Antipseudomonal antibiotics are frequently used in patients admitted to hospitals. Many of these substances are classified as a reserve or watch status by the WHO. Inappropriate risk assessment of invasive detection of P. aeruginosa (PAE) can be a reason for overuse of antipseudomonal antibiotics, therefore it is important to define relevant and specific risk factors for invasive PAE detection, say Reyle, et al. (2025), who sought to identify risk factors for invasive detection of PAE in patients upon hospital admission.

All patients 18 years of age and older with a detection of PAE and/or Enterobacterales in clinical samples taken within 48 hours of admission to one of the hospitals of Charité Universitätsmedizin Berlin between 2015 and 2020 were included into this retrospective cohort study.

Overall, the researchers included a total of 27,710 patients. In 3,764 (13.6%) patients PAE was detected in clinical samples taken within 48 h after admission. The most frequently detected Enterobacterales was E. coli in 14.142 (51%) patients followed by Klebsiella spp. in 4.432 (16%) patients. Multivariable regression analysis identified that prior colonization with a multidrug-resistant PAE or detection of a PAE in clinical samples during a previous hospitalization increased the risk for invasive detection of PAE (OR 39.41; 95% CI 28.54–54.39) and OR 7.87 (95% CI 6.60–9.38) respectively. Admission to a specialized ward for patients with cystic fibrosis was associated with an increased risk (OR 26.99; 95% CI 20.48–35.54). Presence of chronic pulmonary disease (OR 2.05; 95% CI 1.85–2.26), hemiplegia (OR 2.16; 95% CI 1.90–2.45) and male gender (OR 1.60; 95% CI 1.46–1.75) were associated with a modest increase in risk for presence of PAE.

Patients with a prior detection of P. aeruginosa or admission to a cystic fibrosis ward had the highest risk for invasive detection of P. aeruginosa. Adherence to specific risk scores based on local risk factors could help to optimize prescription of anti-pseudomonal antibiotics that categorized as reserve and watch, the authors say.

Reference: Reyle R, et al. Risk factors for detection of Pseudomonas aeruginosa in clinical samples upon hospital admission. Antimicrobial Resistance & Infection Control. Volume 14, article number 17 (2025).