In vitro activity of ceftolozane/tazobactam against clinical isolates of Pseudomonas aeruginosa in the planktonic and biofilm states

Antonio L. Velez Perez, Suzannah M. Schmidt-Malan, Peggy C. Kohner, Melissa J. Karau, Kerryl E. Greenwood-Quaintance, Robin Patel

Research output: Contribution to journalArticle

8 Scopus citations


Pseudomonas aeruginosa causes a variety of life-threatening infections, some of which are associated with planktonic and others with biofilm states. Herein, we tested the combination of the novel cephalosporin, ceftolozane, with the β-lactamase inhibitor, tazobactam, against planktonic and biofilm forms of 54 clinical isolates of P. aeruginosa, using cefepime as a comparator. MIC values were determined following Clinical and Laboratory Standards Institute (CLSI) guidelines. Minimum biofilm inhibitory concentration (MBIC) values were determined using biofilm-laden pegged lids incubated in antimicrobial challenge plates containing varying concentrations of ceftolozane/tazobactam. Pegged lids were then incubated in growth recovery plates containing cation-adjusted Mueller-Hinton broth to determine the minimum biofilm bactericidal concentration (MBBC). Ceftolozane/tazobactam was highly active against planktonic P. aeruginosa, with all 54 isolates studied testing susceptible (MIC ≤4/4μg/mL). On the other hand, 51/54 biofilm P. aeruginosa had MBICs ≥16/4μg/mL, and all 54 isolates had MBBCs >32μg/mL. Of the 54 isolates, 45 (83.3%) tested susceptible to cefepime, with the MIC50/MIC90 being 4/16μg/mL, respectively, and the MBIC90 and MBBC90 both being >256μg/mL. Although ceftolozane/tazobactam is a promising antimicrobial agent for the treatment of P. aeruginosa infections, it is not highly active against P. aeruginosa biofilms.

Original languageEnglish (US)
JournalDiagnostic Microbiology and Infectious Disease
StateAccepted/In press - Nov 25 2015



  • Biofilm
  • Ceftolozane
  • Pseudomonas aeruginosa
  • Tazobactam

ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases

Cite this