Differential Effect of Prior β-lactams and Fluoroquinolones on Risk of Bloodstream Infections Secondary to Pseudomonas Aeruginosa

Objective: This retrospective case-control study examines risk factors for bloodstream infections (BSI) due to Pseudomonas aeruginosa (PSA).

Methods: Hospitalized adults with Gram-negative BSI at Palmetto Health from 2010 to 2015 were identified. Multivariate logistic regression was used to examine PSA BSI risk factors.

Results: Seventy and 910 patients with PSA and Enterobacteriaceae BSI, respectively, were included. Prior use of β-lactams (adjusted odds ratio [aOR] 3.9, 95% confidence intervals [CI]: 2.3-6.9), but not fluoroquinolones (aOR 1.0, 95% CI: 0.4-2.2), was a risk factor for PSA BSI. Immune compromised status (aOR 3.7, 95% CI: 2.0-6.7), respiratory source (aOR 4.4, 95% CI: 2.1-8.9), and prolonged hospitalization (aOR 1.9, 95% CI: 1.1-3.5), were predictors of PSA BSI.

Conclusions: Determination of class of previously used antibiotics among other clinical variables helps identify patients at risk of PSA BSI and offers opportunities to optimize empirical antimicrobial therapy.