Accepted 2nd July, 2014
Localization of antimicrobial resistance genes on mobile genetic elements such as broad-host range plasmids, transposons, and integrons facilitates the horizontal transfer of these genes among bacteria and provides a rapid means of dissemination at the molecular level. In this study, transfer of resistance plasmids from human antibiotics resistance Escherichia coli isolates to laboratory strain was carried out using conjugation experiments. Plasmid-free rifampicin-resistant recipient (gene-hog DH10B) was used in all matings in order to have a selectable marker for selection against the donor. Resistance plasmids were extracted and separated by agarose gel electrophoresis for profiling. The conjugation efficiency of the isolates ranges from 1.0 x 10-6- 7.5 x 10-7 in isolates from south-west region; 1.1 x 10-6- 9.2 x 10-7 in isolates from south-south region; 1.0 x 10-6- 8.2 x 10-7 in isolates from north-north region and 1.1 x 10-6- 7.9 x 10-7 in isolates from south-east region of Nigeria. A total of 146 plasmids were detected with molecular sizes ranging from 1 to 120 KB. The conjugation procedure is efficient enough to obtain transconjugants with sufficient delivery plasmids and therefore provides a simple route for conducting gene disruptions in bacteria. The conjugation efficiency of the isolates showed a high rate of transfer of resistance plasmids from antibiotics resistance strains to susceptible strains which contributes to the dissemination of antibiotics resistance traits in bacteria.
Keyword: Conjugation efficiency, antibiotic resistance, Escherichia coli.