Abstract:

Abstract:Objective To compare the changes of drug-susceptibility in antibiotic and antimicrobial Chinese herbs before and after long time passaged,and to detect the genetic mutation of some resistance genes. Methods The Escherichia coli (E.coli) ATCC25922 was cultured in the M-H broth culture including Levofloxacin or Yinhuamiyanling by 200 passages.The  minimum inhibitory concentration (MIC) of E.coli ATCC25922 of these two medinices was detected and compared with the MIC of untreated E.coli ATCC25922.The bacterial of  the genes encoding gyrase(gyrA) and topoisomerase Ⅳ were amplified by PCR.Results The MIC of the bacterial cultured in the M-H broth culture including Levofloxacin  was increased compared with the MIC of untreated E.coli.There was no significant difference in the MIC of the bacteria cultured in the M-H broth culture including Yinhuamiyanling between before and after treatment(P>0.05).Several mutations were identified in gene of parC.The adenine(A) at the site 381 of parC was converted to thymine(T),and a thymine(T) was inserted in at the site 386.All isolates harbored parC amino acid subctitutions at position 127(Lys127-Asn).The gene gyrA had no mutation.Conclusion Levofloxacin is easier than Yinhuamiyanling to produce the resistance of E.coli ATCC25922,and the mutation of parC gene may be one of reseason of bacterial resistance.

Key words: drug resistance, chromsome, mutational, levofloxacin, yinhuamiyanling