[Evaluation of susceptibility of multidrug-resistant Pseudomonas aeruginosa strains against ceftolozane/tazobactam].

Background: Pseudomonas aeruginosa is an opportunistic pathogen associated with high morbidity and mortality. For multidrug-resistant strains (MDR), ceftolozane/tazobactam (CTZ) has been authorized by the European Medicines Agency (EMA) for complicated urinary tract infections, acute pyelonephritis, and complicated intraabdominal infections.

Aim: To determine the susceptibility to CTZ of P. aeruginosa MDR in isolated clinical samples at the University Hospital Puerto Real.

Methods: The susceptibility according to the EUCAST to CTZ criteria of strains of P. aeruginosa MDR, between January 2015 and August 2017 has been studied. The multiresistance criteria were those defined by the Centers for Disease Control and Prevention. The antibiotic susceptibility was obtained by automated MicroScan® system (Beckman Coulter). Susceptibility to CTZ was determined using gradient strips (Liofilchem®, Werfen).

Results: Of 1253 strains isolated, 7% presented MDR. We studied the susceptibility of a total of 78 strains of MDR P. aeruginosa, of which 5 (6.4%) were resistant to CTZ according to the EUCAST criteria.

Conclusions: In our environment, the in vitro resistance to CTZ in MDR P. aeruginosa strains is approximately 6%. CTZ is an option for the treatment of infections by MDR P. aeruginosa when there is no other alternative and its in-vitro susceptibility has been proven.