Polyhexamethylene Biguanide Research Articles

Necrotic ulcers caused by Loxosceles rufescens bites: a report of seven patients and scanning electron microscopy of the spider.

Loxosceles rufescens is a spider that may bite humans. To describe the clinical manifestations and treatment of patients with bites caused by L. rufescens, and present scanning electron microscopy of the spider. Twelve patients are described, seven with a confirmed aetiological diagnosis as a sample of the spider was captured. In one case, scanning electron microscopy of the spider was performed. Seven patients presented with a single necrotic ulcer of varying morphology, with a purulent-necrotic bed, located on the neck (one patient), buttock (one patient), thigh (one patient), legs (three patients) and foot (one patient). All patients complained of burning and pain. No systemic symptoms were observed. All patients were treated with sodium hypochlorite solution packs, an equine catalase gel, and polyhexamethylene biguanide cream. Oral analgesics were added. In one patient, oral prednisone was prescribed. Two patients with bacterial superinfections were treated with i.v. piperacillin/tazobactam or i.m. ceftriaxone. All patients recovered within eight weeks, however, a scar developed in five of six patients. The sequence of cutaneous manifestations due to L. rufescens bites is typical. At first, erythema and oedema forms, followed by a vesicle, blister or pustule and, finally, an eschar and scar. Systemic symptoms and signs are rare. To consider this spider as an aetiological agent of necrotic ulcers, it is necessary to capture a sample of the spider, dead or alive, which should then be identified by an expert. Corticosteroids, antibiotics and analgesics are frequently used. Surgery is often necessary.

Gas concentration and refractive index sensor based on plasmonic induced absorption in metal-insulator-metal waveguide coupled with arc resonators structure

In this paper, the plasmonic induced absorption (PIA) effect is numerically studied in a plasmonic metal-insulator-metal (MIM) waveguide coupled with disk and arc-shaped resonators. The PIA spectrum characteristics and magnetic field distributions are investigated by the Finite difference-time domain method (FDTD) method, the PIA effect originated from the coupling of two resonance modes excited by the disk resonator and the arc-shaped resonator. The coupling mode theory (CMT) is used to fit the PIA transmission spectrum, and the calculated result fits well with the simulated spectrum. A double PIA spectrum can be observed by introducing another arc-shaped resonator both on the same or the opposite side. Three different structures are designed to achieve the PIA effect, and we found the PIA response can be easily tuned by altering the structure’s parameters. Three structures are designed and compared, the PIA spectra exhibit high refractive index (RI) sensing with maximum sensitivity of 867.2nmRIU−1. Besides, the proposed structure can also be used as a gas concentration (GC) sensor when the polyhexamethylene biguanide (PHMB) is introduced, a maximum sensitivity of 142.1 pm/ppm is achieved for the proposed structure II, the maximum figure of merit (FOM) and Q value are 57.8 and 65.9, respectively. Therefore, the results represented in this paper will be beneficial in the fields of high-performance refractive index and gas sensors.

Management of Pediatric Superficial Partial-Thickness Burns with Polyhexamethylene Biguanide: Outcomes and Influencing Factors.

Background: In burn care, achieving swift healing with minimal complications remains paramount. This investigation assesses the role of polyhexamethylene biguanide (PHMB) in managing pediatric superficial partial-thickness burns, focusing on the effects of various patient-specific factors on recovery. Methods: Through a retrospective analysis of 27 pediatric cases treated with PHMB, we evaluated the impact of age, burn size, dressing frequency, treatment delay, cold therapy application, and analgesic usage on the time until reepithelialization (TTRE). Results: The majority of patients benefited from early cold therapy, yet only 1 in 3 patients received analgesics. A mean healing time of 8.78 (SD: 2.64) days was observed, with the extent of the burn showing a strong correlation (r: 0.63) to TTRE. Most treatments were managed outpatient, evidenced by a negligible average hospital stay (0.96 days), with recorded no complications. Conclusions: Our findings endorse PHMB as a promising treatment for superficial second-degree burns in young patients, due to the observed stable and rapid wound closure without the association of increased risks. Continued exploration into the optimal application of prehospital interventions and the comprehensive benefits of PHMB in pediatric burn management is necessary. Future research should assess long-term outcomes, including functionality, scar quality, and patient satisfaction.

Ouabain, ATPase inhibitor, potentially enhances the effect of polyhexamethylene biguanide on Acanthamoeba castellanii

Acanthamoeba, a free-living amoeba, is commonly found in various natural environments, such as rivers and soil, as well as in public baths, swimming pools, and sewers. Acanthamoeba can cause severe illness such as granulomatous amoebic encephalitis and Acanthamoeba keratitis (AK) in humans. AK, the most recognized disease, can cause permanent visual impairment or blindness by affecting the cornea. AK commonly affects contact lens wearers who neglect proper cleaning habits. The symptoms of AK include epithelial and stromal destruction, corneal infiltrate, and intense ocular pain, occasionally necessitating surgical removal of the entire eyeball. Current AK treatment involves the hourly application of eye drops containing polyhexamethylene biocide (PHMB). However, studies have revealed their ineffectiveness against drug-resistant strains. Acanthamoeba can form cysts as a survival mechanism in adverse environments, though the exact mechanism remains unknown. Our experiments revealed that sodium P-type ATPase (ACA1_065450) is closely linked to encystation. In addition, various encystation buffers, such as MgCl2 or NaCl, induced the expression of P-type ATPase. Furthermore, we used ouabain, an ATPase inhibitor, to inhibit the Na+/K+ ion pump, consequently decreasing the encystation rate of Acanthamoeba. Our primary objective is to develop an advanced treatment for AK. We anticipate that the combination of ouabain and PHMB may serve as an effective therapeutic approach against AK in the future.

Assessment between antiseptic and normal saline for negative pressure wound therapy with instillation and dwell time in diabetic foot infections

Negative pressure wound therapy with instillation and dwell time (NPWTi-d) is increasingly used for a diverse range of wounds. Meanwhile, the topical wound irrigation solution consisting of polyhexamethylene biguanide and betaine (PHMB-B) has shown efficacy in managing wound infections. However, the effectiveness of this solution as a topical instillation solution for NPWTi-d in patients with diabetic foot infections (DFIs) has not been thoroughly studied. The objective of this retrospective study was to evaluate the impact of using PHMB-B as the instillation solution during NPWTi-d on reducing bioburden and improving clinical outcomes in patients with DFIs. Between January 2017 and December 2022, a series of patients with DFIs received treatment with NPWTi-d, using either PHMB-B or normal saline as the instillation solution. Data collected retrospectively included demographic information, baseline wound characteristics, and treatment outcomes. The study included 61 patients in the PHMB-B group and 73 patients in the normal saline group, all diagnosed with DFIs. In comparison to patients treated with normal saline, patients with PHMB-B exhibited no significant differences in terms of wound bed preparation time (P = 0.5034), length of hospital stay (P = 0.6783), NPWTi-d application times (P = 0.1458), duration of systematic antimicrobial administration (P = 0.3567), or overall cost of hospitalization (P = 0.6713). The findings of the study suggest that the use of either PHMB-B or normal saline as an instillation solution in NPWTi-d for DFIs shows promise and effectiveness, yet no clinical distinction was observed between the two solutions.

Polyhexamethylene Biguanide Reduces High-Risk Human Papilloma Virus Viral Load in Cervical Cell Samples Derived from ThinPrep Pap Test.

Human papilloma virus (HPV) infection and its progression still represent a great medical challenge worldwide. Clinical evidence has demonstrated the beneficial effects of polyhexamethylene biguanide (PHMB) on HPV clinical manifestations; however, evidence of the effect of this molecule on HPV viral load is still lacking. In this in vitro study, 13 ThinPrep Papanicolaou (Pap) tests were treated with a PHMB solution (0.10 g/100 mL) for 2 h. We observed no cytological changes but a significant reduction in the viral load of high-risk (HR) HPV after PHMB treatment, also revealing a dose-dependent antiviral effect. In addition, by stratifying the obtained results according to HR-HPV genotype, we observed a significant reduction in the viral load of HPV 16, P2 (56, 59, 66), 31, and P3 (35, 39, 68) and a strong decrease in the viral load of HPV 45, 52, and P1 (33, 58). Overall, 85% of the analyzed cervical cell samples exhibited an improvement in HPV viral load after PHMB exposure, while only 15% remain unchanged. For the first time, the data from this pilot study support the activity of PHMB on a specific phase of the HPV viral lifecycle, the one regarding the newly generated virions, reducing viral load and thus blocking the infection of other cervical cells.

Development and Evaluation of a Novel Antibacterial Wound Dressing: A Powder Preparation Based on Cross-Linked Pullulan with Polyhexamethylene Biguanide for Hydrogel-Transition in Advanced Wound Management and Infection Control.

As antibiotic resistance increasingly undermines traditional infection management strategies, there is a critical demand for innovative wound care solutions that address these emerging challenges. This study introduces a novel antibacterial wound dressing based on Cross-Linked Pullulan (Pul) and Polyhexamethylene Biguanide (PHMB) for enhanced wound management and infection control. The dressing's adsorption rate reached 200% of its original weight within 30 min, exceeded 300% after 5 h, and exhibited significant non-Newtonian fluid properties. The dressings were able to release the loaded medication completely within 20 min; additionally, the dressing demonstrated significant antibacterial activity against a broad spectrum of bacteria. Significantly, the therapeutic effects of the Pul-PHMB/GP dressing were evaluated in a mouse model. Compared to untreated wounds, wounds treated with Pul-PHMB/GP exhibited a significant gelation process within 5 min post-treatment and showed a significant increase in wound healing rate within 12 days. This powder preparation overcomes the limitations associated with liquid and gel dressings, notably in storage and precise application, preventing the premature expansion or dissolution often caused by PHMB in high-humidity environments. The powder form can transform into a gel upon contact with wound exudate, ensuring accurate coverage of irregular wounds, such as those from burns or pressure sores, and offers excellent chemical and physical stability in a dry state, which facilitates storage and transport. This makes the dressing particularly suitable for emergency medical care and precision therapy, significantly improving the efficiency and adaptability of wound treatment and providing robust support for clinical treatments and emergency responses.

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

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. 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. 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. 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.

Bioactive Dressing: A New Algorithm in Wound Healing.

Wound management presents a significant global challenge, necessitating a comprehensive understanding of wound care products and clinical expertise in selecting dressings. Bioactive dressings (BD) represent a diverse category of dressings, capable of influencing wound healing through various mechanisms. These dressings, including honey, hyaluronic acid, collagen, alginates, and polymers enriched with polyhexamethylene biguanide, chitin, and chitosan derivatives, create a conducive environment for healing, promoting moisture balance, pH regulation, oxygen permeability, and fluid management. Interactive dressings further enhance targeted action by serving as substrates for bioactive agents. The continuous evolution of BDs, with new products introduced annually, underscores the need for updated knowledge in wound care. To facilitate dressing selection, a practical algorithm considers wound exudate, infection probability, and bleeding, guiding clinicians through the process. This algorithm aims to optimize wound care by ensuring the appropriate selection of BDs tailored to individual patient needs, ultimately improving outcomes in wound management.

Increasing incidence of contact-lens-related Acanthamoeba keratitis in a tertiary ophthalmology department in an Italian population.

The purpose of this paper is to report the increasing incidence of contact-lens related Acanthamoeba keratitis (AK) in a tertiary ophthalmology department in Umbria, central Italy. Observational and retrospective case series were carried out. A total of nine eyes with a diagnosis of AK were examined. All patients underwent a full slit lamp examination, in vivo confocal microscopy (IVCM) and corneal scraping. The IVCM was repeated at one and two-week and at one, three and six-month intervals. Samples of domestic tap water were also examined for PCR analysis. Patients were treated with levofloxacin0,5%, Polyhexamethylene biguanide 0.02%, and Propamidine Isetionate0,1%. All patients were contact lens wearers. The average patient age was 27.75 (range 18-45), with three men and five women. The main clinical features were ciliary congestion, diffuse epitheliopathy with punctuated keratitis, multiple, small sub-epithelial, greyish, corneal infiltrates with epithelial defect, pseudodendritic corneal lesions, perineural infiltrates, corneal stromal cellularity, and stromal infiltrates. IVCM was indicative of Acanthamoeba in seven out of the nine eyes. All the positive IVCM images were section images showing double walled, bright-spot cysts with a clear chain-like arrangement of five or more cysts identified in three of the patients. PCR analysis of the water was negative in all cases. Although PCR is the most common method used, the increased incidence of AK could mainly be related to a proper IVCM interpretation. A broad-spectrum antibiotic, such as levofloxacin might play a role in the early treatment of AK reducing the virulence of the amoeba.

Ionic conductive soluble starch hydrogels for biocompatible and anti-freezing wearable sensors

Hydrogel sensors have been widely researched for their good biocompatibility and mechanical properties similar to those of human skin, enabling the monitoring and transmission of a wide range of signals, thus promoting the development of flexible wearable electronic devices. However, long-term direct contact between hydrogel sensors and human skin can cause bacterial infection phenomena, and endowing hydrogel materials with antimicrobial properties is an important challenge in sensing applications. Here, an antimicrobial hydrogel was researched and explored via a freeze–thaw method introducing soluble starch, polyhexamethylene biguanide hydrochloride, glycerin, lithium chloride, and polyvinyl alcohol. The hydrogel expressed remarkable frost resistance, water retention, fatigue resistance, stability, sensitivity, responsiveness, electrical conductivity. The hydrogel exhibited an inhibitory loop resistant to Escherichia coli and Bacillus subtilis and emerged an inhibitory stability over 7 days. Simultaneously, the hydrogel expressed biocompatibility without tissue contamination, inflammation and other adverse phenomena under the skin of mice for 14 days. Furthermore, the hydrogel could record the signals of deformation during the process of the human motion. Therefore, the simple strategy is promising for medical fields including human motion detection, physiological signal recording and medical health detection.

Failed Treatment of Multidrug-resistant Acinetobacter Baumannii Keratitis Mistaken for a Mixed Infection

Purpose: To report treatment failure of multidrug-resistant <i>Acinetobacter baumannii</i> keratitis in a patient wearing contact lenses for a long time.Case summary: A 48-year-old man using daytime soft lenses for 20 years was transferred due to decreased visual acuity and eye pain. Slit-lamp biomicroscopy showed a large corneal epithelial defect and stromal infiltration, but no hypopyon. Treatment was initiated with moxifloxacin, polyhexamethylene biguanide eye drops, and oral antibiotics. Corneal infiltration worsened, corneal scrapings and culture were performed. Gram staining showed Gram-positive bacteria, potassium hydroxide (KOH) hyphae-positive, and culture yielded Bacillus. He was hospitalized and vancomycin, voriconazole, and amphotericin B eye drops were administered. Oral antifungal agents were also prescribed. The corneal epithelial defect was restored from temporal side for a while, and then deteriorated with an endothelial plaque. Therefore, voriconazole and amphotericin B were injected intracamerally. All four repeated culture tests were negative. Despite total conjunctival flap, the patient complained of severe pain and eventually underwent evisceration. In the culture of intraocular contents, <i>Acinetobacter baumannii</i>, which is resistant to all drugs except minocycline, was detected.Conclusions: In patients wearing contact lens for a long time, not only mixed infection with acanthamoeba and fungi, but also gram-negative bacteria should be considered first, and multidrug-resistant <i>Acinetobacter baumannii</i> should also be considered.

In Vitro Model to Evaluate the Development of Discolorations on Human Enamel Caused by Treatment with Mouth Rinses and Black Tea Considering Brushing.

The study aimed to develop and test an in vitro model to investigate the staining potential of mouth rinses on human enamel, considering alternating intake of black tea and tooth brushing, thus mimicking the situation in the oral cavity more realistically. Eight mouth rinses with six different active ingredients (benzydamine hydrochloride [BNZ], polyhexamethylene biguanide hydrochloride [PHMB], chlorhexidine digluconate [CHX], hexetidine gluconate [HEX], octenidine dihydrochloride [OCT] and octenidine dihydrochloride + 2-phenoxyethanol [OCTP]) and concentrations were tested. Sets of six halved human molar crowns were initially pretreated by soaking in artificial saliva (30 min). Afterward, the cyclic treatment was started by soaking in artificial saliva (2 min), staining with black tea (1 min), brushing with toothpaste (5 s), and soaking in the mouth rinse (30 s). Samples were rinsed with distilled water after each treatment step. The cyclic treatment was repeated 30 times, mimicking the consumer behavior after 15 days. Photographic images were taken after 0, 10, 20, and 30 cycles. Color measurements were conducted after each staining and brushing step using a VITA-Easyshade spectrophotometer to determine the difference in lightness ∆L and the total color difference ∆E. Analysis of variance and post-hoc Tukey test (α = 0.05) were applied. The new testing model with included brushing sequences allowed to assess the staining behavior on human teeth and provided a clear differentiation between the different investigated products. In detail, up to cycle 10, ΔE values increased for all mouth rinses with each additional cycle number. However, while ΔE values continued to increase for 0.15% BNZ, 0.1% PHMB, and 0.2% CHX between treatment cycle 10 and 30, ΔE values only slightly increased after treatment with 0.08% OCTP, 0.1% OCTP, 0.1% OCT, and 0.1% HEX. After 20 and 30 cycles, significantly less staining was found for 0.08% OCTP, 0.1% OCT, 0.1% HEX as compared to 0.2% CHX, 0.15% BNZ, and 0.1% PHMB (p < 0.05). ΔE-values were significantly lower after treatment with 0.1% OCTP as compared to 0.2% CHX1 and 0.2% CHX2 (p < 0.05). The proposed new methodology was found to be appropriate for assessing the staining progression of mouth rinses over a simulated application period of 15 days. The model allows differentiation of products with different active ingredients and concentrations.

Development of an antimicrobial and antifouling PES membrane with ZnO/poly(hexamethylene biguanide) nanocomposites incorporation

Although polyethersulfone (PES) membranes are extensively utilized in water and wastewater treatment, they typically encounter serious bio/organic fouling problems. In this work, an antimicrobial and antifouling PES membrane was developed through incorporating novel ZnO/PHMB (zinc oxide/ polyhexamethylene biguanide hydrochloride) nanocomposites on the surface of a commercial PES membrane, with PDA (polydopamine) serving as an intermediate connection layer. XPS, along with synchrotron-based XRF and ATR-FTIR results confirmed the successful synthesis of the ZnO/PHMB nanocomposites and ZnO/PHMB membranes. The ZnO/PHMB nanocomposites exhibited an impressive antimicrobial rate of 99.99 % with a minimal amount of PHMB addition (wtZnO:wtPHMB = 1:0.01). The concentration of the ZnO/PHMB nanocomposites had the most significant impact on the antimicrobial performance of the ZnO/PHMB membrane. The 600ZP membrane (i.e., the PES membrane modified with 600 mg/L ZnO/PHMB nanocomposites) emerged as the optimal choice, as evidenced by its commendable antimicrobial performance (92.80 %), water flux (249.02 LMH), RB (Rose Bengal sodium salt) rejection (93.96 %), and cost-benefit considerations. Compared to the pristine PES membrane, the 600ZP membrane showed 5.32 %, 15.76 %, and 7.62 % increased hydrophilicity, water flux, and RB rejection rate, respectively. Additionally, the 600ZP membrane possessed a bactericidal rate of 92.80 % and a flux recovery rate of 89.24 % after three cycles of SA (sodium alginate) filtration, indicating enhanced antimicrobial and antifouling capacities. The 600ZP membrane exhibited a remarkable 91.05 % higher water flux following prolonged (72 h) treatment of secondary effluent, compared to the PES membrane. Attribute to the increased hydrophilicity, outstanding antimicrobial activity, as well as excellent stability and durability, the as-prepared ZnO/PHMB membrane shows great potential for wastewater treatment.

A Systematic Review on Multiple Purpose Solution of Contact Lens Ingredients: Benefits and Risks

Since the past decades, the prevalence of microbial keratitis (MK) has risen notably among contact lens (CL) wearers. The main contributor to this infection is the use of an inefficient CL disinfecting solution. This paper highlights a systematic review of articles from journals on the multipurpose solution (MPS) of CL ingredients available currently in the market. This review emphasizes the compositions of MPS to evaluate their effectiveness and risks to lens wearers. A search for original articles published was conducted through Scopus, PubMed, and Google Scholar databases, focusing on the keywords contact lens ingredients and preservatives, MPS, polyquaternium, biguanides, and MK. A thorough review was conducted to extract the data on the subjects from the generated searches.The review revealed that hydrogen peroxide (H2O2), polyhexamethylene biguanide (PHMB), povidone-iodine (P-I), and polyquaternium-1 (PQ-1) are the preferred MPS formulations in the current industry of CLs. These chemical ingredients are effective against causative agents of keratitis for faster disinfection and lower risks of microbial infections in CL users. Thus, proper hygienic practices must follow the guidance from the respective product manufacturers to prevent harmful risks of ocular diseases.

Chitosan-based multifunctional oxygenating antibiotic hydrogel dressings for managing chronic infection in diabetic wounds.

Current treatment strategies for infection of chronic wounds often result in compromised healing and necrosis due to antibiotic toxicity, and underlying biomarkers affected by treatments are not fully known. Here, a multifunctional dressing was developed leveraging the unique wound-healing properties of chitosan, a natural polysaccharide known for its numerous benefits in wound care. The dressing consists of an oxygenating perfluorocarbon functionalized methacrylic chitosan (MACF) hydrogel incorporated with antibacterial polyhexamethylene biguanide (PHMB). A non-healing diabetic infected wound model with emerging metabolomics tools was used to explore the anti-infective and wound healing properties of the resultant multifunctional dressing. Direct bacterial bioburden assessment demonstrated superior antibacterial properties of hydrogels over a commercial dressing. However, wound tissue quality analyses confirmed that sustained PHMB for 21 days resulted in tissue necrosis and disturbed healing. Therefore, a follow-up comparative study investigated the best treatment course for antiseptic application ranging from 7 to 21 days, followed by the oxygenating chitosan-based MACF treatment for the remainder of the 21 days. Bacterial counts, tissue assessments, and lipidomics studies showed that 14 days of application of MACF-PHMB dressings followed by 7 days of MACF dressings provides a promising treatment for managing infected non-healing diabetic skin ulcers.

Ultra-high strength sodium alginate/PVA/PHMB double-network hydrogels for marine antifouling

Although hydrogel have attracted tremendous attention as antifouling material, it is still challenging to develop an antifouling hydrogel that combines superior mechanical properties with excellent antifouling effect. Here, a high-strength polyvinyl alcohol/sodium alginate double-network (DN) antibacterial and antifouling hydrogel was synthesized by introducing polyhexamethylene biguanide hydrochloride (PHMB) potent fungicide. The as-prepared hydrogel demonstrated high tensile strength (17.23 MPa), excellent anti-protein adhesion ability (0.09 %, anti-diatom adhesion rate), and outstanding antibacterial ability (100 % sterilization rate). The antifouling experiments have verified that DN-PHMB hydrogel remains non-attachment even after >6 months in the actual marine environment. These distinctive capabilities of DN-PHMB hydrogels hold promising candidate for marine antifouling materials.

Preparation and Antimicrobial Activity of a Film-Forming Polyhexamethylene Biguanide Teat Disinfectant.

Bovine mastitis caused by infectious pathogens can lead to a decline in production performance and an increase in elimination rate, resulting in huge losses to the dairy industry. This study aims to prepare a novel dairy cow teat disinfectant with polyhexamethylene biguanide (PHMB) as the main bactericidal component and to evaluate its bactericidal activity in vitro and its disinfection effect in dairy cow teats. PHMB disinfectant with a concentration of 3 g/L was prepared with PVA-1788, propylene glycol and glycerol as excipients. When the dilution ratio is 1:4800 and the action time is 5 min, the PHMB teat disinfectant can reduce the four types of bacteria (S. agalactiae ATCC 12386, S. dysgalactiae ATCC 35666, S. aureus ATCC 6538, and E. coli ATCC 8099) by 99.99%. PHMB teat disinfectant applied on the skin of rabbits with four bacteria types achieved an average log10 reduction greater than 4. After 30 s of PHMB teat disinfectant dipping, the bacteria of cow teats were counted prior to disinfection. The mean log10 reduction in bacteria on the skin surface of 12 cows ranged from 0.99 to 3.52 after applying the PHMB teat disinfectant for 10 min. After 12 h, the PHMB teat disinfectant achieved an average log10 reduction in bacteria from 0.27 to 0.68 (compared with that prior to disinfection). These results suggested that PHMB teat disinfection has the potential to prevent and treat mastitis-causing bacteria in dairy herds.

Polyhexamethylene biguanide promotes adaptive cross-resistance to gentamicin in Escherichia coli biofilms.

Antimicrobial resistance is a critical public health issue that requires a thorough understanding of the factors that influence the selection and spread of antibiotic-resistant bacteria. Biocides, which are widely used in cleaning and disinfection procedures in a variety of settings, may contribute to this resistance by inducing similar defense mechanisms in bacteria against both biocides and antibiotics. However, the strategies used by bacteria to adapt and develop cross-resistance remain poorly understood, particularly within biofilms -a widespread bacterial habitat that significantly influences bacterial tolerance and adaptive strategies. Using a combination of adaptive laboratory evolution experiments, genomic and RT-qPCR analyses, and biofilm structural characterization using confocal microscopy, we investigated in this study how Escherichia coli biofilms adapted after 28 days of exposure to three biocidal active substances and the effects on cross-resistance to antibiotics. Interestingly, polyhexamethylene biguanide (PHMB) exposure led to an increase of gentamicin resistance (GenR) phenotypes in biofilms formed by most of the seven E. coli strains tested. Nevertheless, most variants that emerged under biocidal conditions did not retain the GenR phenotype after removal of antimicrobial stress, suggesting a transient adaptation (adaptive resistance). The whole genome sequencing of variants with stable GenR phenotypes revealed recurrent mutations in genes associated with cellular respiration, including cytochrome oxidase (cydA, cyoC) and ATP synthase (atpG). RT-qPCR analysis revealed an induction of gene expression associated with biofilm matrix production (especially curli synthesis), stress responses, active and passive transport and cell respiration during PHMB exposure, providing insight into potential physiological responses associated with adaptive crossresistance. In addition, confocal laser scanning microscopy (CLSM) observations demonstrated a global effect of PHMB on biofilm architectures and compositions formed by most E. coli strains, with the appearance of dense cellular clusters after a 24h-exposure. In conclusion, our results showed that the PHMB exposure stimulated the emergence of an adaptive cross-resistance to gentamicin in biofilms, likely induced through the activation of physiological responses and biofilm structural modulations altering gradients and microenvironmental conditions in the biological edifice.

Culture Shock: An Investigation into the Tolerance of Pathogenic Biofilms to Antiseptics in Environments Resembling the Chronic Wound Milieu.

Credible assessment methods must be applied to evaluate antiseptics' in vitro activity reliably. Studies indicate that the medium for biofilm culturing should resemble the conditions present at the site of infection. We cultured S. aureus, S. epidermidis, P. aeruginosa, C. albicans, and E. coli biofilms in IVWM (In Vitro Wound Milieu)-the medium reflecting wound milieu-and were compared to the ones cultured in the laboratory microbiological Mueller-Hinton (MH) medium. We analyzed and compared crucial biofilm characteristics and treated microbes with polyhexamethylene biguanide hydrochloride (PHMB), povidone-iodine (PVP-I), and super-oxidized solution with hypochlorites (SOHs). Biofilm biomass of S. aureus and S. epidermidis was higher in IVWM than in MH medium. Microbes cultured in IVWM exhibited greater metabolic activity and thickness than in MH medium. Biofilm of the majority of microbial species was more resistant to PHMB and PVP-I in the IVWM than in the MH medium. P. aeruginosa displayed a two-fold lower MBEC value of PHMB in the IVWM than in the MH medium. PHMB was more effective in the IVWM than in the MH medium against S. aureus biofilm cultured on a biocellulose carrier (instead of polystyrene). The applied improvement of the standard in vitro methodology allows us to predict the effects of treatment of non-healing wounds with specific antiseptics.