RESUMEN
The post-antibiotic effect [PAE] of ceftizoxime was measured alone and in combination with ciprofloxacin and pipracillin against Pseudomonas aeruginosa and Escherichia coli. Ceftizoxime alone had no PAE [0.75 h] against Ps. aeruginosa, also pipracillin showed no PAE [0.62] against E. coli. Ciprofloxacin showed the highest PAEs against the tested bacteria [3-3.8 h]. Combination of ceftizoxime with ciprofloxacin and pipracillin showed longer PAEs against Ps. aeruginosa [PAE = 6.07 and 5.02 h, respectively], whereas E. coli was not affected [PAE = 1.06 and 0.06 h, respectively]. The addition of ceftizoxime during the post-antibiotic phase of the other antibiotics and vice versa showed that ceftizoxime with ciprofloxacin was the only combination with consistent bactericidal activity. These in vitro results suggested that the combination of ceftizoxime with ciprofloxacin is likely to be the most effective of the tested drugs and should be further evaluated in clinical trials