Comparison of antimicrobial resistance in Pseudomonas aeruginosa from intensive care and non-intensive care units and its impact on treatment decisions.

Emergence of difficult-to-treat-resistance (DTR) P. aeruginosa has significant implications for the selection of empirical therapies. This study aims to compare antimicrobial resistance of P. aeruginosa from ICU and non-ICU patients and to discuss empirical treatment options. Three-hundred-nine P. aeruginosa strains isolated from hospitalized patients in 2023 were included. Antimicrobial susceptibility results for six classes with potential activity against P. aeruginosa were collected. Resistance between strains isolated from ICU and non-ICU was compared. Among 309 strains, 30% were isolated from ICU patients, while 70% from non-ICU. Resistance to ciprofloxacin was significantly higher in non-ICU compared to ICU patients (64% vs. 15%, p-value = 0.0001). Resistance to piperacillin-tazobactam was higher in ICU compared to non-ICU patients (36% vs. 22%, p-value = 0.012). Prevalence of DTR P. aeruginosa was similar between the two groups (21% in ICU and 19% in non-ICU patients). Joint resistance to imipenem and ceftazidime was more prevalent in ICU patients (27% vs. 10%, p-value 0.0001). Additionally, carbapenemase-producing strains were more frequent in ICU patients (20% vs. 5%, p-value = 0.0001). Ceftolozane-tazobactam, whose effectiveness against DTR P. aeruginosa remains preserved, as empirical treatment, would improve its adequacy by 21% in ICU and 19% in non-ICU patients, compared to the currently recommended first-line treatments.