[Effect of sub-inhibitory concentrations of cefixime on the morphology, hemagglutination and adhesiveness of urinary strains of Escherichia coli].

The treatment of urinary tract infections is one of the indications of cefixime, a new oral cephem. The aim of the present work was to study the in vitro effect of cefixime sub- and infra-MICs on the morphology, haemagglutination and adhesiveness to epithelial cells of three uropathogenic Escherichia coli strains pretreated with sub-MICs (1/2 to 1/64 the MIC) of cefixime during growth phase (37 degrees C for 18 h). This treatment led to morphological alterations of the bacteria with filament formation. The E. coli strains showed different haemagglutination profiles (MS; MS-MR; MR). In the presence of cefixime sub-MICs (1/2 to 1/32 the MIC), MR E. coli showed a markedly altered capacity for haemagglutination (using guinea pig, human P1 and p erythrocytes). Adhesiveness was studied with human buccal cells for MS adhesins and human urothelial cells for MR adhesins. A significant decrease of adherence (70-90 per cent) was observed after pretreatment of E. coli strains with cefixime (up to 1/32 the MIC). Compared with other antibiotics active against E. coli, such as nalidixic acid, norfloxacin and ampicillin, the effect of 1/8 the MIC of cefixime on adhesiveness, was more pronounced. These results demonstrate that sub-MICs of cefixime induce a marked reduction in adhesiveness of E. coli. This property might potentiate the effectiveness of cefixime in the treatment of urinary tract infections due to E. coli.