title: Identification of genotypes of plasmid-encoded AmpC beta-lactamases from clinical isolates and characterization of mutations in their promoter and attenuator regions.
abstract: We investigated the occurrence of AmpC beta-lactamases among Escherichia coli and Klebsiella pneumoniae isolates and determined the genotype of plasmid-mediated AmpC beta-lactamases at a medical center. The AmpC beta-lactamase promoter and attenuator were amplified from chromosomal DNA of high AmpC-producing E. coli isolates and sequenced. Antibiotic screening and 3D extract tests showed the presence of AmpC beta-lactamase in 3.56% of K. pneumoniae and 1.88% of E. coli isolates. Ten isolates (six K. pneumoniae and four E. coli) were positive for extended spectrum beta-lactamase (ESBL) as indicated by the double disc diffusion method. DHA-1 plasmid-encoded AmpC beta-lactamase was present in 10 K. pneumoniae isolates and four E.coli isolates. E. coli chromosomal AmpC beta-lactamase carried polymorphisms in the -42, -32, and -18 bases of the promoter and in the +26 and +27 bases of the attenuator, which may play a role in antibiotic resistance. The observed mutations may have clinical implications for the management of antibiotic-resistant infections.
authors.affiliation: Department of Medicine Laboratory, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Gui-Ling
authors.initials: GL
authors.lastname: Li
authors.forename: Li-Bo
authors.initials: LB
authors.lastname: Duo
authors.forename: Ying
authors.initials: Y
authors.lastname: Luan
authors.forename: Cheng-Ying
authors.initials: CY
authors.lastname: Wang
authors.forename: Wei-Ping
authors.initials: WP
authors.lastname: Wang
authors.forename: He-Guang
authors.initials: HG
authors.lastname: Zhang
authors.forename: Qi
authors.initials: Q
authors.lastname: Sun
authors.forename: Gui-Yun
authors.initials: GY
authors.lastname: Qi
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D005838:Genotype; D007711:Klebsiella pneumoniae / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D060885:Multiplex Polymerase Chain Reaction; D009154:Mutation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; C048795:AmpC beta-lactamases; D001618:beta-Lactamases
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