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Gene Review

ampC  -  beta-lactamase

Pseudomonas aeruginosa PAO1

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Disease relevance of ampC

  • Pseudomonas aeruginosa isolates from 1 of 17 cystic fibrosis patients produced secondary beta-lactamase in addition to the ampC beta-lactamase [1].
  • Five nonsynonymous nucleotide substitutions of ampC lead to beta-lactamase variants that differ in recognition and turnover of substrate, as deduced from the three-dimensional structure of the highly homologous Enterobacter cloacae beta-lactamase and confirmed by inhibition kinetics [2].
  • In many gram negative organisms, including Enterobacter spp.,Citrobacter freundii, Serratia marcescens, Morganella morganii and Pseudomonas aeruginosa, the expression of chromosomal ampC genes is low but inducible in response to ss-lactams and other stimuli [3].
  • Primer/probe assays for real-time PCR (TaqMan) designed to quantitatively detect the antibiotic resistance genes bla(VIM), vanA, ampC, mecA, and taxon-specific 23S rDNA sequences for Pseudomonas aeruginosa and Enterococcus faecium/faecalis were tested for their sensitivity and amplification robustness [4].

High impact information on ampC

  • Resistance to beta-lactam and FQ was correlated with ampC and mexC gene expression levels, respectively, whereas imipenem resistance was attributable to decreased oprD expression [5].
  • Interplay of Efflux System, ampC, and oprD Expression in Carbapenem Resistance of Pseudomonas aeruginosa Clinical Isolates [6].
  • Although ampD inactivation has been previously found to lead to a partially derepressed phenotype characterized by increased AmpC production but retaining further inducibility, the regulation of ampC in P. aeruginosa is far from well understood [7].
  • All 10 ceftazidime-resistant mutants hyper-produced AmpC (beta-lactamase activities were 12- to 657-fold higher than those of the parent strains), but none of them harbored mutations in ampR or the ampC-ampR intergenic region [8].
  • However, data from this study demonstrate that hypersusceptibility to imipenem can develop without changes in ampC expression or AmpC activity [9].

Chemical compound and disease context of ampC


Biological context of ampC

  • Homology analysis among AmpC enzymes or ampC genes implied that integration of the chromosomal ampC gene into a large resident plasmid, followed by transconjugation, was involved in the evolution of blaMOX-1 [12].
  • Cloning, sequencing and analysis of the structural gene and regulatory region of the Pseudomonas aeruginosa chromosomal ampC beta-lactamase [13].
  • Single point mutations lead to a mean sequence diversity of 0.40%, 0.38% and 0.59% for oriC, ampC and a-type fliC, respectively, but of only 0.05% for b-type flagellin genes [2].
  • Since the IS is adjacent to ampC and bla(OXA) in this A. baumannii strain, it may be that IS(ABA-1) plays an important role in the expression of antibiotic resistance genes in this genus [14].
  • A general ampC active site oligonucleotide probe for gram-negative rods [10].

Other interactions of ampC

  • However, the regulatory gene ampR and a 38-bp AmpR-binding region were not present upstream from blaMOX-1, although the expression of P. aeruginosa ampC is directly regulated by AmpR [12].
  • Hypersusceptibility of the Pseudomonas aeruginosa nfxB mutant to beta-lactams due to reduced expression of the ampC beta-lactamase [15].
  • For the detection of the resistance genes bla(VIM), vanA, ampC, and mecA as well as the enterococci directed PCR only weak or no inhibition due to the impurities or wastewater DNA matrix were demonstrated for the applied target concentrations [4].

Analytical, diagnostic and therapeutic context of ampC


  1. Pseudomonas aeruginosa isolates from patients with cystic fibrosis have different beta-lactamase expression phenotypes but are homogeneous in the ampC-ampR genetic region. Campbell, J.I., Ciofu, O., Høiby, N. Antimicrob. Agents Chemother. (1997) [Pubmed]
  2. Structural and functional implications of sequence diversity of Pseudomonas aeruginosa genes oriC, ampC and fliC. Spangenberg, C., Montie, T.C., Tümmler, B. Electrophoresis (1998) [Pubmed]
  3. Regulation of inducible AmpC beta-lactamase expression among Enterobacteriaceae. Hanson, N.D., Sanders, C.C. Curr. Pharm. Des. (1999) [Pubmed]
  4. Evaluation of inhibition and cross-reaction effects on real-time PCR applied to the total DNA of wastewater samples for the quantification of bacterial antibiotic resistance genes and taxon-specific targets. Volkmann, H., Schwartz, T., Kirchen, S., Stofer, C., Obst, U. Mol. Cell. Probes (2007) [Pubmed]
  5. Development and Persistence of Antimicrobial Resistance in Pseudomonas aeruginosa: a Longitudinal Observation in Mechanically Ventilated Patients. Reinhardt, A., Köhler, T., Wood, P., Rohner, P., Dumas, J.L., Ricou, B., van Delden, C. Antimicrob. Agents Chemother. (2007) [Pubmed]
  6. Interplay of Efflux System, ampC, and oprD Expression in Carbapenem Resistance of Pseudomonas aeruginosa Clinical Isolates. Quale, J., Bratu, S., Gupta, J., Landman, D. Antimicrob. Agents Chemother. (2006) [Pubmed]
  7. Stepwise Upregulation of the Pseudomonas aeruginosa Chromosomal Cephalosporinase Conferring High-Level {beta}-Lactam Resistance Involves Three AmpD Homologues. Juan, C., Moyá, B., Pérez, J.L., Oliver, A. Antimicrob. Agents Chemother. (2006) [Pubmed]
  8. Molecular mechanisms of beta-lactam resistance mediated by AmpC hyperproduction in Pseudomonas aeruginosa clinical strains. Juan, C., Maciá, M.D., Gutiérrez, O., Vidal, C., Pérez, J.L., Oliver, A. Antimicrob. Agents Chemother. (2005) [Pubmed]
  9. AmpC and OprD are not involved in the mechanism of imipenem hypersusceptibility among Pseudomonas aeruginosa isolates overexpressing the mexCD-oprJ efflux pump. Wolter, D.J., Hanson, N.D., Lister, P.D. Antimicrob. Agents Chemother. (2005) [Pubmed]
  10. A general ampC active site oligonucleotide probe for gram-negative rods. Willard, K.E., Moody, J.A., Peterson, L.R. Mol. Cell. Probes (1991) [Pubmed]
  11. Effect of siliconized latex urinary catheters on the activity of carbapenems against Pseudomonas aeruginosa strains with defined mutations in ampC, oprD, and genes coding for efflux systems. Conejo, M.C., Martínez-Martínez, L., García, I., Picabea, L., Pascual, A. Int. J. Antimicrob. Agents (2003) [Pubmed]
  12. Characterization of a plasmid-borne and constitutively expressed blaMOX-1 gene encoding AmpC-type beta-lactamase. Horii, T., Arakawa, Y., Ohta, M., Sugiyama, T., Wacharotayankun, R., Ito, H., Kato, N. Gene (1994) [Pubmed]
  13. Cloning, sequencing and analysis of the structural gene and regulatory region of the Pseudomonas aeruginosa chromosomal ampC beta-lactamase. Lodge, J.M., Minchin, S.D., Piddock, L.J., Busby, J.W. Biochem. J. (1990) [Pubmed]
  14. Is IS(ABA-1) customized for Acinetobacter? Segal, H., Garny, S., Elisha, B.G. FEMS Microbiol. Lett. (2005) [Pubmed]
  15. Hypersusceptibility of the Pseudomonas aeruginosa nfxB mutant to beta-lactams due to reduced expression of the ampC beta-lactamase. Masuda, N., Sakagawa, E., Ohya, S., Gotoh, N., Nishino, T. Antimicrob. Agents Chemother. (2001) [Pubmed]
  16. Investigation of the Pseudomonas aeruginosa ampR gene and its role at the chromosomal ampC beta-lactamase promoter. Lodge, J., Busby, S., Piddock, L. FEMS Microbiol. Lett. (1993) [Pubmed]
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