AmpC β-lactamase: Difference between revisions
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(Created page with "== Background == * Class C serine β-lactamase produced by many Enterobacterales and afermentative Gram-negative bacilli * Production of the β-lactamase may be from: **...") |
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** Plasmid-mediated ''ampC'' genes, including ''bla''<sub>CMY</sub>, ''bla''<sub>FOX</sub>, ''bla''<sub>DHA</sub>, ''bla''<sub>ACT</sub>, and ''bla''<sub>MIR</sub>, and is seen in [[Escherichia coli]], [[Klebsiella pneumoniae]], and [[Salmonella]] |
** Plasmid-mediated ''ampC'' genes, including ''bla''<sub>CMY</sub>, ''bla''<sub>FOX</sub>, ''bla''<sub>DHA</sub>, ''bla''<sub>ACT</sub>, and ''bla''<sub>MIR</sub>, and is seen in [[Escherichia coli]], [[Klebsiella pneumoniae]], and [[Salmonella]] |
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* Chromosomal de-repression and plasmid-mediated expression are both generally constitutively expressed, so treatment may be guided by initial susceptibility testing |
* Chromosomal de-repression and plasmid-mediated expression are both generally constitutively expressed, so treatment may be guided by initial susceptibility testing |
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| + | == Inducible AmpC == |
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* Bacteria with moderate to high risk of clinically-significant AmpC production includes: |
* Bacteria with moderate to high risk of clinically-significant AmpC production includes: |
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** [[Enterobacter cloacae]] |
** [[Enterobacter cloacae]] |
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** [[Klebsiella aerogenes]] |
** [[Klebsiella aerogenes]] |
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** [[Citrobacter freundii]] |
** [[Citrobacter freundii]] |
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| + | * The above three species have inducible AmpC in up to 40% of isolates |
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| − | ** Not necessarily all of the [[SPICE organisms]] |
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| + | *Not necessarily all of the [[SPICE organisms]] have risk of inducible AmpC production, of which only about 5% of isolates will have an inducible AmpC |
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| + | *Antibiotics that are the best inducers include [[aminopenicillins]] ([[amoxicillin]] and [[ampicillin]]), first-generation [[cephalosporins]], and [[cephamycins]] |
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| + | **Also [[imipenem]], though it remains effective even after induction of AmpC overexpression |
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| + | *Antibiotics that are weaker inducers include [[piperacillin]], [[ceftriaxone]], [[ceftazidime]], [[cefepime]], and [[aztreonam]] |
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[[Category:Β-lactamases]] |
[[Category:Β-lactamases]] |
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Latest revision as of 16:17, 24 November 2021
Background
- Class C serine β-lactamase produced by many Enterobacterales and afermentative Gram-negative bacilli
- Production of the β-lactamase may be from:
- Inducible chromosomal resistance, often following a few doses of ceftriaxone or ceftazidime
- Stable chromosomal de-repression, often seen in Escherichia coli and Shigella
- Plasmid-mediated ampC genes, including blaCMY, blaFOX, blaDHA, blaACT, and blaMIR, and is seen in Escherichia coli, Klebsiella pneumoniae, and Salmonella
- Chromosomal de-repression and plasmid-mediated expression are both generally constitutively expressed, so treatment may be guided by initial susceptibility testing
Inducible AmpC
- Bacteria with moderate to high risk of clinically-significant AmpC production includes:
- The above three species have inducible AmpC in up to 40% of isolates
- Not necessarily all of the SPICE organisms have risk of inducible AmpC production, of which only about 5% of isolates will have an inducible AmpC
- Antibiotics that are the best inducers include aminopenicillins (amoxicillin and ampicillin), first-generation cephalosporins, and cephamycins
- Also imipenem, though it remains effective even after induction of AmpC overexpression
- Antibiotics that are weaker inducers include piperacillin, ceftriaxone, ceftazidime, cefepime, and aztreonam
