Detection of plasmid type AmpC lactamase DHA gene in multidrug resistant Entero-bacter cloacae

Objective To analyze plasmid type AmpC β-lactamase DHA gene in 56 strains of Enterobacter cloacae simultaneously resistant to cafotaxime,gentamicin and ciprofloxacin.Methods The clinical isolates of Enterobacter cloacae were examined by standard disk difusion susceptibility tests,three-dimensional methods,isoelectric focusing and microdilution methods.Conjugation experiment was used to study the transfer of resistance.Multiplex PCR and DNA sequencing methods were used for further analysis.Results Five out of a total of 56 isolates tested were shown to be highly AmpC-producing by three-dimensional method.Only one transferred resistance to cefoxitin.IEF showed that this strain produced a AmpC like lactamase with a isoelectric point of 7.8,and DNA sequencing showed that the gene which expressed this AmpC like lactamase was identical to DHA-1,a plasmid mediated cephalosporinase gene.Conclusions The Enterobacter cloacae strains simultaneously resistant to cafotaxime,gentamicin and ciprofloxacin have gained DHA gene in our country,plasmid type AmpC β-lactamase DHA gene can be transferred in bacteria by transforming or integrating and easy to be transferred,the intensive attention should be paid to avoid DHA gene being prevalent in Gram-negative bacteria.