Hexane and methanolic extract of dried aerial parts of Salix acomophylla, Urtica dioica and Calendula officinalis were tested for their antimicrobial and curing activity against two microorganisms: Pseudomonas aeruginosa RB19 and Klebsiella pneumoniae MR1.Chemical investigation on these extracts showed that Salix acomophylla, Urtica dioica and Calendula officinalis methanolic extracts contain flavonoids, glycosides and saponins while the hexane extracts contain terpens.The in vitro test showed that all extracts of Salix acomophylla, Urtica dioica and Calendula officinalis have antimicrobial activity against Pseudomonas aeruginosa RB19 and Klebsiella pneumoniae MR1 growth.Plasmid profile of Pseudomonas aeruginosa RB19 isolate was determined and results showed that, the isolate has a small plasmid DNA bands.To study the plant extracts activity against Pseudomonas aeruginosa RB19 and Klebsiella pneumoniae MR1 plasmids, these isolates were treated firstly with standard curing agents. Results of Pseudomonas aeruginosa RB19 treatment with SDS showed that some colonies of Pseudomonas aeruginosa RB19 isolate lost resistance to neomycin and trimethoprime. And obtain a number of colonies of Kelebsiella pneumonae MR1 lost their resistance to a number of antibiotics after treated with ethidium bromide. Results showed that there were three types of cured colonies, colonies which lost one plasmid (that lost resistance to aztreonam or that lost chloramphenicol resistance), colonies lost two plasmids (that lost chloramphenicol and aztreonam resistance) and colonies lost three plasmids (that lost resistance to ampicilline, chloramphenicol and aztreonam).Treatment of Pseudomonas aeruginosa RB19 and Kelebsiella pneumonae MR1 with Salix acomophylla, Urtica dioica and Calendula officinalis extracts showed that many of these colonies were lost their resistance to antibiotics; these results indicated that extracts of these plants were have a curing effect on the bacterial plasmids and Salix acomophylla methanolic extract was the best extract which give the highest percentage of Pseudomonas aeruginosa RB19 and Kelebsiella pneumonae MR1 cured colonies.
