The efficacy of silver dressings and antibiotics on MRSA and MSSA isolated from burn patients

Incorporation of Silver Nanoparticles in Hydrogel Matrices for Controlling Wound Infection

For centuries, silver has been recognized for its antibacterial properties. With the development of nanotechnology, silver nanoparticles (AgNPs) have garnered significant attention for their diverse uses in antimicrobial gel formulations, dressings for wound healing, orthopedic applications, medical catheters and instruments, implants, and contact lens coatings. A major focus has been determining AgNPs' physical, chemical, and biological characteristics and their potential to be incorporated in biocomposite materials, particularly hydrogel scaffolds, for burn and wound healing. Though AgNPs have been rigorously explored and extensively utilized in medical and nonmedical applications, important research is still needed to elucidate their antibacterial activity when incorporated in wound-healing scaffolds. In this review, we provide an up-to-date, 10-yr (2010-2019), comprehensive literature review on advancements in the understanding of AgNP characteristics, including the particles' preparation and mechanisms of activity, and we explore various hydrogel scaffolds for delivering AgNPs.

Risk and clinical impact of bacterial resistance/susceptibility to silver-based wound dressings: a systematic review

Objective:

To perform a systematic review of the literature on bacterial resistance, tolerance and susceptibility of silver within the context of wound therapy using silver-based dressings.

Methods:

A literature search was carried out using PubMed, Embase and Cochrane Library databases, the focus was whether results from microbiological experimental in vitro tests with reference strains and clinical wound isolates are reflected in clinical practice with regards to their ‘resistance’ profiles, comparable with those observed for antibiotics. The search results were allocated to six categories: resistance and resistance mechanism, in vitro tests with standard strains and wound isolates, prevalence and incidence, impact on clinical practice and impact on antibiotic therapy as well as reviews, expert opinions and consensus.

Results:

Based on all findings of the literature, it cannot be confirmed that a related clinical resistance to silver-ions in silver-based dressings has clinical impact, although endogenous and exogenous genetic resistance patterns have been described and intensively investigated. A translation of these genetic resistance-expression structures to phenotypic appearances, similar to those known for antibiotics, has not been demonstrated for silver in the literature.

Conclusion:

It can be concluded that there is no definitive evidence available and further studies should be conducted.

Role of pH Value in Clinically Relevant Diagnosis

As a highly influential physiological factor, pH may be leveraged as a tool to diagnose physiological state. It may be especially suitable for diagnosing and assessing skin structure and wound status. Multiple innovative and elegant smart wound dressings combined with either pH sensors or drug control-released carriers have been extensively studied. Increasing our understanding of the role of pH value in clinically relevant diagnostics should assist clinicians and improve personal health management in the home. In this review, we summarized a number of articles and discussed the role of pH on the skin surface as well as the factors that influence skin pH and pH-relevant skin diseases, but also the relationship of skin pH to the wound healing process, including its influence on the activity of proteases, bacterial enterotoxin, and some antibacterial agents. A great number of papers discussing physiological pH value have been published in recent decades, far too many to be included in this review. Here, we have focused on the impact of pH on wounds and skin with an emphasis on clinically relevant diagnosis toward effective treatment. We have also summarized the differences in skin structure and wound care between adults and infants, noting that infants have fragile skin and poor skin barriers, which makes them more vulnerable to skin damage and compels particular care, especially for wounds.

In Vitro Assessment of the Antibacterial Potential of Silver Nano-Coatings on Cotton Gauzes for Prevention of Wound Infections

Multidrug-resistant organisms are increasingly implicated in acute and chronic wound infections, thus compromising the chance of therapeutic options. The resistance to conventional antibiotics demonstrated by some bacterial strains has encouraged new approaches for the prevention of infections in wounds and burns, among them the use of silver compounds and nanocrystalline silver. Recently, silver wound dressings have become widely accepted in wound healing centers and are commercially available. In this work, novel antibacterial wound dressings have been developed through a silver deposition technology based on the photochemical synthesis of silver nanoparticles. The devices obtained are completely natural and the silver coatings are characterized by an excellent adhesion without the use of any binder. The silver-treated cotton gauzes were characterized through scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA) in order to verify the distribution and the dimension of the silver particles on the cotton fibers. The effectiveness of the silver-treated gauzes in reducing the bacterial growth and biofilm proliferation has been demonstrated through agar diffusion tests, bacterial enumeration test, biofilm quantification tests, fluorescence and SEM microscopy. Moreover, potential cytotoxicity of the silver coating was evaluated through 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide colorimetric assay (MTT) and the extract method on fibroblasts and keratinocytes. Inductively coupled plasma mass spectrometry (ICP-MS) was performed in order to determine the silver release in different media and to relate the results to the biological characterization. All the results obtained were compared with plain gauzes as a negative control, as well as gauzes treated with a higher silver percentage as a positive control.

Silver-impregnated hydrofiber dressing followed by delayed surgical closure for management of infants born with giant omphaloceles

OBJECTIVE

We successfully employed silver-impregnated hydrofiber dressing for management of giant omphaloceles (GO) followed by delayed surgical closure.

STUDY DESIGN

Between 2005 and 2008, eight consecutive GO infants were cared for at Driscoll Children's Hospital. Four patients had additional congenital anomalies including Beckwith-Wiedemann (n = 1), tetralogy of Fallot (n = 1), pulmonary hypoplasia (n = 1), and ruptured omphalocele (n=1). Infants underwent amnion epithelization using a silver-impregnated hydrofiber dressing over the course of several months followed by delayed surgical closure. Mean ± SD of parameters including maternal age, gestational age, infant weight, size of GO, preoperative intubation, preoperative hospitalization, time to epithelization, days to surgical closure, postoperative hospitalization, postoperative intubation and months of follow-up were studied.

RESULTS

Five patients underwent successful closure, 2 were lost to follow-up and 1 was lost because of withdrawal of support. The maternal age, gestation age and weight of infant were 28 ± 5.3 years, 34 ± 4 weeks and 2.5 ± 0.62 kg, respectively. The GO size was 11 cm in length and 11 cm in width, respectively. Preoperative hospitalization days were 78 ± 74 days. Preoperative intubation was 3.5 ± 3.1 days with 2 neonates requiring tracheostomy and home ventilation owing to additional congenital abnormalities. Time to epithelization was 2.9 ± 0.9 months. Days to surgical closure and postoperative hospitalization were 331 ± 119 days and 5 ± 3.4 days, respectively. Average follow-up was 37 ± 27 months. No treatment associated morbidities are noted.

CONCLUSIONS

Silver-impregnated hydrofiber mediated epithelization of GO followed by delayed surgical closure is safe for management of infants.

Silver and Alginates: Role in Wound Healing and Biofilm Control

Significance: Chronic wounds are known to be a significant issue globally. Of concern in wounds are the numbers and types of residing microorganisms and the ability of the host's immune system to control their proliferation. Wound healing is impeded by colonizing microorganisms growing within the biofilm phenotypic state. In this state microorganisms are recalcitrant to routinely impeded by used antimicrobial interventions. Recent advances: Silver has been reported to demonstrate efficacy on planktonic microorganisms both within the in vitro and in vivo environments. However, when silver is incorporated into a wound dressing, its antimicrobial efficacy on biofilms within the in vivo environment remains contentious. Critical Issues: Unequivocal evidence of the efficacy of silver, and wound dressings containing silver, on biofilms in clinical situations is lacking. This is principally due to the deficiency of definite biofilm definitions, markers, and evidence in the chronic wound environment. Future Direction: Research studies demonstrating antimicrobial efficacy on in vitro biofilms can be used to generate data and information appropriate for extrapolation and applicability to the in vivo environment. It is very important that inventors of antimicrobial wound dressings ensure efficacy against both planktonic and sessile microorganisms, within the in vitro and in vivo environments.

The Use of Vacuum-Assisted Closure and GranuFoam Silver® Dressing in the Management of Diabetic Foot Ulcer

PURPOSE

The aim of this retrospective study was to evaluate the efficacy of vacuum-assisted closure (VAC) and GranuFoam Silver® dressing (KCI, San Antonio, TX) compared with conventional GranuFoam® dressing in the management of diabetic foot ulcers.

PATIENTS AND METHODS

Twenty-one consecutive patients treated with conventional or silver-coated foam dressing were reviewed retrospectively. The wound duration was 6 mo. Group 1 (n=10) received conventional foam dressing (GranuFoam) and group 2 (n=11) received silver-coated foam dressing (GranuFoam Silver). The wound surface area, duration of treatment, bacteriology, and recurrence were compared between the groups. The mean age of the patients was 61.70±10.52 y in group 1 and 67.27±11.28 y in group 2.

RESULTS

In group 1, the average surface area of the wounds was 45.30±46.96 cm2 and 18.40±23.48 cm2 in the pre-treatment and post-treatment periods, respectively. There was a statistically significant difference between two measurements (p=0.005). Average duration of the treatment was 25.50±27.13 d in this group. In group 2, average surface area of the wounds in the pre-treatment and post-treatment periods were 41.55±36.03 cm2 and 7.64±3.91 cm2, respectively. There was a statistically significant difference between two measurements (p=0.003). Average duration of the treatment was 10.09±3.51 d in this group. The patients treated with silver-impregnated polyurethane foam dressing had reduced recurrence (2 vs. 7 wounds, p=0.030) and increased number of the culture-negative cases at the end of the treatment.

CONCLUSION

With the results of the study, it was concluded that VAC GranuFoam silver dressing can be superior to conventional GranuFoam dressing in reducing the recurrence rate of infected diabetic foot ulcers.

Killing bacteria within biofilms by sustained release of tetracycline from triple-layered electrospun micro/nanofibre matrices of polycaprolactone and poly(ethylene-co-vinyl acetate)

We report the controlled release of the antibiotic tetracycline (tet) HCl from a triple-layered electrospun matrix consisting of a central layer of poly(ethylene-co-vinyl acetate (PEVA) sandwiched between outer layers of poly-ε-caprolactone (PCL). These micro/nanofibre layers with tet successfully encapsulated (essentially quantitatively at 3 and 5 % w/w) in each layer, efficiently inhibited the growth of a panel of bacteria, including clinical isolates, as shown by a modified Kirby-Bauer disc assay. Furthermore, they demonstrated high biological activity in increasingly complex models of biofilm formation (models that are moving closer to the situation in a wound) by stopping biofilm formation, by killing preformed biofilms and killing mature, dense biofilm colonies of Staphylococcus aureus MRSA252. Tet is clinically useful with potential applications in wound healing and especially in complicated skin and skin-structure infections; electrospinning provides good encapsulation efficiency of tet within PCL/PEVA/PCL polymers in micro/nanofibre layers which display sustained antibiotic release in formulations that are anti-biofilm.

The increased killing of biofilms in vitro by combining topical silver dressings with topical negative pressure in chronic wounds

Chronic wounds remain a significant medical and financial burden in hospitals of today. A major factor in the transition from an acute to a chronic wound is its bacterial bioburden. Developments in molecular techniques have shown that chronic wounds remain colonised by many species of bacteria and that the bacteria within these chronic wounds exist in two forms. Treatments of chronic wounds have maintained a challenging field and significant ongoing research is being conducted. With the development of an in vitro wound model, we applied topical negative pressure (TNP) dressings to a spectrum of common bacterial biofilms found in chronic wounds and studied the synergistic efficacy between the application of TNP and silver-impregnated foam against these biofilms. This synergistic response was seen within the laboratory strains of staphylococcal biofilms over a 3-day treatment period but lost following the 5 days of treatment. However, combining topical pressure dressings and silver foam lead to a synergistic inactivation in Pseudomonas species over both 3-day and 5-day treatments.

Silver negative pressure dressing with vacuum-assisted closure of massive pelvic and extremity wounds

BACKGROUND

Massive soft tissue loss involving the pelvis and extremities from trauma, infections, and tumors remains a challenging and debilitating problem. Although vacuum-assisted closure (VAC) technology is effective in the management of soft tissue loss, the adjunct of a silver dressing in the setting of massive wounds has not been as well tested.

QUESTIONS/PURPOSES

Does a silver negative pressure dressing used in conjunction with a wound VAC decrease (1) the length of acute hospital stay and overall length of treatment; (2) the number of surgical débridements the patients underwent as part of their care; and (3) the likelihood of wound closure without soft tissue transposition?

METHODS

We evaluated 42 patients with massive (> 200 cm(2)) pelvic and extremity wounds from trauma, infection, or tumor who were treated with the wound VAC with or without a silver negative pressure dressing between January 2003 and January 2010; the first 26 patients were treated with the wound VAC alone, and in the final 16 consecutively treated patients, the silver dressing was added to the regimen. We reviewed medical records to determine length of treatment as well as the number and type of surgical interventions these patients underwent. We compared the group treated with the wound VAC alone with those patients treated with the wound VAC and silver negative pressure dressing.

RESULTS

Hospital stay averaged 19 days in the VAC only group and 7.5 days in the VAC with silver dressing group (p < 0.041), length of overall treatment averaged 33 days in the VAC only group and 14.3 days in the VAC with silver dressing group (p < 0.022), number of operative débridements averaged 7.9 in the VAC alone group and 4.1 in the VAC with silver dressing group (p < 0.001), and success of wound closure without soft tissue transposition was 16 of 26 patients in the VAC alone group and three of 16 patients in the VAC with silver dressing group (p < 0.033).

CONCLUSIONS

Based on the reduced length of care and the number of surgical procedures these patients with massive wounds of the pelvis and extremities underwent, we now use the silver negative pressure dressing in combination with the wound VAC as part of routine care of such patients. These results may be used as hypothesis-generating data for future randomized studies.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Review of burn research for the year 2011

The year 2011 was another robust year for burn research. Over 1100 articles were published on a wide range of burn injury and treatment topics. In this review, we highlight some of the interesting and potentially influential research in the following areas: critical care, infection, inhalation injury, epidemiology, wound characterization and treatment, nutrition and metabolism, pain management, burn reconstruction, psychology, and rehabilitation. As in years past, burn injury research reflects the multidisciplinary and holistic care that is needed to treat this challenging injury condition.

The year in burns 2011

For 2011, approximately 1746 original research articles in burns were published in English in scientific journals. This article reviews those with the most potential impact on for burn therapeutics and outcomes according to the Editor of one of the major journals (Burns) and his colleague. As done previously, articles were found and divided into these topic areas: epidemiology of injury and burn prevention, wound and scar characterisation, acute care and critical care, inhalation injury, infection, psychological considerations, pain and itching management, rehabilitation and long-term outcomes, and burn reconstruction. Each selected article is mentioned briefly with editorial comment.

Chitin membranes containing silver nanoparticles for wound dressing application

Silver nanoparticles are gaining importance as an antimicrobial agent in wound dressings. Chitin is a biopolymer envisioned to promote rapid dermal regeneration and accelerate wound healing. This study was focused on the evaluation of chitin membranes containing silver nanoparticles for use as an antimicrobial wound dressing. Silver nanoparticles were synthesised by gamma irradiation at doses of 50 kGy in the presence of sodium alginate as stabiliser. The UV-Vis absorption spectra of nanoparticles exhibited an absorption band at 415-420 nm, which is the typical plasmon resonance band of silver nanoparticles. The peaks in the X-ray diffraction (XRD) pattern are in agreement with the standard values of the face-centred cubic silver. Transmission electron microscopy (TEM) images indicate silver nanoparticles with spherical morphology and small particle size in the range of 3-13 nm. In vitro antimicrobial tests were performed using Pseudomonas aeruginosa and Staphylococcus aureus to determine the antimicrobial efficiency of the chitin membranes containing 30, 50, 70 and 100 ppm nanosilver. No viable counts for P. aeruginosa were detected with 70 ppm silver nanoparticles dressing after 1-hour exposure. A 2-log reduction in viable cell count was observed for S. aureus after 1 hour and a 4-log reduction after 6 hours with 100 ppm nanosilver chitin membranes. This study demonstrates the antimicrobial capability of chitin membranes containing silver nanoparticles. The chitin membranes with 100 ppm nanosilver showed promising antimicrobial activity against common wound pathogens.

Wound-healing with mechanically robust and biodegradable hydrogel fibers loaded with silver nanoparticles

The objective of this study is to provide a novel synthetic approach for the manufacture of wound-healing materials using covalently cross-linked alginate fibers loaded with silver nanoparticles. Alginate fibers are prepared by wet-spinning in a CaCl(2) precipitation bath. Using this same approach, calcium cross-links in alginate fibers are replaced by chemical cross-links that involve hydroxyl groups for subsequent cross-linking by glutaraldehyde. The cross-linked fibers become highly swollen in aqueous solution due to the presence of carboxyl functional groups, and retain their mechanical stability in physiological fluids owing to the stabilized network of covalent bonds. Alginate fibers can then be loaded with silver ions via the ion-exchange reaction. Silver ions are reduced to yield 11 nm silver nanoparticles incorporated in the polymer gel. This method provides a convenient platform to incorporate silver nanoparticles into alginate fibers in controlled concentrations while retaining the mechanical and swelling properties of the alginate fibers. Our study suggests that the silver nanoparticles loaded fibers may be easily applied in a wound healing paradigm and promote the repair process though the promotion of fibroblast migration to the wound area, reduction of the inflammatory phase, and the increased epidermal thickness in the repaired wound area, thereby improving the overall quality and speed of healing.

The antimicrobial efficacy of silver on antibiotic-resistant bacteria isolated from burn wounds

The antibiotic-resistant bacteria are a major concern to wound care because of their ability to resist many of the antibiotics used today to treat infections. Consequently, other antimicrobials, in particular ionic silver, are considered ideal topical agents for effectively helping to manage and prevent local infections. Little is known about the antimicrobial efficacy of ionic silver on antibiotic-resistant bacteria at different pH values. Consequently, in this study our aim was to evaluate the effect of pH on the antimicrobial efficacy of a silver alginate (SA) and a silver carboxymethyl cellulose (SCMC) dressing on antibiotic-resistant bacteria isolated from burn patients. Forty-nine antibiotic-resistant bacteria, including Vancomycin-resistant Enterococcus faecium, meticillin-resistant Staphylococcus aureus, multidrug-resistant (MDR) Pseudomonas aeruginosa, MDR Vibrio sp, MDR Stenotrophomonas maltophilia, extended-spectrum ß-lactamase (ESBL) producing Salmonella sp, ESBL producing Klebsiella pneumoniae, ESBL producing Proteus mirabilis, ESBL producing Escherichia coli and MDR Acinetobacter baumannii, routinely isolated from burn wounds were used in the study and evaluated for their susceptibility to two silver containing wound dressings using a standardised antimicrobial efficacy screening assay [corrected zone of inhibition (CZOI)]. The mean overall CZOI for the Gram-positive isolates at a pH of 5·5 were very similar for both dressings. A mean CZOI of 5 mm was recorded for the SCMC dressing, which was slightly higher, at 5·4 mm for the SA dressing. At a pH of 7·0 both dressings, in general, showed a similar activity. However, at a pH of 8·5 the mean CZOI of the SCMC dressing was found to be significantly (P < 0·05) higher than the SA dressing for a select number of isolates. The mean overall CZOI for the Gram-negative bacteria followed a similar pattern as observed with the Gram-positive bacteria. Susceptibility to silver ions did vary significantly between genera and species of bacteria. Interestingly, when pH was changed from 8·5 to 5·5 antimicrobial activity for both dressings in general increased significantly (P < 0·05). Overall, all forty-nine antibiotic-resistant bacteria isolated from burn wounds showed susceptibility to the antimicrobial activity of both silver containing wound dressings over all pH ranges. In addition, the study showed that the performance of both dressings apparently increased when pH became more acidic. The findings in this study may help to further enhance our knowledge of the role pH plays in affecting both bacterial susceptibility and antimicrobial activity of silver containing wound dressings.