Rectal Colonization with Carbapenem-Resistant Enterobacterales in Intensive Care Unit Patients: Prevalence, Clinical Outcomes, and Risk of Subsequent Infection

Technical Summary: Rectal Colonization with Carbapenem-Resistant Enterobacterales in ICU Patients

Problem Statement
Carbapenem-resistant Enterobacterales (CRE) represent a critical antimicrobial resistance threat globally, classified as urgent or critical priority pathogens by the CDC and WHO. While the risks of CRE infection are well-documented, the epidemiological patterns of rectal colonization in Intensive Care Unit (ICU) settings remain heterogeneous across different regions and healthcare systems. There is ongoing debate regarding the frequency and duration of surveillance, the efficacy of decolonization strategies, and the precise clinical significance of colonization versus infection. Specifically, data is needed to quantify the progression from colonization to clinical infection, the associated mortality risks, and the optimal timing for intervention in tertiary care ICUs.

Methodology
This study employed a retrospective cohort design conducted at a tertiary-level university hospital in Turkey. The study population consisted of 3,221 adult patients admitted to general and anesthesia ICUs between July 2022 and August 2025.

• Surveillance Protocol: Active surveillance was implemented via rectal swab cultures obtained at ICU admission and weekly thereafter.
• Detection: CRE identification was performed using Chromatic™ CRE Agar Base.
• Data Collection: Demographic data, length of stay, timing of colonization, development of proven CRE infections (via clinical samples such as blood, urine, sputum, and wound cultures), decolonization status, and mortality were extracted from infection control records and the hospital information system.
• Statistical Analysis: Analyses were conducted using SPSS version 26.0. Continuous variables were compared using Student's t-test or Mann–Whitney U test, while categorical variables were analyzed using chi-square or Fisher's exact tests. A p-value < 0.05 was considered statistically significant. The study was powered to detect differences with at least 240 patients (80% power).

Key Results

• Prevalence: Among 3,221 ICU patients, 287 (8.9%) were identified with rectal CRE colonization.
• Timing of Acquisition: 30.7% of colonized patients were colonized upon admission, while 69.3% acquired colonization during their ICU stay. The median time to colonization for acquired cases was 14 days (IQR: 9–22).
• Progression to Infection: Of the 287 colonized patients, 148 (51.6%) developed a clinically proven CRE infection. While the rate of infection was higher in patients who acquired colonization during their stay (54.3%) compared to those colonized at admission (45.5%), this difference was not statistically significant (p = 0.16).
• Mortality Outcomes:
  • CRE-colonized patients had significantly higher mortality than non-colonized patients (64% vs. 40%, p < 0.001).
  • Among colonized patients, those who developed a proven CRE infection had significantly higher mortality than those who did not (72.3% vs. 55.4%, p = 0.003).
  • Mortality was significantly higher in General ICUs (70.2%) compared to Anesthesia ICUs (52.2%) among colonized patients (p = 0.003).
• Infection Characteristics: In patients who developed infection, the most common sites were urinary tract infections (61.5%), bloodstream infections (58.8%), and pneumonia (54.1%). Approximately 65% of infected patients had multiple infection sites.
• Decolonization: Only 35% of colonized patients achieved decolonization during follow-up, with a median time to decolonization of 14 days.

Key Contributions

• High Progression Rate: The study documents a notably high rate of progression from colonization to infection (51.6%), which exceeds pooled estimates from previous systematic reviews (approx. 16.5%) and individual studies (15–30%).
• Mortality Correlation: It provides robust evidence linking CRE colonization directly to increased mortality, even before the onset of clinical infection, and demonstrates that the development of infection further exacerbates mortality risks.
• Acquisition Dynamics: The findings highlight that the majority of colonization events (nearly 70%) are acquired within the ICU environment, reinforcing the unit as a critical reservoir for transmission.
• Decolonization Challenges: The data highlights the difficulty in achieving decolonization, with only a third of patients clearing the carriage, underscoring the lack of standardized and effective decolonization protocols.

Significance and Claims
The authors conclude that rectal CRE colonization is a common and high-risk condition in ICU populations, serving as a significant reservoir for transmission and a precursor to severe, often fatal, clinical infections. The study asserts that colonization is not a benign state but a dynamic condition associated with poor prognosis.

The paper claims that:

1. Active Surveillance is Essential: Early detection and close monitoring of CRE colonization are critical for high-risk populations to manage transmission and clinical outcomes.
2. Risk Stratification: Colonization status should be integrated into routine risk stratification for ICU patients, as these individuals constitute a high-risk subgroup requiring intensified surveillance and tailored management.
3. Intervention Timing: The temporal pattern of colonization (median 14 days) suggests that targeted interventions during the second week of ICU stays may be particularly beneficial.
4. Need for Stewardship: Antimicrobial stewardship programs must specifically address colonized patients to minimize unnecessary antibiotic exposure while ensuring appropriate therapy for infections.

The authors acknowledge limitations, including the retrospective design, lack of molecular typing, and absence of long-term follow-up post-discharge. They emphasize that while their data supports the need for strict infection control and surveillance, future prospective multicenter studies are required to develop predictive models and effective decolonization strategies.