Antimicrobial resistance profiles in multidrug-resistant Pseudomonas aeruginosa isolates in a university hospital in Argentina. Activity of new antibiotic combinations.

Thirty consecutive multidrug-resistant non-carbapenemase-producing Pseudomonas aeruginosa clinical isolates from patients admitted at a university hospital were studied. Resistance rates to ceftazidime/avibactam, aztreonam/avibactam, ceftolozane/tazobactam and imipenem/relebactam were 40%, 88%, 3%, and 20%, respectively. Ceftazidime/avibactam reverted ceftazidime resistance in 25% of the isolates, whereas imipenem/relebactam did so in 77% of the imipenem-resistant isolates. The analysis of the resistance patterns observed suggests a high contribution of non-enzymatic mechanisms such as efflux pumps and porin alterations.