1881. Empiric Pseudomonal Monotherapy vs. Combination Therapy for Community-Onset Pneumonia in Older Adults

BACKGROUND: Patients with pseudomonal pneumonia have a poor prognosis; therefore, IDSA guidelines recommend empiric antipseudomonal combination therapy when Pseudomonas is suspected, at least until treatment can be adjusted based on susceptibilities. However, combination antipseudomonal therapy is controversial. This study compared all-cause 30-day mortality in older patients who received antipseudomonal monotherapy (PMT) or antipseudomonal combination therapy (PCT) for the treatment of community-onset pneumonia. METHODS: This population-based cohort study used data from over 150 Veteran Health Administration hospitals. Patients were classified as low, medium, or high risk of drug-resistant pathogens according to a published rule. Patients were assigned to PCT or PMT groups based on antibiotics received in the first 48 hours of hospital admission. Separate multivariable logistic regression models were constructed to determine whether the choice of PCT or PMT was associated with 30-day mortality, after accounting for divergent baseline characteristics. Adjusted odds ratios (aORs) and 95% confidence intervals (95% CI) were calculated for the overall, low, medium, and high-risk groups. RESULTS: Of the 31,027 patients who met study criteria, 23% received PCT and 77% received PMT. Patients belonged to low (59%), medium (24%), and high (18%) risk groups. 30-day mortality was 18% overall, and increased among the groups: low (13%), medium (21%), and high (36%). Patient age (median of 78 years), race (>80% white), and sex (>98% male) were similar for patients receiving PCT and PMT. The unadjusted mortality difference between PCT and PMT was most pronounced in the low-risk group (18% vs. 8%, 10% absolute risk difference), followed by the medium (24% vs. 18%, 6% difference) and high (39% vs. 33%, 6% difference) risk groups. PCT was associated with higher 30-day mortality than PMT overall (aOR, 1.54; 95% CI, 1.43–1.66), and in all three groups: low (aOR, 1.69; 95% CI, 1.50–1.89), medium (aOR, 1.30; 95% CI, 1.14–1.48), and high (aOR, 1.21; 95% CI, 1.04–1.40). CONCLUSION: Older adults who received empiric combination antipseudomonal therapy for community-onset pneumonia fared worse than those who received monotherapy. Empiric combination antipseudomonal therapy should not be routinely offered to all patients suspected of having pseudomonal pneumonia. DISCLOSURES: All authors: No reported disclosures.