<i>ampR</i>
            Gene Mutations That Greatly Increase Class C β-Lactamase Activity in
            <i>Enterobacter cloacae</i>

Kuga, Akio; Okamoto, Ryoichi; Inoue, Matsuhisa

doi:10.1128/aac.44.3.561-567.2000

Cited by 83 publications

(87 citation statements)

References 39 publications

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“…Interestingly, PBP4 removes the terminal D-Ala residue from PG catabolites prior to being transported to the cytosol for recycling (26), suggesting that the terminal D-Ala residue may be important for AmpC activation. Although occurring less frequently than ampD or dacB null mutations, mutations in ampR have also been found to drive constitutive high level AmpC production (21,25,27,28).…”

Section: Inducible Expression Of Chromosomal Ampcmentioning

confidence: 99%

The β-Lactamase Gene Regulator AmpR Is a Tetramer That Recognizes and Binds the d-Ala-d-Ala Motif of Its Repressor UDP-N-acetylmuramic Acid (MurNAc)-pentapeptide

Vadlamani¹,

Thomas²,

Patel³

et al. 2015

Journal of Biological Chemistry

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Section: Inducible Expression Of Chromosomal Ampcmentioning

confidence: 99%

The β-Lactamase Gene Regulator AmpR Is a Tetramer That Recognizes and Binds the d-Ala-d-Ala Motif of Its Repressor UDP-N-acetylmuramic Acid (MurNAc)-pentapeptide

Vadlamani¹,

Thomas²,

Patel³

et al. 2015

Journal of Biological Chemistry

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“…Ceftazidime is an important and effective antimicrobial agent for the therapy of serious infections due to multidrug resistance in P. aeruginosa. A surge in ceftazidime resistance in human clinical isolates of P. aeruginosa results from the production of acquired β-lactamase, the constitutive overproduction of AmpC, or an activation of the MexAB-OprM or MexXY-OprM efflux systems (Lindberg et al, 1987;Li et al, 1994;Stapleton et al, 1995;Nordmann and Guibert, 1998;Aires et al, 1999;Kuga et al, 2000;Masuda et al, 2000;Livermore, 2002). The molecular mechanism of canine ceftazidime resistance in P. aeruginosa isolates still requires further clarification.…”

mentioning

confidence: 99%

Molecular mechanisms of ceftazidime resistance in Pseudomonas aeruginosa isolates from canine and human infections

Du¹,

Kuo²,

Cheng³

et al. 2010

Vet. Med. - Czech

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Sixty-six clinical P. aeruginosa isolates, 17 obtained from canine otitis specimens and 49 received from human patients with bloodstream infections, were collected between February 2007 and January 2008. The minimal inhibitory concentrations (MICs) of the antimicrobial agents of these isolates were determined. Multidrug resistance was common, with 23 (34.8%) isolates found to be ceftazidime resistant. To explore the mechanisms of ceftazidime resistance, PCR analyses were performed to detect drug-resistance genes. The prevalence rate of Ambler class A, B, and D β-lactamase genes were obtained, with bla TEM-1 100%, bla PSE-1 100%, bla OXA-2 96.2%, bla SHV-18 91.3%, bla OXA-17 78.3%, bla VIM-3 26.1%, bla OXA-10 21.7% and bla SHV-1 8.7%. An efflux inhibition assay with the PAβN compound was conducted. The ceftazidime resistance isolates were also tested by RT-qPCR to determine the mRNA expression levels of the oprM and ampC genes. Five (21.7%) of the ceftazidime resistance isolates appeared to overactivate the OprM efflux system. The ampD, ampE, and ampR genes and the ampC-ampR intergenic region were subsequently amplified and sequenced. Five (21.7%) of the ceftazidime resistance isolates from humans and canines had a point mutation in AmpR (Asp135-Asn, n = 3; Als194-Ser, n = 2), which induces AmpC overproduction from 10-to 80-fold. This study first reported ceftazidime resistance in P. aeruginosa from canine otitis specimens, which are closely related to ESBLs (50%), including the overproduction of AmpC (25%) and the OprM efflux system (25%). The ESBLs (100%) played an important role in all ceftazidime resistance isolates from humans, and either AmpC (21.1%) or OprM (21.1%) might be overexpressed within the same isolate. A human patient isolate (H307B) showed simultaneous expression of ESBLs, the OprM efflux system, and AmpC overproduction.

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“…Previous studies on plasmid-mediated AmpC β-lactamase are largely restricted to the bacterila strains A. cloacae and Cray Borrelia (20)(21)(22). A limited number of studies have analyzed drug resistance in P. aeruginosa plasmid-mediated AmpC β-lactamase.…”

Section: Discussionmentioning

confidence: 99%

Study on drug resistance of Pseudomonas aeruginosa plasmid-mediated AmpC β-lactamase

Zhu

Zhang

Huang

et al. 2012

Molecular Medicine Reports

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Abstract. The aim of the present study was to investigate the resistance of plasmid-mediated AmpC β-lactamase in Pseudomonas aeruginosa, to detect and identify the AmpC genotype and to provide evidence for antibiotic applications in the clinic. Resistance phenotype in 108 strains of clinically isolated P. aeruginosa was determined by Kirby-Bauer disk test and cefoxitin three dimensional test in AmpC-positive strains. Plasmids were extracted from AmpC-positive strains using the SDS-alkali splitting technique. The depurated plasmid was used to amplify AmpC β-lactamase genes by PCR. Positive PCR products were sequenced by the Shanghai Sangon Biological Engineering Technology Company. Gene homology of PCR products with other index sample gene sequences was compared. In the present study, 28 AmpC enzyme-positive P. aeruginosa strains among 108 were identified. Multidrug-resistance to antibiotics was observed in positive AmpC P. aeruginosa strains and a new P. aeruginosa strain of plasmid-mediated CMY-7 type AmpC enzyme was identified. In addition, AmpC type β-lactamases were revealed to be important in the resistance mechanism to antibiotics in P. aeruginosa. This is the first report of CMY-7 plasmid-mediated AmpC enzyme expression in P. aeruginosa. IntroductionThe increasing use and application of broad-spectrum antibiotics has led to increased reports of bacterial drug resistance and clinical infection. At present, drug-resistant bacteria, including methicillin-resistant Staphylococcus aureus, multidrug-resistant Streptococcus pneumoniae, vancomycinresistant Enterococcus, multidrug-resistant Baumanii, Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa are increasingly being detected in clinical and laboratory settings (1). Appearance of pan-resistant bacteria, including Cray Borrelia, which produces New Delhi Metallo β-lactamase-1, an enzyme responsible for generating resistance (2), is causing an even greater challenge to humans. Therefore, study of clinical bacterial drug resistance and mechanisms and the development of solutions to bacterial resistance is important. Previously, Gram-negative bacilli AmpC β-lactamase was understood to be generated by chromosome mediation only. However, Papanicolaou et al (3) identified plasmid-mediated AmpC β-lactamase (MIR-1) in a strain of Cray Borrelia bacterium isolated from a patient in Rhode Island Hospital (USA) in 1989. Following this, the plasmid-mediated AmpC enzyme was rapidly identified in a number of other countries. At present, more than 20 plasmid-mediated AmpC enzymes have been identified. The plasmid-mediated AmpC enzyme is resistant to antibiotics, enabling the plasmid to continue to express the protein at high levels and carry multiple drug-resistant genes. Plasmid-mediated drug resistance is transmitted between members of the same or different bacterial species. Transmission is rapid and performed at a range of distances. Therefore, understanding of the mechanism and elucidation of solutions to plasmid-mediated AmpC enzyme resistance is crucial...

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ampR Gene Mutations That Greatly Increase Class C β-Lactamase Activity in Enterobacter cloacae

Cited by 83 publications

References 39 publications

The β-Lactamase Gene Regulator AmpR Is a Tetramer That Recognizes and Binds the d-Ala-d-Ala Motif of Its Repressor UDP-N-acetylmuramic Acid (MurNAc)-pentapeptide

The β-Lactamase Gene Regulator AmpR Is a Tetramer That Recognizes and Binds the d-Ala-d-Ala Motif of Its Repressor UDP-N-acetylmuramic Acid (MurNAc)-pentapeptide

Molecular mechanisms of ceftazidime resistance in Pseudomonas aeruginosa isolates from canine and human infections

Study on drug resistance of Pseudomonas aeruginosa plasmid-mediated AmpC β-lactamase

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