Enterobacter species
Enterobacter species is a topic covered in the Johns Hopkins ABX Guide.
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MICROBIOLOGY
- Gram-negative, aerobic, motile bacilli of the Enterobacteriaceae family. Ferments lactose and forms mucoid colonies. Commonly found in water, sewage, and soil.[8]
- Opportunistic human pathogen includes E. cloacae (most common), E. aerogenes (renamed Klebsiella aerogenes), E. gergoviae[17] and Pantoea agglomerans.
- E. sakazakii now classified as Cronobacter.[10]
- High levels of drug resistance often seen and due to:
- AmpC β-lactamases - Ambler class C
- Chromosomal AmpC can be constitutive (always active) or inducible (variably active) and are not inhibited by β-lactam β-lactamase inhibitors.[19]
- β-lactams must be present for activation of inducible β-lactamases, so initial susceptibility reports may not detect resistance that can emerge during therapy.
- Plasmid-mediated[9]
- Phenotypic assays are unable to distinguish between AmpC β-lactamase production due to derepression of chromosomal versus plasmid-associated ampC gene.
- Chromosomal AmpC can be constitutive (always active) or inducible (variably active) and are not inhibited by β-lactam β-lactamase inhibitors.[19]
- Plasmid-encoded extended-spectrum β-lactamases (ESBLs)
- ESBL genes include blaCTX-M, blaSHV, and blaTEM. Commercially available molecular platforms limited to detection blaCTX-M.
- Most often such organisms demonstrate elevated MICs to cefepime.
- ESBLs inactivate most penicillins, cephalosporins, and aztreonam.[1]
- Carbapenemases[14]
- Ambler class A - Most common are Klebsiella pneumoniae carbapenemases (KPC) that can be produced by any Enterobactrerales.
- Ambler class B - Metallo-β-lactamases include: New Delhi (NDMs), Verona integron-encoded (VIM), and imipenem-hydrolyzing (IMPs)
- Ambler class D - Oxacillinase (OXA-48-like) carbapenemases
- AmpC β-lactamases - Ambler class C
- Ceftriaxone MIC ≥ 2 is used as a proxy for ESBL production.
- Other resistance mechanisms
- Alterations in the active site of penicillin-binding protein
- Defects in outer membrane permeability that reduce diffusion of β-lactams into the cell
- Presence of efflux pumps that move β-lactams out of the cell
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MICROBIOLOGY
- Gram-negative, aerobic, motile bacilli of the Enterobacteriaceae family. Ferments lactose and forms mucoid colonies. Commonly found in water, sewage, and soil.[8]
- Opportunistic human pathogen includes E. cloacae (most common), E. aerogenes (renamed Klebsiella aerogenes), E. gergoviae[17] and Pantoea agglomerans.
- E. sakazakii now classified as Cronobacter.[10]
- High levels of drug resistance often seen and due to:
- AmpC β-lactamases - Ambler class C
- Chromosomal AmpC can be constitutive (always active) or inducible (variably active) and are not inhibited by β-lactam β-lactamase inhibitors.[19]
- β-lactams must be present for activation of inducible β-lactamases, so initial susceptibility reports may not detect resistance that can emerge during therapy.
- Plasmid-mediated[9]
- Phenotypic assays are unable to distinguish between AmpC β-lactamase production due to derepression of chromosomal versus plasmid-associated ampC gene.
- Chromosomal AmpC can be constitutive (always active) or inducible (variably active) and are not inhibited by β-lactam β-lactamase inhibitors.[19]
- Plasmid-encoded extended-spectrum β-lactamases (ESBLs)
- ESBL genes include blaCTX-M, blaSHV, and blaTEM. Commercially available molecular platforms limited to detection blaCTX-M.
- Most often such organisms demonstrate elevated MICs to cefepime.
- ESBLs inactivate most penicillins, cephalosporins, and aztreonam.[1]
- Carbapenemases[14]
- Ambler class A - Most common are Klebsiella pneumoniae carbapenemases (KPC) that can be produced by any Enterobactrerales.
- Ambler class B - Metallo-β-lactamases include: New Delhi (NDMs), Verona integron-encoded (VIM), and imipenem-hydrolyzing (IMPs)
- Ambler class D - Oxacillinase (OXA-48-like) carbapenemases
- AmpC β-lactamases - Ambler class C
- Ceftriaxone MIC ≥ 2 is used as a proxy for ESBL production.
- Other resistance mechanisms
- Alterations in the active site of penicillin-binding protein
- Defects in outer membrane permeability that reduce diffusion of β-lactams into the cell
- Presence of efflux pumps that move β-lactams out of the cell
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Last updated: February 16, 2023
Citation
Spacek, Lisa A. "Enterobacter Species." Johns Hopkins ABX Guide, The Johns Hopkins University, 2023. Johns Hopkins Guides, www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540201/all/Enterobacter_species.
Spacek LA. Enterobacter species. Johns Hopkins ABX Guide. The Johns Hopkins University; 2023. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540201/all/Enterobacter_species. Accessed March 30, 2023.
Spacek, L. A. (2023). Enterobacter species. In Johns Hopkins ABX Guide. The Johns Hopkins University. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540201/all/Enterobacter_species
Spacek LA. Enterobacter Species [Internet]. In: Johns Hopkins ABX Guide. The Johns Hopkins University; 2023. [cited 2023 March 30]. Available from: https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540201/all/Enterobacter_species.
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T1 - Enterobacter species
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Y1 - 2023/02/16/
BT - Johns Hopkins ABX Guide
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PB - The Johns Hopkins University
DB - Johns Hopkins Guides
DP - Unbound Medicine
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