Cumulative Antimicrobial Susceptibility Data from Intensive Care Units at One Institution: Should Data Be Combined?

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Hospital Epidemiology

Background:

• Cumulative antimicrobial susceptibility test data (CSTD) are crucial for guiding empirical therapy and monitoring antibiotic resistance trends.
• Current guidelines recommend annual CSTD reporting, often leading hospitals to aggregate data from multiple intensive care units (ICUs).
• Aggregating data across diverse ICU patient populations may obscure significant variations in antimicrobial resistance.

Purpose of the Study:

• To evaluate the appropriateness of combining CSTD from different ICUs for empirical therapy guidance.
• To compare a traditional CSTD reporting method with a novel rolling-average CSTD method.
• To assess the impact of different CSTD aggregation strategies on identifying antimicrobial resistance variations.

Main Methods:

• Susceptibility data for common Gram-negative organisms (Escherichia coli, Pseudomonas aeruginosa) and key antibiotics were analyzed.
• Two methods were employed: a traditional CSTD combining data from two ICUs and a rolling-average CSTD pooling 2 years of data per ICU.
• Organism-antimicrobial combinations were examined to identify differences in susceptibility between ICUs and over time.

Main Results:

• The rolling-average method revealed significant between-ICU susceptibility differences in 50% of organism-antimicrobial combinations.
• Median year-over-year susceptibility differences were 3% with the traditional method versus 14% for between-ICU comparisons using the rolling-average method.
• The revised approach led to changes in empirical antibiotic selection, highlighting the limitations of pooled ICU data.

Conclusions:

• Pooling CSTD from ICUs with distinct patient populations may not accurately guide empirical antimicrobial therapy.
• A rolling-average CSTD method offers a more granular approach, providing unit-specific resistance data.
• Implementing a rolling-average strategy can enhance the accuracy of CSTD for individual ICUs and improve antimicrobial stewardship.