Journal Article

Outcomes of Bacteremia due to <i>Pseudomonas aeruginosa</i> with Reduced Susceptibility to Piperacillin-Tazobactam: Implications on the Appropriateness of the Resistance Breakpoint

Vincent H. Tam, Eric A. Gamez, Jaye S. Weston, Laura N. Gerard, Mark T. LaRocco, Juan Pablo Caeiro, Layne O. Gentry and Kevin W. Garey

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 46, issue 6, pages 862-867
Published in print March 2008 | ISSN: 1058-4838
Published online March 2008 | e-ISSN: 1537-6591 | DOI: http://dx.doi.org/10.1086/528712
Outcomes of Bacteremia due to Pseudomonas aeruginosa with Reduced Susceptibility to Piperacillin-Tazobactam: Implications on the Appropriateness of the Resistance Breakpoint

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Background. Bacteremia due to Pseudomonas aeruginosa is associated with grave clinical outcomes. Recent studies have emphasized the importance of appropriate empirical therapy, but controversy arises when piperacillin-tazobactam is used against isolates with reduced susceptibility.

Methods. We performed a retrospective cohort study of pseudomonal bacteremia from 2002 to 2006. Patients were identified by the microbiology laboratory database, and pertinent clinical data (demographic characteristics, baseline Acute Physiology and Chronic Health Evaluation [APACHE] II scores, source of bacteremia, and therapy) were retrieved from the electronic medical records. All patients received appropriate empirical therapy within 24 h of positive culture results. Patients receiving piperacillin-tazobactam were compared with those receiving other agents (control subjects). The primary outcome was 30-day mortality from the first day of bacteremia.

Results. A total of 34 bacteremia episodes were identified involving isolates with reduced susceptibility to piperacillin-tazobactam (minimum inhibitory concentration, 32 or 64 mg/L, reported as susceptible); piperacillin-tazobactam was empirically given in 7 episodes. There was no significant difference in baseline characteristics between the 2 groups. Thirty-day mortality was found to be 85.7% in the piperacillin-tazobactam group and 22.2% in the control group (P=.004). Time to hospital mortality was also found to be shorter in the piperacillin-tazobactam group (P<.001). In the multivariate analysis, 30-day mortality was found to be associated with empirical piperacillin-tazobactam therapy (odds ratio, 220.5; 95% confidence interval, 3.8–12707.4; P=.009), after adjustment for differences in age and APACHE II score.

Conclusions. In P. aeruginosa bacteremia due to isolates with reduced piperacillin-tazobactam susceptibility, empirical piperacillin-tazobactam therapy was associated with increased mortality. Additional studies are warranted to examine the appropriateness of the current Clinical Laboratory Standards Institute resistance breakpoint of piperacillin-tazobactam.

Journal Article.  2816 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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