Evaluation of Gram Positive and Gram Negative Bacteria in a Novel In Vitro Biofilm Model of Penile Prosthesis

Abstract

ABSTRACT Introduction Infection is the most feared complication of inflatable penile prosthesis (IPP), often necessitating complete removal. Late infection after IPP insertion is thought to be due to the slow formation of a biofilm. Understanding and preventing biofilm formation would be a breakthrough in preventing IPP infections. Objective We aimed to develop an in vitro model to compare formation and growth of biofilms on penile implants by bacteria commonly associated with infection. Methods Sterile IPPs (Coloplast Titan) were cut into rings and incubated with S. epidermidis, S. aureus, P. aeruginosa, or K. pneumoniae cultures in tryptic soy broth (TSB) for a 4 h attachment period, and then in only TSB for 120 h. We utilized a published and validated method to measure biofilm mass. Rings were then dipped in deionized water to wash off additional bacteria and either fixed with ethanol (EtOH) or not treated further (no fix). Fixing was employed to preserve biofilm on the rings that otherwise may have been lost during crystal violet staining. Biofilm formation was measured with a spectrophotometer (OD570) after crystal violet staining. Results All bacteria formed substantial biofilm on implant rings as measured by OD570. As expected, the gram-negative bacteria, P. aeruginosa and K. pneumoniae produced significantly more biofilm than the gram-positive S. epidermidis and S. aureus. Interestingly, P. aeruginosa formed the most biofilm by at least a factor of 6 in both testing conditions. The ethanol fixing condition produced more consistent results for the crystal violet assay. Conclusions Our novel in vitro model of biofilm formation of penile implants can be used in future studies to evaluate the effect of different antibiotic dips and anti-infective capacity of pre-coated implants against different bacteria. Our findings suggest gram-negative bacteria form faster and a greater quantity of biofilm on penile implants as compared to gram-positives. P. aeruginosa displayed the strongest predilection to form biofilm on implants compared to all other bacteria studied, and could be investigated as a specific target to reduce delayed post-operative IPP 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, Boston Scientific