الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Antimicrobial resistance in E. coli has been reported worldwide. Pathogen occurrence and susceptibility profiles, however, show substantial geographic variations as well as significant differences in various populations and environments. The emerging resistance to FQs and aminoglycosides by multidrug resistant E. coli strains has caused increasing concern over the last decade due to the limited therapeutic options if infections with these strains occur. Thus, high antibiotic use in the community might have a substantial impact on the development of resistance in bacterial pathogens.
Very recently, a novel plasmid-mediated FQ-resistant determinant, QepA (quinolone efflux protein), was first identified in an E. coli clinically isolated from Japan and later found also in an E. coli isolated in Belgium.
Recently, several 16S rRNA methylases armA and rmt genes have been identified in clinical isolates of Gram-negative bacteria. These enzymes conferred very high-level resistance to most clinically important aminoglycosides, including amikacin and kanamycin.
In a previous study, qepA and rmtB were found to be encoded on the same transferable plasmid in E. coli suggesting the emergence of new molecular mechanism responsible for high-level pan-aminoglycosides resistance as well as quinolone resistance among Gram-negative pathogens that may spread worldwide and thus poses a major public health concern.
Therefore, the present work is focusing on studying the co-resistance to FQs and aminoglycosides involving the determination of the prevalence of plasmid-mediated quinolone resistance qepA and 16S rRNA methylase rmtB among E. coli clinical isolates, evaluating the contribution of efflux pump activity in the development of this phenotypic resistance and checking the potential presence of antagonism between both groups that could represent a selective pressure for the development of this combined resistance.
Two hundred and twenty five non duplicate E. coli isolates collected from patients admitted to 2 medical facilities (Medical Research Institute, Alexandria University and Alexandria Main University) over a period of one year (November 2008 to October 2009) were identified by conventional methods. The isolates were initially tested for their antibiotic sensitivity against quinolones (nalidixic acid, levofloxacin, norfloxacin and ciprofloxacin) and aminolgycosides (amikacin, neomycin, tobramycin and gentamicin) by disc diffusion method on Mueller Hinton agar. In addition to these antibiotics, the test was also performed against ceftriaxone, imipenem, tetracycline, trimethoprim-sulphamethoxazol and chloramphenicol. Isolates with concomitant resistance to quinolones and amnioglycosides were suspended in LB broth with 25% glycerol and stored at -20°C till further analysis and screening of qepA and rmtB genes.