Effect of antibiotic-loaded hydrophilic stent in the prevention of bacterial adherence: a study of the charge, discharge, and recharge concept using ciprofloxacin

Background: Ciprofloxacin prophylaxis significantly prolonged stent patency in cats, but human studies produced conflicting results, possibly due to v arying drug levels in bile. The uptake (charge) and release (discharge) of ciprofloxacin from a hydrophilic stent (HS) in an antibiotic solution and t he effect of a ciprofloxacin-loaded stent (CHS) in inhibiting Escherichia c oil adherence were tested. The adjuvant effect of ciprofloxacin perfusion ( recharge) in the inhibition of E coil adherence was also tested. Methods: Uptake: segments of HS were immersed in 5 mi of ciprofloxacin solu tions for 24 hours. Ciprofloxacin remaining in solution was measured to det ermine the uptake by the HS, Release: CHS were placed in 5 mt water for 24 hours, and released ciprofloxacin was measured. CHS were placed on culture plates with E coli and incubated; diameters of inhibited zones were measure d. CHS 0.5 cm in length were incubated in separate 5 mt E coil suspension ( 10(7) colony forming units [CFU]/mL) in 2% ox bile for 4 hours. E coil adhe red on CHS were measured and compared with control HS, An E coil (10(6) CFU /mL) suspension was perfused through a modified Robbins device (MRD)-contai ning CHS. Stents were removed at regular intervals and processed to determi ne the adherence of E coil; non-loaded us served as controls. The experimen t was repeated by using CHS together with perfusion of ciprofloxacin soluti on (0.3 mug/mL) into the MRD for up to 7 days; normal saline solution was u sed as a control in a second MRD, Stents were removed daily to determine th e adherence of E coli. Results: Uptake and release of ciprofloxacin by HS and CHS, respectively, w ere related to concentration of ciprofloxacin. Between 50% to 90% of the dr ug was released in 24 hours. Zonal inhibition of E coil growth was proporti onal to the concentration of ciprofloxacin on the CHS, There was an initial 10-fold reduction in attached E coli on CHS compared with controls, but th is effect diminished after 24 hours. With ciprofloxacin perfusion, there wa s a 100-fold reduction in adhered E coil on CHS, although there was no chan ge in E coil concentration in bile. Conclusions: There was a free exchange (uptake and release) of ciprofloxaci n along a concentration gradient between the antibiotic solution and us. CH S reduced the number of adhered E coil, but the effect was short-lived. Per fusion of ciprofloxacin offers an adjuvant benefit by enhancing inhibition of E coil adherence on CHS.