Jose Valdes

Interactions of Methicillin Resistant Staphylococcus aureus USA300 and Pseudomonas aeruginosa in Polymicrobial Wound Infection

Understanding the pathology resulting from Staphylococcus aureus and Pseudomonas aeruginosa polymicrobial wound infections is of great importance due to their ubiquitous nature, increasing prevalence, growing resistance to antimicrobial agents, and ability to delay healing. Methicillin-resistant S. aureus USA300 is the leading cause of community-associated bacterial infections resulting in increased morbidity and mortality. We utilized a well-established porcine partial thickness wound healing model to study the synergistic effects of USA300 and P. aeruginosa on wound healing. Wound re-epithelialization was significantly delayed by mixed-species biofilms through suppression of keratinocyte growth factor 1. Pseudomonas showed an inhibitory effect on USA300 growth in vitro while both species co-existed in cutaneous wounds in vivo. Polymicrobial wound infection in the presence of P. aeruginosa resulted in induced expression of USA300 virulence factors Panton-Valentine leukocidin and α-hemolysin. These results provide evidence for the interaction of bacterial species within mixed-species biofilms in vivo and for the first time, the contribution of virulence factors to the severity of polymicrobial wound infections.

Effective Method to Remove Wound Bacteria: Comparison of Various Debridement Modalities in an In Vivo Porcine Model

BACKGROUND Debridement is one of the crucial steps for successful wound care. In addition to removing necrotic tissue, debridement has been shown to reduce wound-associated bacteria that delay healing. Using an in vivo porcine model, we compared the effects of various methods of debridement, including hydrosurgery and plasma-mediated bipolar radiofrequency ablation (PBRA), on bacterial removal and wound healing. METHODS One hundred thirty-five deep dermal wounds were inoculated with methicillin resistant Staphylococcus aureus (MRSA) and covered with a polyurethane dressing for 48 h to allow for biofilm formation. Wounds were then treated with either PBRA (at two settings), hydrosurgery, sharp debridement, or no debridement. Biopsies were collected for microbiology and histologic assessment on d 0, 2, 9, and 21 post-treatment. RESULTS All treatment groups showed a statistically significant reduction in MRSA counts relative to no debridement at all times points (P < 0.05). PBRA at a maximum setting had the lowest MRSA counts at all recovery times and, compared with all other treatment groups, a statistically significant difference was observed on d 21 (P < 0.05). No detrimental effects on the healing process were noted with any of the debridement methods. CONCLUSION While sharp debridement has been established as the traditional gold standard for rapid removal of necrotic, infected tissue, our results suggest that novel debridement modalities show clinical promise for the treatment of chronic ulcers and burn wounds, especially when bacteria are present.

Keratin dressings speed epithelialization of deep partial-thickness wounds.

Keratin gene expression is regarded as a hallmark of epidermal biology. It demarcates the three keratinocyte phenotypes: basal (expressing KRT5 and KRT14), differentiating (expressing KRT1 and KRT10), and activated (wound healing), which is characterized by expression of KRT6, KRT16, and KRT17. Activated keratinocytes are among the first signals of epidermal wound healing. In addition, they are found deregulated in nonhealing chronic wounds. To examine keratins as a potential modality for wound‐healing disorders, we evaluated two different keratin dressings, liquid or solid, and assessed their effects of epithelialization and closure using porcine partial‐thickness wound‐healing model in vivo. We found that both forms of keratin dressings accelerated closure and epithelialization, achieving statistically significant differences on day 5. Evidence suggesting early onset of epithelialization was corroborated further by gene expression analyses revealing induction of KRT6A, KRT16, and KRT17 by day 2 postwounding. The data suggest that keratin dressings may stimulate epithelialization by enhancing the activation of keratinocytes. We conclude that keratin‐containing dressings can accelerate wound healing and closure. Further studies are needed to determine the molecular mechanisms of this activation.

A closer examination of atraumatic dressings for optimal healing.

The concept that undisturbed wound healing, optimised by dressing choice, improves wound outcomes has become a focal point of consideration when evaluating wound management regimens in recent years. However, little evidence exists related to wound contact layers and the potential detrimental effects of the intimate contact with the wound bed. The aim of this study was to evaluate the effects of atraumatic wound contact dressings on the healing of partial‐thickness wounds in comparison to untreated air‐exposed wounds. Using an in vivo porcine wound model the handling properties of each dressing in terms of adhesion were analysed. Methods of wound characterisation included histological analysis of granulation tissue formation and epithelialisation and this was correlated with various clinical observations. Differences were found between dressings in terms of adherence to the wound bed and surrounding skin, capacity to retain wound exudates and enhancement of healing.

The healing effect of over-the-counter wound healing agents applied under semiocclusive film dressing.

IB methods. It was rather surprising that IIF showed positive reactivity with normal human skin, but not 1 mol L 1 NaClsplit skin, because IIF of 1 mol L 1 NaCl-split skin is usually more sensitive. It is possible that 1 mol L 1 NaCl treatment may mask or destroy the epitopes on the BP180 C-terminal domain or b4 integrin, which was specifically reacted to by the patient serum. It was also unknown why IgA antibodies were detected by IB but not by IIF. IB of the BP180 C-terminal domain recombinant protein may be more sensitive in detecting IgA antibodies than immunofluorescence, although the mechanism of this was not clear. The patient has a long-lasting and intractable disease course, which may be caused by the complex autoantibodies involved. It is possible that the two autoantibodies, which developed at variable intervals via the epitope spreading phenomenon, exerted a ‘sum effect’, leading to the lack of response to conventional immunosuppressive therapy. Recently, a combination therapy of rituximab and IVIg was proven to arrest disease progression and prevent total blindness in patients with recalcitrant ocular MMP. In our case, the patient refused to receive additional treatments. Patients with ocular MMP may have serious visual impairments, even blindness, and may need more aggressive treatments. Therefore, accurate and fast diagnosis should be made using various immunofluorescence and IB techniques.

Effectiveness of a polyhexanide irrigation solution on methicillin‐resistant Staphylococcus aureus biofilms in a porcine wound model

Irrigation and removal of necrotic debris can be beneficial for proper healing. It is becoming increasingly evident that wounds colonized with biofilm forming bacteria, such as Staphylococcus aureus (SA), can be more difficult to eradicate. Here we report our findings of the effects of an irrigation solution containing propyl‐betaine and polyhexanide (PHMB) on methicillin‐resistant Staphylococcus aureus (MRSA) biofilms in a porcine wound model. Thirty‐nine deep partial thickness wounds were created with six wounds assigned to one of six treatment groups: (i) PHMB, (ii) Ringers solution, (iii) hypochlorous acid/sodium hypochlorite, (iv) sterile water, (v) octenidine dihydrochloride, and (vi) octenilin. Wounds were inoculated with MRSA and covered with a polyurethane dressing for 24 hours to allow biofilm formation. The dressings were then removed and the wounds were irrigated twice daily for 3 days with the appropriate solution. MRSA from four wounds were recovered from each treatment group at 3 days and 6 days hours after initial treatment. Irrigation of wounds with the PHMB solution resulted in 97·85% and 99·64% reductions of MRSA at the respective 3 days and 6 days assessment times when compared to the untreated group. Both of these reductions were statistically significant compared to all other treatment groups (P values <0·05).

A PEGylated fibrin hydrogel‐based antimicrobial wound dressing controls infection without impeding wound healing

Combat injuries are associated with a high incidence of infection, and there is a continuing need for improved approaches to control infection and promote wound healing. Due to the possible local and systemic adverse effects of standard 1% cream formulation (Silvadene), we had previously developed a polyethylene glycol (PEGylated) fibrin hydrogel (FPEG)‐based wound dressing for the controlled delivery of silver sulfadiazine (SSD) entrapped in chitosan microspheres (CSM). In this study, we have evaluated the antimicrobial and wound healing efficacy of SSD‐CSM‐FPEG using a full‐thickness porcine wound infected with Pseudomonas aeruginosa. Infected wounds treated with a one‐time application of the SSD‐CSM‐FPEG wound dressing demonstrated significantly reduced bacterial bioburden over time (99·99% of reduction by day 11; P < 0·05) compared with all the other treatment groups. The epithelial thickness and granulation of the wound bed was significantly better on day 7 (150·9 ± 13·12 µm), when compared with other treatment groups. Overall, our findings demonstrate that the SSD‐CSM‐FPEG wound dressing effectively controls P. aeruginosa infection and promotes wound healing by providing a favourable environment that induces neovascularisation. Collectively, sustained release of SSD using fibrin hydrogel exhibited enhanced benefits when compared with the currently available SSD treatment, and this may have significant implications in the bacterial reduction of infected wounds in military and civilian populations.

Assessment of Ablative Fractional CO2 Laser and Er:YAG Laser to Treat Hypertrophic Scars in a Red Duroc Pig Model

Hypertrophic scarring is a fibroproliferative process that occurs following a third-degree dermal burn injury, producing significant morbidity due to persistent pain, itching, cosmetic disfigurement, and loss of function due to contractures. Ablative fractional lasers have emerged clinically as a fundamental or standard therapeutic modality for hypertrophic burn scars. Yet the examination of their histopathological and biochemical mechanisms of tissue remodeling and comparison among different laser types has been lacking. In addition, deficiency of a relevant animal model limits our ability to gain a better understanding of hypertrophic scar pathophysiology. To evaluate the effect of ablative fractional lasers on hypertrophic third-degree burn scars, we have developed an in vivo Red Duroc porcine model. Third-degree burn wounds were created on the backs of animals, and burn scars were allowed to develop for 70 days before treatment. Scars received treatment with either CO2 or erbium: yttrium aluminum garnet (YAG) ablative fractional lasers. Here, we describe the effect of both lasers on hypertrophic third-degree burn scars in Red Duroc pigs. In this report, we found that Er:YAG has improved outcomes versus fractional CO2. Molecular changes noted in the areas of dermal remodeling indicated that matrix metalloproteinase 2, matrix metalloproteinase 9, and Decorin may play a role in this dermal remodeling and account for the enhanced effect of the Er:YAG laser. We have demonstrated that ablative fractional laser treatment of burn scars can lead to favorable clinical, histological, and molecular changes. This study provides support that hypertrophic third-degree burn scars can be modified by fractional laser treatment.

The wound‐healing effects of a next‐generation anti‐biofilm silver Hydrofiber wound dressing on deep partial‐thickness wounds using a porcine model

Topical antimicrobials are widely used to control wound bioburden and facilitate wound healing; however, the fine balance between antimicrobial efficacy and non‐toxicity must be achieved. This study evaluated whether an anti‐biofilm silver‐containing wound dressing interfered with the normal healing process in non‐contaminated deep partial thickness wounds. In an in‐vivo porcine wound model using 2 pigs, 96 wounds were randomly assigned to 1 of 3 dressing groups: anti‐biofilm silver Hydrofiber dressing (test), silver Hydrofiber dressing (control), or polyurethane film dressing (control). Wounds were investigated for 8 days, and wound biopsies (n = 4) were taken from each dressing group, per animal, on days 2, 4, 6, and 8 after wounding and evaluated using light microscopy. No statistically significant differences were observed in the rate of reepithelialisation, white blood cell infiltration, angiogenesis, or granulation tissue formation following application of the anti‐biofilm silver Hydrofiber dressing versus the 2 control dressings. Overall, epithelial thickness was similar between groups. Some differences in infiltration of specific cell types were observed between groups. There were no signs of tissue necrosis, fibrosis, or fatty infiltration in any group. An anti‐biofilm silver Hydrofiber wound dressing did not cause any notable interference with normal healing processes.