Evaluation of antimicrobial activities of minocycline and rifampin-impregnated silicone surfaces in an in vitro urinary system model

Objective: To evaluate the antimicrobial activity in urinary catheters and silicones in antibiotic-coated prosthetic urinary systems in order to reduce morbidity and mortality caused by catheter-associated infection. Methods: The study was initiated in 1993 at Houston, USA and continued in Turkey till 1996. A sterile plastic bag was used as kidney in the in vitro urinary system. Physiological renal jet streams (50cc/h) were generated with an intravenous metric pump. The temperature was kept at body temperature. The bladder drainage was achieved at the physiological drainage period of 4-6 hours during the 72-hour experiment. Silicone surfaces coated with pure silicone and impregnated with Minocycline-Rifampin were exposed to the urine contaminated with the targeted bacteria in the in vitro urinarymodel for 72 hours. Antimicrobial activities occurring in the Eosinmethylene blue and blood agar media in the infected silicones were assessed. Results: Minocycline-Rifampin silicone surfaces exposed to the urine contaminated with Escherichia coli and Pseudomonas aeruginosa reported reproduction. No reproduction was observed in the culture of Minocycline- Rifampin-impregnated silicone surfaces for Proteus mirabilis. The difference with the control group was regarded as statistically significant for Proteus mirabilis (p 0.005). Minocycline-Rifampin-coated silicones were closely monitored only for Proteus mirabilis in the in vitro urinary medium. Although inhibition zones ( 10mm) in the cultures were observed for Minocycline-Rifampin-coated silicones for Escherichia coli and Pseudomonas aeruginosa, but the microbial efficacy was not regarded sufficient. Conclusion: There is still need for evidence-based in vivo and in vitro studies where antimicrobial activity is evaluated on the surface of catheters.