Superficial Skin Infections Versus Prosthesis Infections

Superficial surgical site infections at the suture line need to be distinguished from actual infection at the implanted device site. These superficial skin infections are limited to the skin around the suture line without bacterial contamination of device components and present rapidly after implantation similar to other postsurgical incision infections. These infections can successfully be treated with antibiotics. In contrast, actual device-associated infections usually occur months to years after implantation and require surgical therapy. However, they can also develop within days after the implantation and it can be difficult to differentiate them from superficial skin infections. Skin erythema at the suture line is present in both, and there may be some fluctuance surrounding the newly implanted components from postoperative edema. Similarly, in both instances, the patient reports pain or tenderness, which may be postoperative pain due to the space-occupying pump. In the absence of clear evidence of PP infection (eg, purulent drainage, significant and increasing edema), a trial of oral antimicrobials such as bactrim or ciprofloxacin can be attempted. This trial may also be diagnostic, because the symptoms persistently improve in cases of superficial skin infection, whereas the recurrence of symptoms after stopping the antibiotics is consistent with an actual PP infection requiring explantation.

Acute and Chronic Penile Implant Infections

Infections that involve the implanted device can present as acute or chronic infections. In acute infections, patients present within days or weeks after surgery and are often very ill because of systemic effects of the infection. Hallmarks of the physical examination are fever with or without chills, erythema of the scrotum and/or penile shaft, fluctuance around the pump or cylinders, purulent drainage from the incision site, and a pump that may be fixed to the scrotal wall. Imaging such as a computed tomographic (CT) scan or preferably an MRI may aid in the diagnosis and should be considered for evaluating the location and also involvement of the intra-abdominal reservoir. One advantage of the MRI is that it allows assessment of penile anatomy in 3 orthogonal planes and can be used to differentiate PP-associated infections from some of the other conditions associated with similar symptoms. For example, in a patient complaining of shaft pain, the MRI can differentiate a buckling cylinder that is too large for the patient from a soft tissue infection. If the implantation has been recent, however, it may be difficult to discern postoperative edema from infection, particularly on a CT scan.

Chronic infections associated with prostheses present months after surgery with the classic findings of a patient with persistent scrotal or penile pain, whereas systemic symptoms are absent and the patient has a normal white blood cell count. Chronic device infection may ultimately lead to extrusion of the prosthesis. Imaging to confirm the diagnosis is not necessary but may facilitate surgical planning, such as identification of rear-tip extenders that must be removed during explantation.

Microorganisms involved in the device-related infection are usually acquired during the initial surgery and therefore come from the surgical team or the patient himself and usually originate from a cutaneous source. In up to 80% of infected PP, Staphylococcus epidermidis is isolated, and in the remaining 20%, gram-negative bacteria including Proteus mirabilis , Pseudomonas aeruginosa , Escherichia coli, and Serratia marcescens are found. Device contamination during surgery can lead to the generation of biofilm, which is produced by bacteria and results in a glycocalyx-containing slimelike coating of the device. Biofilm protects the contained bacteria from the patient’s immune system as well as from antibiotics at concentrations up to 1500 times higher than those required to affect the same bacteria not protected by biofilm. Furthermore, bacteria in biofilm can exchange plasmids coding for antibiotic resistance. Up to 80% of PP explanted for mechanical failure contain bacteria in the absence of a clinically apparent infection, and a critical threshold of biofilm may exist before an infection becomes apparent. Biofilms persist after device explantation, and thus a thorough washout procedure is critical for salvage reimplantations of PPs.

Risk factors for PP infections are concomitant infections of the urinary tract or other body sites with subsequent hematogenous spread as well as extended operative time, which occurs when the implantation is combined with other reconstructive surgery or when implantation is performed by inexperienced surgeons. There is conflicting evidence regarding whether diabetes mellitus or quadriplegia is a risk factor for implant infection.

Treatment of Infections Associated with Prostheses

Unlike superficial surgical site infections that are amenable to antimicrobial therapy, an infection involving the PP requires removal of the implant. Explantation should also ensue upon suspicion of a device infection to prevent further patient deterioration. During explantation it is crucial that all components of the PP be removed. Although partial removal of infected parts with salvage reimplantation while leaving uninfected parts in place has been described, the eventual outcome can be considered poor. Bacteria migrate along the tubing, and reinfection of any of the components can occur. In addition, implantation of new parts of a device may lead to transition of bacteria contained in biofilm to their planktonic (activated) state. Explantation of an infected prosthesis should occur promptly because the infection progresses and results in tissue edema followed by necrosis of the penile shaft and glans and may culminate in life-threatening sepsis. Systemic antibiotics alone are unable to clear the infection owing to poor tissue penetration because the implant components are encapsulated by dense fibrous tissue with poor vascularization. In addition, the appropriate concentration of antibiotics required to destroy bacteria contained in the biofilm cannot be reached.

In the past 3 decades, immediate salvage procedure algorithms replacing the infected implant with a new prosthesis have become the most commonly performed approach for the treatment of an infection associated with PP. There are 2 important aspects specific to PP explantation. First, the cavity in the corpora cavernosa that is left behind by an explanted cylinder should be filled, for example, with a new PP, because otherwise, in addition to penile shrinkage, the corporal scar makes a later reimplantation attempt very difficult. One alternative to avoid replacement of an infected PP with a new one is to temporarily implant a malleable prosthesis. However, this again requires implantation of a synthetic device that can act as a substrate for the (re-)development of biofilm. The second aspect is that salvage is associated with a reinfection rate of up to 13%. Explantation followed by a prolonged course of antibiotics to further clear remaining organisms has therefore been propagated.

A novel approach combining antibiotic delivery while preserving corporal spaces has recently been described by Swords and colleagues. The investigators describe filling the corpora cavernosa with a cast made of high-purity calcium sulfate that had been mixed with tobramycin and vancomycin and acts as a spacer before reimplantation of an inflatable PP several weeks later. This technique, however, is still in the experimental phase.

Salvage Reimplantation

Salvage reimplantation that combines the explantation of a PP with immediate replacement has become the most popular approach. This procedure is indicated for patients who are not immunosuppressed, who do not have significant comorbidities limiting operative time, and who continue to have an indication for a PP. During explantation, all nonabsorbable sutures that may have been used during the initial implant should be removed because they may harbor microorganisms. A second abdominal incision to remove the reservoir may be necessary. Once the device is removed, cultures are sampled and all areas of prior implant components are irrigated with antiseptic and antibiotic solutions. In the first description of this washout in 1996, the use of vancomycin-gentamicin solution in water followed by half-strength hydrogen peroxide and half-strength povidone-iodine was recommended. Hydrogen peroxide eradicates anaerobic bacteria efficiently, and povidone-iodine is 99% bactericidal. These solutions are injected into the corpora using a 60-mL syringe or through a red rubber catheter to ensure that all areas of the prior implant are reached. Similarly, antibiotic and iodine solution can be injected into the tract of the reservoir; however, hydrogen peroxide should not be used because it may leak into the peritoneal cavity. Mulcahy as well as Brant and colleagues advocate for the use of a water pick to irrigate the cavities mechanically with antibiotic solution to break up and remove the biofilm ; however, the use of a large syringe should also generate sufficient pressure. Finally, all cavities are irrigated with the same solutions in reverse order so that the foamy hydrogen peroxide and the povidone-iodine are cleared by the antibiotic solution. Brant and colleagues recommend changing of gowns and gloves and redraping of the field at this point before implantation of the new PP. The sterile packaging of the new implant should not be opened until this stage to avoid accidental contamination. Once the new device has been implanted and the wound is closed, the patient is administered an antibiotic with good tissue penetration such as trimethoprim-sulfamethoxazole for 30 days. The rationale for this extended course is based on reports by Henry and colleagues who found that the pump scar tissue grew bacteria in 25% of patients after the antiseptic washout, which is putatively eliminated by the oral antibiotic regimen. Overall, the success rates of this salvage procedure are over 80%. Failed salvage procedures have been attributed to short incubation time of washout solutions used, organisms with increased virulence, and also the presence of excessive cellulitis. Excessive cellulitis should be treated with a 3-day course of intravenous antibiotics before salvage reimplantation. Relative contraindications to a salvage procedure are a patient who is too ill to undergo the procedure and an infection that is unlikely to be cleared by the procedure. Examples of these situations are immunocompromised patients, patients with tissue necrosis at the implant sites, and bilateral erosion of cylinders into the fossa navicularis. Of note, unilateral erosion of a cylinder is not a contraindication because the other cylinder may be replaced followed by implantation of the second cylinder at a later time. In certain circumstances, delayed salvage can be considered, which entails explantation of the components of the device and washout with multiple Jackson-Pratt drains placed into the pump, reservoir, and corporal cavities before the wound is closed. Antibiotic solution is instilled through the drains for 72 hours before a new implant is placed. Success rates using this technique are similar to those for immediate salvage.

The Effect of Antibacterial Coatings

One improvement in the design of newer-generation PP was the development of antimicrobial coatings. Rifampin/minocycline coatings help in the prevention of bacterial adherence during and after the procedure, although serum levels of both antibiotics used for impregnation remain very low. Another variation is hydrophilic surface coatings that allow the uptake of antibiotic during soaking before implantation. This variation has the advantage of tailoring the antibiotic to the surgeon’s discretion and the site’s susceptibility profile. In vitro studies have suggested that the hydrophilic coating may have an improved antibacterial effect over rifampin/minocycline coating, yet both coatings seem to be equally effective clinically. A recent report by Serefoglu and colleagues analyzed over 36,000 primary PPs with hydrophilic coating and found that the infection rate of coated devices decreased to 1.4% compared to 4.6% for uncoated models at 11 years follow-up. Similarly, Carson and colleagues analyzed over 35,000 PPs coated with rifampin/minocycline with up to 7.7 years of follow-up and found a 1.1% infection rate compared with 2.5% infection rate of nonimpregnated implants. Although infection rates in diabetic patients were significantly higher at 1.9%, the overall rate remains relatively low. There are concerns in the continuing effectiveness of the antibacterial coatings used mainly in regard to the development of bacterial resistance. However, it seems that the risk of emergence of bacteria resistant to rifampin and minocycline is rather low, as a randomized prospective study on intravenous central line catheters has shown. Overall, the antibacterial modification of PP seems to have significantly reduced the risk of device infection.

Preventing Penile-Prosthesis-Associated Infection

Colonization during implantation is the single most important factor for PP infection. Therefore, prevention of contamination by the surgical team, the patient, and the operating room environment are critical and are summarized in Table 1 . In 2013, a panel of experts defined clinical guidelines to decrease the rates of penile infections and provided the basis for the following recommendations.

Table 1

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