Gene Mutations Responsible for Overexpression of AmpC β-Lactamase in Some Clinical Isolates of<i>Enterobacter cloacae</i>

Kaneko, Ken‐ichi; Okamoto, Ryoichi; Nakano, Ryuichi; Kawakami, Sayoko; Inoue, Matsuhisa

doi:10.1128/jcm.43.6.2955-2958.2005

Cited by 55 publications

(54 citation statements)

References 32 publications

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“…AmpR mutations are less common but can also result in high-constitutive or hyperinducible phenotypes (118,153,165). Least common are mutations in AmpG, which result in constitutive low-level expression.…”

Section: Regulationmentioning

confidence: 99%

AmpC β-Lactamases

2009

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SUMMARY AmpC β-lactamases are clinically important cephalosporinases encoded on the chromosomes of many of the Enterobacteriaceae and a few other organisms, where they mediate resistance to cephalothin, cefazolin, cefoxitin, most penicillins, and β-lactamase inhibitor-β-lactam combinations. In many bacteria, AmpC enzymes are inducible and can be expressed at high levels by mutation. Overexpression confers resistance to broad-spectrum cephalosporins including cefotaxime, ceftazidime, and ceftriaxone and is a problem especially in infections due to Enterobacter aerogenes and Enterobacter cloacae, where an isolate initially susceptible to these agents may become resistant upon therapy. Transmissible plasmids have acquired genes for AmpC enzymes, which consequently can now appear in bacteria lacking or poorly expressing a chromosomal blaAmpC gene, such as Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. Resistance due to plasmid-mediated AmpC enzymes is less common than extended-spectrum β-lactamase production in most parts of the world but may be both harder to detect and broader in spectrum. AmpC enzymes encoded by both chromosomal and plasmid genes are also evolving to hydrolyze broad-spectrum cephalosporins more efficiently. Techniques to identify AmpC β-lactamase-producing isolates are available but are still evolving and are not yet optimized for the clinical laboratory, which probably now underestimates this resistance mechanism. Carbapenems can usually be used to treat infections due to AmpC-producing bacteria, but carbapenem resistance can arise in some organisms by mutations that reduce influx (outer membrane porin loss) or enhance efflux (efflux pump activation).

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Section: Regulationmentioning

confidence: 99%

AmpC β-Lactamases

2009

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“…The absence of ampD leads to the accumulation of anhMurNAc-tripeptide in the cytosol and constitutive overproduction of b-lactamase even in the absence of induction, resulting in a high resistance to b-lactams [163]. The most common mechanism for constitutive ampC overexpression in clinical strains leading to b-lactam resistance in Enterobacteriaceae as well as P. aeruginosa is to mutate ampD [200][201][202][203] (Table 3). P. aeruginosa has three different AmpD homologues, AmpD (PA4522), AmpDh2 (PA5485) and AmpDh3 (PA0807) that are responsible for de-repression of ampC expression in a step-wise manner [139,204].…”

Section: Cell-wall Recycling and Antibiotic Resistancementioning

confidence: 99%

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

Dhar

Kumari

Balasubramanian

et al. 2018

Journal of Medical Microbiology

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The bacterial cell-wall that forms a protective layer over the inner membrane is called the murein sacculus -a tightly crosslinked peptidoglycan mesh unique to bacteria. Cell-wall synthesis and recycling are critical cellular processes essential for cell growth, elongation and division. Both de novo synthesis and recycling involve an array of enzymes across all cellular compartments, namely the outer membrane, periplasm, inner membrane and cytoplasm. Due to the exclusivity of peptidoglycan in the bacterial cell-wall, these players are the target of choice for many antibacterial agents. Our current understanding of cell-wall biochemistry and biogenesis in Gram-negative organisms stems mostly from studies of Escherichia coli. An incomplete knowledge on these processes exists for the opportunistic Gram-negative pathogen, Pseudomonas aeruginosa. In this review, cell-wall synthesis and recycling in the various cellular compartments are compared and contrasted between E. coli and P. aeruginosa. Despite the fact that there is a remarkable similarity of these processes between the two bacterial species, crucial differences alter their resistance to b-lactams, fluoroquinolones and aminoglycosides. One of the common mediators underlying resistance is the amp system whose mechanism of action is closely associated with the cell-wall recycling pathway. The activation of amp genes results in expression of AmpC blactamase through its cognate regulator AmpR which further regulates multi-drug resistance. In addition, other cell-wall recycling enzymes also contribute to antibiotic resistance. This comprehensive summary of the information should spawn new ideas on how to effectively target cell-wall processes to combat the growing resistance to existing antibiotics.

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“…In Enterobacter cloacae, ESBLs have not often been reported (17,21). In this species, the most important mechanism of expanded-spectrum cephalosporin resistance is overproduction of the chromosomal AmpC ␤-lactamase.…”

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confidence: 99%

Nosocomial Outbreak Due to Extended-Spectrum-Beta-Lactamase- Producing Enterobacter cloacae in a Cardiothoracic Intensive Care Unit

et al. 2007

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Enterobacter cloacae has been associated with several outbreaks, usually involving strains that overproduce chromosomal ␤-lactamase or, uncommonly, strains expressing extended-spectrum ␤-lactamases (ESBL). Only sporadic cases of ESBL-producing E. cloacae have been identified in our hospital in recent years. We describe the epidemiology and clinical and microbiological characteristics of an outbreak caused by ESBL-producing E. cloacae in a cardiothoracic intensive care unit (CT-ICU). Prospective surveillance of patients with infection or colonization by ESBL-producing E. cloacae among patients admitted to the CT-ICU was performed during the outbreak. Production of ESBL was determined by decreased susceptibility to expanded-spectrum cephalosporins and a positive double-disk test result. Clone relatedness was determined by pulsed-field gel electrophoresis (PFGE). From July to September 2005, seven patients in the CT-ICU with ESBL-producing E. cloacae were identified (four males; median age, 73 years; range, 45 to 76 years); six patients had cardiac surgery. Four patients developed infections; three had primary bacteremia, one had ventilator-associated pneumonia, and one had tracheobronchitis. ESBLproducing E. cloacae showed resistance to quinolones and aminoglycosides. PFGE revealed two patterns.

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Gene Mutations Responsible for Overexpression of AmpC β-Lactamase in Some Clinical Isolates ofEnterobacter cloacae

Cited by 55 publications

References 32 publications

AmpC β-Lactamases

AmpC β-Lactamases

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

Nosocomial Outbreak Due to Extended-Spectrum-Beta-Lactamase- Producing Enterobacter cloacae in a Cardiothoracic Intensive Care Unit

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