The AHWG determined that PK/ PD was more informative in necessary changes to the PTZ breakpoint for P aeruginosa. The AHWG reported that clinical outcomes data available for PTZ against P aeruginosa were limited by the small cohort sizes, lack of extended-infusing dosing schemes, and nonuse of broth microdilution (BMD) to determine MIC values. 2 Another study evaluating the “microbiological efficacy” of PTZ against P aeruginosa–induced bacteremia found an efficacy rate of 93.3% (28 of 30) for infections caused by isolates with a MIC of 16 µg/mL or less, 55.6% (5 of 9) for 32 µg/mL, and 0.0% (0 of 3) for those with MICs of 64 µg/mL. In another retrospective study, among 170 pediatric patients with P aeruginosa bacteremia, data revealed 9% mortality when the isolate MIC was 16 µg/mL or less, and 24% when the MIC increased to 32 to 64 µg/mL. Findings from 1 retrospective study evaluating 30-day mortality from pseudomonal bacteremia (MIC, 32-64 µg/mL) demonstrated that patients treated with PTZ had significantly higher mortality (85.7%) compared with the control group (22.2%).
The clinical outcomes data revealed increased clinical failure rates when isolated P aeruginosa had higher minimum inhibitory concentration (MIC) values.
