الفهرس 
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Abstract
This thesis aimed to study the antibiotic resistance profile of S. aureus isolated from clinical and environmental sources and to correlate the phenotypic resistance of S. aureus isolates against erythromycin and vancomycin with the presence of genes ermA, ermB, ermC, mef, msrA,vanA and vanB.
In this study 167 S. aureus were isolated from clinical and environmental sources. These clinical and environmental samples were collected from four different hospitals in Cairo, Egypt (El Boos Student hospital, El Amal hospital, Ain Shams university hospitals and Ain shams specialized hospital). 117 clinical S. aureus isolates were collected from nasal swab, sputum, urine,pus discharge,eye swab, blood culture, throat swab and wound swab. also 50 S. aureus isolates were recovered from hospital surrounding samples including Air in ICU, Air from patients room, air from waiting rooms of clinics, and air samples from laboratory.
from antibiotic susceptibility test, it was found that all of S. aureus isolates were resistant to both Amoxicillin, Amoxicillin/Clavulanate, while 93% of isolates were resistant to Cefepime and Ceftriaxone, where 90% of isolates were resistant to Clindamycin and Imipinem, 88 % were resistant to Gentamicin, 87% of S. aureus isolates were resistant to cefoxitin and Erythromycin. 86% of isolates were resistant to Oxytetracycline and Vancomycin,83% were resistant to Ciprofloxacin.
The 145 S. aureus isolates which showed resistance to erythromycin and vancomycin were selected for the study of MIC values against Ciprofloxacin, erythromycin, gentamicin and vancomycin. Results revealed that MIC value of 7.6% of S. aureus isolates against erythromycin was 512 µg/ml, MIC value of 5.5% of isolates against vancomycin was 512 µg/ml, MIC value of 12% of isolates against gentamycin was ≥256 µg/ml, MIC value of 4% of isolates against ciprofloxacin was ≥256 µg/ml.
PCR was used to detect presence of macrolide resistance genes (ermA, ermB, ermC, mef and msrA) and vancomycin resistance genes (vanA and vanB) in 145 resistant S. aureus isolates. Results of PCR revealed that presence of macrolide resistance genes among resistant S. aureus isolates was msrA (70%), ermC (67%), mef (66%), ermB (65%) and ermA (44.5%). 40% of resistant S. aureus isolates carried vanA gene and 55% of isolates harbored vanB gene.
In this study msrA and mef genes were prevalent among clinical S. aureus isolates (70% and 66% respectively) obtained from Egyptian hospitals. This is the first report for prevalence of both msrA and mef genes in Egyptian S. aureus isolates.
Representative PCR products of S. aureus isolate Sa9 for msrA and vanB genes were sequenced. The sequences of msrA and vanB genes were submitted to the Genbank under accession numbers OK480878 and OK624111 respectively.