(143) ANTIFUNGALS AND LOCAL ANESTHETICS DO NOT DIMINISH ANTIBIOTIC BINDING TO PENILE PROSTHESIS HYDROPHILIC SURFACE
Authors: Giordano A , Kambhampati S , Im B , Hickok N , Chung P 
Published: December 2024

Abstract

Introduction
Recent in vitro studies have demonstrated that use of 0.05% chlorhexadine gluconate negatively alters the antimicrobial activity of the hydrophilic surface of inflatable penile prostheses. Antifungals and local anesthetics have also been proposed for use as prophylactic dips for fungal infections and post-operative pain, respectively. The effects of these therapeutics on antimicrobial activity have not been fully elucidated in current literature.

Objective
We aim to evaluate if amphotericin and bupivacaine compete with the binding of antibiotic solutions to the hydrophilic surface of penile prosthesis implants, thereby reducing antimicrobial activity.

Methods
Sterile 8 mm diameter PP discs were submerged for 3 minutes in 3 mL of normal saline (NS), 2 mg/mL vancomycin and 160 μg/mL gentamicin (VG) in NS, 0.02 μg/mL amphotericin in VG (VGA), or 0.25% bupivacaine (2.5 mg/mL) in VG (VGB), rinsed in NS for five seconds to remove any unbound solution, then incubated with 1x10^5 colony forming units per milliliter (CFU)/mL of methicillin-sensitive Staphylococcus aureus ATCC25923 (MSSA) in trypticase soy broth (TSB) for 48 hours. Samples were then rinsed with PBS and biofilm was removed by shaking in 0.3% Tween-20. Suspended bacteria were serially diluted, plated onto 3 M PetriFilms, and counted. Irrigation studies were performed to evaluate the effect of intraoperative irrigation on the binding of the prophylactic dip. The initial dip protocol was followed, with the addition of a subsequent submersion in 3 mL of either NS, VG, VGA, or VGB solution for 2 minutes to mimic intraoperative irrigation. The discs were then incubated in 1x10^5 CFU/mL of MSSA for 48 hours, plated, and counted. Disc-diffusion tests were conducted by pipetting 10 μL of NS, VG, VGA, or VGB on 6 mm implant discs and dried overnight in a laminar flow hood. Treated discs were then placed coated-side down onto plates streaked with clinical strains of the following organisms isolated from clinical penile implant infections: Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. After 24 hours of growth, Zones of Inhibition (ZOI) were measured. Mann–Whitney U tests were performed to compare outcomes, p &lt; 0.05 considered significant.

Results
Average bacterial counts with 95% CI are plotted in Fig. 1a and 1b. There were significant decreases in bacterial counts in all three treatment groups (VG, VGA, VGB) relative to NS controls (p &lt; 0.01), both with and without irrigation. There were no significant differences in bacterial counts between the VG, VGA, and VGB group (p &gt; 0.05). Disc-diffusion studies showed maintained antimicrobial activity across all three treatment groups against clinical strains of Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae as shown by the ZOI presented in Fig. 1c.

Conclusions
The addition of amphotericin or bupivacaine to the antibiotic dip solution does not adversely affect the antimicrobial efficacy of the VG antibiotic dip solution, irrespective of irrigation conditions. Antibiotic dip solutions containing amphotericin and bupivacaine also maintained antimicrobial properties across clinically isolated strains of bacteria collected from penile implant infections.

Disclosure
Yes, this is sponsored by industry/sponsor: Coloplast.
Clarification: Industry funding only - investigator initiated and executed study.
Any of the authors act as a consultant, employee or shareholder of an industry for: Coloplast and Boston Scientific.