Sub-inhibitory doses of Ofloxacin reduce adhesion and biofilm formation of Pseudomonas aeruginosa to biotic and abiotic surfaces

Biofilm formation of Pseudomonas aeruginosa ( P. aeruginosa ) and its adherence increases bacterial virulence to cause the infection. The role of treating P. aeruginosa with sub-inhibitory concentrations of ofloxacin in vitro in reducing bacterial adherence to biotic and abiotic surfaces was evaluated. Ten isolates of P. aeruginosa were isolated from urine samples. Biofilm formation on polystyrene microtiter plates and Minimum inhibitory concentrations (MICs) of ofloxacin against all isolates were evaluated. The effect of sub-MICs of ofloxacin (0.5×MIC, 0.25×MIC, 0.125×MIC, and 0.06×MIX) on biofilm formation (to polystyrene) and adhesion to prepared human epithelial cells (HECs) in vitro was evaluated. The MICs of ofloxacin were lower than 64 µg/ml and all isolates produced biofilm. There was no relationship between the susceptibility of bacterial isolates to ofloxacin and biofilm formation (r:-0.11; P >0.05). It was found that all sub-MIC concentrations of ofloxacin reduced significantly the biofilm formation on polystyrene and adhesion to HECs in a concentration-dependent manner. Electron microscope images showed that the sub-MIC concentrations of ofloxacin prevent biofilm development to maturation. It can be concluded the negative effect of sub-MIC concentrations of ofloxacin on biofilm production and adhesion to biotic and abiotic surfaces in vitro .