SUB-MINIMUM INHIBITORY CONCENTRATIONS OF CEFTIBUTEN REDUCE ADHERENCE OF ESCHERICHIA-COLI TO HUMAN-CELLS AND INDUCES FORMATION OF LONG FILAMENTS

The minimal inhibitory concentrations (MICs) of an antibiotic are pres ent for only a certain period of time, after which they become sub-inh ibitory concentrations (sub-MICs). These sub-MICs are still active bec ause they can interfere with the mechanism of bacterial adhesion, whic h is the first step in the sequence of events leading to infection. Th e purpose of the present study was to investigate the effects of sub-M ICs of ceftibuten, a new third-generation cephalosporin, on the adhesi on of Escherichia coli (E. coli) to human buccal cells. The degree of inhibition was maximal at 1/2 MIC and then gradually returned toward t o the control values at 1/128 the MIC. The differences were statistica lly significant from 1/2 to 1/32 MIC. Since the MIC was 0.5 mug/ml, co ncentrations from 0.25 to 0.015 mug/ml significantly reduce bacterial adhesion. Ceftibuten also caused marked elongation of E. coli. These f indings could help to explain the efficacy showed by ceftibuten in the treatment of respiratory and urinary tract infections when administer ed once daily.