Study on plasmid-mediated cephalosporinase genotypes in Escherichia coli

Objective To investigate the genotype and drug resistance of plasmid-mediated cephalosporinase (AmpC) in Escherichia coli.Methods Twenty-four cefoxitin-resistant strains among 157 strains of Escherichia coli were collected.Genotypes and distribution of AmpC and ESBLs were determined by polymerase chain reaction (PCR) with type-specific primer according to the sequence analysis of AmpC and ESBLs genes.Conjugation test was used to investigate the transfer of cefoxitin resistance mediated by the plasmid including AmpC gene.Results Among the 24 cefoxitin resistance strains, 13 produced CMY-like AmpC enzymes and one produced DHA-1 AmpC enzyme. Among ESBLs genotypes 15 were TEM, 2 were CTX-M and 1 was SHV.Conclusions Among the cefoxitin-resistant Escherichia coli found in Hunan Province 13 strains produced CMY-2-like AmpC and one produced DHA-1 AmpC enzyme. Three strains of Escherichia coli could transfer cefoxition resistance to recipients. The results of sensitivity test showed that the AmpC enzymes were resistant to most new antibiotics for broad beta-lactamas but sensitive to imipenem.