STUDY THE EFFECTS OF ETHIDIUM BROMIDE, SDSAND ELEVATED TEMPERATURE ON STABILITY OFMULTIPLE ANTIBIOTIC RESISTANCES PLASMIDS OFPseudomonas aeruginosa

Three clinical isolates of Pseudomonas aeruginosa were isolated and identified from wound, burns and ear infections. They had multiple resistance to Chloramphenicol, Erythromycin, Lincomycin, Tetracycline, Trimethoprime, Amikacin, Neomycin, Rifampicin, Streptomycin, Pencillins and Cefalosporins antibiotics. All isolates produced pyocyanin and two of them produced extracellular proteases. The plasmid profile of the isolates appeared the presence two small plasmid and single mega-plasmid bands on agarose gel electrophoresis. Spontaneous curing experiment showed all plasmids are stable within bacterial cells. The isolates appeared partial elimination of multiple antibiotic resistances after treated with 700μg/ml ethidium bromide or 1% SDS that indicates they harbor more than one small plasmid had the same molecular size. While elevated temperature (46ºC) is more efficient to cure all plasmids than chemical agents ,therefore the isolates became sensitive to all tested antibiotic except lincomycin. All the curing experiments appeared no effect on lincomycin resistance gene and protease encoding genes or cured them from bacteria that indicates these genes may be located on bacterial chromosomal DNA.