Taxonomy

• Family Enterobacteriaceae (Colloquially Termed “Enteric Bacteria”)

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Organisms

• Citrobacter (see Citrobacter)
• Cronobacter
• Enterobacter (see Enterobacter)
• Escherichia Coli (see Escherichia Coli)
  • Aerobic Gram-Negative Rod
• Hafnia (see Hafnia)
• Klebsiella (see Klebsiella)
  • Aerobic Gram-Negative Rod
• Morganella (see Morganella)
• Pantoea
• Plesiomonas
• Proteus (see Proteus)
• Raoultella
• Salmonella (see Salmonella)
• Serratia (see Serratia)
• Shigella (see Shigella)
• Yersinia (see Yersinia)

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Microbiology

β-Lactamases

General Comments

• β-Lactamases Represent One of the Major Evolving Mechanisms of Antimicrobial Resistance
• Carbapenemases are Capable of Inactivating β-Lactam Antibiotics of All Classes
• The Distinction Between Serine and Metallo-Based Carbapenemases is Important, Since Certain Drugs are Active Against the Serine Enzymes, But Not Against the Metallo Enzymes
  • Example: Ceftazidime + Avibactam is active against serine enzymes, but not against metallo enzymes (see Ceftazidime-Avibactam)

Types of Clinically-Relevant β-Lactamases

• Extended-Spectrum β-Lactamases
  • Escherichia Coli (see Escherichia Coli)
  • Klebsiella (see Klebsiella)
• Chromosomally-Mediated AmpC β-Lactamases
  • Acinetobacter (see Acinetobacter)
  • Citrobacter (see Citrobacter)
  • Enterobacter (see Enterobacter)
  • Proteus (Indole-Positive) (see Proteus)
  • Pseudomonas Aeruginosa (see Pseudomonas Aeruginosa)
  • Serratia (see Serratia)
• Plasmid-Mediated AmpC β-Lactamases
  • Escherichia Coli (see Escherichia Coli)
  • Klebsiella (see Klebsiella)
• Carbapenemases
  • Acinetobacter (see Acinetobacter): via Oxa-type carbapenemase
  • Enterobacteriaceae: via New Delhi metallo-β-lactamase (an Ambler class B metallo-enzyme)
  • Klebsiella Pneumoniae (see Klebsiella Pneumoniae): via Klebsiella Pneumoniae carbapenemase (KPC) (a serine-based carbapenemase)

Carbapenem-Resistant Enterobacteriaceae (CRE)

• Incidence: 2.93 cases/100k population (JAMA, 2015) [MEDLINE]
• Organisms (JAMA, 2015) [MEDLINE]
  • Carbapenem-Resistant (Excluding Ertapenem)/Extended-Spectrum Cephalosporin-Resistant Escherichia Coli (see Escherichia Coli)
  • Carbapenem-Resistant (Excluding Ertapenem)/Extended-Spectrum Cephalosporin-Resistant Enterobacter Aerogenes (see Enterobacter Aerogenes)
  • Carbapenem-Resistant (Excluding Ertapenem)/Extended-Spectrum Cephalosporin-Resistant Enterobacter Cloacae Complex (see Enterobacter Cloacae)
  • Carbapenem-Resistant (Excluding Ertapenem)/Extended-Spectrum Cephalosporin-Resistant Klebsiella Pneumoniae (see Klebsiella Pneumoniae)
  • Carbapenem-Resistant (Excluding Ertapenem)/Extended-Spectrum Cephalosporin-Resistant Klebsiella Oxytoca (see Klebsiella Oxytoca)
• Clinical Associations
  • Most CRE’s were Isolated from a Urinary Source
  • Most CRE’s were Associated with High Prevalence of Prior Hospitalizations, Prior Indwelling Devices, or Discharge to a Long-Term Care Setting

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References

• Carbapenemase-producing Klebsiella pneumoniae bloodstream infections: lowering mortality by antibiotic combination schemes and the role of carbapenems. Antimicrob Agents Chemother. 2014;58(4):2322-2328 [MEDLINE]
• Antibiotic treatment of infections due to carbapenem-resistant Enterobacteriaceae: systematic evaluation of the available evidence. Antimicrob Agents Chemother. 2014;58(2):654-63. doi: 10.1128/AAC.01222-13. Epub 2013 Sep 30 [MEDLINE]
• Combination therapy for carbapenem-resistant Gram-negative bacteria. J Antimicrob Chemother. 2014 Sep;69(9):2305-9. doi: 10.1093/jac/dku168. Epub 2014 May 28 [MEDLINE]
• Epidemiology of Carbapenem-Resistant Enterobacteriaceae in 7 US Communities, 2012-2013. JAMA. 2015 Oct 5:1479-1487. doi: 10.1001/jama.2015.12480 [MEDLINE]
• Spread of KPC-producing carbapenem-resistant Enterobacteriaceae: the importance of super-spreaders and rectal KPC concentration. Clin Microbiol Infect. 2015 May;21(5):470.e1-7. doi: 10.1016/j.cmi.2014.12.015. Epub 2014 Dec 26 [MEDLINE]