A Comparison of a Solid Organ Transplant Population-Specific Antibiogram With the Hospital-Wide Antibiogram

Solid organ transplant (SOT) recipients are vulnerable to infections with multidrug-resistant organisms, and they often do not receive adequate empiric antimicrobials for serious Gram-negative infections. Knowledge of differences in antimicrobial resistance rates in this specific population can help guide empiric antimicrobial choices.

We performed a retrospective cohort study comparing antimicrobial susceptibility patterns of Gram-negative organisms isolated from the adult SOT recipients with documented sepsis with the hospital-wide inpatient antibiogram. To evaluate empiric antimicrobial coverage, we constructed a Weighted-Incidence Syndromic Combination Antibiogram (WISCA) by calculating the proportion of susceptible isolates per antimicrobial agent. We then compared the coverage rates against our institution's sepsis treatment guidelines.

A total of 90 Gram-negative isolates comprised the SOT cohort, while the inpatient antibiogram cohort had 1328 isolates. Pseudomonas aeruginosa (27%) and Escherichia coli (31%) were the most common isolates in the SOT and inpatient antibiogram cohorts, respectively. Overall, antimicrobial resistance rates were higher in the SOT population compared to the hospital-wide inpatient antibiogram population. WISCA analysis showed imipenem was active for 59% of isolates as opposed to the institutional recommendation of piperacillin-tazobactam, which covered 39% of SOT isolates.

Current empiric antimicrobial recommendations for SOT patients are based on data from the general patient population, which may not accurately reflect the resistance patterns in this unique population. Utilizing patient population-specific antibiograms may improve empiric antimicrobial therapy and warrants further research.