Addition of antifungal agents to antibiotic solutions does not diminish the antibacterial properties of penile prosthesis hydrophilic surface dips.

Peri-operative antifungal prophylaxis is increasing, both systemically with intravenous infusion and in dipping solutions for use with hydrophilic penile prosthesis (PP) surfaces. In this study, we explore whether amphotericin B or fluconazole decreases vancomycin and gentamicin (VG) antibiotic efficacy when utilized as dips for the hydrophilic PP surface. We compared antibiotic activity of PP discs dipped for 3 min in normal saline (NS), 2 mg/mL vancomycin and 160 μg/mL gentamicin in NS, 0.05 mg/mL amphotericin B in VG (VGA), or 2 mg/mL VG constituted in a 20 mg/mL fluconazole in NS solution. Discs were incubated in 1 × 105 CFU/mL of methicillin-sensitive Staphylococcus aureus (MSSA) for 48 h, then adherent bacteria were suspended, plated, and counted. The effect of intraoperative irrigation on the antibacterial activity after a prophylactic dip was assessed by submersion in NS, VG, VGA, or VGF for 2 min followed by incubation with MSSA. Zones of Inhibition (ZOI) were obtained by performing Kirby-Bauer Disc Diffusion Assays against S. aureus, Escherichia coli, and Klebsiella pneumoniae. Average bacterial counts (CFU/mL) and ZOI (mm) following a series of treatment protocols of PP discs were obtained. There were significant decreases in bacterial counts in all treatment groups (VG, VGA, and VGF) relative to NS control (P < .001). There were no significant differences in bacterial counts between the treatment groups (P > .05). The greatest decrease in bacterial counts was measured with the VGF/VGF regimen (~6 log, P ≤ .0001). ZOI measurements supported unaltered antibacterial activity across all treatment groups against the different clinical strains. Adding antifungals to the antimicrobial dip solution does not diminish the antimicrobial efficacy of VG antibiotics on the hydrophilic PP surface. This is the first study to demonstrate that the addition of antifungal agents to the antibiotic dip does not diminish the antibacterial efficacy of antimicrobials bound to the hydrophilic surface. Limitations of this study include the use of in vitro studies, which serve as a proxy for in vivo practices and may not be entirely accurate nor translatable in a clinical setting. The hydrophilic PP surface is versatile. The addition of antifungals to dip and irrigation solutions may provide broader antimicrobial coverage in PP implantation without compromising antibacterial protection, favoring fluconazole over amphotericin B.