PMID: 15387969Sep 25, 2004Paper

Experimental study on phenotypic conversion of clinical chloromycetin-resistant strains of E. coli to drug-sensitive strains by using EGS technique in vitro

Zhonghua yi xue za zhi
Mei-Ying GaoJiang-Nan Feng

Abstract

To explore the possibility of phenotypic conversion of clinical chloromycetin (Cm)-resistant isolates of E.coli to drug-sensitive ones with external guide sequences (EGS) in vitro. Recombinant EGS plasmids directed against Cm acetyl transferase (cat) and containing kanamycin (Km) drug-resistance gene and control plasmids only containing kanamycin-resistance gene without EGS were constructed. By using CaCl(2) method, the recombinant plasmids were introduced into the clinically isolated Cm-resistant E.coli strains. Extraction of plasmids and PCR were applied to identify the EGS positive clones; The growth rate in liquid broth culture of Cm-resistant bacteria after EGS containing plasmid transformation was determined by spectrophotometer A(600). Drug sensitivity was tested in solid culture by using KB method. Transformation studies were carried out on 16 clinically isolated Cm-resistant E.coli strains with pEGFP-C1-EGS + cat1 + cat2 recombinant plasmid. Transformants were screened on LB-agar plates containing Km after transformation using EGS. In 4 tested strains of them, transformants with specific EGS plasmid showed growth inhibition when grown in liquid broth culture containing 100 approximately 200 micro g/ml of Cm. They were ...Continue Reading

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