Risk factors for detection of Pseudomonas aeruginosa in clinical samples upon hospital admission

BACKGROUND/INTRODUCTION: 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. OBJECTIVE: The objective of this study was to identify risk factors for invasive detection of PAE in patients upon hospital admission. METHODS: All patients 18 years of age and older with a detection of PAE and/or Enterobacterales in clinical samples taken within 48 h of admission to one of the hospitals of Charité Universitätsmedizin Berlin between 2015 and 2020 were included into this retrospective cohort study. RESULTS: Overall, we 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 colonisation with a multi drug resistant PAE or detection of a PAE in clinical samples during a previous hospitalisation 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 specialised 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. CONCLUSION: 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.