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A functional classification scheme for beta-lactamases and its correlation with molecular structure

TLDR
These enzymes are the major cause of bacterial resistance to b-lactam antibiotics and have been the subject of extensive microbiological, biochemical, and genetic investigations.
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AmpC β-Lactamases

  • G. Jacoby
  • Biology, Medicine
    Clinical Microbiology Reviews
  • 1 January 2009
TLDR
Overexpression confers resistance to broad-spectrum cephalosporins including cefotaxime, ceftazidime, and ceftriaxone and is a problem especially in infections due to Enterobacter aerogenes and Enterobacteria cloacae, where an isolate initially susceptible to these agents may become resistant upon therapy.
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Updated Functional Classification of β-Lactamases

TLDR
The functional classification scheme updated herein is based on the 1995 proposal and includes group 1 (class C) cephalosporinases; group 2 (classes A and D) broad-spectrum, inhibitor-resistant, and extended-spectrums β-lactamases and serine carbapenemases; and group 3 metallo-β-lacticamases.
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The worldwide emergence of plasmid-mediated quinolone resistance.

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Plasmid-Mediated Quinolone Resistance: a Multifaceted Threat

TLDR
The best-described form of PMQR is determined by the qnr group of genes, likely originating in aquatic organisms, which code for pentapeptide repeat proteins that reduce susceptibility to quinolones by protecting the complex of DNA and DNA gyrase or topoisomerase IV enzymes from the inhibitory effect of qu inolones.
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Fluoroquinolone-modifying enzyme: a new adaptation of a common aminoglycoside acetyltransferase

TLDR
Reduced susceptibility to ciprofloxacin in clinical bacterial isolates conferred by a variant of the gene encoding aminoglycoside acetyltransferase AAC(6′)-Ib, first reported in 2003 and now widely disseminated is described.
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qnr Prevalence in Ceftazidime-Resistant Enterobacteriaceae Isolates from the United States

TLDR
ABSTRACT The authors screened 313 ceftazidime-resistant Enterobacteriaceae isolates obtained in the United States from 1999 to 2004 for all three known qnr genes and found qnrA and qnrB occurred with equivalent frequencies and, except for qnrS, were stable over time.
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Mechanisms of resistance to quinolones.

  • G. Jacoby
  • Biology
    Clinical infectious diseases : an official…
  • 15 July 2005
TLDR
Resistance to fluoroquinolones typically arises as a result of alterations in the target enzymes and of changes in drug entry and efflux and can be mediated by plasmids that produce the Qnr protein, which protects the quinolone targets from inhibition.
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Quinolone resistance from a transferable plasmid

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Plasmid-Determined AmpC-Type β-Lactamases

TLDR
The predominant mechanism for resistance to β-lactam antibiotics in gram-negative bacteria is the synthesis of β- lactamase, which has implications for drug resistance and drug discovery.
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