Hydrophobicity and serum sensitivity of Klebsiella pneumoniae treated with sub-MICs of quinolones.

Cell surface hydrophobicity and serum sensitivity of Klebsiella pneumoniae, after treatment with sub-minimum inhibitory concentrations (sub-MICs) of ciprofloxacin, norfloxacin and enoxacin, were studied. The quinolones tested at 1/4, 1/8 and 1/16 of the MICs decreased surface hydrophobicity. The most significant reduction of the bacterial cell surface hydrophobicity was found after treatment with antibiotics at 1/16 of the MICs (to 20.3% for both ciprofloxacin and norfloxacin, and to 23.6% for enoxacin, compared with control values). The most significant increase in the susceptibility of the bacteria to serum bactericidal activity was seen after 180 min incubation with ciprofloxacin and enoxacin at 1/16 of their MICs. Survival of treated bacteria was 55 +/- 8% 56 +/- 10% as compared with controls without antibiotics.