Minocycline-rifampin-impregnated penile prosthesis surfaces retain antimicrobial activity following irrigation with 0.05% chlorhexidine gluconate and antibiotic solutions

Abstract

Background: 0.05% Chlorhexidine gluconate (CHG; Irrisept [IrriMax]) is a commercial wound irrigation solution approved by the Food and Drug Administration that has seen recent adoption in the field of prosthetic urology; however, no study has evaluated whether 0.05% CHG is compatible with the minocycline-rifampin-impregnated surface (InhibiZone) of the AMS 700 penile prosthesis (Boston Scientific).

Aim: To evaluate whether 0.05% CHG alters the antibiotic efficacy of the minocycline-rifampin-impregnated penile prosthesis surface.

Methods: Discs (8 mm) were taken by a punch biopsy (Sklar) from sterile penile prosthesis reservoirs whose surfaces had been impregnated with rifampin and minocycline. Discs (n = 10) were suspended in 0.05% CHG, vancomycin and gentamicin, or normal saline for 2 minutes to simulate intraoperative irrigation. Discs were then rinsed in normal saline to remove any unbound solution and incubated with methicillin-sensitive Staphylococcus aureus for 48 hours. Adherent surface bacteria were suspended by shaking in a 0.3% Tween 20 solution, serially diluted, plated onto 3M PetriFilms, and counted. Kirby-Bauer disc diffusion assays were conducted to generalize findings across various organisms.

Outcomes: Outcomes included (1) bacterial adherence to the implant surface measured as bacterial counts (in colony-forming units per milliliter) and (2) bacterial growth reduction measured as zones of inhibitions (in millimeters).

Results: Incubation of implant surfaces in 0.05% CHG did not alter recovered bacterial counts as compared with normal saline and vancomycin/gentamycin. Similarly, within a single bacterial species, 0.05% CHG and vancomycin/gentamycin did not alter zone-of-inhibition measurements in Kirby-Bauer disc diffusion studies.

Clinical translation: This study demonstrates in vitro that 0.05% CHG may be used directly on the minocycline-rifampin-impregnated surface without altering the antibiotic efficacy of the coating.

Strengths and limitations: Strengths include that this is the first study to evaluate if 0.05% CHG affected the minocycline-rifampin-impregnated surface. Limitations include the use of in vitro studies, which serve as a proxy for in vivo practices and may not be entirely accurate or translatable in a clinical setting.

Conclusion: 0.05% CHG does not alter the antimicrobial activity of the minocycline-rifampin-impregnated surface as compared with vancomycin/gentamycin and normal saline in vitro; however, its efficacy in clinical practice remains to be evaluated.

Keywords: Irrisept; hydrophilic; impregnated; infection; irrigation; penile implant; penile prosthesis.