Polyhexanide based contact lens storage fluids frequently exhibit insufficient antifungal activity against Fusarium species.

PURPOSE: Fusarium keratitis is a severe infection of the anterior eye, frequently leading to keratoplasty or surgical removal of the affected eye. A major risk factor for infection is the use of contact lenses. Inadequate hygiene precautions and mold-growth permissive storage fluids are important risk factors for fungal keratitis. The aim of this study was to comparatively analyze contact lens storage fluids disinfection efficacy against Fusarium species. METHODS: Eleven commercially available storage fluids were tested. The storage fluids were classified according to their active ingredients myristamidopropyldimethylamine (Aldox), polyhexanide and hydrogen peroxide. Efficacy was tested against isolates belonging to the Fusarium solani and Fusarium oxysporum species complexes as the most common agents of mould keratitis. Tests were carried out based on DIN EN ISO 14729. RESULTS: All Aldox and hydrogen peroxide (H2O2) based fluids were effective against Fusarium spp., while the majority of polyhexanide based storage fluids showed only limited or no antifungal effects. Efficacy of polyhexanide could be restored by the addition of the pH-regulating agent tromethamine - an additive component in one commercially available product. CONCLUSIONS: In summary, the use of Aldox- or hydrogen peroxide-based storage fluids may reduce the risk of Fusarium keratitis, while polyhexanide-based agents largely lack efficacy against Fusarium.

Assessing antibacterial efficacy of a polyhexanide hydrogel versus alginate-based wound dressing in burns.

OBJECTIVE: Burn injuries pose a heightened risk of infection, which is primarily responsible for increased morbidity and mortality. Factors such as extensive skin damage and compromised immunity exacerbate this vulnerability. Pseudomonas aeruginosa and Staphylococcus aureus are frequently identified in burns, with Gram-negative Pseudomonas aeruginosa often resistant to antibacterial agents. While Flaminal, an alginate-based wound dressing (Flen Health, Belgium), aids wound healing, its antibacterial effects are limited compared with 1% silver sulfadiazine (1% SSD). In contrast, Prontosan Wound Gel X, a betaine and polyhexanide-based hydrogel (B. Braun Medical AG, Switzerland), has been shown to effectively combat various microbes and promotes wound healing. METHOD: In this study, two research cohorts were retrospectively established (control group: patients receiving standard of care with the alginate-based wound dressing; intervention group: patients receiving the polyhexanide hydrogel wound dressing), comprising patients admitted to a burn centre between 2019 and 2022. Patients were eligible when continuous wound treatment with either of the two wound dressings was performed. Laser Doppler imaging (LDI) scans were conducted. Regions of interest (ROIs) were selected based on LDI scans and divided into healing time categories. Wound swabs were collected and the presence of Pseudomonas aeruginosa and Staphylococcus aureus was documented. Bacterial load was evaluated using a semiquantitative scale. Wound healing was recorded. RESULTS: The control group consisted of 31 patients with 93 ROIs, while the intervention group had 67 ROIs involving 29 patients. Both groups exhibited similar proportions of healing time categories (p>0.05). The polyhexanide hydrogel dressing outperformed the alginate-based dressing in antiseptic efficacy by significantly reducing the incidence of Pseudomonas aeruginosa- and Staphylococcus aureus-positive cultures in patients' wounds. Wound healing time for conservative treatment was comparable between groups. CONCLUSION: In this study, the polyhexanide hydrogel dressing minimised Pseudomonas aeruginosa and Staphylococcus aureus colonisation in burn wounds, demonstrating strong antibacterial properties, emphasising its potential to minimise infections in burn injuries.

The antibiofilm activity of selected substances used in oral health prophylaxis.

Oral health is a window to a patient's general well-being. Balance in oral microbiome functions is crucial for health maintenance. A state of oral dysbiosis may lead to a variety of local and systemic pathological conditions. The presence of dental plaque is related to the majority of oral infections. Proper oral hygiene is crucial and the most economic practice contributing to oral health prophylaxis. Aside from prophylactic treatments provided by dental practitioners, mouth rinses, containing antimicrobial agents, are one of the possible tools used for oral care. Our study was to determine whether available mouth rinses and selected products dedicated for professional use are efficient to eradicate biofilm formed by reference and clinical strains of Streptococcus mutans, Streptococcus sanguinis, Streptococcus oralis, Streptococcus mitis, Staphylococcus aureus, Enterococcus faecalis, Lactobacillus rhamnosus and Candida albicans on the surface of hydroxyapatite - major mineral component of a tooth. Therefore, such antimicrobials as chlorhexidine, cetylpyridine chloride, polyhexanide, silver nanoparticles, sulphonated phenolics, and natural antiplaque essential oils and coconut oil were analyzed. Applied experimental settings in in vitro models were designed to reflect accurately the recommended use of the tested substances, therefore four types of eradication procedure were conducted. Sialorrhea simulation was also performed to evaluate antibiofilm potential of diluted mouth rinses. Biofilm was investigated with quantitative method where absorbance values were measured. Statistical differences were assessed using the Kruskal-Wallis test with a post-hoc Dunnett's analysis. Results have shown that biofilms displayed a diversified sensitivity to the tested antimicrobials. The highest antibiofilm activity was detected for cetylpyridine chloride while the lowest for chlorhexidine. However the differences in E. faecalis biofilm reduction observed after the use of these two compounds were not statistically significant (p > 0.05), whereas all observed differences in S. aureus survival after exposure to the examined antimicrobial agents were statistically significant (p < 0.5). The PHMB, both in standard and in sialorrhea simulated conditions had the highest potential against streptococci. The coconut oil reduced C. albicans fungus biofilm by 65.48% but low eradication level was observed in case of bacterial biofilms. The dehydrating mechanism of action of sulfonated phenolics turned out to be ineffective against streptococcal biofilm which in turn was effectively eradicated by silver nanoparticles. The implementation of Antibiofilm Dressing's Activity Measurement method allowed to observe strain-related differences in terms of antimicrobial sensitivity. The obtained results may be introduced in everyday out-patient dental plaque prophylaxis as well as clinical environment.

Biofilm reduction potential of 0.02% polyhexanide irrigation solution in several types of urethral catheters.

BACKGROUND: Long-term use of urethral catheters is associated with high risk of urinary tract infection (UTI) and blockage. Microbial biofilms are a common cause of catheter blockage, reducing their lifetime and significantly increasing morbidity of UTIs. A 0.02% polyhexanide irrigation solution developed for routine mechanical rinsing shows potential for bacterial decolonization of urethral catheters and has the potential to reduce or prevent biofilm formation. METHODS: Using an in vitro assay with standard market-leading types of catheters artificially contaminated with clinically relevant bacteria, assays were carried out to evaluate the biofilm reduction and prevention potential of a 0.02% polyhexanide solution versus no intervention (standard approach) and irrigation with saline solution (NaCl 0.9%). The efficiency of decolonization was measured through microbial plate count and membrane filtration. RESULTS: Irrigation using a 0.02% polyhexanide solution is suitable for the decolonization of a variety of transurethral catheters. The effect observed is significant compared to irrigation with 0.9% saline solution (p = 0.002) or no treatment (p = 0.011). No significant difference was found between irrigation with 0.9% saline solution and no treatment (p = 0.74). CONCLUSIONS: A 0.02% polyhexanide solution is able to reduce bacterial biofilm from catheters artificially contaminated with clinically relevant bacteria in vitro. The data shows a reduction of the viability of thick bacterial biofilms in a variety of commercially available urinary catheters made from silicone, latex-free silicone, hydrogel-coated silicone and PVC. Further research is required to evaluate the long-term tolerability and efficacy of polyhexanide in clinical practice.

Effect of polyhexanide as antiseptic mouth rinse against oral pathogens in an in vitro biofilm model.

OBJECTIVE: The aim of this study was to evaluate the anti-biofilm effect of polyhexanide mouth rinses against oral pathogens in vitro. MATERIAL AND METHODS: Biofilms of Candida albicans, Streptococcus mutans, Actinomyces naeslundii, Aggregatibacter actinomycetemcomitans, methicillin-resistant Staphylococcus aureus and Fusobacterium nucleatum were grown on 10 mm diameter hydroxyapatite discs for 5 days. Biofilms were exposed to test substances for 30 s (ProntOral, polyhexanide 0.15%, chlorhexidine 0.2%). Another test set simulating blood contamination in the oral cavity was performed by submerging the discs in defibrinated sheep blood prior to antimicrobial exposure. Biofilm mass was determined via crystal violet staining. The proliferation potency of the cells after antimicrobial exposure was evaluated by plating serially diluted suspensions from extracted biofilms on agar plates and determining the number of colony-forming units (CFU/ml). Mann-Whitney-U, Kruskal-Wallis and Dunn's test were used for statistical analyses. RESULTS: Regardless of blood contamination ProntOral led to a significant reduction of biofilm mass in all strains. Chlorhexidine and polyhexanide reduced biofilm mass in five out of six strains and in only four strains after blood contamination. All agents significantly reduced CFU/ml from S. mutans, A. actinomycetemcomitans and F. nucleatum biofilms. C. albicans and S. aureus biofilms were only affected by ProntOral and polyhexanide. None of the antiseptics significantly reduced the CFU/ml for A. naeslundii biofilms. After blood contamination ProntOral and polyhexanide significantly reduced CFU/ml in all strains, whereas CHX tended to increase the CFU/ml. CONCLUSIONS: Polyhexanide mouth rinses seem to be suitable disinfectants against oral pathogens without their anti-biofilm potential being impaired by blood.

IgE-mediated chlorhexidine allergy-Cross-reactivity with other biguanide disinfectants.

BACKGROUND: Chlorhexidine (CHX) is a widely utilized disinfectant that can cause IgE-mediated urticaria/anaphylaxis. The cross-reactivity of patients with IgE-mediated CHX allergy with other disinfectants, which share structural similarities with CHX like polyhexanide (polyhexamethylene biguanide; PHMB), alexidine (ALX), or octenidine (OCT), is unknown. METHODS: Forty-four patients with anaphylaxis or urticaria upon CHX exposure and positive skin prick test (SPT) and/or positive CHX ImmunoCAP test (Phadia TFS, Uppsala, Sweden) were recruited. IgE to the biguanide and/or hexamethylene structure was investigated with PHMB ImmunoCAP (n = 32) and by basophil activation tests (BAT) with CHX and ALX (n = 37). Inhibition tests of CHX and PHMB ImmunoCAPs by CHX, ALX, PHMB, and OCT were performed. RESULTS: IgE reactivity to PHMB as surrogate marker for biguanide/hexamethylene reactivity was detected in 5/32 sera. Seven of 37 patients showed a positive BAT with ALX, but only under optimized conditions. Binding to CHX ImmunoCAP was inhibited by ALX in 1/32 sera, and binding to PHMB was blocked by ALX (1/5) and by OCT in another (1/5). In SPT, 9/10 patients were positive for CHX and 3 of them with ALX (only at highest concentration at 5 mg/mL). A further patient reacted primarily with OCT and showed IgE cross-reactivity with CHX, ALX, and PHMB. CONCLUSION: The IgE response to CHX seems polyclonal. The chloroguanide ending of CHX is the main epitope for the IgE and is suitable as screening assay to detect CHX reactivity. IgE-reactivities with the biguanide or hexamethylene components of other disinfectants (ALX, PHMB) can be detected by SPT, PHMB ImmunoCAP, and ALX-BAT in 15%-33% of CHX-allergic patients.

Tolerability and safety of urotainer® polihexanide 0.02% in catheterized patients: a prospective cohort study.

BACKGROUND: In patients with indwelling bladder catheters for > 2 weeks, bacterial colonization is inevitable, leading to urinary tract infections or encrustations with subsequent catheter blockage. Currently, bladder irrigations are the most frequently used prophylactic means, but the best solution remains yet to be determined. In vitro studies demonstrate that polihexanide is a promising option for catheter irrigation, but no data about safety and tolerability exist. METHODS: In a prospective observational study in patients with indwelling bladder catheter for > 2 weeks, a 0.02% polihexanide solution was used to rinse the catheter on five consecutive days. Adverse events, tolerability and vital signs were assessed before, during, after and at the end of the treatment period. RESULTS: There was no serious adverse event in the study. A total of 28 adverse events (AEs) in 15 (46.88%) participants were experienced. Absolute changes in pain scores were not clinically relevant. No incidences of either flushing or sweating were found during instillation. Bladder spasms during instillation were reported in two cases during a single instillation. Mean pulse rates did not change by more than 3 beats per minute. Mean changes in body temperature did not exceed 0.12 °C. Clinically relevant changes in blood pressure were recorded for 3 patients. CONCLUSIONS: This is the first study to demonstrate that a 0.02% polihexanide solution can safely be used for catheter irrigation. TRIAL REGISTRATION: ClinicalTrials.gov ( NCT02157415 ), June 6th, 2014.

Wound bed preparation: a case series using polyhexanide and betaine solution and gel-a UK perspective.

OBJECTIVE: The burden of wound care within the NHS is estimated at a cost of £5.3 billion per year and is set to rise annually by 30%. This case series describes the results of using polyhexanide (PHMB) and betaine wound irrigation solution and gels (Prontosan, B.Braun Medical Ltd., UK) across the UK in hard-to-heal (also described as chronic) wounds up to 20 years' duration, with an observation period of greater than one month. Over half of the hard-to-heal wounds were healed and vast improvements to all other wounds were observed. Improvements to wound bed condition were reported as early as two days after commencing initial treatment, with decreases in malodour, exudate, slough and pain reported across the case series. In addition to wound bed improvements, a reduction in dressing change frequency of 55% was observed in hard-to-heal wounds under the new treatment regime.

Maintenance of indwelling urinary catheters with a novel polyhexanide-based solution: user experience.

BACKGROUND: Catheter-associated urinary tract infection (CAUTI) can significantly affect patients' quality of life and increase healthcare costs. AIMS: This study aimed to capture patients' and nurses' experience of catheter maintenance using a polyhexanide-based solution (PS) in everyday practice. METHODS: Retrospective analysis of data was collected for a product evaluation. PS was used twice a week for five weeks. FINDINGS: The study included 42 patients, 30 (71%) men and 12 women (29%). After five weeks of rinsing catheters with PS, nine patients reported no or decreased frequency of CAUTI, eight a better quality of life, eight reduced blockage, seven a decrease in odour and five fewer catheter changes. Three patients reported no benefit from PS use. Nurses reported that fewer visits were needed and consumption of disposables was lower. CONCLUSIONS: User experiences suggest that, as a novel means of catheter maintenance, PS has the potential to reduce catheter-associated complications such as CAUTI, improve quality of life and reduce healthcare costs.

Decolonization potential of 0.02% polyhexanide irrigation solution in urethral catheters under practice-like in vitro conditions.

BACKGROUND: Long-term use of indwelling urethral catheters is associated with high risk of urinary tract infection (UTI) and blockage, which may in turn cause significant morbidity and reduce the life of the catheter. A 0.02% polyhexanide irrigation solution has been developed for routine mechanical rinsing together with bacterial decolonization of suprapubic and indwelling urethral catheters. METHODS: Using a practice-like in vitro assay and standard silicon catheters, artificially contaminated with clinically relevant bacteria, experiments were carried out to evaluate the bacterial decolonization potential of polyhexanide vs. 1) no intervention (standard approach) and 2) irrigation with a saline (NaCl 0.9%) solution. Swabbing and irrigation was used to extract the bacteria. RESULTS: Irrigation with polyhexanide reduced the microbial population vs. the control catheters by a factor of 1.64 log10 (swab extraction) and by a factor of 2.56 log10 (membrane filtration). The difference in mean microbial counts between the two groups (0.90) was statistically significant in favor of polyhexanide when the liquid extraction method was used (p = 0.034). The difference between the two groups using the swab extraction method did not reach statistical significance. CONCLUSIONS: The saline and polyhexanide solutions are able to reduce bacterial load of catheters, which shows a combined mechanical and antimicrobial effect. Further research is required to evaluate the long-term tolerability and efficacy of polyhexanide in clinical practice.

Cleansing versus tailored deep debridement, a fresh approach to wound cleansing: an Italian experience.

OBJECTIVE: To evaluate if cleansing, using a solution containing the antimicrobial polyhexanide and the surfactant betaine (polyhexanide propylbetaine [PP], Prontosan Solution, B. Braun), can aid effective wound bed preparation (WBP). METHOD: A solution containing the PP was used in two different treatment regimens. Group A was treated with a single application at different time durations (2, 5, 10 and 15 minutes) to evaluate efficacy in the removal of residues from the wound bed. Group B was treated with PP for 10 minutes, followed by application of an inert dressing, at daily dressing changes for 14 days, to evaluate efficacy of debridement. RESULTS: A total number of 70 patients took part in the study. In Group A (n=40), after the two and five minute application, no change was observed. At 10 minutes, an improvement was seen in 4/10 cases and at 15 minutes the improvement was in 5/10 patients. In Group B (n=30), over the 14 days, an improvement in the condition of the tissue, i.e. the wound bed was cleaned and debrided in 73% of cases, was observed. Patients experienced a reduction in pain and no adverse effect or complication was reported. Periwound skin was improved in 29/30 cases, with only one case where the tissue deteriorated, as determined by the presence of maceration. CONCLUSION: PP is effective in helping debridement during wound cleansing. Efficacy depends on time of application. However, randomisation and further study is required to confirm these results.

A retrospective systematic data review on the use of a polihexanide-containing product on burns in children.

BACKGROUND: It is current practice for physicians to use the Prontosan® range of products in children based on their personal clinical experience, despite the lack of safety data in this population. This retrospective data review was designed to obtain information on the safety profile of the Prontosan® range of products in children in routine clinical practice. METHODS: Data from newborns, infants and children with burns treated with the Prontosan® range were collected retrospectively from patient medical records. RESULTS: The majority of children treated for burns (80.1%) were under the age of four. More boys than girls were subject to burn injury (58.1% vs. 41.9%). The majority of burns (74.7%) were partial thickness burn (IIa and IIb). Safety was analysed based on the adverse events/reactions, infections and interactions/symptoms related to Prontosan® reported in the CRFs. AEs were reported in five children after the use of Prontosan® products: itching (3 cases), rash (1 case) and hypergranulating tissue (1 case). No event was severe and all events resolved favourably with good healing results. In addition, 11 patients developed clinical signs of infection during treatment (mainly Staphylococcus aureus). CONCLUSIONS: The Prontosan® range of products is demonstrated as safe and tolerable for use in children as part of burn treatment. Inclusion of this range of products in the protocol of paediatric burn care allows a good healing process starting with appropriate wound cleansing and maintaining moist wound environment.

Impact of Exposure of Methicillin-Resistant Staphylococcus aureus to Polyhexanide In Vitro and In Vivo.

Methicillin-resistant Staphylococcus aureus (MRSA) resistant to decolonization agents such as mupirocin and chlorhexidine increases the need for development of alternative decolonization molecules. The absence of reported severe adverse reactions and bacterial resistance to polyhexanide makes it an excellent choice as a topical antiseptic. In the present study, we evaluated the in vitro and in vivo capacity to generate strains with reduced polyhexanide susceptibility and cross-resistance with chlorhexidine and/or antibiotics currently used in clinic. Here we report the in vitro emergence of reduced susceptibility to polyhexanide by prolonged stepwise exposure to low concentrations in broth culture. Reduced susceptibility to polyhexanide was associated with genomic changes in the mprF and purR genes and with concomitant decreased susceptibility to daptomycin and other cell wall-active antibiotics. However, the in vitro emergence of reduced susceptibility to polyhexanide did not result in cross-resistance to chlorhexidine. During in vivo polyhexanide clinical decolonization treatment, neither reduced polyhexanide susceptibility nor chlorhexidine cross-resistance was observed. Together, these observations suggest that polyhexanide could be used safely for decolonization of carriers of chlorhexidine-resistant S. aureus strains; they also highlight the need for careful use of polyhexanide at low antiseptic concentrations.

A Case of Severe Anaphylaxis to Polyhexanide: Cross-Reactivity between Biguanide Antiseptics.

We present the case of a 77-year-old female patient who suffered from severe anaphylaxis during wound care. Allergologic evaluation yielded specific IgE antibodies to chlorhexidine, but anaphylaxis to chlorhexidine was not congruent with the patient history and dermal provocation tests. However, skin prick tests provided evidence for a sensitization to polyhexanide that was further supported by the detection of specific IgE antibodies to polyhexanide, the results of basophil activation tests and IgE inhibition analysis. We presume cross-reactive IgE antibodies binding to both biguanide antiseptics and identified polyhexanide as the likely cause of the anaphylactic reaction. We recognize polyhexanide as an emerging allergen that has to be considered as a cause of anaphylaxis.

In Vitro activity of Manuka Honey and polyhexamethylene biguanide on filamentous fungi and toxicity to human cell lines.

Soft-tissue invasive fungal infections are increasingly recognized as significant entities directly contributing to morbidity and mortality. They complicate clinical care, requiring aggressive surgical debridement and systemic antifungal therapy. To evaluate new topical approaches to therapy, we examined the antifungal activity and cytotoxicity of Manuka Honey (MH) and polyhexamethylene biguanide (PHMB). The activities of multiple concentrations of MH (40%, 60%, 80%) and PHMB (0.01%, 0.04%, 0.1%) against 13 clinical mould isolates were evaluated using a time-kill assay between 5 min and 24 h. Concentrations were selected to represent current clinical use. Cell viability was examined in parallel for human epidermal keratinocytes, dermal fibroblasts and osteoblasts, allowing determination of the 50% viability (LD50) concentration. Antifungal activity of both agents correlated more closely with exposure time than concentration. Exophiala and Fusarium growth was completely suppressed at 5 min for all PHMB concentrations, and at 12 and 6 h, respectively, for all MH concentrations. Only Lichtheimia had persistent growth to both agents at 24 h. Viability assays displayed concentration-and time-dependent toxicity for PHMB. For MH, exposure time predicted cytotoxicity only when all cell types were analyzed in aggregate. This study demonstrates that MH and PHMB possess primarily time-dependent antifungal activity, but also exert in vitro toxicity on human cells which may limit clinical use. Further research is needed to determine ideal treatment strategies to optimize antifungal activity against moulds while limiting cytotoxicity against host tissues in vivo.

Proposed phase 2/ step 2 in-vitro test on basis of EN 14561 for standardised testing of the wound antiseptics PVP-iodine, chlorhexidine digluconate, polihexanide and octenidine dihydrochloride.

BACKGROUND: Currently, there is no agreed standard for exploring the antimicrobial activity of wound antiseptics in a phase 2/ step 2 test protocol. In the present study, a standardised in-vitro test is proposed, which allows to test potential antiseptics in a more realistically simulation of conditions found in wounds as in a suspension test. Furthermore, factors potentially influencing test results such as type of materials used as test carrier or various compositions of organic soil challenge were investigated in detail. METHODS: This proposed phase 2/ step 2 test method was modified on basis of the EN 14561 by drying the microbial test suspension on a metal carrier for 1 h, overlaying the test wound antiseptic, washing-off, neutralization, and dispersion at serial dilutions at the end of the required exposure time yielded reproducible, consistent test results. RESULTS: The difference between the rapid onset of the antiseptic effect of PVP-I and the delayed onset especially of polihexanide was apparent. Among surface-active antimicrobial compounds, octenidine was more effective than chlorhexidine digluconate and polihexanide, with some differences depending on the test organisms. However, octenidine and PVP-I were approximately equivalent in efficiency and microbial spectrum, while polihexanide required longer exposure times or higher concentrations for a comparable antimicrobial efficacy. CONCLUSION: Overall, this method allowed testing and comparing differ liquid and gel based antimicrobial compounds in a standardised setting.

In vitro activity of a polyhexanide-betaine solution against high-risk clones of multidrug-resistant nosocomial pathogens.

OBJECTIVE: To determine the in vitro activity of a polyhexanide-betaine solution against collection strains and multidrug-resistant (MDR) nosocomial isolates, including high-risk clones. METHODS: We studied of 8 ATCC and 21 MDR clinical strains of Staphylococcus aureus, Enterococcus faecium, Enterococcus faecalis, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa, including the multiresistant high-risk clones. The MICs and MBCs of a 0.1% polyhexanide-0.1% betaine solution were determined by microdilution. For each species, strains with the highest MICs were selected for further experiments. The dilution-neutralization test (PrEN 12054) was performed by incubating bacterial inocula of 106CFU/mL for 1min with undiluted 0.1% polyhexanide-betaine solution. The CFUs were counted after neutralization. Growth curves and time-kill curves at concentrations of 0.25, 1, 4, and 8×MIC, were performed. MICs of recovered strains were determined when regrowth was observed in time-kill studies after 24h of incubation. Strains with reduced susceptibility were selected by serial passage on plates with increasing concentrations of polyhexanide-betaine, and MICs were determined. RESULTS: Polyhexanide-betaine MIC range was 0.5-8mg/L. MBCs equalled or were 1 dilution higher than MICs. The dilution-neutralization method showed total inoculum clearance of all strains. In time-kill curves, no regrowth was observed at 4×MIC, except for S. aureus (8×MIC). Increased MICs were not observed in time-kill curves, or after serial passages after exposure to polyhexanide-betaine. CONCLUSIONS: Polyhexanide-betaine presented bactericidal activity against all MDR clinical isolates tested, including high-risk clones, at significantly lower concentrations and time of activity than those commercially used.

The effect of negative pressure wound therapy with antibacterial dressings or antiseptics on an in vitro wound model.

OBJECTIVE: The aim of this study was to investigate the bacterial bioburden in experimental in vitro wounds during the application of conventional negative pressure wound therapy (NPWT), with and without antimicrobial dressings (polyhexanide, silver), against NPWT instillation of octenidine. METHOD: Experimental wounds produced in an in vitro porcine wound model were homogenously contaminated with bacterial suspension and treated with NPWT and different options. Group A: non-antimicrobial polyurethane foam dressing; group B: antimicrobial polyurethane foam dressing containing silver; group C: antimicrobial gauze dressing containing polyhexanide; group D: non-antimicrobial polyurethane foam dressing intermittently irrigated with octenidine; group E: negative control (non-antimicrobial polyurethane foam dressing without NPWT). Standard biopsies were harvested after 24 and 28 hours. RESULTS: This study demonstrated that the use of NPWT with intermitted instillation of octenidine (group D) or application of silver-based polyurethane foam dressings (group B) is significantly superior against Staphylococcus aureus colonisation in experimental wounds compared with non-antimicrobial polyurethane foam dressing (group A) after 48 hours. Surprisingly, the polyhexanide-based dressing (group C) used in this model showed no statistical significant effect compared with the control group (group E) after 24 or 48 hours of treatment. CONCLUSION: Both intermitted instillation of octenidine and silver-based dressings in standard NPWT were significantly superior compared with non-antimicrobial polyurethane foam dressings or PHMB coated gauze dressing after 48 hours.