[Effects of quinolones on biofilm formed by Staphylococcus epidermidis isolated from patients with urinary tract infection]

ABSTRACT

Bacterial cells of Staphylococcus epidermidis are naturally occurring on skin and human mucosal membranes. They also cause nosocomial infections. Capability of biofilm formation plays an important role in the bacterial virulence. Quinolones have been used to treat urinary tract infections caused by S. epidermidis for several years. Thus, resistance to this type of antibiotics has emerged among the strains of this organism. Since the bacterial cells residing within biofilm structures are more resistant than those in planctonic stage, we conduct this study to examine the effect of quinolones was the main goal of ones study of higher resistance of native biofilm producing strains is the goal of this project. In this research ten native isolates of S. epidermidis were obtained from patients with urinary tract infection. Also standard strain of S. epidermidis PTCC 1435 was used as a control. Identification of strains was confirmed using morphological and biochemical tests. Challenge tests against the isolated was performed using three quinolone antibiotics including Ciprofluxacin, Ofluxacin, Nalidixic acid, with two different procedures kirby bauer disk diffusion test, and broth dilution test. Average of MICs of above mentioned antibiotics against ten isolated was obtained as follow Ciprofluxacin [7/375 micro g /micro l], Ofluxacin [11/53 micro g /micro l], Nalidixic acid [2597 /2 micro g /micro l]. Experimental biofilm model of these bacteria showed much higher resistance to quinolone antibiotic, from 15 times in case of Nalidixic acid to 18 times greater resistance in case of Ciprofluxacin. Average of MICs among ten isolates against the three antibiotics also showed increased resistance as follow Ciprofluxacin [128/4 micro g /micro l], Ofluxacin [177/8 micro g /micro l], Nalidixic acid [3942/4 micro g /micro l]. S. epidermidis showed increased resistance to different quinolone antibiotics in biofilm structure, comparing to those of planktonic form. Results obtained from this research is in agreement with those of other similar projects; and emphesize on applying of adequate doses of antibiotics against urinary infection caused by biofilmic Staphylococcus epidermidis