# An analysis of the value-added of antibiogram subgroup stratification

## TL;DR

This study shows that using hospital-wide antibiograms can lead to inaccurate antibiotic choices, while unit- and specimen-specific antibiograms provide more accurate guidance for treating specific patient groups.

## Contribution

The study quantifies the added value of stratified antibiograms over hospital-wide ones for more accurate antibiotic susceptibility reporting.

## Key findings

- The ED antibiogram showed higher susceptibility compared to the hospital-wide antibiogram.
- ICU and transplant unit antibiograms showed reduced susceptibility compared to the hospital-wide antibiogram.
- Specimen-specific antibiograms revealed additional susceptibility differences within units.

## Abstract

Stratified antibiograms are recommended to guide empiric clinical treatment. However, which strata to focus on, the limited number of isolates in identified strata, and the heavy associated workload all pose challenges. This study compares differences in antibiotic susceptibility between a hospital-wide, all-specimens antibiogram and stratified antibiograms in order to identify the value-added of antibiogram stratification.

Antibiotic susceptibility of bacterial isolates from 2021 at a quaternary-care academic hospital was obtained from published hospital-wide and unit- and specimen-specific stratified antibiograms. Differences in percent susceptibility by organism and drug between the hospital-wide and stratified antibiograms were calculated. Weighted averages of the difference in percent susceptibility were calculated for each stratified antibiogram compared to the hospital-wide antibiogram and unit-wide antibiograms. Differences were shown through heat maps.

When compared to a hospital-wide, all-specimens antibiogram, the emergency department (ED) antibiogram showed higher susceptibility, whereas the intensive care unit (ICU) and, particularly, the transplant unit antibiograms exhibited reduced susceptibility. Compared to unit level antibiograms, further stratification within each unit to specimen-specific (syndromic) antibiograms revealed additional differences. In the ED, urine and respiratory-stratified antibiograms had lower susceptibility and blood had higher susceptibility. Compared to unit-specific antibiograms, in the ICU, all specimen-stratified antibiograms had lower susceptibility and in the transplant unit, antibiograms for all specimens but urine had lower susceptibility.

Using a hospital-wide all-specimens antibiogram may both overcall and under call susceptibility leading to poor empiric antimicrobial choices. Specimen-specific antibiograms stratified by unit best inform empiric therapy for specific populations.

The online version contains supplementary material available at 10.1186/s12941-025-00787-7.