Susceptibility of ceftolozane/tazobactam against multidrug-resistant and carbapenem-resistant Pseudomonas aeruginosa.

Ceftolozane (CTLZ) is a novel cephalosporin antibiotic that exhibits broad-spectrum activity against gram-negative pathogens, including Pseudomonas aeruginosa, especially when combined with tazobactam (TAZ). We examined the minimum inhibitory concentration (MIC) of CTLZ/TAZ for 21 multidrug-resistant P. aeruginosa (MDRP) and eight carbapenem-resistant P. aeruginosa (CRPA) strains isolated at Okayama University Hospital, Japan. Consequently, 81% (17/21) of the MDRP strains and 25% (2/8) of the CRPA strains were resistant to CTLZ/TAZ (MIC >8 μg/mL). All 18 blaIMP-positive strains showed resistance to CTLZ/TAZ, whereas the drug retained in vitro susceptibility in 54.5% (6/11 strains) of blaIMP-negative strains.