Antimicrobial activity of CXA-101, a novel cephalosporin tested in combination with tazobactam against Enterobacteriaceae, Pseudomonas aeruginosa, and Bacteroides fragilis strains having various resistance phenotypes.

CXA-101, a novel oxyimino-aminothiazolyl cephalosporin, CXA-201 (CXA-101 combined with tazobactam), and various comparators were susceptibility tested by broth microdilution methods against 1,301 well-characterized clinical strains collected worldwide, including ceftazidime-resistant members of the family Enterobacteriaceae and Klebsiella pneumoniae carbapenemase (KPC)- and extended-spectrum β-lactamase (ESBL)-producing strains of Pseudomonas aeruginosa and Bacteroides fragilis. CXA-201 was 2- to 32-fold more active than ceftazidime and piperacillin-tazobactam against ceftazidime-resistant Enterobacteriaceae species but less active than cefepime for some species. CXA-101 and CXA-201 were very active against P. aeruginosa (MIC50, 1 μg/ml for both compounds), including imipenem-resistant strains.