A comparative study of characteristics of current-type and conventional-type cationic bactericides

Polyhexamethylene Guanidine Phosphate Enhanced Procoagulant Activity through Oxidative-Stress-Mediated Phosphatidylserine Exposure in Platelets

Polyhexamethylene guanidine phosphate (PHMG-p) is a common biocidal disinfectant that is widely used in industry and household products. However, PHMG-p was misused as a humidifier disinfectant (HD) in South Korea, which had fatal health effects. Various health problems including cardiovascular diseases were observed in HD-exposed groups. However, the potential underlying mechanism of HD-associated cardiovascular diseases is poorly understood. Here, we examined the procoagulant activity of platelets caused by PHMG-p and clarified the underlying mechanism. PHMG-p enhanced phosphatidylserine (PS) exposure through alteration of phospholipid transporters, scramblase, and flippase. Intracellular calcium elevation, intracellular ATP depletion, and caspase-3 activation appeared to underlie phospholipid transporter dysregulation caused by PHMG-p, which was mediated by oxidative stress and mitochondrial dysfunction. Notably, antioxidant enzyme catalase and calcium chelator EGTA reversed PHMG-p-induced PS exposure and thrombin generation, confirming the contributive role of oxidative stress and intracellular calcium in the procoagulant effects of PHMG-p. These series of events led to procoagulant activation of platelets, which was revealed as enhanced thrombin generation. Collectively, PHMG-p triggered procoagulant activation of platelets, which may promote prothrombotic risks and cardiovascular diseases. These findings improve our understanding of HD-associated cardiovascular diseases.

Inhalation toxicity of polyhexamethylene guanidine-phosphate in rats: A 4-week inhalation exposure and 24-week recovery period study

Humidifier disinfectant (HD) is a causative agent of atypical lung injury reported in 2011 in South Korea, and various diseases caused by HD after exposure cessation have been reported to date. However, there is limited research on most of the reported diseases in terms of their association with HD exposure, and information on the progression of diseases caused by HD exposure is also limited. Therefore, we investigated the effects of HD inhalation on the body in rats. Rats were exposed to 0.15, 0.50, and 1.60 mg/m³ polyhexamethylene guanidine-phosphate (PHMG-p), which is the major component of HDs and most closely related to HD-associated lung injury. We conducted necropsy four times during the recovery period (0, 4, 12, and 24 weeks) and evaluated general systemic toxicities. There were significant changes in the mortality rate, body weight, and food consumption in the PHMG-p-exposed groups. Hematology revealed changes in hemoglobin level, hematocrit, red blood cell, reticulocyte, and white blood cell counts until 12 weeks of the recovery period. PHMG-p induced a delay in prothrombin time until 12 weeks of the recovery period. The aspartate aminotransferase, alanine aminotransferase, total bilirubin, and triglyceride levels were higher in the PHMG-p-exposed groups than in the control group at week 4 of the recovery period, and these parameters normalized after 12 weeks of the recovery period. Histopathological examination in PHMG-p exposed groups revealed several changes in the lungs, including the presence of alveolar macrophages, chronic inflammation, squamous metaplasia, alveolar emphysema, and pulmonary fibrosis. The severity of these symptoms was maintained or exacerbated till 24 weeks. Overall, PHMG-p inhalation can induce irreversible histological changes in the lungs and cause various types of damage throughout the body, even after exposure ends.

Toxicity of humidifier disinfectant polyhexamethylene guanidine hydrochloride by two-week whole body-inhalation exposure in rats

The use of polyhexamethylene guanidine hydrochloride (PHMG·HCl) as a humidifier disinfectant caused an outbreak of pulmonary disease, leading to the deaths of pregnant women and children in South Korea. However, limited information is available on the inhalation toxicity of PHMG·HCl. Therefore, this study aimed to characterize the subacute inhalation toxicity of PHMG·HCl by whole-body exposure in rats. F344 rats were exposed to 0 mg/m³, 1 mg/m³, 5 mg/m³, or 25 mg/m³ of PHMG·HCl for 6 h/day, 5 days/week for two weeks via whole-body inhalation. Emaciation and rale were observed in rats in the 25 mg/m³ PHMG·HCl group. Significant changes in body weight, hematology, serum chemistry and organ weight were observed in all PHMG·HCl-exposed groups. Gross lesions showed ballooning or red focus in the lungs of rats in the PHMG·HCl-exposed groups. In histopathological examination, most of histological lesions (including degeneration, atrophy, ulcer, inflammatory cell infiltration, inflammation, and fibrosis in nasal cavity, larynx, trachea, and lungs) indicated tissue damage by PHMG·HCl in all PHMG·HCl-exposed groups. Additionally, atrophy of the spleen, thymus, and reproductive organs; immaturity of the testes; and cell debris in the epididymides were affected by the reduction in body weight in PHMG·HCl-exposed groups. In conclusion, two-week repeated whole-body inhalation exposure of rats to PHMG·HCl reveled toxic effects on the respiratory system and secondary effects on other organs. The results of this study indicate that the no observable adverse effect level (NOAEL) for PHMG·HCl is below 1 mg/m³.

Properties of Polyhexamethylene Guanidine (PHMG) Associated with Fatal Lung Injury in Korea

The use of humidifier disinfectant (HD) has been determined to be associated with lung injuries (HDLI) in Korea. Although HD brands containing polyhexamethylene guanidine (PHMG) oligomers have been found to cause more HDLI compared to brands containing other disinfectants, the physicochemical properties of PHMG have been poorly defined. We aimed to quantify the PHMG dissolved in HD brands, characterize the number-average (Mn) and weight-average (Mw) molecular masses, and identify the polymerization degree of PHMG. Analysis of the PHMG oligomers was performed using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF MS) operated in positive-ion reflectron mode. Eight brands of HD containing PHMG were identified. The PHMG concentrations in these brands ranged from 160 to 37,200 ppm (mean = 3100.9 ppm). Concentration was a significant variable among and within HD brands. The degree of PHMG oligomerization fell within the range of two to four. The averages of Mn and Mw were 517.2 g/mol (range: 422-613 g/mol) and 537.3 g/mol (range: 441.0-678.0 g/mol), respectively. Based on the average molecular weight and the degree of polymerization, the PHMG examined here could be regarded as oligomers, which may be associated with the highest proportion of HDLI being caused by PHMG.

A Phenotypic and Genotypic Evaluation of Developmental Toxicity of Polyhexamethylene Guanidine Phosphate Using Zebrafish Embryo/Larvae

Polyhexamethylene guanidine-phosphate (PHMG-P), a guanidine-based cationic antimicrobial polymer, is an effective antimicrobial biocide, potent even at low concentrations. Due to its resilient bactericidal properties, it has been used extensively in consumer products. It was safely used until its use in humidifiers led to a catastrophic event in South Korea. Epidemiological studies have linked the use of PHMG-P as a humidifier disinfectant to pulmonary fibrosis. However, little is known about its harmful impacts other than pulmonary fibrosis. Thus, we applied a zebrafish embryo/larvae model to evaluate developmental and cardiotoxic effects and transcriptome changes using RNA-sequencing. Zebrafish embryos were exposed to 0.1, 0.2, 0.3, 0.4, 0.5, 1, and 2 mg/L of PHMG-P from 3 h to 96 h post fertilization. 2 mg/L of PHMG-P resulted in total mortality and an LC₅₀ value at 96 h was determined at 1.18 mg/L. Significant developmental changes were not observed but the heart rate of zebrafish larvae was significantly altered. In transcriptome analysis, immune and inflammatory responses were significantly affected similarly to those in epidemiological studies. Our qPCR analysis (Itgb1b, TNC, Arg1, Arg2, IL-1β, Serpine-1, and Ptgs2b) also confirmed this following a 96 h exposure to 0.4 mg/L of PHMG-P. Based on our results, PHMG-P might induce lethal and cardiotoxic effects in zebrafish, and crucial transcriptome changes were linked to immune and inflammatory response.

Polyhexamethylene Guanidine Phosphate Damages Tight Junctions and the F-Actin Architecture by Activating Calpain-1 via the P2RX7/Ca2+ Signaling Pathway

Polyhexamethylene guanidine phosphate (PHMG-p), a member of the polymeric guanidine family, has strong antimicrobial activity and may increase the risk of inflammation-associated pulmonary fibrosis. However, the effect of PHMG-p on the barrier function of the bronchial epithelium is unknown. Epithelial barrier functioning is maintained by tight junctions (TJs); damage to these TJs is the major cause of epithelial barrier breakdown during lung inflammation. The present study showed that, in BEAS-2B human bronchial epithelial cells, exposure to PHMG-p reduced the number of TJs and the E-cadherin level and impaired the integrity of the F-actin architecture. Furthermore, exposure to PHMG-p stimulated the calcium-dependent protease calpain-1, which breaks down TJs. However, treatment with the calpain-1 inhibitor, ALLN, reversed the PHMG-p-mediated impairment of TJs and the F-actin architecture. Furthermore, exposure to PHMG-p increased the intracellular Ca²⁺ level via P2X purinoreceptor 7 (P2RX7) and inhibition of P2RX7 abolished the PHMG-p-induced calpain-1 activity and protein degradation and increased the intracellular Ca²⁺ level. Although exposure to PHMG-p increased the extracellular ATP level, hydrolysis of extracellular ATP by apyrase did not influence its detrimental effect on bronchial epithelial cells. These results implicate the impairment of TJs and the F-actin architecture in the pathogenesis of pulmonary diseases.

Evaluation of disinfectant efficacy against multidrug-resistant bacteria: A comprehensive analysis of different methods

BACKGROUND

Multidrug-resistant gram-negative bacteria (MDR-GNB) constitute a threat to health care worldwide. Disinfectants are used to prevent and control the spread of MDR-GNB in a hospital setting but their efficacy might be impaired by bacterial mechanisms that may act on both antimicrobials and disinfectants. Determination of minimum inhibitory concentrations is mainly used to determine bacterial susceptibility against disinfectants, but practical tests on surfaces might be more suitable to predict in-use conditions. Our objective was to compare and evaluate 4 different methods widely used to assess surface disinfectant efficacy.

METHODS

The efficacy of benzalkonium chloride (BAC), peracetic acid (PAA), and ethanol (ETH) against multidrug-resistant Acinetobacter, Pseudomonas, and Klebsiella strains was assessed by minimum inhibitory concentration determinations, quantitative suspension tests, qualitative suspension tests, and carrier tests. Test results were compared to ascertain the most appropriate method.

RESULTS

ETH, PAA, and BAC were highly effective against MDR-GNB, but we observed marked differences in efficacious concentrations (up to 100-fold) as a function of the test method applied. Minimum inhibitory concentration determination was not reliable for evaluating susceptibility or resistance to BAC.

CONCLUSIONS

Surface tests should be used to determine bacterial susceptibility against disinfectants. Moreover, suitable guidelines are needed that allow for the standardization and comparison of bactericidal values obtained by different investigators.

Polyhexamethyleneguanidine Phosphate-Induced Cytotoxicity in Liver Cells Is Alleviated by Tauroursodeoxycholic Acid (TUDCA) via a Reduction in Endoplasmic Reticulum Stress

Polyhexamethyleneguanidine phosphate (PHMG-P) is a widely used polymeric antimicrobial agent known to induce significant pulmonary toxicity. Several studies have reported that the liver also can be a target organ of polyhexamethyleneguanidine (PHMG) toxicity, but the exact effect of this compound on liver cells is not well understood. To identify the mechanism of PHMG hepatotoxicity, HepG2 cells were exposed to PHMG-P for 72 h. The cell viability was significantly decreased by PHMG-P in a time- and concentration-dependent manner. The mitochondrial membrane potential was markedly reduced by PHMG-P and the apoptotic signaling cascade was activated. The increases observed in C/EBP homologous protein (CHOP), p-IRE, and p-JNK levels in PHMG-P-treated cells indicated the induction of endoplasmic reticulum stress. To verify the role of ER stress in PHMG-P-induced cytotoxicity, HepG2 cells were pretreated with the chemical chaperone, tauroursodeoxycholic acid (TUDCA) and then co-treated with TUDCA and PHMG-P for 24 h. Interestingly, TUDCA inhibited PHMG-P-induced ER stress and cytotoxicity in a dose-dependent manner. The apoptotic cell death and mitochondrial depolarization were also prevented by TUDCA. The proteins involved in the apoptotic pathway were all normalized to their control levels in TUDCA-treated cells. In conclusion, the results suggest that PHMG-P induced significant cytotoxicity in liver cells and ER stress-mediated apoptosis, which may be an important mechanism mediating this hepatotoxicity.

Time course of polyhexamethyleneguanidine phosphate-induced lung inflammation and fibrosis in mice

Pulmonary fibrosis is a chronic progressive disease with unknown etiology and has poor prognosis. Polyhexamethyleneguanidine phosphate (PHMG-P) causes acute interstitial pneumonia and pulmonary fibrosis in humans when it exposed to the lung. In a previous study, when rats were exposed to PHMG-P through inhalation for 3 weeks, lung inflammation and fibrosis was observed even after 3 weeks of recovery. In this study, we aimed to determine the time course of PHMG-P-induced lung inflammation and fibrosis. We compared pathological action of PHMG-P with that of bleomycin (BLM) and investigated the mechanism underlying PHMG-P-induced lung inflammation and fibrosis. PHMG-P (0.9 mg/kg) or BLM (1.5 mg/kg) was intratracheally administered to mice. At weeks 1, 2, 4 and 10 after instillation, the levels of inflammatory and fibrotic markers and the expression of inflammasome proteins were measured. The inflammatory and fibrotic responses were upregulated until 10 and 4 weeks in the PHMG-P and BLM groups, respectively. Immune cell infiltration and considerable collagen deposition in the peribronchiolar and interstitial areas of the lungs, fibroblast proliferation, and hyperplasia of type II epithelial cells were observed. NALP3 inflammasome activation was detected in the PHMG-P group until 4 weeks, which is suspected to be the main reason for the persistent inflammatory response and exacerbation of fibrotic changes. Most importantly, the pathological changes in the PHMG-P group were similar to those observed in humidifier disinfectant-associated patients. A single exposure of PHMG-P led to persistent pulmonary inflammation and fibrosis for at least 10 weeks.

Antimicrobial polymeric materials with quaternary ammonium and phosphonium salts

Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers.

Structure-activity relationships among antifungal nylon-3 polymers: identification of materials active against drug-resistant strains of Candida albicans

Fungal infections are a major challenge to human health that is heightened by pathogen resistance to current therapeutic agents. Previously, we were inspired by host-defense peptides to develop nylon-3 polymers (poly-β-peptides) that are toxic toward the fungal pathogen Candida albicans but exert little effect on mammalian cells. Based on subsequent analysis of structure-activity relationships among antifungal nylon-3 polymers, we have now identified readily prepared cationic homopolymers active against strains of C. albicans that are resistant to the antifungal drugs fluconazole and amphotericin B. These nylon-3 polymers are nonhemolytic. In addition, we have identified cationic-hydrophobic copolymers that are highly active against a second fungal pathogen, Cryptococcus neoformans, and moderately active against a third pathogen, Aspergillus fumigatus.

C-terminal functionalization of nylon-3 polymers: effects of C-terminal groups on antibacterial and hemolytic activities

Nylon-3 polymers contain β-amino-acid-derived subunits and can be viewed as higher homologues of poly(α-amino acids). This structural relationship raises the possibility that nylon-3 polymers offer a platform for development of new materials with a variety of biological activities, a prospect that has recently begun to receive experimental support. Nylon-3 homo- and copolymers can be prepared via anionic ring-opening polymerization of β-lactams, and use of an N-acyl-β-lactam as coinitiator in the polymerization reaction allows placement of a specific functional group, borne by the N-acyl-β-lactam, at the N-terminus of each polymer chain. Controlling the unit at the C-termini of nylon-3 polymer chains, however, has been problematic. Here we describe a strategy for specifying C-terminal functionality that is based on the polymerization mechanism. After the anionic ring-opening polymerization is complete, we introduce a new β-lactam, approximately 1 equiv relative to the expected number of polymer chains. Because the polymer chains bear a reactive imide group at their C-termini, this new β-lactam should become attached at this position. If the terminating β-lactam bears a distinctive functional group, that functionality should be affixed to most or all C-termini in the reaction mixture. We use the new technique to compare the impact of N- and C-terminal placement of a critical hydrophobic fragment on the biological activity profile of nylon-3 copolymers. The synthetic advance described here should prove to be generally useful for tailoring the properties of nylon-3 materials.

Comparative biocidal activity of peracetic acid, benzalkonium chloride and ortho-phthalaldehyde on 77 bacterial strains

Despite numerous reports on biocide activities, it is often difficult to have a reliable and relevant overview of bacterial resistance to disinfectants because each work challenges a limited number of strains and tested methods are often different. The aim of this study was to evaluate the bactericidal activity of three different disinfectants commonly used in industrial or medical environments (peracetic acid, benzalkonium chloride and ortho-phthalaldehyde) against 77 bacterial strains from different origins using one standard test method (NF EN 1040). Results highlight the existence of high interspecific variability of resistance to disinfectants and, contrary to widespread belief, Gram-positive strains generally appeared more resistant than Gram-negative strains. Resistance was also variable among strains of the same species such as Bacillus subtilis to peracetic acid, Pseudomonas aeruginosa to benzalkonium chloride and Staphylococcus aureus to ortho-phthalaldehyde.

Structure-activity relationships among random nylon-3 copolymers that mimic antibacterial host-defense peptides

Host-defense peptides are natural antibiotics produced by multicellular organisms to ward off bacterial infection. Since the discovery of these molecules in the 1980s, a great deal of effort has been devoted to elucidating their mechanisms of action and to developing analogues with improved properties for possible therapeutic use. The vast majority of this effort has focused on materials composed of a single type of molecule, most commonly a peptide with a specific sequence of alpha-amino acid residues. We have recently shown that sequence-random nylon-3 copolymers can mimic favorable properties of host-defense peptides, and here we document structure-activity relationships in this polymer family. Although the polymers are heterogeneous in terms of subunit order and stereochemistry, these materials display structure-activity relationships comparable to those that have been documented among host-defense peptides and analogous synthetic peptides. Previously such relationships have been interpreted in terms of a specific and regular folding pattern (usually an alpha-helix), but our findings show that these correlations between covalent structure and biological activity do not require the adoption of a specific or regular conformation. In some cases our observations suggest alternative interpretations of results obtained with discrete peptides.

Plasma-enhanced synthesis of bactericidal quaternary ammonium thin layers on stainless steel and cellulose surfaces

We have investigated bottom-up chemical synthesis of quaternary ammonium (QA) groups exhibiting antibacterial properties on stainless steel (SS) and filter paper surfaces via nonequilibrium, low-pressure plasma-enhanced functionalization. Ethylenediamine (ED) plasma under suitable conditions generated films rich in secondary and tertiary amines. These functional structures were covalently attached to the SS surface by treating SS with O 2 and hexamethyldisiloxane plasma prior to ED plasma treatment. QA structures were formed by reaction of the plasma-deposited amines with hexyl bromide and subsequently with methyl iodide. Structural compositions were examined by electron spectroscopy for chemical analysis and Fourier transform infrared spectroscopy, and surface topography was investigated with atomic force microscopy and water contact angle measurements. Modified SS surfaces exhibited greater than a 99.9% decrease in Staphylococcus aureus counts and 98% in the case of Klebsiella pneumoniae. The porous filter paper surfaces with immobilized QA groups inactivated 98.7% and 96.8% of S. aureus and K. pneumoniae, respectively. This technique will open up a novel way for the synthesis of stable and very efficient bactericidal surfaces with potential applications in development of advanced medical devices and implants with antimicrobial surfaces.

Structure-activity relationships of oligoguanidines-influence of counterion, diamine, and average molecular weight on biocidal activities

A series of different oligomeric guanidines was prepared by polycondensation of guanidinium salts and four different diamines under varying conditions. The antimicrobial activities were evaluated against two to four microorganisms. MALDI-TOF-MS was used to analyze the different oligomers. It was found that in each case three major product type series are dominating. These series are linear and terminated with one guanidine and one amino group (type A), two amino groups (type B), or two guanidine groups (type C), respectively. By using 1,2-bis(2-aminoethoxy)ethane as the amino component, a considerable amount of two additional product series, consisting of cyclic structures, was detected (type D and E). It turned out that an average molecular mass of about 800 Da is necessary for an efficient antimicrobial activity. Lower Mw's result in a rapid decrease of activity. By using guanidinium carbonate as the starting material, oligomers with low biocidal activity were obtained, which was caused by incorporation of urea groups during the polycondensation. The diamine determines the distance between two guanidinium groups. It was shown that both 1,2-bis(2-aminoethoxy)ethane and hexamethylenediamine give oligomers with high biocidal activity. By increasing the chain length of the diamine, the biocidal activity drops again.