Volume 56 (2006) Issue: 2006 No#4

The investigation of resistance gene presence in plasmids isolated from E. coli and salmonella strains originating from domestic animals by the method of plasmid DNA transformation into competent cells

Author(s): Mišić D, Ašanin Ružica

Keywords:E.coli, Salmonella, plasmid

The investigation of the presence of plasmids was performed on E. coli and Salmonella strains, originating from dogs, cats, cattle, pigs and poultry. The investigated bacterial strains were isolated from ear and skin swabs, vaginal swabs, faeces and urine, obtained from healthy and diseased animals of various age and breed categories. Up to now 45 E. coli and 35 Salmonella strains have been isolated, but the presence of plasmids was investigated in 42 strains of bacteria resistant to at least 3 or more antibiotics (23 E.coli and 4 Salmonella strains). The plasmids were isolated from 2 E. coli strains originating from dogs, 4 E. coli strains originating from cattle, 2 E.coli strains originating from pigs, 1 E. coli strain originating from a cat and 2 Salmonella strains originating from poultry. The obtained approximate size values of isolated plasmids from investigated strains, expressed in base pairs were from 2,4 kb to 17,5 kb. After the transformation process was completed and the E. coli DH 5
transformants streaking was done on LB agar with added antibiotics, the visible growth of transformed bacteria meant that the competent cells have received DNA (plasmid) with the resistance gene for the antibiotic. Lack of growth in transformants meant that the resistance gene was to be found on the chromosome.