New Method for Detecting Plasmid-mediated AmpC Beta-lactamases / 中华医院感染学杂志

ABSTRACT

OBJECTIVE To establish a convenient method for detecting plasmid-mediated AmpC beta-lactamases in Enterobacteriaceae lacking chromosomal AmpC beta-lactamases and to investigqte their genotype.METHODS Fifteen isolates of Klebsiella pneumoniae were collected and the diameters of inhibitory zone of cefoxitin in combination with or without cloxacillin were measured separately by standard disc diffusion test.The M3D assay was used as control method.And the activity of AmpC beta-lactamases of all isolates was simultaneously assayed.Multiplex PCR was performed to determine the genotype of AmpC beta-lactamases.RESULTS Among 15 isolates,8 isolates were identified to have plasmid-mediated AmpC beta-lactamases.The sensitivity and specificity of AmpC beta-lactamases phenotypic confirmatory test were 100%.Eight of 15 isolates were identified to be DHA-1 beta-lactamases by multiplex PCR.CONCLUSIONS The new AmpC beta-lactamases phenotypic confirmatory test is a reliable method for detecting plasmidmediated AmpC beta-lactamases in Enterobacteriaceae lacking chromosomal AmpC beta-lactamases.DHA-1 beta-lactamases are the main genotypes of plasmid-mediated AmpC beta-lactamases in Hubei Province of China.