Efficacy of antimicrobial-impregnated silicone sections from penile implants in preventing device colonization in an animal model

Combatting fungal biofilm formation by diffusive release of fluconazole from heptylamine plasma polymer coating

A drug-eluting coating applied onto biomedical devices and implants is an appropriate way to ensure that an inhibitory concentration of antimicrobial drugs is present at the device surface, thus preventing surface colonization and subsequent biofilm formation. In this study, a thin polymer coating was applied to materials, and it acted as a drug-delivery reservoir capable of surface delivery of the antifungal drug fluconazole to amounts up to 21 μg/cm². The release kinetics into aqueous solution were quantified by UV spectroscopy and conformed to the Ritger-Peppas and Korsmeyer-Peppas model. Complementary microbiological assays were used to determine effectiveness against Candida albicans attachment and biofilm formation, and against the control heptylamine plasma polymer coating without drug loading, on which substantial fungal growth occurred. Fluconazole release led to marked antifungal activity in all assays, with log 1.6 reduction in CFUs/cm². Cell viability assays and microscopy revealed that fungal cells attached to the fluconazole-loaded coating remained rounded and did not form hyphae and biofilm. Thus, in vitro screening results for fluconazole-releasing surface coatings showed efficacy in the prevention of the formation of Candida albicans biofilm.

In vitro methods for the evaluation of antimicrobial surface designs

Bacterial adhesion and subsequent biofilm formation on biomedical implants and devices are a major cause of their failure. As systemic antibiotic treatment is often ineffective, there is an urgent need for antimicrobial biomaterials and coatings. The term "antimicrobial" can encompass different mechanisms of action (here termed "antimicrobial surface designs"), such as antimicrobial-releasing, contact-killing or non-adhesivity. Biomaterials equipped with antimicrobial surface designs based on different mechanisms of action require different in vitro evaluation methods. Available industrial standard evaluation tests do not address the specific mechanisms of different antimicrobial surface designs and have therefore been modified over the past years, adding to the myriad of methods available in the literature to evaluate antimicrobial surface designs. The aim of this review is to categorize fourteen presently available methods including industrial standard tests for the in vitro evaluation of antimicrobial surface designs according to their suitability with respect to their antimicrobial mechanism of action. There is no single method or industrial test that allows to distinguish antimicrobial designs according to all three mechanisms identified here. However, critical consideration of each method clearly relates the different methods to a specific mechanism of antimicrobial action. It is anticipated that use of the provided table with the fourteen methods will avoid the use of wrong methods for evaluating new antimicrobial designs and therewith facilitate translation of novel antimicrobial biomaterials and coatings to clinical use. The need for more and better updated industrial standard tests is emphasized.

STATEMENT OF SIGNIFICANCE

European COST-action TD1305, IPROMEDAI aims to provide better understanding of mechanisms of antimicrobial surface designs of biomaterial implants and devices. Current industrial evaluation standard tests do not sufficiently account for different, advanced antimicrobial surface designs, yet are urgently needed to obtain convincing in vitro data for approval of animal experiments and clinical trials. This review aims to provide an innovative and clear guide to choose appropriate evaluation methods for three distinctly different mechanisms of antimicrobial design: (1) antimicrobial-releasing, (2) contact-killing and (3) non-adhesivity. Use of antimicrobial evaluation methods and definition of industrial standard tests, tailored toward the antimicrobial mechanism of the design, as identified here, fulfill a missing link in the translation of novel antimicrobial surface designs to clinical use.

Efficacy of Local Rifampin/Minocycline Delivery (AIGISRX®) to Eliminate Biofilm Formation on Implanted Pacing Devices in a Rabbit Model

Purpose

Device-related infections represent a significant clinical challenge. Once established, these infections prove difficult to treat with existing antibiotic regimens, compromising the health of device recipients, and usually requiring surgical intervention to resolve. The purpose of this study was to determine the ability of the AIGISRX® Anti-Bacterial envelope to reduce the formation of bacterial biofilm on implanted pacing devices.

Methods

An infection was established in a rabbit model by creating bilateral subcutaneous implant pockets, into which a pacing device with or without AIGISRX® was placed. The incisions were closed, and a defined dose of bacteria was infused into each implant pocket. After seven days, devices were explanted and assessed for viable bacteria by a sonication/vortex procedure to quantify bacteria, and by imaging of the device surface by scanning electron microscopy and laser scanning confocal microscopy.

Results

The presence of the AIGISRX® envelope eliminated recoverable, viable bacteria from the explanted devices using a vortex/sonication technique from in vivo models of Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus capitis, and Escherichia coli infections. Scanning electron microscopy and confocal microscopy demonstrate greatly reduced biological material on the pacemaker surfaces in the presence of the AIGISRX® envelope compared to untreated controls.

Conclusion

These results demonstrate that in this animal model, the AIGISRX® device reduces the formation of adherent bacteria and reduces bioburden on implanted, infected pacemaker devices.

Infections Associated with Inflatable Penile Prostheses

INTRODUCTION

The implantation of inflatable penile prosthesis (IPP) has become a successful method for the treatment of erectile dysfunction. Infections are rare but they can result in devastating complications following surgical implantation of the prosthesis.

AIM

To discuss pathogenesis, risk factors, and microbiology of IPP infections, summarize clinical manifestation and diagnostic methods, and discuss future directions of prevention and management.

METHODS

A PubMed search was performed of all articles published from 1960 to present relating to IPP infections.

MAIN OUTCOME MEASURE AND RESULTS

Skin flora organisms such as Staphylococcus epidermis are the most common source of infection. Several host and surgical risk factors for prosthesis infection have been demonstrated, including uncontrolled diabetes mellitus and previous surgical interventions. Biofilms play an important role in the pathogenesis of device-related infections. Pain, fever, drainage, and device extrusions are suggestive of IPP infection. Preventive methods include preoperative skin cleansing, systemic antibiotic prophylaxis, and the use of surface-modified prostheses. The most frequently utilized surgical management is a single-stage approach that comprises aggressive irrigation and debridement, removal of all components of the infected prosthesis, and placement of a new IPP in the same surgical setting.

CONCLUSION

Advances in systemic antimicrobial prophylaxis, skin cleansing and surface-modification of the devices, as well as a number of other potentially protective measures, have decreased the rates of infections. Currently, most infected IPP are surgically managed by adopting the salvage approach. Al Mohajer M and Darouiche RO. Infections associated with inflatable penile prostheses. Sex Med Rev 2014;2:134-140.

Inflatable penile prostheses for the treatment of erectile dysfunction

Male erectile dysfunction is a common medical condition. Recent advances in our understanding of corpora cavernosa physiology have resulted in three effective oral medications (sildenafil, vardenafil and tadalafil--all phosphodiesterase type 5 inhibitors), which can effectively treat many men with erectile dysfunction. However, a large number of men are not adequately treated by these medications due to their cost, side effects, contraindications or lack of a satisfactory erectile response. For men who do not respond to less invasive therapy, an inflatable penile prosthesis can provide an excellent alternative. This article will review and critique the currently available inflatable penile prostheses in the treatment of erectile dysfunction.

Long-term infection outcomes after original antibiotic impregnated inflatable penile prosthesis implants: up to 7.7 years of followup

PURPOSE

Although some studies suggest that most infections associated with inflatable penile prosthesis implantation develop within year 1 after surgery, device related infections have been reported 5 years after implantation or later and the infection risk with time is not well characterized. We previously reported a statistically significantly lower infection rate for original inflatable penile prostheses impregnated with antibiotic treatment with minocycline and rifampin vs nonimpregnated inflatable penile prostheses at 1-year followup. Long-term data are now available on infection revision after initial implantation of antibiotic impregnated vs nonimpregnated prostheses.

MATERIALS AND METHODS

We retrospectively reviewed patient information forms voluntarily filed with the manufacturer after the initial implantation of more than 39,000 inflatable penile prostheses to compare the revision rate due to infection for antibiotic impregnated vs nonimpregnated implants between May 1, 2001 and December 31, 2008. Life table analysis was used to evaluate device survival from revision surgery.

RESULTS

On life table survival analysis initial revision events due to infection were significantly less common in the impregnated vs the nonimpregnated group (log rank p <0.0001). At up to 7.7 years of followup 1.1% of 35,737 vs 2.5% of 3,268 men with impregnated vs nonimpregnated implants underwent initial revision due to infection.

CONCLUSIONS

To our knowledge this long-term outcome analysis provides the first substantial clinical evidence of a decrease in costly infection related revision using an antibiotic impregnated inflatable penile prosthesis.

Inhibition of Staphylococcus aureus biofilms by a novel antibacterial envelope for use with implantable cardiac devices

Biofilm formation on representative implantable medical devices using a known human pathogen (Staphylococcus aureus) was significantly reduced (p < 0.01) at all time points measured (24,48, and 72 hours) by employing a novel antibacterial envelope (AIGIS Rx). The result was demonstrated using a standard US Centers for Disease Control (CDC) bioreactor model and the results were confirmed by Scanning Electron Microscopy (SEM). The antibacterial envelope used in the study is coated with a proprietary combination broad spectrum antibiotics (rifampin and minocycline) embedded in a resorbable polymeric coating. The antibiotics are designed to elute out of the coating over a multi-day period for controlled, site-specific drug delivery. The infection rate for patients receiving pacemakers and defibrillators is increasing faster than the rate of new implants and the growing resistance of S. aureus strains suggests that conventional, systemic antibiotic prophylaxis may have limited future utility. Moreover, emerging evidence suggests that bacterial biofilms result in infections of implantable medical devices. These findings demonstrate the in vitro efficacy of a new means to address potential biofilm-derived Hospital Acquired Infections (HAIs) related to implantable medical devices composed of titanium inclusive of pacemakers and defibrillators by means of a locally delivered, low dose, combination antibacterial treatment.

A multilevel antimicrobial coating based on polymer-encapsulated ClO(2)

A multilevel antimicrobial coating with "release-killing", "contact-killing" and "anti-adhesion" properties was prepared from polymer-encapsulated chlorine dioxide (ClO(2)), water-in-oil-in-water (w/o/w) double emulsion. A slow sustained release of gaseous ClO(2) at a rate sufficient to inhibit bacterial growth (approximately 1300 microg of ClO(2).g(-1).day(-1)) was demonstrated for a prolonged period of time (i.e., 28 days). Touch and infectious droplets triggered an increased release of the biocides at the sites of contamination, resulting in rapid disinfection. Zinc chloride (i.e., 30 ppm) was added to provide "contact-killing" properties, while bacterial adhesion was prevented by the Pluronic polymer used to encapsulate ClO(2). The new antimicrobial coating is effective against Gram positive and Gram negative bacteria, including Bacillus subtilis , Staphylococcus aureus , and Escherichia coli. A greater than 5 log (i.e., >or= 99.999%) reduction of viable bacteria was obtained at a short contact time of 10 min.

Comparative assessment of antimicrobial activities of antibiotic-treated penile prostheses

BACKGROUND

Although infections associated with penile implants are relatively infrequent, they result in serious medical consequences. Because treatment of these infections usually requires removal of the infected penile implant, prevention of infection is crucial. Since bacterial colonization of the implant is a prelude to clinical infection, antimicrobial modification of the devices may inhibit device colonization and subsequent infection.

OBJECTIVE

We compared the spectrum and durability, both in vitro and in vivo, of two antibiotic-treated penile prostheses: InhibiZone implants pre-impregnated with minocycline and rifampin (M/R) and Titan implants dipped in vancomycin.

DESIGN, SETTING, AND PARTICIPANTS

1×1-cm cylinder segments of (1) control untreated, (2) M/R-impregnated, and (3) vancomycin-dipped implants were studied. Baseline zones of inhibition (ZI) were determined against clinical isolates, including methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), vancomycin-resistant Enterococcus (VRE), and Escherichia coli. In addition, ZI against methicillin-susceptible S. aureus were compared both in vitro after being washed in a flow chamber and after subcutaneous implantation in rabbits for 1, 2, 7, and 14 d.

MEASUREMENTS

ZI were measured as the diameter of the clear zone around each test device minus the external diameter of the device.

RESULTS AND LIMITATIONS

Implants pre-impregnated with M/R displayed a broader spectrum of antimicrobial activity than vancomycin-dipped implants against both gram-positive and -negative bacteria. The M/R-impregnated devices also yielded significantly larger zones of inhibition against S. aureus than vancomycin-dipped implants, both in vitro (p<0.003) and in vivo throughout the 14-d period of device implantation in rabbits (p≤0.03).

CONCLUSIONS

Penile prostheses impregnated with M/R have a broader spectrum in vitro and a more durable antimicrobial activity in vitro and in an animal model than implants dipped in vancomycin. Therefore, along with being a more practical model for incorporating antimicrobials onto the device, the use of implants pre-impregnated with M/R may help reduce the incidence of penile implant infection.

Inflatable penile prostheses for the treatment of erectile dysfunction: an update

Male erectile dysfunction (ED) is a common medical condition. Three oral medications (sildenafil, vardenafil and tadalafil, all phosphodiesterase type 5 inhibitors) have been developed and approved for the treatment of ED by the US FDA. Extensive worldwide marketing of these medications has raised public awareness of ED, and allowed many previously untreated men to seek and receive effective therapy. A variety of other ED treatments are available and approved by the FDA, including vacuum-constriction devices and intracavernous or intraurethral alprostadil. However, roughly 30-40% of men with ED are not adequately served by these treatments due to their cost, side effects, contraindications, the need to 'time' sexual activity, or lack of satisfactory erectile response. For men who do not respond to less invasive therapy, an inflatable penile prosthesis can provide a satisfying and effective alternative. This article will review and critique the inflatable penile prostheses that are currently available in the USA and the EU for the treatment of ED.

Outcomes and satisfaction rates for the redesigned 2-piece penile prosthesis

PURPOSE

We evaluated long-term viability, quality of life and satisfaction with the redesigned 2 piece Ambicor inflatable penile prosthesis. This device underwent revision of the rear tip extender and reinforcement of the pump tubing connection to decrease fluid leak failure in 1998.

MATERIALS AND METHODS

In this retrospective analysis we evaluated 146 men with erectile dysfunction at 2 centers who underwent device implantation between June 1999 and October 2004 with the redesigned prosthesis. Patient information forms were completed, including patient history, surgical information and revision data. Patients were mailed a modified Erectile Dysfunction Inventory of Treatment Satisfaction questionnaire, a modified Erectile Dysfunction Inventory of Treatment Satisfaction Partner survey and a questionnaire regarding pertinent inflatable penile prosthesis questions.

RESULTS

A total of 146 men with a mean age of 58.7 years (range 25 to 78) were evaluated after inflatable penile prosthesis placement. Time from implant to followup was 3 to 73 months (mean 38). Only 1 device (0.7%) was removed due to infection. One implant (0.7%) was replaced due to fluid loss and 1 (0.7%) was revised due to improper sizing. Kaplan-Meier life table analysis indicated that the percent of patients free from reoperation was 99.2% at 12 months, 99.2% at 36 months and 91% at 48 months or greater. Of the 101 subjects completing the survey the average patient used the prosthesis 5 times monthly and 88.9% reported continued use. Of the patients 91% said that it was easy to use and 95% had little to no trouble learning to use it, while 84% stated that the inflatable penile prosthesis provided good to excellent rigidity for coitus. Overall patient and partner satisfaction was 85% and 76%, respectively. Of the patients 86% said that they would recommend the prosthesis to friends or if need be undergo the procedure again.

CONCLUSIONS

The redesigned Ambicor 2-piece penile prosthesis appears to be safe and effective. It is associated with a low rate of revision as well as high patient and partner satisfaction.

Risk of Infection With an Antibiotic Coated Penile Prosthesis at Device Replacement for Mechanical Failure

PURPOSE

The inflatable penile prosthesis is well established as an effective treatment for select patients with organic erectile dysfunction. The risk of prosthetic infection at primary implantation is approximately 2%. However, for revision or replacement procedures the risk of infection has been reported to be as high as 13.3%. To minimize the overall risk of prosthetic infection an antibiotic coated inflatable penile prosthesis (InhibiZone) has been developed. To assess the impact on infection rates we reviewed our experience with the use of this device at prosthesis replacement for mechanical failure.

MATERIALS AND METHODS

We retrospectively reviewed the records of all patients undergoing inflatable penile prosthesis replacement for mechanical failure with an antibiotic coated prosthesis between May 2001 and November 2004. Salvage procedures for clinically infected prostheses were excluded from analysis. Chart review was performed with examination of operative notes, all postoperative contacts and microbiological data.

RESULTS

A total of 55 patients underwent replacement of an inflatable penile prosthesis for mechanical failure using a device coated with rifampin and minocycline HCL (InhibiZone). In all patients before reimplantation component spaces were irrigated in standard fashion. With a median followup of 32 months (range 12 to 54) postoperative device infection requiring explantation developed in 1 patient (1.8%). Intraoperative cultures from the pump site grew coagulase negative staphylococcus.

CONCLUSIONS

Our data suggest that an antibiotic coated inflatable penile prosthesis may lead to decreased infection rates in patients undergoing penile prosthesis replacement for mechanical failure.

Two-level antibacterial coating with both release-killing and contact-killing capabilities

Using a combination of an aqueous layer-by-layer deposition technique, nanoparticle surface modification chemistry, and nanoreactor chemistry, we constructed thin film coatings with two distinct layered functional regions: a reservoir for the loading and release of bactericidal chemicals and a nanoparticle surface cap with immobilized bactericides. This results in dual-functional bactericidal coatings bearing both chemical-releasing bacteria-killing capacity and contact bacteria-killing capacity. These dual-functional coatings showed very high initial bacteria-killing efficiency due to the release of Ag ions and retained significant antibacterial activity after the depletion of embedded Ag because of the immobilized quaternary ammonium salts.

Pore formers promoted release of an antifungal drug from functionalized polyurethanes to inhibit Candida colonization

AIMS

As a preventive strategy to inhibit fungal biofilm formation on medical devices, we planned experiments based on polyurethane loading with fluconazole plus pore-former agents in order to obtain a promoted release of the antifungal drug.

METHODS AND RESULTS

Different functional groups including carboxyl, hydroxyl, primary and tertiary amino groups, were introduced in polyurethanes. Fluconazole was adsorbed in higher amounts by the most hydrophilic polymers and its release was influenced by the degree of polymer swelling in water. The entrapping in the polymer of polyethylenglycol as a pore former significantly improved the fluconazole release while the entrapping of the higher molecular weight porogen albumin resulted in a controlled drug release and in an improved antifungal activity over time.

CONCLUSIONS

Among the tested in vitro models, best results were achieved with an hydrophobic polymer impregnated with 25% (w/w) albumin and fluconazole which inhibited Candida albicans growth and biofilm formation on polymeric surfaces up to 8 days.

SIGNIFICANCE AND IMPACT OF THE STUDY

The combined entrapping in polymers of pore formers and an antifungal drug and the consequent controlled release over time is a novel, promising approach in the development of medical devices refractory to fungal colonization.

In Vivo Testing of an Infection-Resistant Annuloplasty Ring

BACKGROUND

An infection-resistant surface incorporated into a prosthetic cardiac valve has great potential clinical applications.

STUDY DESIGN

A sewing ring construct was created using ciprofloxacin-treated polyester. Then ciprofloxacin-treated and untreated constructs were implanted subcutaneously on the dorsum of rats and inoculated with Staphylococcus aureus. At 7, 14, and 30 days animals were sacrificed and the implants were retrieved. Each implant was assessed for frank purulence and gross tissue incorporation by a blinded observer. The implants were processed for conventional histology and examined by a blinded Pathologist. Ciprofloxacin-treated rings were also implanted in the absence of a bacterial challenge. At explantation, a maximal zone of inhibition, if present, was measured. Finally, ciprofloxacin was eluted with methanol from the explanted segments and the concentration of ciprofloxacin eluted was determined.

RESULTS

Ciprofloxacin-treated sewing rings had greater gross tissue incorporation than untreated rings in the presence of a bacterial challenge (P=0.005). Ciprofloxacin-treated rings also had a lower incidence of frank purulence, but this did not reach statistical significance. After 14 days of implantation, ciprofloxacin treated rings had fewer neutrophils (P=0.018) and greater histological tissue incorporation (P=0.017) than untreated rings. The explanted ciprofloxacin-treated rings maintained a zone of inhibition of 3.0+/-1.0 mm after 1 day of implantation and 1.3+/-0.6 mm after 2 days. Ciprofloxacin could be eluted in significant quantities from the explanted rings after 7 days of implantation.

CONCLUSIONS

Ciprofloxacin treated polyester can be incorporated into an annuloplasty ring construct that demonstrates excellent tissue incorporation and infection resistance. This study supports the use of this construct in the mitral position in a large animal model.

ORIGINAL RESEARCH—SURGERY: Antibiotic Coating Reduces Penile Prosthesis Infection

AIM

To evaluate the efficacy of a new antibiotic-coated (rifampicin+monocycline) penile prosthesis in prevention of bacterial adhesion and reduction of penile prosthesis infection.

METHODS

In a retrospective analysis of medical records of men who had undergone implantation of American Medical Systems (AMS) inflatable penile prostheses between July 1990 and November 2003, we compared patients with AMS antibiotic-coated prostheses and patients with AMS nonantibiotic-coated prostheses. A total of 152 men aged from 27 to 79 years with erectile dysfunction underwent implantation of the AMS inflatable penile prosthesis. Fifty-eight patients received the antibiotic-coated prosthesis between July 2001 and November 2003, and 94 patients received the nonantibiotic-coated prosthesis between July 1990 and June 2001.

RESULTS

In most cases infection was present; it was detected 1-2 days or up to 3-6 months after implantation. Complications including infection, which required surgical intervention, were observed in 15 patients of the nonantibiotic-coated prosthesis group (three reoperations for infection), and noninfection-related failure in five patients of the antibiotic-coated prosthesis group. In the nonantibiotic-coated prosthesis group of patients, time to infection ranged from 1 day to 6 months (mean 3.5 months). The antibiotic-coated prosthesis group of patients immediately after surgery and during the short- and intermediate-term follow-up had no infection of the penile prosthesis.

CONCLUSIONS

We suggest that the antibiotic locally delivered from the prosthesis coating might be an effective supplement for prevention of prosthesis-related infection in penile prosthesis surgery.

In Vitro Activity and In Vivo Efficacy of Antimicrobial-coated Vascular Grafts

The serious medical consequences and costly management of infections associated with vascular grafts have prompted an expanding interest in examining the preventive efficacy of antimicrobial-coated vascular grafts. The purpose of antimicrobial coating of vascular grafts is to reduce bacterial colonization of the device and, hopefully, the occurrence of clinical infection. In this study we demonstrated that expanded-polytetrafluoroethylene vascular grafts coated with minocycline and rifampin provide broad-spectrum antimicrobial activity in vitro, as reflected by zones of inhibition, against Staphylococcus epidermidis, S. aureus, Enterococcus faecium, and Pseudomonas aeruginosa. We also showed in a rabbit model that subcutaneously placed minocycline/rifampin-coated vascular grafts have lower rates of staphylococcal device colonization (1/24 = 4% vs. 8/30 = 27%, p = 0.033) and device-related infection (0/24 = 0% vs. 6/30 = 20%, p = 0.028) than uncoated grafts. These promising results encourage the clinical evaluation of vascular grafts coated with minocycline and rifampin.