A novel variant of topoisomerase IV gene in a group of pan-drug resistant Acinetobacter baumannii
Objective To investigate the existence and variance of quinolone-resistance genes in a group of pan-drug resistant of Acinetobacter baumannii ( A.baumannii ).Methods Twenty strains of pandrug resistant A.baumannii were isolated from patients registered in Affiliated Hospital of Nantong University from January 2011 to April 2011.Drug target genes to quinolone (gyrA,parC) and quinolone-resistance genes mediated by mobile genetic elements [ qnrA,qnrB,qnrS,aac(6')-Ⅰ b-cr,qepA] were analyzed by PCR and verified by DNA sequencing.Results In all 20 strains of A.baumannii,the sense mutation was found in the quinolone resistance-determining region of the gyrA gene in the form of TCA to TTA at codon 83 (Ser-83-Leu).Moreover,in the quinolone resistance-determining region of the parC gene sense mutation was found in the form of TCG to TTG at codon 80 (Ser-80-Leu) and 3 synonymous mutations were CCC to CCT at codon 40,GTA to GT]T at codon 41 and CGT to CGC at codon 44.And parC gene was a new mutation.However,mutations were not found in quinolone-resistance genes mediated by mobile genetic elements [ qnrA,qnrB,qnrS,aac( 6 ' )-Ⅰ b-cr,qepA ].Conclusion Quinolone-resistance-determining region play a key role in resistance to quinolones in this group of A.baumannii.To our knowledge,this is first report about the emergence of the new mutation of parC gene in China. 
 
Key words: 
Acinetobacter baumannii;  Quinolone;  Pan-drug resistance;  parC;  Novel variant