• Polyvinylpyrrolidone (PVP);
  • Bioflex;
  • Penile Prosthesis;
  • Infection;
  • Hydrophilic

Conflict of Interest. The present study was supported by a grant received from Mentor Corporation.


Objectives.  To find conditions that reduce the susceptibility of penile prostheses to infection, we studied the effect of coating the surface of polyurethane (Bioflex) with a hydrophilic material with and without antibiotics in decreasing bacterial colony counts both in vitro and in experiments in rats.

Materials and Methods.  The in vitro experiment was performed using seven strips each of polyvinylpyrrolidone (PVP)-coated and uncoated polyurethane. These strips were dipped in saline for 5 minutes followed by incubation in a suspension of Staphylococcus epidermidis (SE) for a period of 10 minutes. Colony counts were determined after sonication of strips. For the in vitro experiments, 60 rats were used. Thirty animals each had uncoated or coated polyurethane implanted subcutaneously. In each group, strips were implanted after dipping them in either saline (N = 15) or an antibiotic solution (N = 15) consisting of 1 g/L vancomycin and 160 mg/L gentamicin. A bacterial suspension containing SE was then directly introduced into the subcutaneous pockets of all the animals prior to closure. After 7 days, strips were explanted along with 0.5 × 0.5 cm of surrounding tissue, and sonicated. Colony counts were performed on each sonicate. The data were analysed using Student's t-test. A P-value less than or equal to 0.05 was considered to be statistically significant.

Results.  The in vitro study demonstrated a statistically significant (41%) reduction in the colony count of SE within the coated polyurethane strips compared to the uncoated Bioflex strips (150 ± 44.7 CFU vs. 253 ± 45.0 CFU, respectively, P-value < 0.05). Animal studies showed that bacterial CFU was highest in the uncoated Bioflex strip (29 ± 24.5 CFU), followed by uncoated Bioflex with antibiotic treatment (24 ± 28.1 CFU), coated Bioflex (17 ± 25.2 CFU) and coated Bioflex with antibiotic treatment (13 ± 16.1 CFU). Antibiotic treatment of coated Bioflex caused a significant reduction in the bacterial CFU compared to uncoated Bioflex (13 ± 16.1 vs. 29 ± 24.5 CFU, respectively, P = 0.04). This represents a 55% reduction in the bacterial count. While the reduction in the bacterial count in the coated Bioflex strip was not statistically different from that in the uncoated strip, a trend towards significance was noted with a 41% reduction (P > 0.05) in bacterial count in the coated Bioflex group compared to uncoated Bioflex.

Conclusions.  In conclusion, in vitro studies demonstrate a significant (41%) reduction in the colony count of SE in PVP-coated polyurethane compared to uncoated polyurethane. In vivo study in rats showed that antibiotic treatment of PVP-coated Bioflex resulted in a statistically significant reduction (55%) in colony count of SE compared to uncoated Bioflex.