What does CRE (carbapenem‑resistant Enterobacteriaceae) mean?

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What Does CRE Mean?

CRE stands for Carbapenem-Resistant Enterobacteriaceae—a family of bacteria that have developed resistance to carbapenem antibiotics, which are typically reserved as last-line agents for serious infections. 1

Definition and Clinical Significance

CRE refers to species within the Enterobacteriaceae family that demonstrate resistance to at least one carbapenem antibiotic (such as imipenem, meropenem, or ertapenem) through laboratory testing, or that produce carbapenemase enzymes capable of breaking down these drugs 1, 2. This resistance pattern represents a critical public health threat because carbapenems are broad-spectrum antibiotics traditionally used when other options have failed.

Why CRE Matters for Patient Outcomes

CRE infections are associated with high rates of morbidity and mortality, particularly in critically ill patients. The clinical impact is severe 1:

  • Mortality: CRE infections carry significantly increased death rates compared to susceptible organisms
  • Morbidity: Prolonged hospitalizations, especially in intensive care units, with increased complications
  • Quality of Life: Extended recovery periods, increased exposure to invasive devices (ventilators, central lines), and limited treatment options

Most Common CRE Species

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is the most frequently encountered CRE species in the United States 1. The resistance has spread dramatically—from less than 1% of Klebsiella isolates in 2000 to 8% by 2007, with continued increases since 1, 3.

Resistance Mechanisms

CRE organisms employ two main resistance strategies 1, 2:

  1. Carbapenemase-producing Enterobacteriaceae (CP-CRE): Produce enzymes that destroy carbapenem antibiotics

    • Most important enzyme: KPC (Klebsiella pneumoniae carbapenemase)
    • Other common types: NDM, OXA-48
    • The genes encoding these enzymes sit on mobile genetic elements, facilitating rapid spread between bacteria

  2. Non-carbapenemase-producing CRE: Resistant through other mechanisms without producing carbapenemase enzymes

High-Risk Populations

Patients at greatest risk for CRE colonization and infection include 1, 4:

  • Those with prolonged hospitalization or previous ICU stays
  • Critically ill patients requiring invasive devices (ventilators, central venous catheters, urinary catheters)
  • Patients with prior antibiotic exposure, especially carbapenems, cephalosporins, or glycopeptides
  • Individuals with high APACHE II scores
  • Those undergoing invasive procedures (endoscopy, tracheostomy, hemodialysis)

Clinical Context

CRE are resistant to almost all available antimicrobial agents, making treatment extremely challenging 1. The limited therapeutic options, combined with the severity of infections in vulnerable populations, underscore why CRE represents one of the WHO's top ten global public health threats 5. Most CRE cases (92%) occur in patients with substantial healthcare exposures 3, making hospital infection control measures critical for prevention.

References

2
Research

Carbapenem-Resistant Enterobacteriaceae.

Clinics in laboratory medicine, 2017

3
Research

Vital signs: carbapenem-resistant Enterobacteriaceae.

MMWR. Morbidity and mortality weekly report, 2013

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.