Microbiologic profile of ceftibuten, a new oral cephalosporin

The bactericidal activity of ceftibuten, alone and in combination with other drugs, has been assessed in vitro. The ability to induce a post-antibiotic effect (PAE), the rate of emergence of spontaneous resistant mutants, and the presence of Eagle's phenomenon were also investigated. Ceftibuten rapidly killed most Enterobacteriaceae, Haemophilus, Moraxella and Streptococcus species tested, including beta-lactamase-producing strains with over 90% cfu reduction after only 2 h. Using chequerboard and time-kill tests, ceftibuten was found to react synergistically with aminoglycosides, and to give an indifferent response with ofloxacin against a large number of Gram-negative aerobes and streptococci. Antagonism was never observed. Ceftibuten induced a PAE of approximately 1 h on S. pneumoniae. As expected, no PAE was observed with Gram-negative species. Spontaneous emergence of ceftibuten-resistant strains exposed to supra-MICs of the drug was rare (< or = 10(-8)) in all pathogens tested. No marked Eagle effect was detected when bacteria were treated with ceftibuten at concentrations exceeding 100-fold their MICs. This rules out the possibility that in vivo the high concentrations of ceftibuten reached in the urinary tract may hinder its excellent bactericidal activity.