Prevalence of plasmid-mediated AmpC beta-lactamases in Escherichia coli and Klebsieila spp. isolated in children

Objective To study the plasmid-mediated AmpC β-lactamases and the genotypes of Escherichia coli and Klebsieila spp. in children. Methods Escherichia coli and Klebsieila spp. of strains were isolated at our division from January to December 2009. Cefoxitin disk diffusion method was used to screen Escherichia coli and Klebsieila spp. for phenotypic AmpC enzyme. Multiple PCR method was adopted to test the genotypes of AmpC enzyme-positive Escherichia coli and Klebsieila spp. strains. Results Of all Escherichia coli and Klebsieila spp. , 65 were insensitive to cefoxitin disk and 17 strains carried DHA type AmpC gene. The prevalence of plasmid-mediated AmpC enzyme in Escherichia coli and Klebsieila spp. was 26. 2% (17/65). Among plasmid-mediated AmpC enzyme isolates, 14 (38.9%) Klebsiella pneurnoniae strains, 2 (7.7%) Escherichia coli strains and 1 (33.3%) Klebsiella oxytoca strains carried the DHA-1 AmpC gene. The genes of MOX, CIT, DHA, ACC, MIR and FOX were not found in other 48 strains. Conclusions The identified plasmid-mediated AmpC genes are all of DHA-1 genotype in Escherichia coli and Klebsieila spp. The prevalence of plasmid-mediated AmpC enzyme in Klebsiella pneumoniae isolates is relatively high in children. Key words: Escherichia; Klebsiella; Plasmids; Child; AmpC beta-lactamases