Outcomes of adult patients in the intensive care unit with Pseudomonas aeruginosa pneumonia who received an active anti-pseudomonal β-lactam: Does "S" equal success in the presence of resistance to other anti-pseudomonal β-lactams?

Study objectives: The most commonly prescribed antibiotics for patients with hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP) due to Pseudomonas aeruginosa are the conventional anti-pseudomonal β-lactams (APBLs) (ie, ceftazidime, cefepime, meropenem, or piperacillin-tazobactam). Similar resistance mechanisms in P. aeruginosa affect the APBLs, and it is unclear if resistance to one APBL can affect the effectiveness of other APBLs. This exploratory, hypothesis-generating analysis evaluates the impact of APBL resistance among patients in the intensive care unit (ICU) with P. aeruginosa HABP/VABP who initially receive a microbiologically active APBL.

Design: A retrospective cohort [GJ1] [LT2] study.

Setting: Kaiser Permanente Southern California members (01/01/2011-12/31/2017).

Patients: The study included adult patients admitted to the ICU with a monomicrobial P. aeruginosa HABP/VABP who received a microbiologically active APBL within 2 days of index P. aeruginosa respiratory culture.

Intervention: Patients were stratified by presence of resistance to APBL on index P. aeruginosa (0 vs. ≥1 resistant APBL).

Measurements: Primary outcomes were 30-day mortality and discharge to home.

Main results: Overall, 553 patients were included. Thirty-day mortality was 28%, and 32% of patients were discharged home. Eighty-eight patients (16%) had a P. aeruginosa HABP/VABP that was resistant to ≥1 APBL (other than active empiric treatment). Relative to patients with no APBL resistance, patients with resistance to ≥1 APBL had a higher 30-day mortality (adjusted odds ratio (aOR) [95% confidence interval (CI)]: 1.65 [1.02-2.66]) and were less likely to be discharged home (adjusted hazard ratio (aHR) [95% CI]: 0.50 [0.29-0.85]).

Conclusion: Further study is needed, but this exploratory analysis suggests that the full APBL susceptibility profile should be considered when selecting therapy for patients with P. aeruginosa HABP/VABP.