RT Journal Article SR Electronic(1) A1 Roh, Kyoung Ho A1 Song, Wonkeun A1 Chung, Hae-Sun A1 Lee, Yang Soon A1 Yum, Jong Hwa A1 Yi, Ha Na A1 Chun, Jong Sik A1 Yong, Dongeun A1 Lee, Kyungwon A1 Chong, YunsopYR 2012 T1 Chromosomal cephalosporinase in Enterobacter hormaechei as an ancestor of ACT-1 plasmid-mediated AmpC β-lactamase JF Journal of Medical Microbiology, VO 61 IS 1 SP 94 OP 100 DO https://doi.org/10.1099/jmm.0.032573-0 PB Microbiology Society, SN 1473-5644, AB In this study of the diversity of AmpC β-lactamase in clinical isolates of Enterobacter spp., a strain was found carrying the plasmid-mediated AmpC β-lactamase ACT-1 gene on its chromosome. The strain was identified as Enterobacter hormaechei using phylogenetic analysis of 16S rRNA and hsp60 genes. In addition, the species was confirmed by DNA–DNA hybridization. The genetic environment of the bla ACT-1 gene was characterized, including the ampR and ampG genes, using a two-step PCR. The amino acid sequences of AmpR at serine 35, arginine 86, glycine 102, aspartic acid 135 and tyrosine 264 were conserved. Measurement of the transcription level of the bla ACT-1 gene using real-time quantitative PCR showed that it increased 1.98-fold following cefoxitin induction. These results suggest that the plasmid-mediated bla ACT-1 gene originated from the chromosome of E. hormaechei., UL https://www.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.032573-0