Assessing Antimicrobial Prescribing for FEP-Susceptible ESBL-E BSIs

The Infectious Diseases Society of America discourages against the use of piperacillin-tazobactam (TZP) and cefepime (FEP) in treating bloodstream infections (BSIs) caused by extended spectrum β-lactamase Enterobacterales (ESBL-E).

At the microbiology laboratory at the University of Pennsylvania Health System in Philadelphia, they suppress TZP susceptibilities on Escherichia coli and Klebsiella pneumoniae blood isolates nonsusceptible to ceftriaxone (CRO) or ceftazidime (CAZ) and specifies the presence of a multidrug resistant organism.

Investigators within the health system set out to study antimicrobial prescribing for the treatment of FEP-susceptible ESBL-E BSIs with the University of Pennsylvania’s our current susceptibility reporting practices.

The investigators did a retrospective study and observed patients with blood cultures positive for E coli, K oxytoca, K pneumoniae, and Proteus mirabilis nonsusceptible to ceftriaxone (CRO) or ceftazidime (CAZ) but susceptible to FEP.

During the study period of 3 years, 38 patients were observed. Within this group, “52.6% (n=20) received appropriate therapy with an average time to appropriate therapy of 3.7 (SD 2.1) h,” the investigators wrote. “Among patients receiving inappropriate therapy (n=18), 50% (n=9) were changed to appropriate therapy >24 h after susceptibility results, with an average time to appropriate therapy of 46.5 (SD 44.4) h. The remaining 9 patients (23.7%) did not receive appropriate therapy beyond 24 h.”

“What we gathered from this was that our current reporting methods may lead to our providers having to interpret the susceptibility patterns themselves, and potentially leads to starting of less preferred therapies in the setting of a ESBL bacteremia,” Emerald O'Rourke, PharmD, clinical pharmacist at Penn Presbyterian Medical Center, said in an interview with Contagion. O'Rourke presented the subsequent poster from the study, “Antimicrobial Prescribing Patterns in Bloodstream Infections Caused by Cefepime-Susceptible Extended Spectrum β-lactamase Enterobacterales,”at ID Week 2022.

O'Rourke sat down to talk with Contagion to discuss the study’s results, the practical implications of the results, and how her health system interprets breakpoints.