The Ciprofloxacin Impact on Biofilm Formation by Proteus Mirabilis and P. Vulgaris Strains

BACKGROUND Proteus spp. bacilli belong to opportunistic human pathogens, which are primarily responsible for urinary tract and wound infections. An important virulence factor is their ability to form biofilms that greatly reduce the effectiveness of antibiotics in the site of infection. OBJECTIVES The aim of this study was to determine the value of the minimum concentration of ciprofloxacin that eradicates a biofilm of Proteus spp. strains. MATERIALS AND METHODS A biofilm formation of 20 strains of P. mirabilis and 20 strains of P. vulgaris were evaluated by a spectrophotometric method using 0.1% 2, 3, 5-Triphenyl-tetrazolium chloride solution (TTC, AVANTORTM). On the basis of the results of the absorbance of the formazan, a degree of reduction of biofilm and minimum biofilm eradication (MBE) values of MBE50 and MBE90 were determined. RESULTS All tested strains formed a biofilm. A value of 1.0 μg/mL ciprofloxacin is MBE50 for the strains of both tested species. An MBE90 value of ciprofloxacin for isolates of P. vulgaris was 2 μg/mL and for P. mirabilis was 512 μg/mL. CONCLUSIONS Minimum biofilm eradication values of ciprofloxacin obtained in the study are close to the values of the minimal inhibition concentration (MIC).