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Copyright of Revista Española de Quimioterapia is the property of Sociedad Espanola de Quimioterapia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Española de Quimioterapia is the property of Sociedad Espanola de Quimioterapia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: Ceftolozane/tazobactam has shown excellent activity against Pseudomonas aeruginosa, but this drug is not always included in commercial panels. The aim of the study was to evaluate the performance of 2 gradient strips (BioMérieux and Liofilchem) and a commercial microdilution panel (Sensititre, EURGNCOL panel) using this combination against carbapenem-resistant P. aeruginosa isolates., Methods: Three commercial methods were tested with 41 metallo-beta-lactamase-producing and 59 non-carbapenemase-producing P. aeruginosa isolates. Broth microdilution was used as reference., Results: All carbapenemase-producing isolates and only one non-producing isolate were resistant to this antibiotic. Both essential agreement and bias were outside the acceptance intervals since MIC values were higher than reference values for all three methods. The Kappa index indicated poor or weak agreement. Changes in clinical categories were observed in 3 isolates., Conclusions: The three methods yielded poor agreement with the reference. Despite the differences in MIC values, fewer than 3% involved category changes., (Copyright © 2022 Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. Published by Elsevier España, S.L.U. All rights reserved.)

Introduction: Pseudomonas aeruginosa displays resistance to several available antibiotics. Infections caused by this pathogen are associated with a high mortality, morbidity, and considerable healthcare resource utilization and costs. This study was aimed at describing the use of ceftolozane/tazobactam (C/T) for the treatment of patients with P. aeruginosa infections., Methods: Case series analysis of hospitalized patients treated with C/T for P. aeruginosa infections in five public Portuguese hospitals. Patients presenting with infections caused by this pathogen and receiving C/T for at least 72h during hospitalization were eligible., Results: Sixty-four hospitalized patients with P. aeruginosa infections treated with C/T were evaluated between December 2016 and July 2019. Most patients were aged between 60 and 79 years (53.9%). Patients presented a total of 68 P. aeruginosa infections, with respiratory infections being the most common (28.1%, 18 out of 64). Most P. aeruginosa strains (85.9%, 55 out of 64) were extensively drug-resistant (XDR). C/T was mostly used as targeted therapy (98.4%, 63 out of 64 patients) and as monotherapy (72.7%, 47 out of 64 patients). Combination therapy was used in 47.4% (9 out of 19) of patients with bacteriemia. Most patients had successful microbiological (79.2%, 42 out of 53) and clinical (78.7%, 48 out of 61) outcomes. All-cause in-hospital mortality rate was 34.4%., Conclusion: The present case series contributes to the body of evidence suggesting that C/T is an effective and safe option for treating P. aeruginosa infections, namely those caused by XDR strains, both when used as mono- or combination therapy., (Copyright © 2022 Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. Published by Elsevier España, S.L.U. All rights reserved.)

Introduction: We characterized AmpC β-lactamase mutations that resulted in ceftolozane/tazobactam resistance in extensively drug-resistant (XDR) Pseudomonas aeruginosa isolates recovered from patients treated with this agent from June 2016 to December 2018., Methods: Five pairs of ceftolozane/tazobactam susceptible/resistant P. aeruginosa XDR isolates were included among a total of 49 patients treated. Clonal relationship among isolates was first evaluated by pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing (MLST) was further performed. AmpC mutations were investigated by PCR amplification of the blaPDC gene followed by sequencing., Results: The ST175 high-risk clone was detected in four of the pairs of isolates and the ST1182 in the remaining one. All resistant isolates showed a mutation in AmpC: T96I in two of the isolates, and E247K, G183V, and a deletion of 19 amino acids (G229-E247) in the other three. The G183V mutation had not been described before. The five isolates resistant to ceftolozane/tazobactam showed cross-resistance to ceftazidime/avibactam and lower MICs of imipenem and piperacillin/tazobactam than the susceptible isolates., Conclusions: Ceftolozane/tazobactam resistance was associated in all of the cases with AmpC mutations, including a novel mutation (G183V) not previously described. There is a vital need for surveillance and characterization of emerging ceftolozane/tazobactam resistance, in order to preserve this valuable antipseudomonal agent., (Copyright © 2020 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.)