Activity of ceftolozane/tazobactam against Pseudomonas aeruginosa and Enterobacterales isolates recovered from intensive care unit patients in Spain: The SUPERIOR multicentre study

ABSTRACT Patients in intensive care units (ICUs) present a high risk of developing an infection caused by multidrug-resistant bacteria. Consequently, new antimicrobials and combinations are required. In this study, the activity of ceftolozane/tazobactam (C/T) was evaluated against Enterobacterales ( n  = 400) and Pseudomonas aeruginosa ( n  = 80) clinical isolates collected from patients in Spanish ICUs with complicated urinary tract infections (cUTI) and complicated intra-abdominal infections (cIAI). Overall susceptibility to C/T in P. aeruginosa isolates by infection type was 95.7% in cUTI (MIC 50/90 , 1/4 mg/L) and 85.3% in cIAI (MIC 50/90 , 1/64 mg/L). Activity against P. aeruginosa was maintained regardless of its resistance pattern, confirming that C/T is one of the best antipseudomonal agents along with colistin and amikacin. Susceptibility to C/T in Enterobacterales by infection type was 79.5/81.9% and 89.3/92.3% (EUCAST/CLSI) in cIAI and cUTI isolates, respectively. Activity was excellent against wild-type organisms, with 100% susceptible and inhibited at MIC ≤1 mg/L. Nevertheless, C/T susceptibility decreased against extended-spectrum β-lactamase (ESBL)-producing isolates: Escherichia coli (80.4/84.8% susceptible by EUCAST/CLSI) and Klebsiella pneumoniae (59.1/77.3% susceptible by EUCAST/CLSI). No activity of C/T was observed in carbapenemase-producing isolates. The in vitro activity of C/T observed in this surveillance study suggests that this agent can be considered as a therapeutic option for cUTI and cIAI due to Enterobacterales and P. aeruginosa in ICU patients, particularly when carbapenemase-producing isolates are not involved.