Effect of subminimal inhibitory concentrations of three fluoroquinolones on adherence of uropathogenic strains of Escherichia coli

The effect of subinhibitory concentrations (1/2-1/32 x MIC) of ciprofloxacin, ofloxacin and levofloxacin on the adherence of three strains of Escherichia coli (a mannose-resistant haemagglutinating clinical isolate, a non-haemagglutinating clinical isolate and the mannose-resistant haemagglutinating ATCC 25922 strain) were studied. Ciprofloxacin had the lowest MIC values but only the 1/2 MIC concentration inhibited adherence of mannose-resistant haemagglutinating strains after exposure to subMIC values. Significant inhibition of adherence was observed with 1/4 x MIC ofloxacin for both haemagglutinating isolate (27096) and the ATCC strain. Levofloxacin might be more effective and safer than ciprofloxacin and ofloxacin as a long acting fluoroquinolone at subMIC values in patients with UTI.