A review of studies that examine the impact of infection on the normal wound-healing process

Psychological, behavioural and relevant factors affecting wound healing, and the buffering role of interventions

Wound healing is a complex process accompanying numerous health conditions, and millions of people across the world experience deleterious impacts caused by wounds. There are many non-biological factors that can directly or indirectly affect the health outcomes of patients with wounds. The purpose of this review was to investigate the effects of psychological, behavioural and other relevant factors on wound healing. In addition, as the possible associations among these factors have, in the authors' view, not been addressed appropriately, we also aimed to examine if there were specific relationships among these factors and between these factors and health outcomes. Finally, we reviewed the role of various interventions in buffering negative impacts during health procedures.

Skin Deep: The Potential of Microbiome Cosmetics

The interplay between the skin microbiome and its host is a complex facet of dermatological health and has become a critical focus in the development of microbiome cosmetics. The skin microbiome, comprising various microorganisms, is essential from birth, develops over the lifespan, and performs vital roles in protecting our body against pathogens, training the immune system, and facilitating the breakdown of organic matter. Dysbiosis, an imbalance of these microorganisms, has been implicated in a number of skin conditions such as acne, atopic dermatitis, and skin cancer. Recent scientific findings have spurred cosmetic companies to develop products that preserve and enhance the skin's microbial diversity balance. These products may incorporate elements like prebiotics, probiotics, and postbiotics, which are beneficial for the skin microbiome. Beyond topical products, there's increasing interest in ingestible beauty supplements (i.e. oral probiotics), highlighting the connection between the gut and skin. This review examines the influence of the microbiome on skin health and the emerging trends of microbiome skincare products.

Wound healing and microbiome, an unexpected relationship

Skin wounds are common and represent a major public health and economical problem, with risks of complications and a significant negative impact on the quality of life of patients. Cutaneous wound healing is a tightly regulated process resulting in the restoration of tissue integrity. Wound healing involves the interaction of several skin, immune and vascular cells, growth factors and cytokines. However, external actors can play an important role in wound healing, such as the skin microbiome, which is the microbial commensal collection of bacteria, fungi and viruses inhabiting the skin. Indeed, recent advances have featured the interactions, within the wound environment, between different microbial species and between microbial species and the host immune system. This article reviews the relationship between the skin microbiome and the wound healing process. Although cutaneous wounds are a potential entry site for infection, the wound microbiome can have either a detrimental or a beneficial role on wound healing. Thus, targeting the skin microbiome could represent an essential part of wound healing management.

Multidisciplinary treatment of thoracic fistulous empyema caused by pulmonary infection: a retrospective study

Background

In cases of thoracic empyema, the presence of a fistula is known to be difficult to treat and associated with a poor prognosis. Few reports have described the management of fistulous empyema caused by lung parenchymal infection. The aim of this study was to describe the outcomes of multidisciplinary management of fistulous empyema caused by pneumonia or lung abscess due to common bacteria and mycobacteria.

Methods

Among 108 cases of empyema surgically treated at Kanagawa Hospital over a 10-year period, 14 patients with fistulous empyema due to common bacteria (CBFE) or fistulous empyema due to mycobacteria (MFE) were analyzed. Fistulous empyema due to lung resection was excluded.

Results

Eight out of the 9 patients with CBFE and 4 out of the 5 patients with MFE were male. Patients with CBFE were more likely to be >65 years of age (p=0.052) and to have a poor performance status (p=0.078). The time from onset to first surgical treatment was significantly longer in MFE (median, 5 months; p=0.004). Five patients with CBFE and two patients with MFE underwent open window thoracostomy, while three patients with CBFE and four patients with MFE underwent endobronchial occlusion (EBO). Six patients (66%) with CBFE and 3 patients (60%) with MFE achieved fistula closure. Of the patients who underwent EBO, fistula closure was achieved in 3 (100%) of the patients with CBFE and in 2 (50%) of the patients with MFE. Fistula closure was not achieved in any case with non-tuberculous mycobacteria.

Conclusions

Fistulous empyema caused by common bacteria or Mycobacterium tuberculosis could be cured by surgical treatment and endobronchial intervention with adequate antimicrobial therapy, but fistulous empyema caused by non-tuberculous mycobacteria proved to be intractable. The challenge in the treatment of fistulous empyema due to non-tuberculous mycobacteria is the achievement of bacterial negativity.

Healing of colonic anastomosis in rats under obstructive ileus conditions

BACKGROUND

The anastomosis leak in colon resections is a crucial post-operative complication with significant morbidity and mortality.  Methods: Forty (40) Wistar rats were allocated in two groups. In SHAM group only anastomosis was performed. In ILEUS group anastomosis was performed following one day of ileus. Animals in both groups were subdivided in two groups according to the day they were sacrificed, 4th or 8th post-operative day. A number of variables between the groups were estimated.

RESULTS

Body weight loss was higher following obstructive ileus on both days. Adhesion score in 4th and 8th post-operative day was higher in ILEUS1, ILEUS2 groups compared to SHAM1, SHAM2 groups respectively (p<0.001 for both). Neovascularization decreased following obstructive ileus compared to control on the 4th day (ILEUS1 vs. SHAM1, p=0.038). Bursting pressure was lower in ILEUS2 group than SHAM2 group (p<0.001). The number of fibroblasts decreased following obstructive ileus compared to control on the 4th and 8th day (ILEUS1 vs. SHAM1, p=0.001, ILEUS2 vs SHAM2, p=0.016). Hydroxyproline concentration was decreased in ILEUS2 group compared to SHAM2 group (p<0.001).

CONCLUSIONS

The balance of collagenolysis and collagenogenesis plays a decisive role in the healing of anastomoses following bowel obstruction. Under those circumstances, anastomosis' bursting pressure is reduced owning to decreased neovascularization, reduced fibroblast presence and lower hydroxyproline concertation. In our study, local inflammation, neocollagen concentration and collagenase activity were not associated with this adverse effect. However, further research should delineate the mechanisms of healing of colonic anastomoses and identify those factors that can improve our outcomes.

Negative-Pressure Wound Therapy in Foot and Ankle Surgery

Negative Pressure Wound Therapy (NPWT) is frequently utilized to manage complex wounds, however its mechanisms of healing remain poorly understood. Changes in growth factor expression, micro- and macro-deformation, blood flow, exudate removal, and bacterial concentration within the wound bed are thought to play a role. NPWT is gaining widespread usage in foot and ankle surgery, including the management of traumatic wounds; diabetic and neuropathic ulcers; wounds left open after debridement for infection or dehiscence; high-risk, closed incisions; tissue grafts and free flaps. This article reviews the rationale for NPWT, its proposed mechanisms of action, and the evidence regarding its clinical applications within the field of foot and ankle surgery. Level of Evidence: Level V, expert opinion.

A microbiome and metabolomic signature of phases of cutaneous healing identified by profiling sequential acute wounds of human skin: An exploratory study

Profiling skin microbiome and metabolome has been utilised to gain further insight into wound healing processes. The aims of this multi-part temporal study in 11 volunteers were to analytically profile the dynamic wound tissue and headspace metabolome and sequence microbial communities in acute wound healing at days 0, 7, 14, 21 and 28, and to investigate their relationship to wound healing, using non-invasive quantitative devices. Metabolites were obtained using tissue extraction, sorbent and polydimethylsiloxane patches and analysed using GCMS. PCA of wound tissue metabolome clearly separated time points with 10 metabolites of 346 being involved in separation. Analysis of variance-simultaneous component analysis identified a statistical difference between the wound headspace metabolome, sites (P = 0.0024) and time points (P<0.0001), with 10 out of the 129 metabolites measured involved with this separation between sites and time points. A reciprocal relationship between Staphylococcus spp. and Propionibacterium spp. was observed at day 21 (P<0.05) with a statistical correlation between collagen and Propionibacterium (r = 0.417; P = 0.038) and Staphylococcus (r = -0.434; P = 0.03). Procrustes analysis showed a statistically significant similarity between wound headspace and tissue metabolome with non-invasive wound devices. This exploratory study demonstrates the temporal and dynamic nature of acute wound metabolome and microbiome presenting a novel class of biomarkers that correspond to wound healing, with further confirmatory studies now necessary.

Antimicrobial Photodynamic Therapy in Infected Diabetic Foot Ulcers: A Multicenter Preliminary Experience

BACKGROUND

The increasing resistance of bacteria to antibiotics and the frequency of comorbid conditions of patients make the treatment of diabetic foot infections problematic. In this context, photodynamic therapy could be a useful tool to treat infected wounds. The aim of this study was to evaluate the effect of repeated applications of a phthalocyanine derivative (RLP068) on the bacterial load and on the healing process.

METHODS

The present analysis was performed on patients with clinically infected ulcers who had been treated with RLP068. A sample for microbiological culture was collected at the first visit before and immediately after the application of RLP068 on the ulcer surface, and the area was illuminated for 8 minutes with a red light. The whole procedure was repeated three times per week at two centers (Florence and Arezzo, Italy) (sample A), and two times per week at the third center (Stuttgart, Germany) (sample B) for 2 weeks.

RESULTS

Sample A and sample B were composed of 55 and nine patients, respectively. In sample A, bacterial load decreased significantly after a single treatment, and the benefit persisted for 2 weeks. Similar effects of the first treatment were observed in sample B. In both samples, the ulcer area showed a significant reduction during follow-up, even in patients with ulcers infected with gram-negative germs or with exposed bone.

CONCLUSIONS

RLP068 seems to be a promising topical wound management procedure for the treatment of infected diabetic foot ulcers.

Evaluation of wound healing and postoperative pain after oral mucosa laser biopsy with the aid of compound with chlorhexidine and sodium hyaluronate: a randomized double blind clinical trial

OBJECTIVES

The aim of this study is to evaluate secondary intention healing process and postoperative pain of oral soft tissues after laser surgery with the use of a compound containing chlorhexidine and sodium hyaluronate.

MATERIALS AND METHODS

This double-blind, randomized clinical study included 56 patients affected by benign oral lesions and subjected to excisional biopsy with diode laser and randomly divided into three groups. Study group (SG) received 0.2% chlorhexidine digluconate and 0.2% sodium hyaluronate treatment; control group (CG) received 0.2% chlorhexidine digluconate; and placebo group (PG) followed the same protocol, taking a neutral solution having the same organoleptic characteristics. Wound healing was evaluated using percentage healing index (PHI). Numeric rating scale (NRS) was used to evaluate postoperative pain.

RESULTS

PHI (T1 = 7 days) was 67.25% for SG, 58.67% for CG, and 54.55% for PG. PHI (T2 = 14 days) was 94.35% for SG, 77.79% for CG, and 78.98% for PG. A statistically significant difference was between the groups for PHI at T2 p = 0.001. No difference was detectable for pain index.

CONCLUSIONS

A solution containing sodium hyaluronate and chlorhexidine is a good support to increase wound healing by secondary intention after laser biopsy, but no differences were in postoperative perception of pain.

CLINICAL RELEVANCE

The use of the tested solution can be recommended after laser oral biopsies, to achieve a healing without suture. About the postoperative pain, the compound has not showed the same results and did not have measurable effects.

Biofilms and delayed healing - an in vitro evaluation of silver- and iodine-containing dressings and their effect on bacterial and human cells

This study investigated whether there are differences in the ability of wound dressings to modulate certain factors known to affect wound healing. A selection of antimicrobial dressings (AQUACEL® Ag Extra™ , AQUACEL® Ag+ Extra™ , IODOFLEX™ , ACTICOAT™ 7 and PROMOGRAN PRISMA™ matrix) were tested for their effect on both bacterial bioburden and human dermal fibroblasts. Some dressings underwent further evaluation for activity against Pseudomonas aeruginosa biofilms using a colony-drip flow reactor model. The ability of in vitro biofilms to produce proteases, and the effect of PROMOGRAN PRISMA matrix on such proteases, was also investigated. All antimicrobial dressings tested reduced vegetative bacterial load; however, only PROMOGRAN PRISMA matrix was able to significantly reduce biofilm populations (P = 0·01). Additionally, PROMOGRAN PRISMA matrix was the only dressing that did not inhibit dermal fibroblast growth. All other dressings were detrimental to cell viability. In vitro biofilms of Pseudomonas aeruginosa were demonstrated as being capable of releasing bacterial proteases into their surroundings, and incubation with PROMOGRAN PRISMA matrix led to a 77% reduction in activity of such proteases (P = 0·002). The unique ability of PROMOGRAN PRISMA matrix to reduce in vitro vegetative bacteria, biofilm bacteria and bacterial proteases while still allowing dermal fibroblast proliferation may help rebalance the wound environment and reduce the occurrence of infection.

Cutaneous wound biofilm and the potential for electrical stimulation in management of the microbiome

Infection contributes significantly to delayed cutaneous wound healing, which impacts patient care. External application of electrical stimulation (ES) has beneficial effects on wound repair and regeneration. The majority of studies to date have explored ES in relation to planktonic microorganisms, yet evidence indicates that bacteria in chronic wounds reside as antibiotic-resistant polymicrobial biofilms, which contribute to impairing wound healing. Culture-independent sequencing techniques have revolutionized our understanding of the skin microbiome and allowed a more accurate determination of microbial taxa and their relative abundance in wounds allowing a greater understanding of the host–microbial interface. Future studies combining the fields of ES, biofilm and microbiome research are necessary to fully elucidate the use of ES in the management of wound infection.

Occlusive bandaging of wounds with decreased circulation promotes growth of anaerobic bacteria and necrosis: case report

Background

Topical occlusive/semi-occlusive dressings that induce a damp and trapped environment are widely used in wound treatment. Subjecting the wound with impaired circulation to such trapped/air-free environment potentiates the growth of anaerobic bacteria and risk for serious infection.

Case presentation

We present a case of previously healthy Swedish male that had a muscle contusion after heavy trauma that induced impaired circulation. The application of an occlusive bandage to the post-traumatic wound on the patient resulted in a poly-microbial anaerobic infection and necrosis. These complications were treated successfully with antibiotics and open dressing of the wound.

Conclusion

The pathophysiology of difficult- to- treat ulcers should be reviewed by the physician and occlusive dressing should be avoided when treating wounds with impaired circulation.

Outcome Measurements in Wound Healing Are Not Inclusive: A Way Forward

Standardized outcome measurement in wound healing has been an elusive goal. Whilst research into wound healing science and technology continues to progress rapidly, the lack of a uniform outcome assessment is making comparative analysis of results difficult. This paper seeks to outline the reported clinical, physiological, and histological outcomes that have been utilized in the literature. A minimal data set base for wound outcome evaluation is also established to be validated by future multivariate analysis of patient data.

Wound healing efficacy of a chitosan-based film-forming gel containing tyrothricin in various rat wound models

The objective of this study was to evaluate the healing effects of a chitosan-based, film-forming gel containing tyrothricin (TYR) in various rat wound models, including burn, abrasion, incision, and excision models. After solidification, the chitosan film layer successfully covered and protected a variety of wounds. Wound size was measured at predetermined timepoints after wound induction, and the effects of the film-forming gel were compared with negative (no treatment) and positive control groups (commercially available sodium fusidate ointment and TYR gel). In burn, abrasion and excision wound models, the film-forming gel enabled significantly better healing from 1 to 6 days after wound induction, compared with the negative control. Importantly, the film-forming gel also enabled significantly better healing compared with the positive control treatments. In the incision wound model, the breaking strength of wound strips from the group treated with the film-forming gel was significantly increased compared with both the negative and positive control groups. Histological studies revealed advanced granulation tissue formation and epithelialization in wounds treated with the film-forming gel. We hypothesize that the superior healing effects of the film-forming gel are due to wound occlusion, conferred by the chitosan film. Our data suggest that this film-forming gel may be useful in treating various wounds, including burn, abrasion, incision and excision wounds.

High bacterial load in negative pressure wound therapy (NPWT) foams used in the treatment of chronic wounds

No earlier study has investigated the microbiology of negative pressure wound therapy (NPWT) foam using a standardized manner. The purpose of this study is to investigate the bacterial load and microbiological dynamics in NPWT foam removed from chronic wounds (>3 months). To determine the bacterial load, a standardized size of the removed NPWT foam was sonicated. The resulting sonication fluid was cultured, and the colony-forming units (CFU) of each species were enumerated. Sixty-eight foams from 17 patients (mean age 63 years, 71% males) were investigated. In 65 (97%) foams, ≥ 1 and in 37 (54%) ≥ 2 bacterial types were found. The bacterial load remained high during NPWT treatment, ranging from 10(4) to 10(6) CFU/ml. In three patients (27%), additional type of bacteria was found in subsequent foam cultures. The mean bacterial count ± standard deviation was higher in polyvinyl alcohol foam (6.1 ± 0.5 CFU/ml) than in polyurethane (5.5 ± 0.8 CFU/ml) (p = 0.02). The mean of log of sum of CFU/ml in foam from 125 mmHg (5.5 ± 0.8) was lower than in foam from 100 mmHg pressure (5.9 ± 0.5) (p = 0.01). Concluding, bacterial load remains high in NPWT foam, and routine changing does not reduce the load.

Effects of topically applied agents on intra-oral wound healing in a rat model: a clinical and histomorphometric study

OBJECTIVES

Topically applied chlorhexidine and hyaluronan have many studies supporting their use to enhance oral wound healing. Allantoin is widely used topically to promote epithelial proliferation and wound healing, with very little scientific evidence to support such uses. This study investigated and compared the influence of these agents on the healing of intra-oral excisional wounds with large epithelial and connective tissue defects.

METHODS

Excisional wounds, 3 mm in diameter, were made at the centre of the palate of 125 Wistar male albino rats. Five animals constituted the baseline group at time 0. The remaining animals were divided into four experimental and one control groups, in which chlorhexidine digluconate gel 0.2% (Perio.Kin®), hyaluronan gel (Gengigel®), allantoin 0.5% in vehicle gel, vehicle gel alone and nothing were applied daily to the wounds. The wound areas were measured photographically and the epithelialization rates were determined histologically at 0, 3, 7, 14 and 21 days post-surgery.

RESULTS

The mean wound area and mean distance between the epithelial margins decreased significantly with time in all experimental and control groups (P < 0.05). A significant rate of wound area reduction was observed following the use of Perio.Kin® and Gengigel® at 7 and 14 days. Perio.Kin® showed a significant rate of wound epithelialization at 7 days. Allantoin did not positively or negatively affect wound healing.

CONCLUSIONS

None of the tested agents had a negative effect on the rate of wound healing when applied on an excisional wound with epithelial and connective tissue defect. Positive results were achieved with Perio.Kin® and Gengigel®.

Biofilms and bacterial imbalances in chronic wounds: anti-Koch

Microbial imbalances and synergistic relationships between bacteria in medically important biofilms are poorly researched. Consequently, little is known about how synergy between bacteria may increase the net pathogenic effect of a biofilm in many diseases and infections, including chronic wounds. Microbial synergy in chronic wounds may increase virulence and pathogenicity, leading to enhanced tissue degradation, malodour and in some cases, an impairment of the host immune response. Microbial synergy and growth within a biofilm provide a competitive advantage to the microorganisms cohabiting in a wound, thereby promoting their survival and tolerance and resistance to antimicrobial agents. The aim of this article was to provide greater insight into microbial imbalances found within wound biofilms and the significance they may have on non healing and infected wounds. We also present two possible hypotheses which could explain the role microorganisms play in non healing chronic wounds and offer possible strategies for combating harmful and detrimental biofilms.