Plasmid exchange between different strains of bacteria of the same species or different strains of different species is a recognized source for the rapid spread of antimicrobial resistance. In this study, 89 human isolates of Escherichia coli from five major geopolitical zones of Nigeriawere isolated and tested against 14 antibiotics by the disk diffusion method. Resistance plasmids were extracted and separated by agarose gel electrophoresis for profiling. In all, 42 different antibiotics resistance pattern was observed, with all the isolates showing resistance to at least four or more drugs tested. Plasmid profiling revealed that the isolates contained various size of R-plasmids. A total of 146 plasmids were detected with molecular sizes ranging from 1 to 120 KB. Of all the plasmids detected, the 120 KB plasmid occurred most frequently in all the geopolitical zones. Although some strains exhibited different antibiotic resistance patterns, some of their plasmids had similar migration patterns on agarose gel electrophoresis. Multiple resistances were conferred by R-plasmids of different sizes. The high prevalence of antibiotic resistance conferring plasmids observed in this study may be due to the increasing widespread use of antibiotics.
Key words: Plasmid profile, Escherichia coli, antibiotic resistance, Nigeria
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