Genetic analysis of tetracycline-resistant plasmids in enteropathogenic Escherichia coli isolated from patients in Nigeria.

Genetic analysis of antibiotic-resistant plasmids from 102 serologically defined strains of enteropathogenic Escherichia coli from Nigeria was carried out. All the isolates were screened for susceptibility to antibiotics, and 47 were found resistant to tetracycline. A total of 138 plasmids was isolated by agarose gel electrophoresis. Transformation and conjugation experiments showed that 57.4% of the resistant strains carried R-plasmids ranging in sizes from 2 to 46 x 10(6) daltons. Plasmid-determined resistance to tetracycline, ampicillin and streptomycin was found. Restriction endonuclease analysis of three of the commonest plasmids: p1679, p529 and p1479 revealed relatedness with respect to function and structure. The DNA segment on which TcR gene is located on each of them was identified by cloning into the vector plasmid pGL101. The recombinant plasmids pOADI and pOAD2 gave full expression of TcR gene when transformed into E. coli DHI. Furthermore, the tetracycline-resistant strains were examined for their phenotypic behaviour with respect to tetracycline and its lipophilic analogs.