effects of antibiotics on adhesion and invasion of proteus mirabilis

the ability of subminimum inhibitory concentrations (sub-mics) of antibiotics to affect the virulence factors of bacteria may be an important criterion in selecting an antibiotic for therapy. proteus mirabilis is one of the most frequently seen pathogens in urinary tract infections. the aim of this study was to analyze the effects of some antibiotics on two important virulence factors of p. mirabilis. in this study the effects of 1/2, 1/4 and 1/8 of the mic of amoxicillin, gentamicin and nalidixic acid on adhesion and invasiveness of two clinical isolates of p. mirabilis were evaluated. sub-mics of ampicillin significantly reduced adhesion of p. mirabilis to uroepithelial cells and gentamicin exerted the same effect to lesser extent. invasion of kidney epithelial cells by p. mirabilis in the presence of antibiotics was also evaluated. ampicillin and nalidixic acid caused a reduction in the number of intracellular bacteria. gentamicin showed the lowest inhibitory effect on cell invasion. the results indicate that the sub-mics of antibiotics can affect virulence factors of p. mirabilis. the presence of sub-mic effect of antibiotics may be an important factor in determining the dosing regimen for urinary tract infections.