Role of topical application of gentamicin containing collagen implants in cardiac surgery

Surgical Site Infection in Cardiac Surgery

Surgical site infections (SSIs) are one of the most significant complications in surgical patients and are strongly associated with poorer prognosis. Due to their aggressive character, cardiac surgical procedures carry a particular high risk of postoperative infection, with infection incidence rates ranging from a reported 3.5% and 26.8% in cardiac surgery patients. Given the specific nature of cardiac surgical procedures, sternal wound and graft harvesting site infections are the most common SSIs. Undoubtedly, DSWIs, including mediastinitis, in cardiac surgery patients remain a significant clinical problem as they are associated with increased hospital stay, substantial medical costs and high mortality, ranging from 3% to 20%. In SSI prevention, it is important to implement procedures reducing preoperative risk factors, such as: obesity, hypoalbuminemia, abnormal glucose levels, smoking and S. aureus carriage. For decolonisation of S. aureus carriers prior to cardiac surgery, it is recommended to administer nasal mupirocin, together with baths using chlorhexidine-based agents. Perioperative management also involves antibiotic prophylaxis, surgical site preparation, topical antibiotic administration and the maintenance of normal glucose levels. SSI treatment involves surgical intervention, NPWT application and antibiotic therapy.

Pharmaceutical, Biomedical and Ophthalmic Applications of Biodegradable Polymers (BDPs): Literature and Patent Review

In the last few decades, the interest in biodegradable materials for biomedical applications has increased significantly. Both natural and synthetic biodegradable polymers (BDPs) have been broadly explored for various biomedical applications. These include sutures and wound dressings, screws for bone fracture, scaffolds in tissue engineering, implants, and other carriers for targeted and sustained release drug delivery. Owing to their unique characteristics, including their surface charge variable copolymer block and composition and film-forming properties, BDPs have been widely used as favourable materials for ophthalmic drug delivery. Mucoadhesive BDPs have been used in ophthalmic formulations to prolong drug retention time and improve bioavailability, allowing ophthalmic controlled release systems to design. Furthermore, BDPs-based implants, microneedles, and injectable nano- and micro-particles enabled ocular posterior segment targeting and, most importantly, circumvented the need for removing the delivery systems after application. This review outlines the major advances of BDPs and highlights the latest progress of employing natural and synthetic BDPs for various biomedical applications, emphasising the treatment and management of ophthalmic conditions.

Gentamicin-Containing Collagen Implant May Reduce Surgical Site Infections After Open Infrainguinal Arterial Revascularization

BACKGROUND

Deep-space surgical site infections carry significant morbidity and mortality. The evidence for gentamicin-containing collagen implants at reducing surgical site infections in open infrainguinal arterial surgery is limited. This study examined whether gentamicin-containing collagen implants reduces 30-day surgical site infections and their severity following open infrainguinal arterial surgery.

METHODS

A retrospective observational cohort study that included all patients undergoing infrainguinal arterial bypass or endarterectomy between November 2015 and March 2019 at a single tertiary vascular unit. Patients with contaminated/infected surgical fields, surgical wounds treated with negative pressure therapy, or the usage of antimicrobial implants and dressings other than Collatamp G^Ⓡ (Aralez Pharmaceuticals, Canada) were excluded. Patients with gentamicin-containing collagen implants placed abutting vasculature were compared against patients without gentamicin-containing collagen implants. Outcomes included the rate of surgical site infections and their severity within 30 days after the operation.

RESULTS

In 159 procedures (mean age 67.7 years, 74.8% male, 33.3% diabetic, 16.4% chronic renal failure, 25.2% anticoagulated postoperatively, 32.7% with prosthetic implants), 55 (34.6%) procedures received gentamicin-containing collagen implants. There were significantly more males (85.5% vs. 69.2%; P = 0.025), higher rates of obesity (41.8% vs. 26.0%; P = 0.041), and hyperlipidemia (65.5% vs. 49.0%; P = 0.048) in the gentamicin-containing collagen implant group. In total, 6 (3.8%) procedures developed deep-space surgical site infections (1 with gentamicin-containing collagen implant, 5 without) and 13 (8.2%) had severe surgical site infections that required re-intervention (1 with gentamicin-containing collagen implant, 12 without). On logistic regression analysis, the absence of gentamicin-containing collagen implants statistically significantly increased the odds of overall surgical site infections (OR = 2.50; 95% CI 1.01 - 6.19; P = 0.047). There was no statistically significant difference in the odds of deep-space surgical site infections or the severity and need for reintervention of surgical site infections.

CONCLUSIONS

This is the first study that examined the effect of gentamicin-containing collagen implants on the severity of surgical site infections in vascular surgery. Gentamicin-containing collagen implants may reduce the odds of overall surgical site infections. It did not reduce the odds of deep-space surgical site infections or the severity and reintervention rate of surgical site infections following infrainguinal arterial revascularization. Larger studies are required to achieve adequate power to assess for these outcomes.

Vancomycin-releasing cross-linked collagen sponges as wound dressings

The study presents a novel vancomycin-releasing collagen wound dressing derived from Cyprinus carpio collagen type I cross-linked with carbodiimide which retarded the degradation rate and increased the stability of the sponge. Following lyophilization, the dressings were subjected to gamma sterilization. The structure was evaluated via scanning electron microscopy images, micro-computed tomography, and infrared spectrometry. The structural stability and vancomycin release properties were evaluated in phosphate buffered saline. Microbiological testing and a rat model of a wound infected with methicillin-resistant Staphylococcus aureus (MRSA) were then employed to test the efficacy of the treatment of the infected wound. Following an initial mass loss due to the release of vancomycin, the sponges remained stable. After 7 days of exposure in phosphate buffered saline (37°C), 60% of the material remained with a preserved collagen secondary structure together with a high degree of open porosity (over 80%). The analysis of the release of vancomycin revealed homogeneous distribution of the antibiotic both across and between the sponges. The release of vancomycin was retarded as proved by in vitro testing and further confirmed by the animal model from which measurable concentrations were observed in blood samples 24 hours after the subcutaneous implantation of the sponge, which was more than observed following intraperitoneal administration. The sponge was also highly effective in terms of reducing the number of colony-forming units in biopsies extracted from the infected wounds 4 days following the inoculation of the wounds with the MRSA solution. The presented sponges have ideal properties to serve as wound dressing for prevention of surgical site infection or treatment of already infected wounds.

Recent developments in controlling sternal wound infection after cardiac surgery and measures to enhance sternal healing

One of the major risks of cardiac surgery is the occurrence of infection at the sternal wound site. Sternal wound infections are primarily classified into superficial infection and deep sternal wound infection or mediastinitis. A patient is diagnosed with mediastinitis if microorganisms are present in their mediastinal tissue/fluid or with the observation of sternal wound infection during operation and with characteristic symptoms including chest pain, fever, and purulent drainage from the mediastinum. It is usually caused by Staphylococcal organisms in 75.8% of cases and the rest is caused by gram-negative bacteria. Currently, in cardiac surgery, hemostasis is achieved using electrocautery and bone wax, and the sternum is closed using wire cerclage. Several studies show that bone wax can act as a nidus for initiation of infection and the oozing blood and hematoma at the site can promote the growth of infectious organisms. Many research groups have developed different types of biomaterials and reported on the prevention of infection and healing of the sternum. These materials are reported to have both positive and negative effects. In this review, we highlight the current clinical practices undertaken to prevent infection and bleeding as well as research progress in this field and their outcomes in controlling bleeding, infection, and enhancing sternal healing.

Antibacterial-Integrated Collagen Wound Dressing for Diabetes-Related Foot Ulcers: An Evidence-Based Review of Clinical Studies

Diabetic foot ulcer (DFU) is a chronic wound frequently delayed from severe infection. Wound dressing provides an essential barrier between the ulcer and the external environment. This review aimed to analyse the effectiveness of antibacterial collagen-based dressing for DFU treatment in a clinical setting. An electronic search in four databases, namely, Scopus, PubMed, Ovid MEDLINE(R), and ISI Web of Science, was performed to obtain relevant articles published within the last ten years. The published studies were included if they reported evidence of (1) collagen-based antibacterial dressing or (2) wound healing for diabetic ulcers, and (3) were written in English. Both randomised and non-randomised clinical trials were included. The search for relevant clinical studies (n) identified eight related references discussing the effectiveness of collagen-based antibacterial wound dressings for DFU comprising collagen impregnated with polyhexamethylene biguanide (n = 2), gentamicin (n = 3), combined-cellulose and silver (n = 1), gentian violet/methylene blue mixed (n = 1), and silver (n = 1). The clinical data were limited by small sample sizes and multiple aetiologies of chronic wounds. The evidence was not robust enough for a conclusive statement, although most of the studies reported positive outcomes for the use of collagen dressings loaded with antibacterial properties for DFU wound healing. This study emphasises the importance of having standardised clinical trials, larger sample sizes, and accurate reporting for reliable statistical evidence confirming DFU treatment efficiency.

The Efficacy of Breast Implant Irrigant Solutions: A Comparative Analysis Using an In Vitro Model

BACKGROUND

Infections are challenging complications of implant-based breast reconstruction and augmentation. They pose a clinical challenge, with significant economic implications. One proposed solution is implant irrigation at the time of placement. There is no consensus on the optimal irrigant solution.

METHODS

The authors tested the relative efficacy of 10% povidone-iodine, Clorpactin, Prontosan, triple-antibiotic solution, or normal saline (negative control) against two strains each of methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis. Sterile, smooth silicone implant disks were immersed in irrigant solution, then incubated in suspensions of methicillin-resistant S. aureus or S. epidermidis overnight. The disks were rinsed and sonicated to displace adherent bacteria from the implant surface, and the displaced bacteria were quantified. Normalized values were calculated to characterize the relative efficacy of each irrigant.

RESULTS

Povidone-iodine resulted in reductions of the bacterial load by a factor of 10 to 10 for all strains. Prontosan-treated smooth breast implant disks had a 10-fold reduction in bacterial counts for all but one methicillin-resistant S. aureus strain. In comparison to Prontosan, triple-antibiotic solution demonstrated a trend of greater reduction in methicillin-resistant S. aureus bacterial load and weaker activity against S. epidermidis strains. Clorpactin reduced the recovered colony-forming units for only a single strain of S. epidermidis. Povidone-iodine demonstrated the greatest efficacy against all four strains. However, Clorpactin, triple-antibiotic solution, and Prontosan demonstrated similar efficacies.

CONCLUSIONS

Povidone-iodine was the most efficacious of the irrigants at reducing methicillin-resistant S. aureus and S. epidermidis contamination. Given the recent lifting of the U.S. Food and Drug Administration moratorium, larger clinical studies of povidone-iodine as a breast implant irrigant solution are warranted.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Optimizing Breast Pocket Irrigation: The Breast Implant-Associated Anaplastic Large Cell Lymphoma (BIA-ALCL) Era

BACKGROUND

Specific antimicrobial breast pocket irrigations have been proven over the past 20 years to reduce the incidence of capsular contracture by a factor of 10, and the emergence of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) and its link to bacteria/technique has created renewed interest in different antimicrobial breast pocket preparation agents. Our previous studies have identified that both Betadine-containing and non-Betadine-containing antimicrobial irrigations provide excellent broad-spectrum bacterial coverage. The current science of BIA-ALCL has implicated the Gram-negative microbiome as a key in pathogenesis.

OBJECTIVES

The aim of this study was to revisit the antimicrobial effectiveness of clinically utilized Betadine and non-Betadine solutions, along with other antimicrobial agents that have not yet been tested, against multiple organisms, including additional common Gram-negative bacteria associated with chronic breast implant infections/inflammation.

METHODS

Current and new antimicrobial breast irrigations were tested via standard techniques for bactericidal activity against multiple Gram-positive and Gram-negative strains. Test results are detailed and clinical recommendations for current antimicrobial irrigations are provided.

RESULTS

Betadine-containing irrigations were found to be superior according to the testing performed.

CONCLUSIONS

There are quite few misconceptions with regard to antimicrobial breast pocket irrigation. These are discussed and final evidence-based recommendations for practice are given.

A novel gentamicin-releasing wound dressing prepared from freshwater fish Cyprinus carpio collagen cross-linked with carbodiimide

Our study presents a novel collagen wound dressing prepared from freshwater fish skin ( Cyprinus Carpio) collagen type I. Half of the sponges were cross-linked with carbodiimide. The cross-linked and non-cross-linked collagen sponges were subsequently impregnated with gentamicin and lyophilized thus allowing for the attainment of the appropriate gentamicin content without the removal thereof during the cross-linking stage. The structure was evaluated via micro-CT and infrared spectrometry and the structural stability and gentamicin release properties were evaluated in phosphate buffer solution. The sponges were further tested via a rat model of an infected wound with Pseudomonas aeruginosa inoculation and compared with a reference commercial product. The sponges thus prepared provided a degree of open porosity that was comparable to or higher than that of the reference commercial product. Spectrometry analysis revealed that the cross-linked collagen sponge and reference commercial product sponge preserved their secondary collagen structure after 168 h while early accelerated degradation was observed with respect to the non-cross-linked collagen sponge. Gentamicin was released rapidly from all the sponges. Compared to those animals with gentamicin-containing sponges or gentamicin administered intramuscularly, the animals with the cross-linked collagen sponge without gentamicin exhibited marked clinical and laboratory infection signs. Both the administration routes (intramuscular and via gentamicin-containing sponges) provided similar gentamicin plasma levels. The resulting highly homogeneous product which was characterized by excellent structural and clinical properties proved effective in terms of the treatment of a surgical wound infection in a rat model. We demonstrated that all the gentamicin was released from the sponge and was absorbed in the systemic circulation. This is the first time that Cyprinus Carpio collagen has been used in the preparation of wound dressings. Thus, gentamicin-containing sponges provide a promising tool for the treatment and prevention of surgical site infections.

Antibiotic treatment of biofilm infections

Bacterial biofilms are associated with a wide range of infections, from those related to exogenous devices, such as catheters or prosthetic joints, to chronic tissue infections such as those occurring in the lungs of cystic fibrosis patients. Biofilms are recalcitrant to antibiotic treatment due to multiple tolerance mechanisms (phenotypic resistance). This causes persistence of biofilm infections in spite of antibiotic exposure which predisposes to antibiotic resistance development (genetic resistance). Understanding the interplay between phenotypic and genetic resistance mechanisms acting on biofilms, as well as appreciating the diversity of environmental conditions of biofilm infections which influence the effect of antibiotics are required in order to optimize the antibiotic treatment of biofilm infections. Here, we review the current knowledge on phenotypic and genetic resistance in biofilms and describe the potential strategies for the antibiotic treatment of biofilm infections. Of note is the optimization of PK/PD parameters in biofilms, high-dose topical treatments, combined and sequential/alternate therapies or the use antibiotic adjuvants.

Gentamicin-Impregnated Collagen Sponge: Effectiveness in Preventing Sternal Wound Infection in High-Risk Cardiac Surgery

Sternal wound infections represent one of the most frequent complications after cardiac surgery and are associated with high postoperative mortality. Several preventive methods have been introduced, and recently, gentamicin-impregnated collagen sponges (GICSs) have shown a promising effect in reducing the incidence of this type of complications. Gentamicin is an aminoglycoside antibiotic that has been widely used to treat infections caused by multiresistant bacteria; despite its effectiveness, its systemic use carries a risk of toxicity. GICSs appear to overcome this side effect, topically delivering high antibiotic concentrations to the wound and thus reducing the toxic-related events. Although several retrospective analyses and randomized controlled trials have studied the use of GICSs in cardiac surgery, conclusions regarding their efficacy in preventing sternal wound infection are inconsistent. We have reviewed the current literature focusing on high-risk patients.