RESUMEN
Objective To explore the potential of converting the chloramphenicol resistant clinical E. Coli isolates to chloramphenicol sensitive ones by employing external guide sequence(EGS) technique in vitro. Methods Recombinant plasmids with EGScat 1+2 and tetracycline resistant gene, named PAlterl EGScat1+2, was constructed. Routine Cacl 2 method was used to introduce recombinant plasmid into the chloramphenicol resistant clinical isolates E. Coli 4758. Colony PCR was used to test and A600 was used to detect growth rates in liquid and solid culture of various concentrations of chloramphenicol. Results The chloramphenicol resistant clinical isolates E. Coli 4758 grew well in chloramphenicol(35 ?g/ml, 70 ?g/ml, 105 ?g/ml, 170 ?g/ml) plates whereas the transformants tE4758 with PAlter1 EGScat 1+2 failed to grow in these concentrations, which indicated its resistance to the chloramphenicol was reversed. Conclusions EGS molecules are able to convert the drug resistance in clinical E. Coli isolates in vitro.