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SEARCH FOR DRUG AND METAL RESISTANCE PLASMIDS FROM INDIGENOUS CLINICAL PSEUDOMONADS

SHEIKH AJAZ RASOOL, ASIM AWAN AND BILAL AHMED

Abstract: On the bases of morphology, cultural and biochemical characteristics, 50 indigenous clinical pseudomonads were identified as Pseudomonas aeruginosa. Resistance patterns of antibiotics upto 500 µg mL^-1 and inorganic metallic ions upto 3 mg m^-1 were determined by medium incorporation method. Five of the isolates lost their resistance to erythromycin after curing for plasmid elimination with 5 mg mL^-1 of acridine orange, thereby indicating the extrachromosomal location of the resistance determinants. Agarose gel electrophoresis using 'Mini prep' method for plasmid isolation revealed that six isolates harbour plasmids of different molecular weights (5-28 kb) with Hind III digest of λ DNA as ladder. Some of the pseudomonad isolates were able to transfer their resistance to Escherichia coli BU 40 by in vivo gene transfer plasmid conjugation.

Department of Microbiology, University of Karachi, Karachi-75270, Pakistan.