Bacterial Reduction Rates Research Articles

One-pot fabrication of durable antibacterial cotton fabric coated with silver nanoparticles via carboxymethyl chitosan as a binder and stabilizer

In this article, durable antimicrobial cotton fabric was prepared by a one-pot modification process using a colloidal solution of silver nanoparticles (Ag NPs) stabilized by carboxymethyl chitosan (CMC). Due to coordination bonds between the amine groups of CMC and the Ag NPs and the ester bonds present between the carboxyl groups of CMC and the hydroxyl groups of cellulose, the Ag NPs were tightly immobilized onto the cotton fiber surface. As a result, the Ag NPs that were adhered on the cotton fabrics have uniform dispersion and small size, ranging from 10 nm to 80 nm. This provides the cotton fabric with remarkable and durable antibacterial activity against both S. aureus and E. coli. After 50 laundering cycles, the bacterial reduction rate (BR) for the modified cotton fabric remained over 94%. This method is simple, and it is particularly suitable for the industrial finishing process.

New insights on phage efficacy to control Aeromonas salmonicida in aquaculture systems: An in vitro preliminary study

A major source of financial loss for the fish-farming industry is the occurrence of bacterial infections. Phage therapy can be a useful alternative tool to conventional treatments to control bacterial infections in aquaculture. The promising results obtained with phage AS-A to control the agent of furunculosis, Aeromonas salmonicida, led us to isolate two new phages and evaluate their dynamics, in cocktails and individually, to control this pathogenic bacterium. Moreover, considering that in outdoor facilities aquaculture water is exposed to the natural variability of physical and chemical parameters, the influence of pH, salinity, temperature, solar radiation and UV radiation on phage AS-D stability was also evaluated in this study, in order to develop an effective phage therapy protocol. Phages were assigned to the family Myoviridae and revealed identical morphological characteristics. Phage AS-A presents a higher burst size and a shorter latent period, decreasing the concentration of A. salmonicida sooner than phages AS-D and AS-E. However, phage AS-D presented higher rate of bacterial reduction, inducing also less bacterial resistance. Bacterial control with the cocktails was higher, namely when phage AS-A was combined with one of the two new phages or with both, but the main difference in the bacterial control was in the treatment time. Phage cocktails decrease the concentration of A. salmonicida sooner than single suspensions. The use of phage cocktails, in general, decreased phage-resistant mutants. The survival of AS-D phage was mostly affected by sunlight exposure (decrease of 3 log PFU/mL after 12 h) and high temperatures (decrease of 3 PFU/mL after 21 days and of 7 log PFU/mL after 49 days at 37 °C, but no decrease after 21 and 49 days at 25 °C and decrease of only 1 and 2 log PFU/mL after 21 and 49 days, respectively, at ambient temperature). The high bacterial control and low development of phage-resistant bacterial clones suggest that these phages can be used to control the furunculosis in aquaculture. Nonetheless, the stability of the phages was affected by solar radiation, this can be overcome by the application of phages at the end of the day or at night.

Eco-friendly and Durable Antibacterial Cotton Fabrics Prepared with Polysulfopropylbetaine

A novel antibacterial agent polysulfopropylbetaine (PSPB) bearing carboxyl groups was synthesized and its application on cotton fabric to provide durable antibacterial property was also presented. The successful synthesis of PSPB and its immobilization onto the cotton fabric surface were verified by a series of tests including FTIR, 1H NMR, XPS and SEM. Viable cell counting method was employed to investigate antibacterial properties of the finished cotton fabrics. It was found that the cotton fabrics treated with PSPB were endowed with desirable antibacterial activity against both gram-negative bacteria Esherichia coli (E.coli, AATCC 6538) and gram-positive bacteria Staphylococcus aureus (S.aureus, AATCC 25922), with the bacterisotatic rates of 99.69 % and 99.95 %, respectively. Notably, the bacterial reduction rates still maintained over 90 % against both bacteria even after 50 consecutive laundering cycles. Moreover, tests concerning the hydrophilicity, air permeability, water vapor transmission, mechanical properties as well as thermal properties were carried out systematically. The experimental results indicated the hydrophilic performance, air permeability and moisture penetrability of the cotton fabrics finished with PSPB were improved greatly in spite of a slight reduction in thermal performance and little obvious influence on mechanical performance. The antibacterial cotton fabric has the potential to be applied in sportswear, underwear, household textiles, medical fields and much more.

Preparation of Copper Nanoparticles Coated Cotton Fabrics with Durable Antibacterial Properties

When copper nanoparticles (Cu NPs) were applied as an antimicrobial agent to finish cotton fabrics, there are two issues should be solved: the oxidization and the weak adsorbability onto cotton fiber surface. In the present work, we developed a new method that can achieve both immobilization and protection of the Cu NPs at the same time. As an effective binder, thioglycolic acid (TGA) was covalently linked to cotton fiber surface via an esterification with the hydroxyl groups of cellulose, then Cu NPs were introduced on the fabric surface in the presence of a protective reagent, citric acid. Due to the doubled stabilization acts of TGA and citric acid, the Cu NPs immobilized on the fabric surface showed an excellent antibacterial effect and outstanding laundering durability. Even after 50 consecutive laundering tests, the modified cotton fabrics still showed satisfactory antibacterial ability against both S. aureus and E. coli, which the bacterial reduction rates are all higher than 96 %. It is believed that this methodology has potential applications in a wide variety of textile productions such as sportswear, socks, and medical textiles.

소방추출액으로 염색한 키토산ᆞ나노실버 복합섬유 혼방 부직포의 염색성과 항균성

This study examines the dyeing properties, light fastness, washing fastness, and antibacterial ability of four kinds of non-woven fabrics dyed with an extracted solution from Caesalpinia sappan. L. These fabrics include: 100% cotton non-woven fabric, 95% cotton/5% chitosan-nano silver composite non-woven fabric, 90% cotton/10% chitosan-nano silver composite non-woven fabric, and 70% cotton/10% chitosan-nano silver composite non-woven fabric. Caesalpinia sappan. L. dyeing was conducted through a process of pre- and post-mordanting with alum, iron, which induced different colors on the dyed fabrics. The results show that, first, the K/S value of chitosan and nano silver composite non-woven fabrics was higher than that of the 100% cotton non-woven fabrics in the dyed condition with an extracted solution from Caesalpinia sappan. L., and second, mordants treatment influenced dyeability. K/S values of dyeing fabrics was recognized by the mordants treatment, especially iron. K/S values of pre-mordanting were higher than post-mordanting. Mordants and the mordants treatment method affected the dye uptake. In the case of Caesalpinia sappan. L., the light fastness was increased by the mordants treatment. The light fastness of the chitosan and nano silver composite non-woven fabrics was better than that of the 100% cotton non-woven fabrics. The washing fastness was not affected by mordants treatment and the chitosan-nano silver content increased from 5% to 30%. Regarding the results of antibacterial ability, the bacterial reduction rate of chitosan and nano silver composite non-woven fabrics and chitosan and nano silver composite non-woven fabrics dyed with Caesalpinia sappan. L. was more than 99.9% resistant to Staphylococcus aureus and Klebsiella pneumoniae.

Silver-based, single-sided antibacterial cotton fabrics with improved durability via an l-cysteine binding effect

The main purpose of this work was to obtain durable antimicrobial cotton textiles functionalized with l-cysteine (Cys) and silver nanoparticles (Ag NPs). Cys molecules were covalently linked to cotton fibers via esterification with the cellulose hydroxyl groups, and the Ag NPs tightly adhered to the fiber surface via coordination bonds with the Cys thiol groups. As a result, the Ag NPs coating on the cotton fabric showed an excellent antibacterial function with an outstanding laundering durability. Even after 90 consecutive laundering tests, the modified cotton fabrics still showed satisfactory bacterial reduction rates against both Staphylococcus aureus and Escherichia coli, and the rates were are all higher than 94%. These findings will allow for broader applications of antimicrobial cotton textiles with a decreased safety risk and lower environmental impact due to the Ag NPs.

Multifunctional Surface Modification of Mulberry Silk Fabric via PNIPAAm/Chitosan/PEO Nanofibers Coating and Cross-Linking Technology

Multifunctional mulberry silk fabrics with excellent temperature- and pH-sensitivity, antibacterial properties and permeability are successfully prepared by surface modification with PNIPAAm/chitosan/poly(ethylene oxide) nanofibers. The nanofibers deposited on the surface of mulberry silk fabric are produced by the electrospinning technique. The surface properties of mulberry silk fabrics were changed by coating process and glutaraldehyde vapor cross-linking technology. The PNIPAAm/chitosan/PEO nanofibers have good apparent morphology and uniform fiber diameter. The contact angle of modified mulberry silk obviously increases with the increasing temperature. The bacterial reduction rates of modification of mulberry silk against E. coli and S. aureus all reach above 80%. Permeability test results show that it can largely improve the poor permeability of coated fabric by intelligent nanofiber modification technology. The air permeability of temperature- and pH-sensitivity mulberry silk fabric modified with PNIPAAm/chitosan/PEO nanofibers, which has reached about 5.1 × 102 L/m2/s, is higher than that of the silk fabric coated with PNIPAAm/chitosan/PEO solution that reached 1.5 × 102 L/m2/s. The nanofibers coated with mulberry silk fabrics show outstanding temperature- and pH-sensitivity, antibacterial properties and permeability, and may be a potential application in medical care, intelligent materials and textiles.

Surface modification by carboxymethy chitosan via pad-dry-cure method for binding Ag NPs onto cotton fabric

To obtain durably antimicrobial cotton fabric, carboxymethyl chitosan (CMC) was covalently linked to cotton fibers via an esterification with the cellulose hydroxyl groups, and the silver nanoparticles (Ag NPs) were adhered to the fiber surface by the coordination bonds with the amino groups of CMC. The finished cotton fabrics have an excellent antibacterial function and outstanding laundering durability. Even after 50 consecutive laundering tests, the modified cotton fabrics still show satisfactory bacterial reduction rates (BR) against both S. aureus and E. coli, which are all higher than 94%. These findings allow for broader applications of antimicrobial cotton textiles with a decreased safety risk and lower environmental impact arise from the Ag NPs.

Does adding an instrument after root preparation with Reciproc® R25 increase bacterial reduction?

Aim:The aim of this study was to compare the bacterial reduction achieved with reciprocating instruments such as Reciproc® R25 (VDW GMBH, Munich, Germany) and Reciproc® R25 combined with rotary file Mtwo 40.04 (VDW GMBH) during root canal preparation.Materials and Methods:Fifty mesiobuccal root canals of maxillary molars were contaminated with Enterococcus faecalis broth culture and then an initial bacterial sample was collected from the root canal with paper cones and plated on brain–heart infusion agar. The root canals were divided into four groups as follows: Reciproc® R25 (n = 20) and Reciproc® R25 combined with Mtwo 40.04 instrument (n = 20). The negative controls consisted of five uncontaminated root canals and the positive control consisted of five contaminated roots that were not subjected to any decontamination procedure. Irrigation was performed using sodium chloride. After instrumentation, samples were collected with paper cones and the rate of bacterial reduction was calculated. Microbiological testing (colony-forming units [CFUs]) was performed to quantify the decontamination obtained by the proposed protocols. Statistical analysis was performed by paired t-test and analysis of variance test.Results:Both techniques significantly reduced the number of bacteria in the root canal (P < 0.05), with no significant difference among them (P > 0.05).Conclusion:The addition of the instrument Mtwo 40.04 after the root preparation with the instrument R25 does not improve its decontamination capability.

Antibacterial cotton fabric with enhanced durability prepared using L-cysteine and silver nanoparticles

L-cysteine (Cys) and silver nanoparticles (Ag NPs) were successfully linked onto the cotton fabric surfaces. The Cys molecules were covalently linked to the cotton fibers via esterification with the cellulose hydroxyl groups, and the Ag NPs tightly adhered to the fiber surface via coordination bonds with the Cys thiol groups. As a result, the Ag NPs coating on the cotton fabric showed an excellent antibacterial function with an outstanding laundering durability. The bacterial reduction rates (BR) efficiency reached 100 % for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). After 50 consecutive laundering cycles, the bacterial reduction rates (BR) against E. coli and S. aureus were maintained over 97 %. It has potential applications in a wide variety of fields such as sportswear, socks, and medical textile.

Antimicrobial Properties of Copper-Doped ZnO Coatings under Darkness and White Light Illumination.

We report the first antimicrobial study of transparent and robust Cu-doped ZnO coatings that displayed potent antimicrobial activity that resulted in bacterial (Escherichia coli) reduction below detection limits within 6 h of illumination via a white light source that is found in hospital environments. The same bacterial reduction rate was observed even under darkness for 4.0 atom % Cu-doped ZnO films thus providing an efficient 24 h disinfection. All films were produced via a novel, inexpensive, and easily scalable route and were also thoroughly analyzed for their material properties.

Synthesis of non-water soluble polymeric guanidine derivatives and application in preparation of antimicrobial regenerated cellulose

In order to prepare antimicrobial regenerated cellulose fibers from blended spinning solutions, three non-water soluble polymeric guanidine derivatives, polyhexamethylene guanidine dodecyl benzene sulfonate (PHGDBS), polyhexamethylene guanidine dodecyl sulfate (PHGDSA), and polyhexamethylene guanidine laurylsulfonate (PHGLSO) were synthesized. And the chemical structure of these agents was verified by element analysis, Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (1H-NMR). The antimicrobial activity of the three agents as well as cellulose films containing PHGDBS was also studied. The results showed that the compounds we prepared had strong properties against both bacterial and fungus, including Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Candida albicans, and Aspergillus niger. Moreover, it was found that three antimicrobial agents were insoluble in water but they can dissolve in solvents of cellulose such as 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and N-methylmorpholine-N-oxide monohydrate (NMMO·H2O). Meanwhile, it was also proved that [BMIM]Cl had little effect on the antimicrobial properties of these agents. The cellulose films containing only 1.0 wt% PHGDBS showed 99.94 % and 96.95 % bacterial reduction rates for S. aureus and E. coli, respectively. Moreover, still over 91 % of bacterial reduction was maintained after 15 laundering cycles. It suggests that the three agents will be suitable to prepare antimicrobial regenerated cellulose fibers or films.

Pharmacodynamic activity of fosfomycin simulating urinary concentrations achieved after a single 3-g oral dose versus Escherichia coli using an in vitro model

We assessed the activity of fosfomycin simulating urinary concentrations achieved after a single 3-g oral dose against Escherichia coli using an in vitro pharmacodynamic model. Eleven urinary isolates of E. coli were studied. Isolates were ESBL-producing or carbapenemase-producing. The in vitro pharmacodynamic model was inoculated with an inoculum of (~1×106cfu/mL). Fosfomycin was administered to simulate maximum free (ƒ) urine (U) concentrations and a t1/2 obtained after a standard single 3-g oral dose in healthy volunteers (ƒUmax, 4000mg/L; t1/2, 6h). Sampling was performed over 48h to assess the rate and extent of bacterial reduction as well as resistance selection. Complete bacterial eradication from the model was defined by no regrowth over the 48h study period. Fosfomycin MICs ranged from 1 to 4μg/mL for ESBL producers, while all 3 carbapenemase-producing E. coli demonstrated a fosfomycin MIC of 2μg/mL. Fosfomycin ƒT>MIC of 100% (ƒAUC0–24/MIC, ≥~7250) resulted in bacterial killing (reductions in log10 CFU assessed relative to the starting inoculum at 2, 4, 6, 12, 24, and 48h of ≥3.0) at each time-point versus all isolates of ESBL-producing and carbapenemase-producing E. coli. We conclude that fosfomycin urinary concentrations obtained after a single 3-g oral dose were bactericidal as early as 1h after dosing with complete bacterial eradication at all time-points over the 48h testing period against urinary isolates of E. coli (including MDR ESBL- and/or carbapenemase-producing strains). Our data help to explain the high (>90%) microbiological and clinical cure rates achieved with fosfomycin when used as a single 3-g oral dose to treat patients with acute uncomplicated cystitis.

온주밀감 미숙과의 열수추출물을 이용한 견직물의 염색 특성과 항미생물성

This study was aimed at optimizing the dyeing conditions of silk fabrics by using a hot-water extract from an unripe Citrus unshiu, and investigating the fastness and various microbial activities of the dyed fabrics depending on their surface hue/tone. The citrus extract powder was characterized by FT-IR and was employed to dye silk fabric at various conditions including temperature, duration, pHs, dye concentration, and mordanting. Finally, the dyed fabrics were evaluated for fastness and antimicrobial activity by bacterial reduction rate depending on the surface hue and tone of the dyed fabric. The citrus extract was identified as containing nobiletin, a type of flavonoid. The fabric was optimized for maximum dye uptake at a dyeing temperature of <TEX>$80^{\circ}C$</TEX>, dyeing duration of 60 min, and dye concentration of 600% owf. The dye uptake was found to be superior when the dye process was conducted at a pH of 3 and when post-mordanted with iron. The color gamut derived from dyeing with the citrus showed a total of five different tones including light grayish, grayish, dull, soft, and dark grayish with a single hue of yellow. Some of dyed fabrics showed good fastness in terms of dry-cleaning, perspiration, and rubbing. Antimicrobial activity was found to be excellent at all dye concentrations against Staphylococcus aureus.

Antibacterial Bombyx Mori silk fabric modified with reactive chitosan quaternary ammonium salt and its laundering durability

A new fiber-reactive chitosan derivative was synthesized in two steps from a chitosan of low molecular weight. First, a water-soluble chitosan derivative, N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (short for HTCC), was prepared by reacting chitosan with 2,3-epoxypropyltrimethylammonium chloride. Second, HTCC was further modified by reacting with N-(hydroxymethyl)-acrylamide to prepare a fiber-reactive chitosan derivative, O-methyl acrylamide quaternary ammonium salt of chitosan (short for NMA-HTCC), which can form covalent bonds with silk fiber under alkaline conditions. The chemical structure of NMA-HTCC was characterized by Fourier transform infrared spectrum (FTIR) and nuclear magnetic resonance (NMR). The substitution degree of HTCC and the double-bond content of NMA-HTCC were tested. Then NMA-HTCC was used for antibacterial finishing of Bombyx Mori silk fabric. The results showed that silk fabric treated with NMA-HTCC had a significantly improved antibacterial activity to Staphylococcus aureus and Escherichia coli, and the antibacterial activity of silk fabric finished by NMA-HTCC was much better than that finished by chitosan and HTCC. Bombyx Mori silk fabric modified with NMA-HTCC demonstrated excellent durable antibacterial activity, even after 50 repeated launderings, the bacterial reduction rate of silk fabric maintained over 95 %.

Durable antibacterial cotton modified by silver nanoparticles and chitosan derivative binder

This article focuses on the functional finishing of textiles using silver nanoparticles (AgNPs) and chitosan derivative binder, which was synthesized by a modification of chitosan using α-ketoglutaric acid. The binder covalently linked to cotton fabric via esterification of the hydroxyl groups on the cotton surface, and tightly adhered to surface of the AgNPs by coordination bonds. As a result, the coating of AgNPs on the cotton fabric showed excellent antibacterial property and laundering durability. After 30 consecutive laundering cycles, the Ag content on the fabrics decreased to 37.6 %, but the bacterial reduction rates against both S. aureus and E. coli were maintained over 95 %. It has potential applications in a wide variety of fields such as sportswear, socks, and medical textile.

A comparison of Fe(III) reduction rates between fresh and aged biogenic iron oxides (BIOS) by Shewanella putrefaciens CN32

This study compared the chemical and physical properties of freshwater biogenic iron oxides (BIOS) aged at 4°C for ~5years in the dark to simulate early diagenesis to previously published findings from fresh samples. In addition, the reactivity of aged BIOS in the presence of a well-characterized iron reducing bacterium, Shewanella putrefaciens CN32, was investigated. The composition and proportion of the iron minerals were examined using XRD, Fe k-edge EXAFS, and chemical extractions, and results were similar in both fresh and aged BIOS. Aged BIOS were dominated by 2-line ferrihydrite indicating that the intermixed bacterial cells and their exudates inhibited the transformation of 2-line ferrihydrite into crystalline phases. However, despite the similarity of mineralogy between aged and fresh BIOS, the rates of bacterial iron reduction in aged BIOS were found to be significantly lower than that of their fresh counterparts. Further characterization of aged BIOS by TEM revealed unique morphologies which were not previously observed in fresh BIOS. TEM also showed thickly coated bacterial exudates and presumably those formed as a result of continued accretion or aggregation of iron oxide nanoparticles. Aggregation of the iron oxide particles and subsequent decrease in solubility are likely responsible for the low rates of bacterial iron reduction in aged BIOS. Phase stability and aggregation in BIOS have important implications for the long-term reactivity of BIOS and the preservation of organic matter in the environment.

Fabrication and Super-Antibacterial Property of Nanosilver/Sericin/Poly(ethylene oxide) Nanofibers through Electrospinning-Combined Postdeposition Method

Nanosilver particle has been used in the nanofiber mats by mixing the nanosilver with the spinning solution for improving the antibacterial property. Although studies have shown that the antibacterial property of nanofiber mats gets increasing, the higher silver content and the larger released resistance of nanosilver from nanofiber mats are obvious. Here, the electrospinning-combined postdeposition method was used to prepare the nanosilver/sericin/poly(ethylene oxide) (Ag/SS/PEO) nanofiber mats and the bacterial reduction rates againstStaphylococcus aureus(S. aureus) andEscherichia coli(E. coli) were analyzed. We found that the Ag/SS/PEO nanofiber mats were excellent antibacterial properties at the lower silver content and the bacterial reduction rates againstS. aureusandE. coliall reached above 99.99%. Our data suggests that the antibacterial property can be improved by introducing the electrospinning-combined postdeposition method.

Preparation of Ag/HBP/PAN Nanofiber Web and Its Antimicrobial and Filtration Property

To widen the application of nanofibers web in the field of medical health materials, a new Ag/amino-terminated hyperbranched polymer (HBP)/polyacrylonitrile (PAN) nanofiber web with excellent antimicrobial activity and filtration property was produced with Ag/HBP dispersion solution and PAN nanofiber. Ag/HBP dispersion solution was prepared with HBP as reducer and stabilizer, and Ag/HBP/PAN nanofiber was prepared by modifying electrospun PAN nanofiber with Ag/HBP aqueous solution. The characterization results showed that spherical Ag nanoparticles were prepared and they had a narrow distribution in HBP aqueous solution. The results of Ag/HBP/PAN nanofiber characterized with SEM and EDS showed that the content of silver nanoparticles on the surface of PAN nanofiber was on the increase when the treating temperature rose. The bacterial reduction rates of HBP-treated PAN nanofiber againstS. aureusandE. coliwere about 89%, while those of the Ag/HBP/PAN nanofiber againstS. aureusandE. coliwere 99.9% and 99.96%, respectively, due to the cooperative effects from the amino groups in HBP and Ag nanoparticles. Moreover, the small pores and high porosity in Ag/HBP/PAN nanofiber web resulted in high filtration efficiency (99.9%) for removing smaller particles (0.1 μm~0.7 μm), which was much higher than that of the gauze mask.

Antimicrobial Activity of Different Molecular Weight Chitosans Produced from Shrimp Shells Against Different Plant Pathogens

The effect of ten chitosan products, obtained from shrimp shells, with a viscosity-average molecular weight ranged from 22 to 387 kDa on antimicrobial activity against different plant pathogenic bacteria and fungi, was investigated in vitro and compared with standard high molecular weight chitosan (846 kDa). The antibacterial activity was estimated by broth microdilution and agar dilution techniques as a minimum inhibitory concentration (MIC) against Agrobacterium tumefaciens, Erwinia carotovora, Corynebacterium fascians, and Pseudomonas solanacearum. The MIC was dependent on the bioassay test and the bacterial reduction rate increased with the decreasing of the molecular weight (MW). The antifungal activity against Alternaria alternata, Fusarium graminearum, F. oxysporum, F. solani, Phytophthora infestans, and Rhizoctonia solani was evaluated by mycelia radial growth technique. The effective concentration producing 50% mycelia growth inhibition (EC50) of the chitosans ranged from 480 to 3037 mg/L depending on the fungus tested and the MW of the chitosan products. F. graminearum, F. oxysporum, and R. solani were relatively less susceptible, while A. alternata, F. solani, and P. infestans were relatively more sensitive to the chitosan compounds. Keywords: Antibacterial and antifungal activities, chitosan products, molecular weight effect, plant pathogens.