Abstract: Objective To study the function of active efflux pump gene cmr in clinical isolates of Shigella.Methods The active efflux pump gene cmr of Shigella sonnei H₂₄ was amplified by PCR and ligated with pMD18-T to construct the recombinant plasmid pMD-cmr,and the pMD-cmr was transformed into E.coli DH5α.The positive recombinant plasmid was identified by restriction enzyme digestion and the gene was sequenced and analyzed.Drug susceptibility of the recombinant strain was tested by the two fold agar dilution technique;The MICs of the seven antibiotics were also determined by adding CCCP.Results The E.coli strain with cmr gene was more resistant to tetracycline and erythromycin than the strain without it,and the resistances could be inhibited by proton pump inhibitor CCCP.Conclusion The gene cmr is related with the resistance of tetracycline and erythromycin in the drug resistant-strain H₂₄.