[A comparative in vitro study of cell toxicity of clinically used antiseptics]

Safety and effectiveness of an antiseptic wound cleansing and irrigation solution containing polyhexamethylene biguanide

OBJECTIVE

There is currently a wide range of cleansing and irrigation solutions available for wounds, many of which contain antimicrobial agents. The aim of this study was to assess the safety of HydroClean Solution (HARTMANN, Germany), a polyhexamethylene biguanide (PHMB)-containing irrigation solution, in a standard cytotoxicity assay, and to assess its effect in a three-dimensional (3D) full-thickness model of human skin.

METHOD

A number of commercially available wound cleansing and irrigation solutions, including the PHMB-containing irrigation solution, were tested in a cytotoxicity assay using L929 mouse fibroblasts (ISO 10993-5:2009). The PHMB-containing irrigation solution was then assessed in an in vitro human keratinocyte-fibroblast 3D full-thickness wounded skin model to determine its effect on wound healing over six days. The effect of the PHMB-containing irrigation solution on tissue viability was measured using a lactate dehydrogenase (LDH) assay, and proinflammatory effects were measured using an interleukin-6 (IL-6) production assay.

RESULTS

The PHMB-containing irrigation solution was shown to be equivalent to other commercially available cleansing and irrigation solutions when tested in the L929 fibroblast cytotoxicity assay. When assessed in the in vitro 3D human full-thickness wound healing model, the PHMB-containing irrigation solution treatment resulted in no difference in levels of LDH or IL-6 when compared with levels produced in control Dulbecco's phosphate-buffered saline cultures. There was, however, a pronounced tissue thickening of the skin model in the periwound region.

CONCLUSION

The experimental data presented in this study support the conclusion that the PHMB-containing irrigation solution has a safety profile similar to other commercially available cleansing and irrigation solutions. Evidence also suggests that the PHMB-containing irrigation solution does not affect tissue viability or proinflammatory cytokine production, as evidenced by LDH levels or the production of IL-6 in a 3D human full-thickness wound healing model. The PHMB-containing irrigation solution stimulated new tissue growth in the periwound region of the skin model.

Comparison of different concentrations of chlorhexidine-iodophor composite solution on human skin fibroblasts

OBJECTIVE

Chlorhexidine-iodophor (CHX-IP) composite solution is a polymer of chlorhexidine and iodophor produced with new technology, for use in diabetic foot infection. However, the effect of CHX-IP on the growth activity of fibroblasts remains unknown, thus the effects of different concentrations of CHX-IP composite solution on the viability and micromorphology of human skin fibroblasts were studied in vitro cell culture in this study.

METHOD

A cell viability assay was applied to calculate cell viability and an inverted fluorescence microscope was used to observe cell morphology over five days.

RESULTS

The results showed that the toxic effect of CHX-IP on fibroblasts was solution concentration-dependent and decreased over time. When the concentration of CHX-IP was 5.0mg/ml, 2.5mg/ml, 0.625mg/ml, 0.15625mg/ml, 0.078125mg/ml or 0mg/ml, the difference of optical density (OD) value on different days was statistically significant (p<0.05). There were statistically significant differences in the OD value of fibroblasts among different concentrations of CHX-IP on: day 2 (F=4.809, p=0.004); day 3 (F=21.508, p<0.001); day 4 (F=63.952, p<0.001); and day 5 (F=160.407, p<0.001). In addition, a concentration of 5.0mg/ml CHX-IP resulted in a fibroblastic viability rate of 0% on day 4, when CHX-IP was diluted to 2.5mg/ml or 1.25 mg/ml, fibroblastic viability rate decreased to 0% day 5. However, when the CHX-IP was diluted to 0.15625mg/ml or 0.078125mg/ml, the fibroblastic cell viability rate increased slightly on day 5. The morphology of cells observed under microscope indirectly supported this result.

CONCLUSION

The findings of this study showed that the toxic effect of CHX-IP on fibroblasts was solution concentration-dependent and decreased over time.

Effect of Commercially Available Wound Irrigation Solutions on Uninfected Host Tissue in a Murine Model

Background

Commercially available irrigation solutions are used to reduce bacterial contamination and prevent surgical site infections. However, the effect of these solutions on the healing capacity of tissue has not been well-established. The purpose of this study was to investigate the effects of 5 commercially available irrigation solutions on host tissue in a murine model.

Methods

There were 5 treatment groups: bacitracin, Clorpactin, Irrisept, Prontosan, Bactisure, and normal saline control. The irrigation solutions were applied to the wound for 30 seconds or 1 minute, as per the manufacturer's instructions, and then washed with normal saline. Mice were sacrificed at 3 days and 10 days. The tissue was examined histologically for inflammation, edema, granulation tissue formation, and re-epithelialization. Granulation tissue formation and re-epithelialization were surrogates for effective wound healing.

Results

All of the irrigation solutions had negative effects on host tissue in the acute phase. The inflammation and edema were improved in the later phase (10 days). Recovery and healing of the open wounds were observed for all groups at 10 days. The antiseptic irrigation solutions had similar cytotoxic effects on host tissue at 3 days and did not have delayed or compromised wound healing at 10 days when compared to normal saline control.

Conclusions

Single short-duration use of these commercially available antiseptic irrigation solutions appears to be safe in an uninfected wound. Data from this study will provide surgeons with useful information regarding the safety of using antiseptic wound irrigation solutions intraoperatively for prevention of surgical site infections.

Antimicrobials cetylpyridinium-chloride and miramistin demonstrate non-inferiority and no "protein-error" compared to established wound care antiseptics in vitro

Concern about microbial tolerance and resistance to established antimicrobials drives research into alternatives for local antiseptic wound treatment. Precise efficacy profiles are thereby important in the evaluation of potential alternative antimicrobials, and protein interference ("protein error") is a key factor. Here, the antimicrobial efficacy of cetylpyridinium chloride (CPC) and miramistin (MST) was compared to the established antimicrobials octenidine (OCT), povidon-iodine (PVP-I), polyhexamethylene-biguanide (PHMB) and chlorhexidine (CHX). Efficacy was evaluated after 0.5, 1, 3, 5 and 10 min against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecium and Candida albicans using an in vitro quantitative suspension method (based on DIN EN 13727). To investigate protein interference, 0.3% or 3% bovine albumin was used as the challenge. OCT and PVP-I demonstrated a significant efficacy within 0.5 min, regardless of the microbial organism and protein challenge (p < 0.01). CPC and MST showed no inferiority in efficacy, with only MST needing up to 3 min to achieve the same microbial reduction. PHMB and CHX also achieved significant reduction rates over the tested time-course, yet demonstrated a necessity for prolonged exposure (up to 10 min) for comparable reduction. A protein interference was predominantly observed for PHMB against S. aureus, but without statistically significant differences in antimicrobial efficacy between the 0.3% and 3% protein challenges. All other tested agents showed no relevant interference with the presence of protein. CPC and MST proved to be non-inferior to established wound antiseptics agents in vitro. In fact, CPC showed a more efficient reduction than PHMB and CHX despite there being an introduced protein challenge. Both agents demonstrated no significant "protein error" under challenging conditions (3% albumin), posing them as valid potential candidates for alternative antimicrobials in wound management.

An Overview of Biofilm Formation-Combating Strategies and Mechanisms of Action of Antibiofilm Agents

Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.

PHMB-loaded PDMS and its antimicrobial properties for biomedical applications

Given the global panorama of demands in the health area, the development of biomaterials becomes irreducible for the maintenance and/or improvement in the quality of life of the human being. Aiming to reduce the impacts related to infections in the healing processes of the dermal structure, the present work proposes the development of polydimethylsiloxane (PDMS) based membranes with the incorporated polyhexamethylenebiguanide (PHMB) antimicrobial agent. In the present study, the antimicrobial and antibiofilm properties of polydimethylsiloxane (PDMS) films incorporated with 0.1, 0.3, and 0.5% (w/w) of polyhexamethylene biguanide (PHMB) were evaluated, aiming the development of a protective biomaterial that avoids cutaneous infections from the autochthonous and allochthonous microbiota. The disk diffusion of PHMB-loaded PDMS has shown the growth inhibition of Escherichia coli (ATCC 9637), Pseudomonas aeruginosa (ATCC 27953), Acinetobacter baumannii (ATCC 19606), Staphylococcus aureus (ATCC 6538), Staphylococcus epidermidis (ATCC 12228), Streptococcus pyogenes (ATCC 19615), Bacillus subtilis (ATCC 6633) and also yeast-like fungi Candida albicans, all microorganisms found on the epidermal surface. Likewise, the present study demonstrated low cytotoxicity of the PHMB-loaded PDMS on HaCaT and L929 cells at lower concentrations (0.1% w/w), indicating the possibility of using the developed material as a dressing for wounds, burns, and post-surgical procedures.

Antibacterial Anacardic Acid Derivatives

We report on the antibacterial activity of five phenolic lipids derived from anacardic acid characterized by increasing alkyl chain lengths with 6, 8, 10, 12, or 14 carbon atoms. The compounds were profiled for their physicochemical properties, transport across epithelial monolayers, cytotoxicity, and antibacterial activity as compared to common antibiotics. No cytotoxicity was reported in cell lines of fibroblast, hepatic, colorectal, or renal origin. C₁₀ and C₁₂ significantly increased the survival in a Galleria mellonella model infected with multi-drug-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococci (VRE) as compared to the untreated control group. Future studies are required to corroborate these findings in relevant animal model systems of infection.

Strategies for combating bacterial biofilms: A focus on anti-biofilm agents and their mechanisms of action

Biofilm refers to the complex, sessile communities of microbes found either attached to a surface or buried firmly in an extracellular matrix as aggregates. The biofilm matrix surrounding bacteria makes them tolerant to harsh conditions and resistant to antibacterial treatments. Moreover, the biofilms are responsible for causing a broad range of chronic diseases and due to the emergence of antibiotic resistance in bacteria it has really become difficult to treat them with efficacy. Furthermore, the antibiotics available till date are ineffective for treating these biofilm related infections due to their higher values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), which may result in in-vivo toxicity. Hence, it is critically important to design or screen anti-biofilm molecules that can effectively minimize and eradicate biofilm related infections. In the present article, we have highlighted the mechanism of biofilm formation with reference to different models and various methods used for biofilm detection. A major focus has been put on various anti-biofilm molecules discovered or tested till date which may include herbal active compounds, chelating agents, peptide antibiotics, lantibiotics and synthetic chemical compounds along with their structures, mechanism of action and their respective MICs, MBCs, minimum biofilm inhibitory concentrations (MBICs) as well as the half maximal inhibitory concentration (IC₅₀) values available in the literature so far. Different mode of action of anti biofilm molecules addressed here are inhibition via interference in the quorum sensing pathways, adhesion mechanism, disruption of extracellular DNA, protein, lipopolysaccharides, exopolysaccharides and secondary messengers involved in various signaling pathways. From this study, we conclude that the molecules considered here might be used to treat biofilm-associated infections after significant structural modifications, thereby investigating its effective delivery in the host. It should also be ensured that minimum effective concentration of these molecules must be capable of eradicating biofilm infections with maximum potency without posing any adverse side effects on the host.

Inactivation of Acinetobacter baumannii Biofilms on Polystyrene, Stainless Steel, and Urinary Catheters by Octenidine Dihydrochloride

Acinetobacter baumannii is a major nosocomial pathogen causing human infections with significant mortality rates. In most cases, infections are acquired through exposure to A. baumannii biofilms that persist on contaminated hospital equipment and surfaces. Thus, it is imperative to develop effective measures for controlling A. baumannii biofilms in nosocomial settings. This study investigated the efficacy of octenidine dihydrochloride (OH), a new generation disinfectant for reducing A. baumannii biofilms on polystyrene, stainless steel and catheters. OH at 0.3% (5 mM), 0.6% (10 mM), and 0.9% (15 mM) was effective in significantly inactivating A. baumannii biofilms on all tested surfaces (P < 0.05). Furthermore, OH was equally effective in inactivating biofilms of multidrug resistant and drug susceptible A. baumannii isolates. In addition, confocal imaging revealed the predominance of dead cells in the OH-treated samples in comparison to the control. Further, scanning electron microscopy of biofilms formed on catheters revealed that OH treatment significantly reduced A. baumannii biofilm populations in corroboration with our antibiofilm assay. These data underscore the efficacy of OH in inactivating A. baumannii biofilms, thereby suggesting its potential use as a disinfectant or a catheter lock solution to control A. baumannii infections.

Pathogen- and Host-Directed Antileishmanial Effects Mediated by Polyhexanide (PHMB)

BACKGROUND

Cutaneous leishmaniasis (CL) is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. CL causes enormous suffering in many countries worldwide. There is no licensed vaccine against CL, and the chemotherapy options show limited efficacy and high toxicity. Localization of the parasites inside host cells is a barrier to most standard chemo- and immune-based interventions. Hence, novel drugs, which are safe, effective and readily accessible to third-world countries and/or drug delivery technologies for effective CL treatments are desperately needed.

METHODOLOGY/PRINCIPAL FINDINGS

Here we evaluated the antileishmanial properties and delivery potential of polyhexamethylene biguanide (PHMB; polyhexanide), a widely used antimicrobial and wound antiseptic, in the Leishmania model. PHMB showed an inherent antileishmanial activity at submicromolar concentrations. Our data revealed that PHMB kills Leishmania major (L. major) via a dual mechanism involving disruption of membrane integrity and selective chromosome condensation and damage. PHMB's DNA binding and host cell entry properties were further exploited to improve the delivery and immunomodulatory activities of unmethylated cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODN). PHMB spontaneously bound CpG ODN, forming stable nanopolyplexes that enhanced uptake of CpG ODN, potentiated antimicrobial killing and reduced host cell toxicity of PHMB.

CONCLUSIONS

Given its low cost and long history of safe topical use, PHMB holds promise as a drug for CL therapy and delivery vehicle for nucleic acid immunomodulators.

Antimicrobial functionalization of bacterial nanocellulose by loading with polihexanide and povidone-iodine

Bacterial nanocellulose (BNC) is chemically identical with plant cellulose but free of byproducts like lignin, pectin, and hemicelluloses, featuring a unique reticulate network of fine fibers. BNC sheets are mostly obtained by static cultivation. Now, a Horizontal Lift Reactor may provide a cost efficient method for mass production. This is of particular interest as BNC features several properties of an ideal wound dressing although it exhibits no bactericidal activity. Therefore, BNC was functionalized with the antiseptics povidone-iodine (PI) and polihexanide (PHMB). Drug loading and release, mechanical characteristics, biocompatibility, and antimicrobial efficacy were investigated. Antiseptics release was based on diffusion and swelling according to Ritger-Peppas equation. PI-loaded BNC demonstrated a delayed release compared to PHMB due to a high molar drug mass and structural changes induced by PI insertion into BNC that also increased the compressive strength of BNC samples. Biological assays demonstrated high biocompatibility of PI-loaded BNC in human keratinocytes but a distinctly lower antimicrobial activity against Staphylococcus aureus compared to PHMB-loaded BNC. Overall, BNC loaded with PHMB demonstrated a better therapeutic window. Moreover, compressive and tensile strength were not changed by incorporation of PHMB into BNC, and solidity during loading and release could be confirmed.

[Severe complications after non-intended usage of octenidine dihydrochloride. A case series with four dogs]

OBJECTIVE

Case series of four dogs in which extensive bite wounds had been treated using octenidine dihydrochloride (Octenivet® or Octenisept®) flushing. The dogs subsequently developed severe local complications.

MATERIAL AND METHODS

Retrospective evaluation of clinical symptoms, diagnostics, therapy and course of the disease.

RESULTS

In four dogs, severe necrosis and persistent edematous changes of the treated area developed after the application of octenidine dihydrochloride. The clinical course was comparable to complications described previously in human medicine. Therapy was protracted and complicated by secondary wound infection.

CONCLUSION AND CLINICAL RELEVANCE

Irrigation of deep wounds, particularly bite wounds, using octenidine dihydrochloride without drainage may lead to persistent edematous changes, inflammatory reactions and necrosis. The inappropriate application of octenidine dihydrochloride for wound irrigation should be avoided in veterinary medicine.

Antimicrobial and antiseptic strategies in wound management

Wounds, especially chronic wounds, represent a global problem costing millions of dollars per year in developed countries and are characterised by microbial complications including local or overt infection, delayed healing and spread of multiresistant germs. Therefore, antimicrobial wound management is a major challenge that continues to require new solutions against microbes and their biofilms. As systemic antibiotics can barely penetrate into wound biofilms and topically applied ones can easily lead to sensitisation, antisepsis is the method of choice to treat germs in wounds. This brief review discusses the role of antiseptics in reducing bioburden in chronic wounds. Balancing antimicrobial potency and tolerability of antiseptic procedures is critical in wound therapy. However, antiseptics alone may not be able to achieve wound healing without addressing other factors regarding the patient's general health or the wound's physical environment. Although the precise role of bioburden in chronic wounds remains to be evaluated, planktonic as well as biofilm-bound microbes are indications for antiseptic intervention. Octenidine dihydrochloride and polyhexanide are the most effective, as well as best tolerated, antiseptics in wound management today, and new strategies to reduce bacterial wound burden and support the body's immune response are being developed.

Antibiofilm Effect of Octenidine Hydrochloride on Staphylococcus aureus, MRSA and VRSA

Millions of indwelling devices are implanted in patients every year, and staphylococci (S. aureus, MRSA and vancomycin-resistant S. aureus (VRSA)) are responsible for a majority of infections associated with these devices, thereby leading to treatment failures. Once established, staphylococcal biofilms become resistant to antimicrobial treatment and host response, thereby serving as the etiological agent for recurrent infections. This study investigated the efficacy of octenidine hydrochloride (OH) for inhibiting biofilm synthesis and inactivating fully-formed staphylococcal biofilm on different matrices in the presence and absence of serum protein. Polystyrene plates and stainless steel coupons inoculated with S. aureus, MRSA or VRSA were treated with OH (zero, 0.5, one, 2 mM) at 37 °C for the prevention of biofilm formation. Additionally, the antibiofilm effect of OH (zero, 2.5, five, 10 mM) on fully-formed staphylococcal biofilms on polystyrene plates, stainless steel coupons and urinary catheters was investigated. OH was effective in rapidly inactivating planktonic and biofilm cells of S. aureus, MRSA and VRSA on polystyrene plates, stainless steel coupons and urinary catheters in the presence and absence of serum proteins. The use of two and 10 mM OH completely inactivated S. aureus planktonic cells and biofilm (>6.0 log reduction) on all matrices tested immediately upon exposure. Further, confocal imaging revealed the presence of dead cells and loss in biofilm architecture in the OH-treated samples when compared to intact live biofilm in the control. Results suggest that OH could be applied as an effective antimicrobial to control biofilms of S. aureus, MRSA and VRSA on appropriate hospital surfaces and indwelling devices.

Active wound dressings based on bacterial nanocellulose as drug delivery system for octenidine

Although bacterial nanocellulose (BNC) may serve as an ideal wound dressing, it exhibits no antibacterial properties by itself. Therefore, in the present study BNC was functionalized with the antiseptic drug octenidine. Drug loading and release, mechanical characteristics, biocompatibility, and antimicrobial efficacy were investigated. Octenidine release was based on diffusion and swelling according to the Ritger-Peppas equation and characterized by a time dependent biphasic release profile, with a rapid release in the first 8h, followed by a slower release rate up to 96 h. The comparison between lab-scale and up-scale BNC identified thickness, water content, and the surface area to volume ratio as parameters which have an impact on the control of the release characteristics. Compression and tensile strength remained unchanged upon incorporation of octenidine in BNC. In biological assays, drug-loaded BNC demonstrated high biocompatibility in human keratinocytes and antimicrobial activity against Staphylococcus aureus. In a long-term storage test, the octenidine loaded in BNC was found to be stable, releasable, and biologically active over a period of 6 months without changes. In conclusion, octenidine loaded BNC presents a ready-to-use wound dressing for the treatment of infected wounds that can be stored over 6 months without losing its antibacterial activity.

[Microbial stress of skin and wounds in clinical aspects and practice. Between search and destroy and monitor and relax]

The antibiotic treatment of microbial pathogens of the skin and wounds could so far not fulfil the expectations of an effective and permanent elimination of pathogens so that local treatment with antiseptic agents as a flanking measure to wound cleansing and debridement has become increasingly more established. Because an antiseptic treatment does not actually represent a treatment of infections, the current antimicrobial treatment strategy for infections in skin and wound areas consists of combined antibiotic and flanking antiseptic administration following debridement. However, the combined therapy is not always successful. There is an urgent need for new forms of therapy particularly to combat multiresistant pathogens in biofilms in infections of chronic and other complicated wounds.

[Bone infections]

Even in recent traumatology and orthopedic surgery infectious diseases of the bone (i.e. osteomyelitis) and it's surrounding tissues remain serious complications. The therapy is demanding and oftenly does not lead to a complete restitutio ad integrum. In order to create the optimal treatment one has to have a profound knowledge about the "state of the art" therapy of bone infections and the basic phases: Reassurance of the local infection (bone and surrounding tissues) and reconstruction of the bone and surrounding tissues. The local infection treatment is based on the consequent surgical eradication of infected tissue. In addition (as a supportive therapy) antibiotics have to be applied according to the local and systemic response of the patient to the infection. Also further supportive methods like hyperbaric oxygenation may be taken into consideration. The following paper provides an overview of diagnostic features and the different surgical procedures as well as the current literature in order to reach the above mentioned goals.

Wound irrigation within the surgical treatment of osteomyelitis

The basic treatment of osteomyelitis remains even today the surgical debridement in combination with a wound irrigation by lavage systems. Next to a comprehensive knowledge of the surgical techniques a profound knowledge of the lavage systems, the rinsing solutions used and the philosophies of revision programs are a must. In this article the typical hardware of modern lavage systems is analysed, their advantages and disadvantages are pointed out. In addition we investigate the value of common antiseptic wound irrigation solutions for their use in osteomyelitis therapy. Finally the two basic philosophies of wound revision and irrigation in the course of osteomyelitis therapy are presented and discussed.

Classification of wounds at risk and their antimicrobial treatment with polihexanide: a practice-oriented expert recommendation

Currently, there are no generally accepted definitions for wounds at risk of infection. In clinical practice, too many chronic wounds are regarded as being at risk of infection, and therefore many topical antimicrobials - in terms of frequency and duration of use - are applied to wounds. Based on expert discussion and current knowledge, a clinical assessment score was developed. The objective of this wounds at risk (W.A.R.) score is to allow decision-making on the indication for the use of antiseptics on the basis of polihexanide. The proposed clinical classification of W.A.R. shall facilitate the decision for wound antisepsis and allow an appropriate general treatment regimen with the focus on the prevention of wound infection. The W.A.R. score is based on a clinically oriented risk assessment using concrete patient circumstances. The indication for the use of antiseptics results from the addition of differently weighted risk causes, for which points are assigned. Antimicrobial treatment is justified in the case of 3 or more points.