Disease relevance of ampC

• Genetic and functional characterization of the cephalosporinases produced by 65 clonally unrelated clinical Escherichia coli isolates revealed genetic diversity of the ampC genes and showed that Gln287, Cys287, Pro296, Leu298, and Phe350 substitutions were involved in extension of the hydrolysis spectrum to include ceftazidime and cefepime [1].
• The chromosomal ampC beta-lactamase in Citrobacter freundii and Enterobacter cloacae is inducible by beta-lactam antibiotics [2].
• Inducible expression of the chromosomal cdiA from Citrobacter diversus NF85, encoding an ambler class A beta-lactamase, is under similar genetic control to the chromosomal ampC, encoding an ambler class C enzyme, from Citrobacter freundii OS60 [3].

High impact information on ampC

• Addition of the muropeptide, anhMurNAc-tripeptide, which accumulates in beta-lactamase-overproducing mutants, counteracts the negative effect of UDP-MurNAc-pentapeptide, restoring the innate ability of AmpR to induce ampC expression in vitro [4].
• The murein precursor, UDP-MurNAc-pentapeptide, decreases AmpR-mediated transcriptional activation in vitro, but has no effect on an AmpR(G102E) mutant that mediates constitutive activation of ampC in vivo [4].
• When an inducible ampC gene is introduced on a plasmid into Escherichia coli together with its transcriptional regulator ampR, the plasmid-borne beta-lactamase is still inducible [2].
• The low-level cephalosporin resistance of the remaining isolates (n = 85; 49%) was inferred to result from reduced permeability or, in E. coli, from hyperexpression of chromosomal ampC [5].
• Furthermore, pulse-chase experiments using this mutant revealed that the 17% of the beta-lactamase precursor accumulated in the cell after a 4-min chase in the absence of IPTG, although almost all of the precursors were converted into the mature from after a 1-min chase in the presence of IPTG [6].

Chemical compound and disease context of ampC

• All ampicillin- and streptomycin-resistant E. coli O26 carried ampC and strA-strB gene sequences, respectively [7].

Biological context of ampC

• This ability was due to direct transcriptional activation of the beta-lactamase gene, ampC, rather than complementation of the CS51 mutation [8].
• Eleven cefoxitin-resistant, AmpC PCR-negative isolates had ampC promoter region mutations [9].
• The nucleotide sequence of the NF85 cdiA was identical to that of the published C. diversus ULA27 ampC sequence [3].

Anatomical context of ampC

• The expression of Vitreoscilla hemoglobin (VHb) in Escherichia coli JM101 (pRED2) causes the incorporation of the TEM beta-lactamase precursor into cytoplasmic inclusion bodies (IBs) [10].

References