Prevalence and Resistance Patterns of Pseudomonas aeruginosa in a Tunisian Intensive Care Unit

Pseudomonas aeruginosa is a major cause of health care-associated infections, particularly in intensive care units (ICUs). To the best of our knowledge, this is one of the rare studies reporting the prevalence and antimicrobial resistance patterns of P. aeruginosa in a Tunisian ICU. This retrospective study included all P. aeruginosa strains isolated from ICU patients in Sfax, Tunisia, between 2017 and 2024. A total of 1,126 nonredundant P. aeruginosa strains were obtained from 767 patients. P. aeruginosa strains accounted for 21.1% of all clinical isolates in the ICU. The majority of strains were isolated from respiratory samples (54.6%) and blood cultures (14.3%). The prevalence of resistance rates was highest for ticarcillin (48.3%) and ticarcillin-clavulanic acid (48.6%). The resistance to both ceftazidime and imipenem was observed in 33.6% of P. aeruginosa strains. The prevalence of resistance of P. aeruginosa was 29.8% and 26.2% to ceftazidime-avibactam (CAV) and ceftolozane-tazobactam (C/T), respectively. The prevalence of resistance to amikacin and ciprofloxacin was 36.2% and 37.9%, respectively. Of the 1,126 isolates, 346 (30.7%) were multidrug-resistant P. aeruginosa (MDR-PA) strains, presenting resistance to ceftazidime, ciprofloxacin, and amikacin simultaneously. Since 2022, a significant increase in the MDR rate was observed, reaching 46.3% in 2024 (P <0.001). The resistance rates of MDR-PA were 52.5% and 56.8% to C/T and CAV, respectively. None of the tested MDR-PA strains showed resistance to colistin. This study highlights a high prevalence of MDR strains of P. aeruginosa in our ICU, with increasing resistance over recent years. Prevention is highly warranted.