Comparison of In Vitro Activities of Cefiderocol, Imipenem/Relebactam and other Antibiotics against Carbapenem-Resistant Pseudomonas aeruginosa Isolates

Objective: Carbapenems are commonly used in treatment of severe infections caused by Pseudomonas aeruginosa . However, carbapenem-resistant P. aeruginosa isolates have increased in recent years and have become a public health threat. The objective of this study was to compare in vitro activities of cefiderocol, imipenem/relebactam and other antibiotics against clinical isolates of carbapenem-resistant P. aeruginosa . Methods: A total of 92 carbapenem-resistant P. aeruginosa isolates (all isolates were resistant to imipenem according to both CLSI and EUCAST; all isolates were resistant to meropenem according to CLSI; 84 isolates were resistant and 8 isolates were ‘I - Susceptible, increased meropenem, piperacillin/tazobactam and ceftazidime were determined by gradient diffusion method. Results were interpreted according to CLSI and EUCAST criteria. Results: The most active antibiotic tested against isolates were cefiderocol. All isolates were susceptible to cefiderocol using CLSI criteria, whereas 97.8% of isolates were susceptible to cefiderocol using EUCAST criteria. Gentamicin was the most active antibiotic after cefiderocol. Eighty-seven percent of isolates were susceptible to gentamicin. The imipenem/relebactam susceptibility rate among isolates were 66.3% and 73.9% according to CLSI and EUCAST criteria, respectively. Levofloxacin showed the lowest in vitro activity against isolates. The levofloxacin resistance rate among isolates were 70.7% and 82.6% according to CLSI and EUCAST criteria, respectively. Conclusion: Cefiderocol may be an option for treatment of infections caused by carbapenem-resistant P. aeruginosa .