In vitro antimicrobial activity of ceftolozane/tazobactam against P. aeruginosa and other non-fermenting gram-negative organisms in adults with cystic fibrosis

INTRODUCTION: Pulmonary exacerbations in people with Cystic Fibrosis (CF), with chronic Gram-negative pathogens, are associated with reduced survival. These pathogens are usually treated with repeated courses of systemic antibiotics. However there is a linked emergence of multidrug resistant (MDR) pathogens. Ceftolozane/tazobactam is a new cephalosporin/beta-lactamase inhibitor combination that has been demonstrated to have good activity against MDR Pseudomonas aeruginosa.

MATERIAL & METHODS: In this study ceftolozane/tazobactam was compared to other commonly used intravenous antibiotics against 193 non-fermenting Gram-negative bacteria isolated from CF sputum specimens, including P. aeruginosa, Achromobacter xylosoxidans, Stenotrophomonas maltophilia and Burkholderia. MICs to ceftolozane/tazobactam were determined by standard E-test assay and interpreted according to current EUCAST guidelines.

RESULTS: Ceftolozane/tazobactam had good in vitro antimicrobial activity against CF clinical isolates of P. aeruginosa in comparison to other antimicrobials with the exception of colistin. Ceftolozane/tazobactam also had activity against S. maltophilia, but was not active against B. cenocepacia and A. xylosoxidans.

DISCUSSION: ceftolozane/tazobactam showed excellent in vitro activity against P. aeruginosa from CF clinical isolates. This antibiotic is a potential therapeutic option when presented with challenging MDR P. aeruginosa and S. maltophilia exacerbations. Further clinical experience and trials in CF are required to determine the place of this antimicrobial in clinical practice.