Bacterial Contact Research Articles

Expression of α- and ε-toxin genes in Clostridium perfringens type D vaccine strain in contact with the Caco-2 cell line.

Clostridium perfringens commonly resides in the gastrointestinal tract and can survive in different environmental conditions. This pathogen produces several protein toxins including the potent ε-toxin which is classified as a category B toxin by the Centers for Disease Control and Prevention (CDC). In several studies, the induction of C. perfringens type C or D to produce toxins much more rapidly by close contact of bacteria with Caco-2 cells has been reported. The effect of close contact of enterocyte-like Caco-2 cells with C. perfringens type D (vaccine strain) on the production time of ε- and α-toxins was studied. During C. perfringens type D contact with Caco-2 cells for 5 h, ε- and α-toxins expressions (at 0, 2, and 5 h) were evaluated by a quantitative real-time PCR assay. Non-contacted bacteria with cells were included as the negative control in this research. Bacterial contact with the Caco-2 cells induces a significant effect on the mean expression of the ε-toxin gene (etx) (P<0.05). Two h after contact, the highest level of gene expression was detected in the experimental group. Bacterial harvesting time, cell treatment, and their interactions did not affect significantly the mean expression of the α-toxin gene (cpa) (P>0.05). According to the findings of the present study, 2 h of bacterial contact with Caco-2 cells could stimulate etx gene expression in the C. perfringens type D vaccine strain.

RETRACTED: Anti-microbial/oxidative/inflammatory nanogels accelerate chronic wound healing

The most common cause of delayed healing in chronic wounds is microbial pathogenesis, in which localized colonization can cause severe inflammation, systemic infection, and even sepsis in some cases. Towards this end, we have developed a multifunctional nanogel possessing antimicrobial/oxidative/inflammatory characteristics for rapid wound healing. We first employed quercetin (Qu) to prepare carbonized nanogels (CNGs) through polymerization and mild carbonization. The Qu–CNGs with antioxidant activity were further used as templates to prepare multifunctional nanogels containing copper sulfide (CuS) nanoclusters that possess superior catalytic and photoresponsive properties. The minimum inhibitory concentration of the nanogels (CuS/Qu–CNGs) towards tested bacteria is ∼125-folds lower than monomeric Qu or Qu–CNGs under NIR-II light irradiation. Furthermore, CuS/Qu–CNGs demonstrated efficient penetration into the extracellular biofilm matrix, resulting in eradication of methicillin-resistant Staphylococcus aureus (MRSA) associated biofilm on diabetic mice wounds. The CuS/Qu–CNGs nanogels suppressed proinflammatory cytokines (IL-1β) in the infectious wound sites and regulated the expression of anti-inflammatory IL-10 and TGF-β1 during and after recovery from infection, respectively. Along with in vivo bactericidal effects, the CuS/Qu–CNGs promote angiogenesis, epithelialization, and collagen synthesis to accelerate wound healing. Faster wound healing was attributed to the triple features (i) antioxidant Qu-CNGs reduced the pathogen-induced oxidative stress, (ii) enhanced bacterial contact due to polyphenolic groups of Qu facilitated CuS induced localized photothermal and photodynamic therapies, and (iii) enzyme mimic response of CuS nanoclusters contributed to the elimination of microbial pathogenesis.

Polysilsesquioxane with potent resistance to intraoral stress: Functional coating material for the advanced dental materials

Since the oral cavity is a harsh environment where various germs and chemical and mechanical stress exist simultaneously, well-organized hybrid technology should be considered in the design of cutting-edge dental materials. Although the Clear Overlay Appliance (COA) is widely used as a transparent orthodontic device, it still requires specific modifications to overcome the poor durability and frequent contamination that cause the patient's therapeutic burden. Herein, robust polysilsesquioxane (PSQ) containing quaternary ammonium cations (QACs) and long alkyl chains (LACs) in a durable siloxane matrix are reported as coating materials for the advanced COAs. The PSQ coatings are engineered to have a ladder-like structure that exhibits excellent stability under various pH and enzymatic conditions. Experiments simulating the dynamic intraoral are established to investigate the effects of PSQ coatings for the functional improvement of COA. The QACs and LACs firmly fixed to the siloxane matrix cause bacterial contact killing to prevent the contamination of COAs in the environment exposed to bacteria. The ladder-like siloxane matrix of the coating protects the COAs from intraoral abrasion forces and shearing movements with its flexible adaptability to external stresses. This study clarifies the clinical application potential of the coated COAs via in-vivo experiments using the beagle model.

Antibiofilm activity of nanosilver coatings against Staphylococcus aureus

Implant infections due to bacterial biofilms constitute a major healthcare challenge today. One way to address this clinical need is to modify the implant surface with an antimicrobial nanomaterial. Among such nanomaterials, nanosilver is arguably the most powerful one, due to its strong and broad antimicrobial activity. However, there is still a lack of understanding on how physicochemical characteristics of nanosilver coatings affect their antibiofilm activity. More specifically, the contributions of silver (Ag)+ ion-mediated vs. contact-based mechanisms to the observed antimicrobial activity are yet to be elucidated. To address this knowledge gap, we produce here nanosilver coatings on substrates by flame aerosol direct deposition that allows for facile control of the coating composition and Ag particle size. We systematically study the effect of (i) nanosilver content in composite Ag silica (SiO2) coatings from 0 (pure SiO2) up to 50 wt%, (ii) the Ag particle size and (iii) the coating thickness on the antibiofilm activity against Staphylococcus aureus (S. aureus), a clinically-relevant pathogen often present on the surface of surgically-installed implants. We show that the Ag+ ion concentration in solution largely drives the observed antibiofilm effect independently of Ag size and coating thickness. Furthermore, co-incubation of both pure SiO2 and nanosilver coatings in the same well also reveals that the antibiofilm effect stems predominantly from the released Ag+ ions, which is especially pronounced for coatings featuring the smallest Ag particle sizes, rather than direct bacterial contact inhibition. We also examine the biocompatibility of the developed nanosilver coatings in terms of pre-osteoblastic cell viability and proliferation, comparing it to that of pure SiO2. This study lays the foundation for the rational design of nanosilver-based antibiofilm implant coatings.

Comparative Evaluation of Antibacterial Effect of Propolis and Aloe Vera, Xylitol, and Cpp-Acp Gels on Streptococcus mutans and Lactobacillus in Vitro.

Introduction Early childhood caries is a kind of caries occurring in deciduous teeth. Bacteria are among the main factors. Antibacterial agents such as fluoride are used in both prevention and treatment, but their application in children faces limitations such as fluorosis. Therefore, novel methods of caries prevention among the children are mainly focused on the use of fluoride-free active ingredients. In this comparative study, antibacterial effects of gels containing propolis and aloe vera, fluoride, xylitol, and CPP-ACP were investigated. Methods This is an in vitro study. By plate well technique, plates containing gels were created in the culture medium of Streptococcus mutans and Lactobacillus, and their antibacterial impacts were evaluated by measuring the inhibition zone after 24, 48, and 72 hours. Then, different concentrations of each gel were evaluated in the same way for the antibacterial properties. For each sample, this process was iterated 3 times, where the average was declared as the final number. The collected data were entered in SPSS 24. Results In both bacteria, propolis gel and aloe vera had the highest zone of inhibition, followed by fluoride and xylitol in the second and third places, respectively. Different concentrations of gels are significantly different in terms of antimicrobial effect (P value ≤ 0/05). The antimicrobial effect of propolis and aloe vera gel was kept up to the concentration of 1/16. As the bacterial and gel contact time is prolonged, the antibacterial effect of different gels increases, but the difference is not statistically significant (P value = 0.109). CPP-ACP gel had no antimicrobial effect at any concentration. Conclusion Propolis and aloe vera gel had a greater antimicrobial effect than other gels, where such effect was observed in low concentrations. CPP-ACP gel had no antimicrobial properties.

High-Resolution Microscopical Studies of Contact Killing Mechanisms on Copper-Based Surfaces.

The mechanisms of bacterial contact killing induced by Cu surfaces were explored through high-resolution studies based on combinations of the focused ion beam (FIB), scanning transmission electron microscopy (STEM), high-resolution TEM, and nanoscale Fourier transform infrared spectroscopy (nano-FTIR) microscopy of individual bacterial cells of Gram-positive Bacillus subtilis in direct contact with Cu metal and Cu5Zn5Al1Sn surfaces after high-touch corrosion conditions. This approach permitted subcellular information to be extracted from the bioinorganic interface between a single bacterium and Cu/Cu5Zn5Al1Sn surfaces after complete contact killing. Early stages of interaction between individual bacteria and the metal/alloy surfaces include cell leakage of extracellular polymeric substances (EPSs) from the bacterium and changes in the metal/alloy surface composition upon adherence of bacteria. Three key observations responsible for Cu-induced contact killing include cell membrane damage, formation of nanosized copper-containing particles within the bacteria cell, and intracellular copper redox reactions. Direct evidence of cell membrane damage was observed upon contact with both Cu metal and Cu5Zn5Al1Sn surfaces. Cell membrane damage permits copper to enter into the cell interior through two possible routes, as small fragmentized Cu2O particles from the corrosion product layer and/or as released copper ions. This results in the presence of intracellular copper oxide nanoparticles inside the cell. The nanosized particles consist primarily of CuO with smaller amounts of Cu2O. The existence of two oxidation states of copper suggests that intracellular redox reactions play an important role. The nanoparticle formation can be regarded as a detoxification process of copper, which immobilizes copper ions via transformation processes within the bacteria into poorly soluble or even insoluble nanosized Cu structures. Similarly, the formation of primarily Cu(II) oxide nanoparticles could be a possible way for the bacteria to deactivate the toxic effects induced by copper ions via conversion of Cu(I) to Cu(II).

Comparison of the behavior of negative electrically charged E. coli and E. faecalis bacteria under electric field effect

The negative electrical charge of Escherichia coli and Enterococcus faecalis bacteria is an indication that they can be affected by an electric field. To show that the movements of electrically charged bacteria can be controlled, impedance spectroscopy method was used on a porous silicon (PS) structure with 60 % porosity and 7−12 μm pore size. The main purpose of this study is to use the electric charge of these two bacterial species to bring bacteria closer to the sensors with the help of an electric field, and to compare the behavior of these bacterial species in the process. The effect of bacterial contact on porous silicon surface impedance spectra was studied under electrical fields between 0 and 5 kV/cm at a constant bacterial concentration. It was observed that both bacteria can be approximated to the PS surface by the electric field effect. However, the shape and dimensional differences of these two bacterial species caused differences both in their movements in the electric field and in their settlement on the PS surface, and these differences were interpreted. In addition, similar experiments were repeated for dead bacteria and it was determined that the electric field control was not the same as for living bacteria.

Ag immobilized lignin-based PU coating: A promising candidate to promote the mechanical properties, thermal stability, and antibacterial property of paper packaging

A lignin-based PU coating was prepared for paper-based green packaging. Two representative diisocyanate were used to prepare the coatings. Due to the rigid aromatic, the physical properties of the TDI system reached the maximum below the lignin content of 40%. The HDI that contains flexible aliphatic chains alleviated the brittleness of coating, and it showed physical advantages when the lignin content was more than 50%. Owing to the high lignin content, the coating presented enhanced thermal stability. After coated with the lignin-based PU coatings, the dry tensile strength of coated paper was improved by 126%. Amazingly, the wet strength was increased from 0.31 to 12.6 MPa with an improvement nearly 40 times. Based on the coordination of lignin, Ag+ was introduced into the PU matrix, which imparted the coating with excellent antibacterial ability. The colony forming units of E. coli and S. aureus were both less than 1. However, no inhibition halo was observed, which indicated that the Ag was firmly anchored on the coating and the antibacterial ability is only available when the bacterial contact the coating surface. The lignin-based PU coating with favorable sustainability and properties shows great potential in paper-based green packaging fields.

In-vitro evaluation of bactericidal activity of antiseptics and disinfectants commonly used in healthcare settings

Introduction: Healthcare-associated infections are common problems found in healthcare systems in most of the countries. Proper use of antiseptics and disinfectants is useful in reducing the magnitude of such infections. The aim of this study was to evaluate the bactericidal effect of different concentrations of selected antiseptics and disinfectants. Methods: Bactericidal activity of different concentrations of antiseptics and disinfectants; isopropyl alcohol, povidone iodine, chlorhexidine gluconate, sodium hypochlorite, hypertonic saline, peracetic acid and mixture of 2-aminoethanol, dodecyl dimethyl ammonium chloride, potassium carbonate &amp; bis(3-aminopropyl) dodecylamine were evaluated against nine strains of American Type Culture Collections and 11 strains isolated from the hospitals. Bacterial suspensions were prepared equal to 0.5 McFarland turbidity standards and 100 μl of each was mixed with 3 ml of antiseptic/ disinfectant solution. After desired contact time (1 minute, 15 minutes and 24 hours), 20 μl of reaction mixer was transferred into 4 ml of sterile physiological saline, mixed well and 20 μl of solution was evenly spread throughout Muller Hinton agar/ blood agar plates. Growth control was done using 3 ml of distilled water instead of 3 ml of antiseptic/ disinfectant solution. All plates incubated at 35oC ± 2oC for 18 – 24 hours. Colonies were counted and reduction percentage was calculated. Results: All concentrations of isopropyl alcohol, povidone iodine, chorhexidine, sodium hypochlorite, peracetic acid and the mixture of 2-aminoethanol, didecyldimethylammonium chloride, potassium carbonate and bis(3-aminopropyl)dodecylamine showed 100% bactericidal activities against all tested bacterial strains in1-minute contact time. Bactericidal activity of hypertonic saline was varied against tested bacterial strains with higher bactericidal activity against Gram positive organisms than Gram negative organisms. Conclusions: Currently using concentrations of antiseptics and disinfectants evaluated in this study have 100% bactericidal activity other than hypertonic saline.

Azospirillum brasilense Sp245 triggers cytokinin signaling in root tips and improves biomass accumulation in Arabidopsis through canonical cytokinin receptors.

The plant growth promoting rhizobacterium Azospirillum brasilense Sp245 enhances biomass production in cereals and horticultural species and is an interesting model to study the physiology of the phytostimulation program. Although auxin production by Azospirillum appears to be critical for root architectural readjustments, the role of cytokinins in the growth promoting effects of Azospirillum remains unclear. Here, Arabidopsis thaliana seedlings were co-cultivated in vitro with A. brasilense Sp245 to assess whether direct contact of roots with bacterial colonies or exposure to the bacterial volatiles using divided Petri plates would affect biomass production and root organogenesis. Both interaction types increased root and shoot fresh weight but had contrasting effects on primary root length, lateral root formation and root hair development. Cell proliferation in root meristems analyzed with the CYCB1;1::GUS reporter decreased over time with direct contact, but was augmented by plant exposure to volatiles. Noteworthy, the expression of the cytokinin-inducible reporters TCS::GFP and ARR5::GUS increased in root tips in response to bacterial contact, without being affected by the volatiles. In A. thaliana having single (cre1-12, ahk2-2, ahk3-3), double (cre1-12/ahk2-2, cre1-12/ahk3-3, ahk2-2/ahk3-3) or triple (cre1-12/ahk2-2/ahk3-3) mutations in canonical cytokinin receptors, only the triple mutant had a marked effect on plant growth in response to A. brasilense. These results show that different mechanisms are elicited by A. brasilense, which influence the cytokinin-signaling pathway.

The IgGFc-binding protein FCGBP is secreted with all GDPH sequences cleaved but maintained by interfragment disulfide bonds

Mucus forms an important protective barrier that minimizes bacterial contact with the colonic epithelium. Intestinal mucus is organized in a complex network with several specific proteins, including the mucin-2 (MUC2) and the abundant IgGFc-binding protein, FCGBP. FCGBP is expressed in all intestinal goblet cells and is secreted into the mucus. It is comprised of repeated von Willebrand D (vWD) domain assemblies, most of which have a GDPH amino acid sequence that can be autocatalytically cleaved, as previously observed in the mucins MUC2 and mucin-5AC. However, the functions of FCGBP in the mucus are not understood. We show that all vWD domains of FCGBP with a GDPH sequence are cleaved and that these cleavages occur early during biosynthesis in the endoplasmic reticulum. All cleaved fragments, however, remain connected via a disulfide bond within each vWD domain. This cleavage generates a C-terminal-reactive Asp-anhydride that could react with other molecules, such as MUC2, but this was not observed. Quantitative analyses by MS showed that FCGBP was mainly soluble in chaotropic solutions, whereas MUC2 was insoluble, and most of the secreted FCGBP was not covalently bound to MUC2. Although FCGBP has been suggested to bind immunoglobulin G, we were unable to reproduce this binding in vitro using purified proteins. In conclusion, while the function of FCGBP is still unknown, our results suggest that it does not contribute to covalent crosslinking in the mucus, nor incorporate immunoglobulin G into mucus, instead the single disulfide bond linking each fragment could mediate controlled dissociation.

Moisture-associated skin damage (MASD): A best practice recommendation from Wund-D.A.CH.

Wund-D.A.CH., as the umbrella organization of German-speaking wound treatment societies, has currently developed a best practice recommendation for skin damage caused by body fluids, which is known as moisture-associated skin damage (MASD) in English-speaking countries. In this expert consensus, the diseases incontinence-associated dermatitis (IAD), intertriginous dermatitis, including intertrigo, gram-negative bacterial toe web infection and toxic contact dermatitis, including periwound and peristomal dermatitis are presented in a differentiated manner. A common feature of these clinical diseases is a deterioration of skin integrity due to prolonged exposure to body fluids such as urine, stool, sweat or wound exudate with associated physical-irritative and/or chemical irritation. In addition, other comorbidities and cofactors play an important role. The diagnosis of these interdisciplinary and interprofessionally relevant MASD is difficult in everyday clinical practice because there are currently no uniform definitions and many relevant differential diagnoses. Effective strategies for the prevention and therapy of these skin diseases are, for example, continence management, use of efficient, absorbent aids with good retention as well as consistent skin protection and adequate skin care. Another important aspect is the education of patients and relatives about the origin, treatment and prevention of MASD.

Antibacterial and antiviral N-halamine nanofibrous membranes with nanonet structure for bioprotective applications

The recent outbreak of a coronavirus disease (COVID-19) has posed a great threat to public health and financial system. Most current masks used to prevent the spread of COVID-19 are typically absence of biocidal properties. We designed a novel polymer, polystyrene grafted by 5, 5-dimethylhydantoin and trimethylamine (PSDT), which possesses halamine site and cationic quaternary ammonia salt site. Furthermore, PSDT/PU nanofiber@net membranes (PSDT/PU NNMs) were obtained by electrospinning technology. Our strategy enables inherent N-halamine and quaternary ammonia salt (QAS) group to be covalently integrated into membranes, realizing the efficient and stable biocidal properties. Meanwhile, the introduction of nanonets endows electrospun membranes with prominent air filtration performance. The resulting membranes exhibit integrated properties of high interception of fine particles (96.7%) and low pressure drop (95.4 Pa). Besides, chlorinated PSDT/PU nanofiber@net membranes (with active chlorine content of 0.60 wt% and quaternary ammonia salt content of 2.20 wt%) exhibited superior bactericidal (>99.9999%) and virucidal (>99.999%) efficiency in a short time (2 min), which enables chlorinated PSDT/PU NNMs to be served as the filtration material by providing bacterial interception (99.77%) and contact killing against pathogens. The successful synthesis of PSDT/PU NNMs provide innovative insights for exploring filtration materials in a nanonet and biocidal form.

Bioleaching of Pyrrhotite with Bacterial Adaptation and Biological Oxidation for Iron Recovery

The microbially mediated recovery of valuable metals contained in mining waste presents an economical alternative to conventional hydrometallurgical processes. In order to investigate the effect of bacterial adaptation and biological oxidation on bioleaching, the microbially mediated bioleaching of a pyrrhotite sample from mine waste, with indigenous bacteria existing in acid mine drainage, was studied. The indigenous bacteria were sub-cultured repeatedly for iron adaptation, and Acidithiobacillus ferrooxidans was identified as the dominant member of the microbial consortium. The point of zero charge (PZC) of pyrrhotite sampled from mine waste was determined as 3.0. The performance of bioleaching by contact and non-contact biological oxidation was compared by conducting bioleaching under different initial pH (pHini) conditions (2.8 and 3.2). Negatively charged bacteria could be attached onto the pyrrhotite, which has a positive surface charge at lower pHini (2.8) than the PZC (3.0). Bacteria attachment and corrosion pits on the surface of the pyrrhotite residues were observed at pHini of 2.8. Under bacteria-adapted conditions, the leaching concentration of Fe (44.2 mg/L) at pHini of 2.8 was 2.1 times greater than that (21.3 mg/L) at pHini of 3.2. Under non-adapted bacteria conditions, the extent of Fe leaching was not significantly different between the pHini of 2.8 and 3.2. This could be attributed to the fact that the adapted bacteria could more easily attach onto the pyrrhotite surfaces at pHini 2.8, allowing contact biological oxidation during the bioleaching experiments. We demonstrate here that the bioleaching of pyrrhotite could increase Fe recovery through bacterial adaptation and contact biological oxidation.

Rotatable central composite design versus artificial neural network for modeling biosorption of Cr6+ by the immobilized Pseudomonas alcaliphila NEWG-2

Heavy metals, including chromium, are associated with developed industrialization and technological processes, causing imbalanced ecosystems and severe health concerns. The current study is of supreme priority because there is no previous work that dealt with the modeling of the optimization of the biosorption process by the immobilized cells. The significant parameters (immobilized bacterial cells, contact time, and initial Cr6+ concentrations), affecting Cr6+ biosorption by immobilized Pseudomonas alcaliphila, was verified, using the Plackett–Burman matrix. For modeling the maximization of Cr6+ biosorption, a comparative approach was created between rotatable central composite design (RCCD) and artificial neural network (ANN) to choose the most fitted model that accurately predicts Cr6+ removal percent by immobilized cells. Experimental data of RCCD was employed to train a feed-forward multilayered perceptron ANN algorithm. The predictive competence of the ANN model was more precise than RCCD when forecasting the best appropriate wastewater treatment. After the biosorption, a new shiny large particle on the bead surface was noticed by the scanning electron microscopy, and an additional peak of Cr6+ was appeared by the energy dispersive X-ray analysis, confirming the role of the immobilized bacteria in the biosorption of Cr6+ ions.

Enhanced E. coli Capturing Efficacy Over Magnetic Dextrin–Cobalt Sulfide Nanohybrid as a Promising Water Disinfection System

The aim of this research is synthesis of a promising bacterial elimination nanohybrid for water disinfection. Hence dextrin, a carbohydrate polymer composed of linear α-(1,4)-linked d-glucose, is used as an intermediate to prepare Fe3O4–dextrin–CoS nanohybrid. At the first step magnetic dextrin was prepared by one step ultrasound assisted route using Fe2+ as iron source and dextrin as capping agent. At the second step functional groups of dextrin was employed to trap Co2+ ions for decorating CoS at the biosorbent structure through refluxing route. The structure of the magnetic dextrin and nanohybrid was studied by XRD, EDX, FESEM, TGA and zeta potential measurement. EDX and TGA results confirmed that the CoS has been decorated with high density onto magnetite dextrin structure. The prepared nanohybrid has been employed to capture Escherichia coli as a sample pathogen from water solution. Effective parameters on bacterial elimination, i.e., pH, contact time, nanohybrid dosage and presence of anions have been studied. Results showed that at pH of 3.5, contact time of 15 min and nanohybrid dosage of 20 mg E. coli capturing efficacy was more than 99% which confirmed high efficiency of the nanosystem in bacteria elimination from water solution.

Protective Face Mask Filter Capable of Inactivating SARS-CoV-2, and Methicillin-Resistant Staphylococcus aureus and Staphylococcus epidermidis.

Face masks have globally been accepted to be an effective protective tool to prevent bacterial and viral transmission, especially against indoor aerosol transmission. However, commercial face masks contain filters that are made of materials that are not capable of inactivating either SARS-CoV-2 or multidrug-resistant bacteria. Therefore, symptomatic and asymptomatic individuals can infect other people even if they wear them because some viable viral or bacterial loads can escape from the masks. Furthermore, viral or bacterial contact transmission can occur after touching the mask, which constitutes an increasing source of contaminated biological waste. Additionally, bacterial pathogens contribute to the SARS-CoV-2-mediated pneumonia disease complex, and their resistance to antibiotics in pneumonia treatment is increasing at an alarming rate. In this regard, herein, we report the development of a non-woven face mask filter fabricated with a biofunctional coating of benzalkonium chloride that is capable of inactivating more than 99% of SARS-CoV-2 particles in one minute of contact, and the life-threatening methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis (normalized antibacterial halos of 0.52 ± 0.04 and 0.72 ± 0.04, respectively). Nonetheless, despite the results obtained, further studies are needed to ensure the safety and correct use of this technology for the mass production and commercialization of this broad-spectrum antimicrobial face mask filter. Our novel protective non-woven face mask filter would be useful for many healthcare workers and researchers working in this urgent and challenging field.

A mathematical model and inference method for bacterial colonization in hospital units applied to active surveillance data for carbapenem-resistant enterobacteriaceae.

Widespread use of antibiotics has resulted in an increase in antimicrobial-resistant microorganisms. Although not all bacterial contact results in infection, patients can become asymptomatically colonized, increasing the risk of infection and pathogen transmission. Consequently, many institutions have begun active surveillance, but in non-research settings, the resulting data are often incomplete and may include non-random testing, making conventional epidemiological analysis problematic. We describe a mathematical model and inference method for in-hospital bacterial colonization and transmission of carbapenem-resistant Enterobacteriaceae that is tailored for analysis of active surveillance data with incomplete observations. The model and inference method make use of the full detailed state of the hospital unit, which takes into account the colonization status of each individual in the unit and not only the number of colonized patients at any given time. The inference method computes the exact likelihood of all possible histories consistent with partial observations (despite the exponential increase in possible states that can make likelihood calculation intractable for large hospital units), includes techniques to improve computational efficiency, is tested by computer simulation, and is applied to active surveillance data from a 13-bed rehabilitation unit in New York City. The inference method for exact likelihood calculation is applicable to other Markov models incorporating incomplete observations. The parameters that we identify are the patient–patient transmission rate, pre-existing colonization probability, and prior-to-new-patient transmission probability. Besides identifying the parameters, we predict the effects on the total prevalence (0.07 of the total colonized patient-days) of changing the parameters and estimate the increase in total prevalence attributable to patient–patient transmission (0.02) above the baseline pre-existing colonization (0.05). Simulations with a colonized versus uncolonized long-stay patient had 44% higher total prevalence, suggesting that the long-stay patient may have been a reservoir of transmission. High-priority interventions may include isolation of incoming colonized patients and repeated screening of long-stay patients.

Bactericidal effect of cationic hydrogels prepared from hydrophilic polymers

AbstractThis study investigated whether hydrogels comprising hydrophilic cationic polymers have similar bactericidal effects. Bacteria were seeded on hydrogels and agar and their viability was assessed with time. Cationic hydrogels displayed bactericidal effects upon long‐term bacterial contact. Furthermore, we assessed the areal density of cationic monomer unit of the cationic hydrogels, water content, and the initial elastic modulus. We examined correlations between each factor and bacterial death ratios; consequently, the bacterial death ratios were strongly correlated with the areal density of cationic hydrogel monomers. Elastic energy (Wel) generated at the cytomembrane ion‐binding region and the cationic hydrogel and the cytomembrane interfacial energy (Wf) were estimated; consequently, Wel exceeded Wf at higher contact areas. The cationic hydrogel may extract cytomembranes with a reasonable adsorption area. Therefore, cationic hydrogels may be used as probes for ultrasonic echo to sterilize medical equipment.

A Review on Production of Exopolysaccharide and Biofilm in Probiotics Like Lactobacilli and Methods of Analysis

Synthesis of exopolysaccharides (EPSs) by lactic acid bacteria is well known and the EPS produced by Lactobacillus has been highly regarded in recent years because of its unique physical and chemical application in the food and pharmaceutical industry. One of the capabilities of probiotics is the use of EPS to form a biofilm produced in tense environments. In this paper after a short description about EPS, the reason for production in bacterial cells, and its biosynthesis pathways; the capability of Lactobacilli for EPS and biofilm formation are reviewed. The chemical composition of EPS, its role in the bacterial life cycle as well as applications for humankind have been studied. Then the important components in biofilm formation are described and variable influencing on biofilm formation (surface, bacterial cell surface, contact time and environmental characteristics) are reviewed. The relationship between EPS and extracellular polymeric precursors as well as the relationship between biofilm formation and EPS production are mentioned. Finally, methods for quantification of carbohydrate (enzymatic, physical, chemical methods), biofilm formation and EPS extraction (Tallon and Bajpai methods) are reviewed and advantages of methods are compared. EPSs produced by probiotics is important due to the application as a thickening agent, emulsifier, heavy metal eliminator, and drug delivery carrier. Also, it has been considered for its anti-cancer, anti-viral, and cholesterol-lowering properties. So forming biofilm by some probiotics in simple and mixed culture are discussed, the relationship between EPS and biofilm production are discussed. When probiotics produce biofilm, they can be more tolerated in the processing of food production and in the gastrointestinal tract. So the efficacy of probiotic transfer may increase by a self-protection potency without any required encapsulation processing, solvent residue, time and energy consumption, etc. Also, identification and measurement methods are reviewed and compared.