AmpC β-lactamase is one of the leading causes of Pseudomonas aeruginosa (P. aeruginosa) resistance to cephalosporins. FR259647 is a cephalosporin having a novel pyrazolium substituent at the 3-position and exhibits excellent activity (MIC= 1μg/mL) against the AmpC β-lactamase overproducing P. aeruginosa FP1380 strain in comparison with the third-generation cephalosporins FK518 [Abstracts of Papers, 30th Interscience ...