) for each. The results of antimicrobial susceptibility of MRSA revealed that the highest sensitivity values 34 isolates (68%) were found with Trimethoprim/ sulfamethoxazole (SXT), linezolid (LZD) and Chloramphenicol (C) agents while lower sensitivity 33 isolates (66%) was found with Rifampin (RA) followed by levofloxacin (LEV) 31 isolates (62%). Sensitivity values dropped to 19 isolates (38%) with clindamycin (DA) agent followed by Deoxycycline (DO) and Ciprofloxacin (CIP) with sensitivity in 18 isolates (36%) of the cases. Highest resistance pattern was to Erythromycin (E) 27 isolates (54%) and 48 isolates (96%) were resistant to Penicillin (P). All isolates (100%) were positive to mecA gene while only 3 isolates (6%) were positive to both mecA and mecC genes, where 2 (66.7%) of them were resistant to Oxacillin E-test and 1 (33.3%) was sensitive, while 47 MRSA isolates were mecC negative 11(23.4%) were sensitive to Oxacillin E-test and 36 (76.6) were resistant to Oxacillin.