Antibacterial effects of chitosan solution against Legionella pneumophila, Escherichia coli, and Staphylococcus aureus

Ultra-/Small Angle X-ray Scattering (USAXS/SAXS) and Static Light Scattering (SLS) Modeling as a Tool to Determine Structural Changes and Effect on Growth in S. epidermidis

Usually, to characterize bacterial cells' susceptibility to antimicrobials, basic microbiology techniques such as serial dilutions or disk assays are used. In this work, we present an approach focused on combining static light scattering (SLS) and ultra-/small angle X-ray scattering (USAXS/SAXS). This approach was used to support microbiology techniques, with the aim of understanding the structural changes caused to bacteria when they are exposed to different stresses like pH, oxidation, and surfactants. Using USAXS/SAXS and SLS data, we developed a detailed multiscale model for a Gram-positive bacterium, S. epidermidis, and we extracted information regarding changes in the overall size and cell thickness induced by different stresses (i.e., pH and hydrogen peroxide). Increasing the concentration of hydrogen peroxide leads to a progressive reduction in cell wall thickness. Moreover, the concomitant use of pH and hydrogen peroxide provides evidence for a synergy in inhibiting the S. epidermidis growth. These promising results will be used as a starting base to further investigate more complex formulations and improve/refine the data modeling of bacteria in the small angle scattering regime.

Effect of nano-zinc oxide and nano-chitosan particles on the shear bond strength of dental composites used as orthodontic adhesive

BACKGROUND

This study aimed to evaluate the effect of the combination of zinc oxide nanoparticles (NPs) and chitosan NPs on the shear bond strength (SBS) of composites used for orthodontic bonding.

METHODS

Four groups of composites (n = 10), containing 0%, 1%, 5%, and 10% w/w NP fillers, respectively, were used to bond brackets to the surfaces of 40 intact bovine incisors. After 1000 rounds of thermal cycling at 5°C-55°C, all specimens were mounted in acrylic blocks. The SBS was tested using a universal testing machine, and the adhesive remnant index scores were registered using a stereomicroscope. Data were statistically analyzed using a 1-way ANOVA and the Kruskal-Wallis test.

RESULTS

The highest value of mean SBS was found in the control group, and the lowest value was found in the group with composite containing 10% NPs. The adhesive remnant index did not differ significantly among the groups (P = 0.823).

CONCLUSIONS

Incorporation of 1% and 5% zinc oxide and chitosan NPs had no effect on the SBS of composite, and the obtained SBS values were similar to that of the control group.

Insights into Emergence of Antibiotic Resistance in Acid-Adapted Enterohaemorrhagic Escherichia coli

The emergence of multidrug-resistant pathogens presents a global challenge for treating and preventing disease spread through zoonotic transmission. The water and foodborne Enterohaemorrhagic Escherichia coli (EHEC) are capable of causing intestinal and systemic diseases. The root cause of the emergence of these strains is their metabolic adaptation to environmental stressors, especially acidic pH. Acid treatment is desired to kill pathogens, but the protective mechanisms employed by EHECs cross-protect against antimicrobial peptides and thus facilitate opportunities for survival and pathogenesis. In this review, we have discussed the correlation between acid tolerance and antibiotic resistance, highlighting the identification of novel targets for potential production of antimicrobial therapeutics. We have also summarized the molecular mechanisms used by acid-adapted EHECs, such as the two-component response systems mediating structural modifications, competitive inhibition, and efflux activation that facilitate cross-protection against antimicrobial compounds. Moving beyond the descriptive studies, this review highlights low pH stress as an emerging player in the development of cross-protection against antimicrobial agents. We have also described potential gene targets for innovative therapeutic approaches to overcome the risk of multidrug-resistant diseases in healthcare and industry.

Degradable hyaluronic acid/chitosan polyelectrolyte multilayers with marine fouling-release properties

Polysaccharide multilayers consisting of hyaluronic acid and chitosan were prepared by layer-by-layer assembly. To be used in seawater, the multilayers were crosslinked to a different degree using thermal or chemical methods. ATR-FTIR revealed different amide densities as a result of the crosslinking conditions. AFM showed that the crosslinking affected the roughness and swelling behavior of the coatings. The stability and degradability of the multilayers in aqueous environments were monitored with spectroscopic ellipsometry. The resistance of the coatings against non-specific protein adsorption was characterized by SPR spectroscopy. Settlement assays using Ulva linza zoospores and removal assays using the diatom Navicula incerta showed that the slowly degradable coatings were less prone to fouling than the strongly crosslinked ones. Thus, the coatings were a suitable model system to show that crosslinking the multilayers under mild conditions and equipping the coatings with controlled degradation rates enhances their antifouling and fouling-release properties against marine fouling organisms.

Antibacterial and antifungal impacts of combined silver, zinc oxide, and chitosan nanoparticles within tissue conditioners of complete dentures in vitro

BACKGROUND

Tissue conditioners are suitable places for colonization of microorganisms. A combination of tissue conditioners with antibacterial and antifungal materials inhibits the growth of microorganisms.

AIMS

Here, we aimed to investigate the antibacterial and antifungal effects of silver (Ag), zinc oxide (ZnO), and chitosan nanoparticles on tissue conditioners in complete dentures.

METHODS

The growth of four microorganisms in six different concentrations of Ag, ZnO, and chitosan nanoparticles was investigated after 24 and 48 h. Nanoparticles were synthesized using optical sequestration and approved by scanning electron microscope, x-ray diffraction, and infrared (FT-IR) methods. Nanoparticles were combined at 0.5, 0.25, and 0.25 ratios (chitosan, Ag, and ZnO, respectively) with 0.625, 1.25, 2.5, 5, 10, and 20 mass percentages. Tissue conditioners with nanoparticles were entered to test tubes containing microorganisms, and the growth rate was measured using the turbidity method by spectrophotometer after 24 and 48 h of incubation at 37 °C.

RESULTS

Growth inhibition of Candida albicans occurred at 2.5% concentration. However, the growth inhibition of Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa occurred at 5% after both 24 and 48 h. Also, the optimum nanoparticle concentration for Candida albicans was found to be 1.25% for both timings. On the other hand, the optimum nanoparticle concentration for Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa was 2.5% for both time scales.

CONCLUSIONS

The combination of Ag, ZnO, and chitosan nanoparticles inhibited the growth of fungi and bacteria in tissue conditioners. These nanoparticles inhibited the growth of fungi more effectively than bacteria.

Effect of TiO2 nanoparticles incorporation on antibacterial properties and shear bond strength of dental composite used in Orthodontics

Introduction:

Plaque accumulation and bond failure are drawbacks of orthodontic treatment, which requires composite for bonding of brackets. As the antimicrobial properties of TiO₂ nanoparticles (NPs) have been proven, the aim of this study was to evaluate the antimicrobial and mechanical properties of composite resins modified by the addition of TiO₂ NPs.

Methods:

Orthodontics composite containing 0%, 1%, 5% and 10% NPs were prepared. 180 composite disks were prepared for elution test, disk agar diffusion test and biofilm inhibition test to collect the counts of microorganisms on three days, measure the inhibition diameter and quantify the viable counts of colonies consequently. For shear bond strength (SBS) test, 48 intact bovine incisors were divided into four groups. Composites containing 0%, 1%, 5% and 10% NPs were used for bonding of bracket. The bracket/tooth SBS was measured by using an universal testing machine.

Results:

All concentration of TiO₂ NPs had a significant effect on creation and extension of inhibition zone. For S. mutans and S. sanguinis, all concentration of TiO₂ NPs caused reduction of the colony counts. Composite containing 10% TiO₂ NPs had significant effect on reduction of colony counts for S. mutans and S. sanguinis in all three days. The highest mean shear bond strength belonged to the control group, while the lowest value was seen in 10% NPs composite.

Conclusions:

Incorporating TiO₂ nanoparticles into composite resins confer antibacterial properties to adhesives, while the mean shear bond of composite containing 1% and 5% NPs still in an acceptable range.

Effectiveness of Chitosan Films Impregnated With Ciprofloxacin for the Prophylaxis of Osteomyelitis in Open Fractures: An Experimental Study in Rats

Background

The systemic antimicrobial prophylaxis is the standard treatment in the prevention of osteomyelitis after open fractures, with topical application of antimicrobials as an alternative due to their high concentrations at the site of the fracture, low systemic concentrations and fewer side effects.

Objectives

This study aimed to evaluate the effectiveness of prophylaxis of osteomyelitis through experimental model of open fractures with the use of chitosan films, whether or not impregnated with ciprofloxacin.

Materials and Methods

In this experimental study, 24 Holtzman rats were distributed into 4 groups of 6 rats each. The CT (control of treatment) group: an open fracture model treated with systemic antimicrobial; the IC (infection control) group: an open fracture untreated model; the C (chitosan) group: an open fracture model treated using a chitosan film; and the CA (chitosan with antimicrobial) group: an open fracture model treated using a chitosan film impregnated with antimicrobial. After 3 weeks the animals were killed by an overdose of anesthetic, and a fragment osseous was removed for histological and microbiological analysis. The comparisons between the groups considered significant values of P ≤ 0.05.

Results

In cultures of the CT group, there was less bacterial growth compared to the results of the cultures of the IC (P = 0.005), C (P = 0.005) and CA (P = 0.009) groups. The inflammation was lower in the CT group compared to the IC (P = 0.014), C (P = 0.001) and CA (P = 0.007) groups.

Conclusions

In this experimental model of open fracture, the chitosan film pure or impregnated with ciprofloxacin was not effective in the prophylaxis of osteomyelitis.

The effect of nanochitosans particles on Candida biofilm formation

Background and Purpose:

In people wearing dentures, the growth of various Candida species under the prosthesis leads to the formation of biofilm, which can play the role of a reservoir for Candida and other kinds of microbes. Since nano-chitosan particles can cause lasting antimicrobial activity, a more recent approach that utilizes acrylic resins with nano-chitosan particles is proposed. Therefore, we aimed to study the inhibitory effect of nano-chitosan particles on the biofilm formation of Candida species in acrylic resins.

Materials and Methods:

In this analytical in-vitro study, acrylic resins with nano-chitosan particles with concentrations of 0, 1%, 5%, and %10 were put adjacent to the suspension of Candida cells isolated from the individuals’ mouth and biofilm formation on resins was measured and compared. Finally, the data were analyzed using Kruskal-Wallis and Chi-square tests.

Results:

The observed differences between unmodified acrylic resin (control) and acrylic resin with nano-chitosan particles in terms of biofilm formation were significant (P<0.05) but no significant difference was found in the formation of biofilm species on resins.

Conclusion:

Biofilm formation of Candida species depends on acrylic resin type, in a way that by adding nano-chitosan particles to acrylic resins, biofilm formation of Candida species was significantly reduced. To decrease the organization of biofilm and denture stomatitis, the use of acrylics with nano-chitosan particles in producing dentures is recommended.

Waterborne microorganisms and biofilms related to hospital infections: strategies for prevention and control in healthcare facilities

Water is the main stimulus for the development of microorganisms, and its flow has an important role in the spreading of contaminants. In hospitals, the water distribution system requires special attention since it can be a source of pathogens, including those in the form of biofilms often correlated with resistance of microorganisms to various treatments. In this paper, information relevant to cases of nosocomial infections involving water circuits as a source of contaminants is compiled, with emphasis on the importance of microbiological control strategies to prevent the installation, spreading and growth of microorganisms in hospitals. An overview of the worldwide situation is provided, with emphasis on Brazilian hospitals. Different approaches normally used to control the occurrence of nosocomial infections due to waterborne contaminants are analyzed, and the use of the polysaccharide chitosan for this specific application is briefly discussed.

Chitosan coating to enhance the therapeutic efficacy of calcium sulfate-based antibiotic therapy in the treatment of chronic osteomyelitis

We demonstrate that coating calcium sulfate with deacetylated chitosan enhances the elution profile of daptomycin by prolonging the period during which high concentrations of antibiotic are released. Coatings reduced initial bolus release of daptomycin by a factor of 10 to approximately 1000 µg/ml, and levels remained above 100 µg/ml for up to 10 days. Chitosan-coated and uncoated calcium sulfate implants with and without 15% daptomycin were evaluated in an experimental model of staphylococcal osteomyelitis through bacteriology scores, radiology, histopathology, and Gram staining. Significant reduction in bacteriology scores was observed for implants containing daptomycin and coated with chitosan compared with all the other groups. We confirm that the use of chitosan-coated calcium sulfate beads for local antibiotic delivery can be correlated with an improved therapeutic outcome following surgical debridement in the treatment of chronic osteomyelitis.

Interaction of O-acylated chitosans with biomembrane models: probing the effects from hydrophobic interactions and hydrogen bonding

One of the major challenges in establishing the mechanisms responsible for the chitosan action in biomedical applications lies in the determination of the molecular-level interactions with the cell membrane. In this study, we probed hydrophobic interactions and H-bonding in experiments with O,O'-diacetylchitosan (DACT) and O,O'-dipropionylchitosan (DPPCT) incorporated into monolayers of distinct phospholipids, the zwitterionic dipalmitoyl phosphatidyl choline (DPPC), and the negatively charged dipalmitoyl phosphatidyl glycerol (DPPG) and dimyristoyl phosphatidic acid (DMPA). The importance of hydrophobic interactions was confirmed with the larger effects observed for DACT and DPPCT than for parent chitosan (Chi), particularly for the more hydrophobic DPPCT. Such larger effects were noted in surface pressure isotherms and elasticity of the monolayers. Since H-bonding is hampered for the chitosan derivatives, which have part of their hydroxyl groups shielded by O-acylation, these effects indicate that H-bonding does not play an important role in the chitosan-membrane interactions. Using polarization-modulated infrared reflection absorption (PM-IRRAS) spectroscopy, we found that the chitosan derivatives were incorporated into the hydrophobic chain of the phospholipids, even at high surface pressures comparable to those in a real cell membrane. Taken together, these results indicate that the chitosan derivatives containing hydrophobic moieties would probably be more efficient than parent chitosan as antimicrobial agents, where interaction with the cell membrane is crucial.

3D differentiation of neural stem cells in macroporous photopolymerizable hydrogel scaffolds

Neural stem/progenitor cells (NSPCs) are the stem cell of the adult central nervous system (CNS). These cells are able to differentiate into the major cell types found in the CNS (neurons, oligodendrocytes, astrocytes), thus NSPCs are the mechanism by which the adult CNS could potentially regenerate after injury or disorder. Microenviromental factors are critical for guiding NSPC differentiation and are thus important for neural tissue engineering. In this study, D-mannitol crystals were mixed with photocrosslinkable methacrylamide chitosan (MAC) as a porogen to enhance pore size during hydrogel formation. D-mannitol was admixed to MAC at 5, 10 and 20 wt% D-mannitol per total initial hydrogel weight. D-mannitol crystals were observed to dissolve and leave the scaffold within 1 hr. Quantification of resulting average pore sizes showed that D-mannitol addition resulted in larger average pore size (5 wt%, 4060±160 µm(2), 10 wt%, 6330±1160 µm(2), 20 wt%, 7600±1550 µm(2)) compared with controls (0 wt%, 3150±220 µm(2)). Oxygen diffusion studies demonstrated that larger average pore area resulted in enhanced oxygen diffusion through scaffolds. Finally, the differentiation responses of NSPCs to phenotypic differentiation conditions were studied for neurons, astrocytes and oligodendrocytes in hydrogels of varied porosity over 14 d. Quantification of total cell numbers at day 7 and 14, showed that cell numbers decreased with increased porosity and over the length of the culture. At day 14 immunohistochemistry quantification for primary cell types demonstrated significant differentiation to the desired cells types, and that total percentages of each cell type was greatest when scaffolds were more porous. These results suggest that larger pore sizes in MAC hydrogels effectively promote NSPC 3D differentiation.

Action of chitosan against Xanthomonas pathogenic bacteria isolated from Euphorbia pulcherrima

The antibacterial activity and mechanism of two kinds of chitosan were investigated against twelve Xanthomonas strains recovered from Euphorbia pulcherrima. Results indicated that both chitosans markedly inhibited bacterial growth based on OD loss. Furthermore, the release of DNA and RNA from three selected strains was increased by both chitosans. However, the release of intracellular proteins was inhibited by both chitosans at different concentration and incubation times, except chitosan A at 0.1 mg/mL for 0.5 h incubation and 0.2 mg/mL for 2.0 h incubation increased the release of proteins, indicating the complexity of the interaction and cell membranes, which was affected by incubation time, bacterial species, chitosan type and concentration. Transmission electron microscopic observations revealed that chitosan caused changes in protoplast concentration and surface morphology. In some cells, the membranes and walls were badly distorted and disrupted, while other cells were enveloped by a thick and compact ribbon-like layer. The contrary influence on cell morphology may explain the differential effect in the release of material. In addition, scanning electron microscope and biofilm formation test revealed that both chitosans removed biofilm biomass. Overall, this study showed that membrane and biofilm play an important role in the antibacterial mechanism of chitosan.

Growth rate inhibition of phytopathogenic fungi by characterized chitosans

The inhibitory effects of fifteen chitosans with different degrees of polymerization (DP) and different degrees of acetylation (FA) on the growth rates (GR) of four phytopathogenic fungi (Alternaria alternata, Botrytis cinerea, Penicillium expansum, and Rhizopus stolonifer) were examined using a 96-well microtiter plate and a microplate reader. The minimum inhibitory concentrations (MICs) of the chitosans ranged from 100 μg ×mL(-1) to 1,000 μg ×mL(-1) depending on the fungus tested and the DP and FA of the chitosan. The antifungal activity of the chitosans increased with decreasing FA. Chitosans with low FA and high DP showed the highest inhibitory activity against all four fungi. P. expansum and B. cinerea were relatively less susceptible while A. alternata and R. stolonifer were relatively more sensitive to the chitosan polymers. Scanning electron microscopy of fungi grown on culture media amended with chitosan revealed morphological changes.

Antioxidant, antifungal and antiviral activities of chitosan from the larvae of housefly, Musca domestica L

Antioxidant activity of the chitosan from the larvae of Musca domestica L. was evaluated in two different reactive oxygen species assays, and inhibitory effects against seven fungi were also tested. The results showed that the chitosan had scavenging activity for hydroxyl and superoxide radicals which were similar to that of ascorbic acid. Also the chitosan exhibited excellent antifungal activity, especially in the low concentration, it could significantly inhibit the growth of Rhizopus stolonifer. Besides, antiviral results demonstrated that the chitosan could effectively inhibit the infection of AcMNPV and BmNPV. These results suggested that the chitosan from the larvae of housefly could be effectively used as a natural antioxidant to protect the human body from free radicals and retard the progress of many chronic diseases. Furthermore, the chitosan with antiviral and antifungal activity might provide useful information for antiviral breeding technology of economic insect and development of plant pathological control.

Antibacterial characteristics and activity of water-soluble chitosan derivatives prepared by the Maillard reaction

The antibacterial activity of water-soluble chitosan derivatives prepared by Maillard reactions against Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Escherichia coli, Shigella dysenteriae, and Salmonella typhimurium was examined. Relatively high antibacterial activity against various microorganisms was noted for the chitosan-glucosamine derivative as compared to the acid-soluble chitosan. In addition, it was found that the susceptibility of the test organisms to the water-soluble chitosan derivative was higher in deionized water than in saline solution. Metal ions were also found to reduce the antibacterial activity of the water-soluble chitosan derivative on S. aureus. The marked increase in glucose level, protein content and lactate dehydrogenase (LDH) activity was observed in the cell supernatant of S. aureus exposed to the water-soluble chitosan derivative in deionized water. The results suggest that the water-soluble chitosan produced by Maillard reaction may be a promising commercial substitute for acid-soluble chitosan.

Characteration of Protein Loaded Chitosan Nanoparticles at Different pH Values

In this paper, the properties of chitosan (CS) nanoparticles (CS NPs) and Bovine Serum Albumin (BSA) loaded chitosan nanoparticles (BSA-loaded CS NPs) prepared with sodium tripolyphosphate (TPP) at different pH values were discussed. In addition, BSA encapsulation efficiency, zeta potentials and size of CS NPs and BSA-loaded CS NPs were characterized. The results indicated that sizes of CS NPs presented “V” change along with increase of pH values, while the size of BSA-loaded CS NPs showed “U” shape change. BSA encapsulation efficiency reached the biggest value when the pH value was 5.5. Zeta potentials of CS NPs and BSA-loaded CS NPs kept going down when the pH values were increasing, and positive potential of CS-loaded BSA CS NPs became higher than that of CS NPS when the pH value was more than 5.5. BSA-loaded CS NPs prepared at pH 5.5 exhibited regular and close to spherical in shape under transmission electron microscopy (TEM) sight.

Antibiotic-loaded chitosan film for infection prevention: A preliminary in vitro characterization

The growing infection rate by methicillin-resistant Staphylococcus aureus, especially with bone fracture fixation implants, is a major concern in extremity musculoskeletal wound treatment. This preliminary investigation evaluates the ability of chitosan film to be loaded with daptomycin and vancomycin in the operating room, in situ loading, and applied to musculoskeletal fixation devices to lessen or prevent infection. Films with 61, 71, and 80% degrees of deacetylation (DDA) made using lactic or acetic acid solvents were analyzed for their antibiotic uptake, elution, and activity along with film swelling ratio, ultimate tensile strength, Young's modulus, adhesive strength, and degradation. Chitosan films after 1 min of rehydration were able in a simulated, clinical setting to maintain mechanical integrity and adhesive strength to be applied to bone fracture fixation devices or implant surfaces. The film percent degradation increased with DDA increasing from 61 to 80%, but film degradation rate decreased in the presence of antibiotics. Eighty percent DDA chitosan films were optimal for absorbing and eluting antibiotics. Antibiotics eluted by the films were active against Staphylococcus aureus. These findings indicate that an 80% DDA chitosan film is potentially advantageous as a clinically adjunctive treatment in musculoskeletal injuries to lessen or prevent infections.

Antimicrobial activity of lactoferrin against foodborne pathogenic bacteria incorporated into edible chitosan film

The objectives of this research were to develop and characterize edible chitosan film containing lactoferrin as a natural antimicrobial agent, and to investigate the combination effects of lactoferrin with lysozyme in chitosan film against the growth of Escherichia coli O157:H7 and Listeria monocytogenes. Chitosan films containing lactoferrin, lysozyme, or nisin were fabricated, and the antimicrobial concentrations were 0.5, 1, or 2 mg in a circular disc of chitosan film. Three concentrations of lactoferrin or EDTA (0.28, 0.56, or 1.12 mg per disc) were also incorporated into the chitosan film containing lysozyme to investigate the combination effects of lactoferrin. The water barrier properties of the chitosan films containing lactoferrin were characterized. The antimicrobial activities against E. coli O157:H7 and L. monocytogenes were determined using the agar diffusion assay and cell count assay. The chitosan films containing lactoferrin less than 1 mg per disc did not alter the water vapor permeability of the chitosan film. Although the film containing lysozyme exhibited significant antimicrobial activity, the incorporation of lactoferrin alone into chitosan film did not exhibit significant antimicrobial activity against both E. coli O157:H7 and L. monocytogenes. However, the combination of lactoferrin with lysozyme-containing chitosan film significantly decreased the growth of E. coli O157:H7, exhibiting a comparable effect to that of the combination of EDTA with lysozyme (P < 0.05). Furthermore, the combination of lactoferrin with lysozyme in chitosan film exhibited greater reduction in the growth of L. monocytogenes than did the combination EDTA with lysozyme, resulting in an approximate 3-log reduction.