Mortality After Piperacillin-Tazobactam-Resistant vs -Susceptible Bloodstream Infection

Area of Science:

• Infectious Diseases
• Clinical Microbiology
• Public Health Surveillance

Background:

• Increasing use of piperacillin-tazobactam (TZP) for bloodstream infections (BSIs) globally.
• Emergence of antimicrobial resistance to TZP in various European countries.
• Need to understand the clinical impact of TZP-resistant BSIs in specific healthcare settings.

Purpose of the Study:

• To evaluate the 30-day mortality associated with TZP-resistant BSIs.
• To compare mortality rates between TZP-resistant and TZP-susceptible BSIs caused by Escherichia coli and Klebsiella pneumoniae in Denmark.

Main Methods:

• Retrospective cohort study using Danish national health registers (November 2018 - November 2024).
• Inclusion of adult patients (≥18 years) with monomicrobial E. coli or K. pneumoniae BSI.
• Analysis of 30-day mortality using univariable and multivariable Cox regression models, adjusted for key risk factors.

Main Results:

• A total of 34,379 patients were included; 5.9% of E. coli and 9.5% of K. pneumoniae BSIs were TZP-resistant.
• After adjusting for baseline risk factors, no significant difference in 30-day mortality was observed between TZP-resistant and TZP-susceptible BSIs for both E. coli (aHR, 1.09) and K. pneumoniae (aHR, 1.15).
• Crude mortality rates were slightly higher for TZP-resistant BSIs but did not reach statistical significance after adjustment.

Conclusions:

• In the Danish healthcare system, TZP-resistant E. coli and K. pneumoniae BSIs were not associated with significantly increased 30-day mortality compared to susceptible strains.
• These findings are relevant given the rising trend of TZP resistance in Europe and warrant further investigation into treatment outcomes.
• The study underscores the importance of real-time data collection for monitoring antimicrobial resistance and its clinical implications.