The analysis of plasmid-mediated AmpC enzyme genotype and epidemiology of Escherichia coli and Klebsiella pneumoniae

Objective To investigate the prevalence,genotype and epidemiology of plasmid- mediated AmpC enzyme of Escherichia coli and Klebsiella pneumoniae.Methods A total of 67 clinical isolates of nonrepetitive cefoxitin-resistant Escherichia coli and Klebsiella pneumoniae collected by Fuzhou General Hospital and Fujian Provincial Hospital during a period of Sept.2004 to Mar.2005 were detected by three-dimensional extract test for AmpC enzyme,and PCR for AmpC enzyme and other β-lactamase gene amplification and DNA sequencing were carried out for genotype of β-lactamase.Plasmid transformation experiment was used to study the transfer of cefoxitin resistance.The homology of the isolates was determined by ERIC-PCR fingerprinting.Results At two hospitals in Fuzhou,the prevalence of plasmid-mediated AmpC enzyme among cefoxitin-resistant Escherichia coli and Klebsiella pneumoniae were 16.7% and 10.5%, 8.0% and 0,respectively.Two isolates of Klebsiella pneumoniae produced DHA-1 plasmid-mediated AmpC enzyme,and 4 isolates of Escherichia cob and one strain of Escherichia coli produced CMY-2 and CMY-22 plasmid-mediated AmpC enzyme respectively.Furthermore,5 strains of Escherichia coli with CMY AmpC enzyme were also found simuhaneously to produce TEM-144,CTX-M-27,CTX-M-14 and TEM-1 β-lactamase respectively.Three strains of Escherichia coli and one isolate of Klebsiella pneumoniae could transfer cefoxitin resistance to acceptant bacillus.ERIC-PCR fingerprinting reveals 2 strains of Klebsiella pneumoniae came from same clone,but 5 strains of Escherichia coli came from different clones.Conclusions The clinical isolates of Klebsiella pneumoniae producing DHA-1 plasmid-mediated AmpC enzyme and Escherichia coli producing CMY-2,CMY-22 plasmid-mediated AmpC enzyme are found in Fuzhou.CMY-22 AmpC enzyme and TEM-144 β-lactamase are the first reported in the world,GenBank accession number: DO256079,DO256080