Efficacy of treating bacterial bioaerosols with weakly acidic hypochlorous water: A simulation chamber study

The COVID-19 pandemic highlighted the dangers of airborne transmission and the risks of pathogen-containing small airborne droplet inhalation as an infection route. As a pathogen control, Weakly Acidic Hypochlorous Water (WAHW) is used for surface disinfection. However, there are limited assessments of air disinfection by WAHW against airborne pathogens like bioaerosols. This was an empirical study evaluating the disinfection efficacy of WAHW in an atmospheric simulation chamber system against four selected model bacteria. The strains tested included Staphylococcus aureus (SA), Escherichia coli (EC), Pseudomonas aeruginosa (PA), and Pseudomonas aeruginosa (PAO1). Each bacterial solution was nebulized into the chamber system as the initial step, and bioaerosol was collected into the liquid medium by a bio-sampler for colony forming units (CFU) determination. Secondly, the nebulized bacterial bioaerosol was exposed to nebulized double distilled water (DDW) as the control and nebulized 150 ppm of WAHW as the experimental groups. After the 3 and 30-min reaction periods, the aerosol mixture inside the chamber was sampled in liquid media and then cultured on agar plates with different dilution factors to determine the CFU. Survival rates were calculated by a pre-exposed CFU value as a reference point. The use of WAHW decreased bacterial survival rates to 1.65-30.15% compared to the DDW control. PAO1 showed the highest survival rates and stability at 3 min was higher than 30 min in all experiments. Statistical analysis indicated that bacteria survival rates were significantly reduced compared to the controls. This work verifies the bactericidal effects against Gram-positive/negative bioaerosols of WAHW treatment. As WAHW contains chlorine in the acid solution, residual chlorine air concentration is a concern and the disinfection effect at different concentrations also requires investigation. Future studies should identify optimal times to minimize the treated time range and require measurements in a real environment.

Lignin nanoparticles from hydrotropic fractionation of giant reed and eucalypt: Structural elucidation and antibacterial properties

A hydrotropic solution of maleic acid (MA) was exploited to fractionate giant reed (AD) and eucalypt (EUC). The pre-treatment was successful for AD, while it was unsatisfactory for EUC, likely due to unoptimized reaction conditions. Interestingly, lignin nanoparticles (LNP) were produced via spontaneous aggregation following spent liquor dilution. LNP were studied by a plethora of analytical techniques, such as thermogravimetry, electron microscopy, and Nuclear Magnetic Resonance spectroscopy (NMR). Notwithstanding LNP from both AD and EUC showed similar thermal behaviour and morphology, a greater content of aliphatic hydroxyl, carboxyl, guaiacyl and p-hydroxyphenyl moieties was reported for AD-LNP, whereas EUC-LNP had a larger amount of syringyl groups and a higher S/G ratio. Also, the 1H-DOSY NMR indicated the lower size of AD-LNP. Moreover, the LNP were found to negatively impact on the development of several human or plant pathogens, and their bioactivity was related to the occurrence of guaiacyl and p-hydroxyphenyl moieties and a lower the LNP size. We therefore found that MA delignification allows both to achieve high delignification efficiency and to obtain LNP with promising antibacterial effect. Such LNP may help counteracting the antibiotics resistance and sustain the quest for finding sustainable agrochemicals.

Radical generation and bactericidal activity of nanobubbles produced by ultrasonic irradiation of carbonated water

Our previous study showed that nanobubbles (NBs) encapsulating CO2 gas have bactericidal activity due to reactive oxygen species (ROS) (Yamaguchi et al., 2020). Here, we report that bulk NBs encapsulating CO2 can be efficiently generated by ultrasonically irradiating carbonated water using a piezoelectric transducer with a frequency of 1.7 MHz. The generated NBs were less than 100 nm in size and had a lifetime of 500 h. Furthermore, generation of ROS in the NB suspension was investigated using electron spin resonance spectroscopy and fluorescence spectrometry. The main ROS was found to be the hydroxyl radical, which is consistent with our previous observations. The bactericidal activity lasted for at least one week. Furthermore, a mist generated by atomizing the NB suspension with ultrasonic waves was confirmed to have the same bactericidal activity as the suspension itself. We believe that the strong, persistent bactericidal activity and radical generation phenomenon are unique to NBs produced by ultrasonic irradiation of carbonated water. We propose that entrapped CO2 molecules strongly interact with water at the NB interface to weaken the interface, and high-pressure CO2 gas erupts from this weakened interface to generate ROS with bactericidal activity.

A C-type lectin-like receptor CD302 in yellow drum (Nibea albiflora) functioning in antibacterial activity and innate immune signaling

Molecular dissection of disease resistance against Vibrio harveyi infection in yellow drum at the genome-wide level uncovered a C-type lectin-like receptor cluster of differentiation CD302 (named as YdCD302) in our previous study. Here, the gene expression pattern of YdCD302 and its function in mediating the defense response to V. harveyi attack were investigated. Gene expression analysis demonstrated that YdCD302 was ubiquitously distributed in various tissues with the highest transcript abundance in liver. The YdCD302 protein exhibited agglutination and antibacterial activity against V. harveyi cells. Binding assay indicated that YdCD302 can physically interact with V. harveyi cells in a Ca2+-independent manner, and the interaction can activate reactive oxygen species (ROS) production in the bacterial cells to induce RecA/LexA-mediated cell death. After infection with V. harveyi, the expression of YdCD302 can be up-regulated significantly in the main immune organs of yellow drum and potentially further trigger the cytokines involved innate immunity. These findings provide insight into the genetic basis of the disease resistance trait in yellow drum and shed light on the functioning of the CD302 C-type lectin-like receptor in host-pathogen interactions. The molecular and functional characterization of YdCD302 is a significant step towards a better understanding of disease resistance mechanisms and the development of new strategies for disease control.

Effects of dietary Scutellaria baicalensis extract on growth performance, immune-related genes expression, and resistance against Vibrio parahaemolyticus in white shrimp (Litopenaeus vannamei)

In this study dietary Scutellaria baicalensis extract (SBE) was used to improve the shrimps' immune response and its resistance to Vibrio parahaemolyticus. SBE obtained by solid-liquid extraction (SLE) has shown stronger antibacterial activity against V. parahaemolyticus compared to extracts obtained through the pressurized liquid extraction (PLE) method. A stronger immune response, such as the production of reactive oxygen species and the induction of expression of immune genes in hemocytes was seen in the SBE (SLE) treated group in vitro. SBE (SLE) had better immune stimulation effects and bactericidal activity than SBE (PLE) and therefore was chosen for in vivo feeding trial. The group fed with 1% SBE showed a better growth performance after 2 weeks of the feeding trial, but the growth-promoting effects did not last until the end of the trial at week four. Higher SBE intake reduced shrimp resistance to V. parahaemolyticus on week two but showed better resistance than the control group on the fourth week. Gene expression assays were used to investigate contradictory responses of the SBE-fed groups to V. parahaemolyticus at different times. Most of the genes examined in the selected tissues were not significantly changed, suggesting that the higher mortality of shrimp fed with high dose of SBE was not due to suppression of immune-related genes at earlier time point. Collectively, the bioactivity of SBE is influenced by the extraction conditions. Higher dietary doses of SBE (1% and 5%) improved the resistance of the white shrimp to V. parahaemolyticus after a longer feeding period (week four), but caution should be taken when applying SBE in the feed since a vulnerable status (week two) was seen during the feeding trial.

Heat shock protein 70 is involved in polaprezinc driven cell protection against Helicobacter pylori-induced injury

Polaprezinc (PZ) plays a role in the protection of gastric mucosa and inhibiting Helicobacter pylori (H. pylori) growth in vitro. The objective of this study was to determine the protective effects of PZ on human gastric epithelial cells (GES-1) against H. pylori-induced damage, while also examining heat shock protein 70 (HSP70) as a potential underlying factor in this protection. Our findings revealed that PZ exerted bactericidal effects against H. pylori strains. We also observed that PZ mitigated the H. pylori-induced damage to GES-1 cells by increasing cell viability, reducing LDH release, and decreasing the secretion of pro-inflammatory factors such as MCP-1 and IL-6. Co-culturing PZ with GES-1 cells significantly up-regulated the GES-1 HSP70 expression in both a time and dose-dependent manner. Pre-incubating (for 12 h) or co-culturing (for 24 h) GES-1 cells with PZ reversed the down-regulation of HSP70 in GES-1 cells caused by H. pylori infection. However, when quercetin was used to inhibit the up-regulation of HSP70 in GES-1 cells, the protective effect of PZ on GES-1 cells was significantly reduced. Based on the results of this study, PZ exhibits a protective role on GES-1 cells against H. pylori injury, as well as a direct bactericidal effect on H. pylori. HSP70 is involved in the PZ-driven host cell protection against H. pylori injury. These findings provide insight into alternative strategies for H. pylori treatment.

Pepper growth promotion and biocontrol against Xanthomonas euvesicatoria by Bacillus cereus and Bacillus thuringiensis formulations

Background

Bacillus genus has been used in horticultural crops as a biocontrol agent against insect pests, microbial phytopathogens, and plant growth-promoting bacteria (PGPB), representing an alternative to agrochemicals. In particular, B. cereus (Bc) and B. thuringiensis (Bt) have been studied for their fungicidal and insecticidal activities. However, their use as biofertilizer formulations and biocontrol agents against phytopathogenic bacteria is limited.

Objective

To evaluate Bc and Bt formulations as PGPB and biocontrol agents against the bacterial spot agent Xanthomonas euvesicatoria (Xe) in greenhouse-grown chili peppers.

Methods

Bc and Bt isolates obtained from soil samples were identified and characterized using conventional biochemical and multiplex PCR identification methods. Bioassays to determine Bc and Bt isolates potential as PGPB were evaluated on chili pepper seedlings in seedbeds. In addition, formulations based on Bc (F-BC26 and F-BC08) and Bt (F-BT24) strains were assessed as biofertilizers on pepper, under controlled conditions. Furthermore, in vitro antagonism assays were performed by confronting Bc and Bt isolate formulations against Xe isolates in direct (foliage) and indirect (resistance induction) phytopathogen biocontrol assays on pepper plants, which were grown under controlled conditions for 15 d after formulations treatment.

Results

Isolates were identified as Bc and Bt. Formulations significantly improved pepper growth in seedbeds and pots, whereas in vitro bioassays demonstrated the bactericidal effect of Bc and Bt strains against Xe isolates. Furthermore, assays showed significant plant protection by F-BC26, F-BC08, and F-BT24 formulated strains against Xe.

Conclusion

Results indicated that F-BT24 and F-BC26 isolates formulations promoted pepper growth and protected it against Xanthomonas euvesicatoria.

The bactericidal effect of far-UVC on ESBL-producing Escherichia coli

Because extended-spectrum beta-lactamase (ESBL) infections can cause life-threatening disease and effective treatments need to be developed, we examined the bactericidal effect of far-ultraviolet C (far-UVC) light therapy on ESBL-producing Escherichia coli (E. coli). The bactericidal effect on 2 types of ESBL-producing E. coli was the same as that on the wild strain although the results of drug resistance tests varied among these strains. We believe that irradiation with far-UVC is effective in preventing infection by ESBL-producing E. coli in health care settings.

New options for bloodstream infections caused by colistin- or ceftazidime/avibactam-resistant Klebsiella pneumoniae

Concerns regarding carbapenem-resistant Klebsiella pneumoniae (CR-Kp), especially in bloodstream infections (BSIs), are continuing to increase worldwide. Several novel agents with activity against BSI CR-Kp have been approved or are in late-stage clinical development. In this study, the antibacterial effects of ceftazidime/avibactam (CZA), aztreonam/avibactam (AZA), meropenem/vaborbactam (MEV), imipenem-cilastatin/relebactam (ICR) and eravacycline (ERV) against three colistin-resistant CR-Kp (COLR-Kp) and four CZA-resistant CR-Kp (CZAR-Kp) were tested by time-kill assay. Klebsiella pneumoniae ATCC® BAA-1705TM was used as a control strain. Two COLR-Kp isolates carried the blaKPC-2 gene and four CAZR-Kp isolates carried metallo-β-lactamase genes. The results revealed that ERV resulted in re-growth of seven tested isolates. CZA and MEV showed a bactericidal effect against isolates harbouring blaKPC-2. ICR reduced the population of six isolates to >5 log10 CFU/mL compared with the initial count. AZA showed a bactericidal effect (>5 log10 CFU/mL) against seven isolates and a bacteriostatic effect (<3 log10 CFU/mL) against one CZAR-Kp isolate. Therefore, AZA and ICR are effective therapeutic candidates for COLR-Kp and CZAR-Kp isolates.

Evaluation of bactericidal effects of ultraviolet light C irradiation on cariogenic bacteria: An in vitro study

Backgrounds

Ultraviolet light C (UVL-C) irradiation has demonstrated an antimicrobial action against various pathogens. This study aimed to evaluate the bactericidal effect of UVL-C irradiation against cariogenic oral bacteria (Streptococcus mutans) in single layers and colonies grown on solid surfaces.

Methods

Two different experiments were performed. In the first experiment, a single layer of Streptococcus mutans bacteria on agar plates was exposed to UVL-C irradiation at energies from 0 to 21 mWs/cm². The second experiment was conducted to inhibit viability of bacterial colonies on solid surfaces. The samples were derived from saliva from a patient where bacteria were grown on plastic strips and then exposed to UVL-C. The highest energy was 1050 mWs/cm².

Results

Exposure to 21 mWs/cm² was bactericidal in single layers of Streptococcus mutans. The result for bacterial colonies on solid surfaces indicated only a bacteriostatic effect, even at energies of 1050 mWs/cm².

Conclusions

Ultraviolet light C exhibits bactericidal effects on single layers of Streptococcus mutans but has a limited effect on bacterial colonies in a biofilm. It is a matter of debate whether these in vitro results would have the same effect in clinical setting.

Eu3+-doped layered gadolinium hydroxides as drug carriers and their bactericidal behavior

Layered rare earth hydroxides (LRHs) due to outstanding photoluminescence (PL) properties and anion exchangeability are extensively reported in multiple fields. In this work, the drug-loaded and bactericidal behaviors of Eu³⁺-doped layered gadolinium hydroxides (LGdHs:Eu) as optical carriers were explored through intercalation and release of cephalexin (CE). In the intercalation state, the PL intensity of CE--LGdHs:Eu obviously decreased because of the quenching effect of CE-. And the PL intensity of LGdHs:Eu was restored with the release of CE- ions in phosphate buffer solutions (PBS). A significant functional relationship between the drug releasing amount and PL intensity ratio was found, providing a novel optical method to specify the drug dosage. And CE--LGdHs:Eu showed the excellent bactericidal properties in both in vivo and in vitro experiments.

Antibacterial effect of silver diamine fluoride and potassium iodide against E. faecalis, A. naeslundii and P. micra

Background

The aim of this study was to determine in vitro the bactericidal potential of 38% silver diamine fluoride (SDF) alone, potassium iodide (PI) alone, and the two in combination (SDF + PI) against three bacterial species commonly found in root canal samples (Enterococcus faecalis, Actinomyces naeslundii and Parvimonas micra).

Methods

The potential bactericidal rates for SDF, PI and SDF + PI against E. faecalis, A. naeslundii and P. micra were calculated as reduction of bacteria colony forming units.

Results

The bactericidal potential of SDF was at 99.97–100% against E. faecalis and 100% against A. naeslundii and P. micra. SDF + PI showed a 100% bactericidal effect against P. micra, 99.89–99.98% against E. faecalis and 99.98–100% against A. naeslundii. The bactericidal effect of PI was 99.51–99.98% against E. faecalis, 99.27–99.95% against A. naeslundii and 99.93–100% against P. micra. The differences between controls and bacteria exposed to the antibacterial agents were statistically significant (p < 0.05).

Conclusions

SDF had an effective bactericidal effect against the examined bacteria. However, the limitations of this in vitro study do not allow a recommendation of the employment of these solutions as root canal irrigants. Additional investigations are necessary to assess their endodontic clinical applicability.

Hemocyte extracellular traps of Manila clam Ruditapes philippinarum: Production characteristics and antibacterial effects

Extracellular traps (ETs) have been found to be an important strategy of mammals to immobilize and kill invading microorganisms. In the present study, we observed the formation of ETs in the hemocytes of marine mollusks Ruditapes philippinarum in response to challenge from bacteria Vibrio anguillarum, and examined the potential factors and signaling pathways underling this process. We detected an increase of reactive oxygen species (ROS) and myeloperoxidase (MPO) production during ETosis, accompanied by significantly up-regulated expression of ROS-related and MPO genes. The suppression of ETs structures by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor (diphenyleneiodonium chloride, DPI) and MPO inhibitor (aminobenzoic acid hydrazide, ABAH) further confirmed the essential roles ROS and MPO played in ETosis. Furthermore, ET production could be inhibited by phosphotidylinsitol-3-kinase (PI3K) inhibitor (LY294002) and extracellular regulated protein kinase (ERK) inhibitor (U0126), suggesting the idea that both the PI3K and ERK pathways were suggested to function during ETosis. In addition, the ETosis process was accompanied by enhancement of glycolysis-related enzymatic activities, e.g., pyruvate kinase (PK) and hexokinase (HK), and over-expression of the glycolysis-related genes, e.g., PK, HK and glucose transport protein (GLUT), indicating high involvement of glycolysis in the ETosis process. Furthermore, our scanning electron microscopy (SEM) observation and antibacterial activities test successfully showed the patterns how clam ETs entrapped and killed the invading V. anguillarum. Taken together, our results revealed that ETosis with bactericidal effect increased ROS, MPO and glycolysis level and carried out in a ROS-, MPO-, PI3K-ERK-dependent manner.

Characterization, modes of action, and application of a novel broad-spectrum bacteriocin BM1300 produced by Lactobacillus crustorum MN047

Bacteriocins are ribosomally synthesized peptides with antibacterial activity against food-borne pathogenic bacteria that cause spoilage, possessing important potential for use as a natural preservative in the food industry. The novel bacteriocin BM1300 produced by Lactobacillus crustorum MN047 was identified after purification in this study. It displayed broad-spectrum antibacterial activity against some selected Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) values of BM1300 against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 were 13.4 μg/mL and 6.7 μg/mL, respectively. Moreover, BM1300 showed excellent thermal (between 60 and 120 °C), pH (2-11), and chemical (Tween-40, Tween-80, Triton X-100, and EDTA) stabilities. Time-kill curves revealed that BM1300 exhibited bactericidal activity against S. aureus and E. coli. The scanning and transmission electron microscopy indicated that BM1300 acted by disrupting the cell membrane integrity and increasing cell membrane permeabilization of indicator bacteria. The disruption of cell membrane integrity caused by BM1300 was further demonstrated by the uptake of propidium iodide (PI) and the release of intracellular lactate dehydrogenase (LDH) and nucleic acid and proteins. Moreover, BM1300 affected cell cycle distribution to exert antibacterial activity collaboratively. Meanwhile, BM1300 inhibited the growth of S. aureus and E. coli of beef meat and improved the microbiological quality of beef meat. These findings place BM1300 as a potential biopreservative in the food industry.

The Effects of Peptidoglycan on the Photocatalytic Bactericidal Activity of Titanium Dioxide

For the elucidation of the mechanism underlying the photocatalytic bactericidal activity of titanium dioxide (TiO₂), we focused on the peptidoglycan layer, a component of the bacterial cell wall. The effect of this layer on the photocatalytic bactericidal activity of TiO₂ was evaluated by determining the survival rates of Lactobacillus plantarum (intact cells) and its protoplast cells. Mesoplasma florum, which does not originally possess the peptidoglycan layer, was also used. Our results revealed that the survival rates of the intact cells were lower than those of the protoplast cells. In addition, there was no significance between the survival rates of M. florum cells and the protoplast cells of L. plantarum. It was suggested that the presence of the peptidoglycan layer increases the bactericidal effect by the photocatalysis.

A synergistic bactericidal effect of low-frequency and low-intensity ultrasound combined with levofloxacin-loaded PLGA nanoparticles on M. smegmatis in macrophages

Purpose

Tuberculosis (TB) is a highly infectious disease caused by Mycobacterium tuberculosis (Mtb), which often parasites in macrophages. This study is performed to investigate the bactericidal effect and underlying mechanisms of low-frequency and low-intensity ultrasound (LFLIU) combined with levofloxacin-loaded PLGA nanoparticles (LEV-NPs) on M. smegmatis (a surrogate of Mtb) in macrophages.

Methods and results

The LEV-NPs were prepared using a double emulsification method. The average diameter, zeta potential, polydispersity index, morphology, and drug release efficiency in vitro of the LEV-NPs were investigated. M. smegmatis in macrophages was treated using the LEV-NPs combined with 42 kHz ultrasound irradiation at an intensity of 0.13 W/cm² for 10 min. The results showed that ultrasound significantly promoted the phagocytosis of nanoparticles by macrophages (P < 0.05). In addition, further ultrasound combined with the LEV-NPs promoted the production of reactive oxygen species (ROS) in macrophage, and the apoptosis rate of the macrophages was significantly higher than that of the control (P < 0.05). The transmission electronic microscope showed that the cell wall of M. smegmatis was ruptured, the cell structure was incomplete, and the bacteria received severe damage in the ultrasound combined with the LEV-NPs group. Activity assays showed that ultrasound combined with the LEV-NPs exhibited a tenfold higher antibacterial activity against M. smegmatis residing inside macrophages compared with the free drug.

Conclusion

These data demonstrated that ultrasound combined with LEV-NPs has great potential as a therapeutic agent for TB.

The bactericidal efficacy of femtosecond laser-based therapy on the most common infectious bacterial pathogens in chronic wounds: an in vitro study

We investigated the influence of femtosecond laser irradiation on the growth of the two most common infectious bacterial pathogens in wounds; Staphylococcus aureus and Pseudomonas aeruginosa as an attempt to validate optimum parameters for a laser-based bactericidal modality to be used clinically. Bacterial cultures were exposed to femtosecond laser irradiation at different wavelengths, exposure times, and laser powers. The source of femtosecond laser was INSPIRE HF100 laser system, Spectra-Physics, which is pumped by a mode-locked femtosecond Ti: sapphire laser MAI TAI HP, Spectra-Physics. After irradiation, bacterial cells' survival was monitored by observing the clear zones of inhibition in cultured agar plates. Results for all strains indicated that the exposure to femtosecond laser irradiation with a wavelength ranging from ultraviolet (λ > 350 nm) to blue laser light (λ < 480 nm), for a period above 20 min and with a power density of ≈ 0.063 W/cm², was enough to inhibit both bacterial pathogens with the results maintained for 1 week following irradiation.

Chlorinated plastoquinone analogs that inhibit Staphylococcus epidermidis and Candida albicans growth

Infectious diseases are the significant global health problem because of drug resistance to most classes of antimicrobials. Interest is growing in the development of new antimicrobials in pharmaceutical discovery. For that reason, the urgency for scientists to find and/or develop new important molecules is needed. Many natural active molecules that exhibit various biological activities have been isolated from the nature. For the present research, a new selected set of aminobenzoquinones, denoted as plastoquinone analogs (PQ1-24), was employed for their in vitro antimicrobial potential in a panel of seven bacterial strains (three Gram-positive and four Gram-negative bacteria) and three fungi. The results revealed PQ analogs with specific activity against bacteria including Staphylococcus epidermidis and pathogenic fungi, including Candida albicans. PQ8 containing methoxy group at the ortho position on the phenylamino moiety exhibited the highest growth inhibition against S. epidermidis with a minimum inhibitory concentration of 9.76 μg/mL. The antifungal profile of all PQ analogs indicated that five analogs (while PQ1, PQ8, PQ9, PQ11, and PQ18 were effective against Candida albicans, PQ1 and PQ18 were effective against Candida tropicalis) have potent antifungal activity. Selected analogs, PQ1 and PQ18, were studied for biofilm evaluation and time-kill kinetic study for better understanding.

Attenuation of Fe(III)-reducing bacteria during table fluctuation of groundwater containing Fe2

Groundwater table fluctuation during natural and anthropogenic processes can facilitate the interaction between oxygen (O₂) from the unsaturated zone and ferrous iron (Fe²⁺) from the saturated zone. In light of previous findings that Fe(III)-reducing bacteria can be killed by the reactive oxidants produced from Fe²⁺ oxidation under static oxic conditions, we hypothesize that Fe(III)-reducing bacteria will be attenuated during groundwater table fluctuations. To test this hypothesis, this study explored the variations of cell numbers of Shewanella oneidensis strain MR-1 (MR-1), a typical strain of Fe(III)-reducing bacteria, together with dissolved oxygen (DO) and Fe²⁺, at different points during controlled groundwater table fluctuations in a sand column. The results showed that, during the rise of the water table, O₂ in the pore air was entrapped by the deoxygenated groundwater, and Fe²⁺ in the groundwater was oxidized by the entrapped O₂. In this process, 1.40-2.42 orders of magnitude of viable MR-1 cells were killed at different points in the column. Further investigation proposed that the death of MR-1 is caused by the production of intracellular reactive oxidants, such as O₂•^- and OH•, from the oxidation of adsorbed/absorbed Fe²⁺ instead of by bulk reactive oxidants, such as OH• and Fe(IV), produced from the oxidation of aqueous Fe²⁺. The findings here provide new insights for Fe biogeochemical cycling in the redox-dynamic zone.

The effect of water hardness on the toxicity of graphene oxide to bacteria in synthetic surface waters

Graphene oxide (GO), used in a wide variety of applications, is increasingly being introduced into aquatic environments; this situation calls for research on GO toxicity to assess its environmental risks. In this study, the toxic effect of GO to E.coli was studied before and after its aggregation equilibrium in the synthetic surface waters (the soft water, moderately hard water, and hard water) to reveal the effects of GO aggregation and solution hardness. The cytotoxicity of GO increased with increasing solution hardness while decreased after GO aggregation. The 3 h 50% inhibitory concentration (IC₅₀) values of dispersed GO in the soft water, moderately hard water, and hard water were 12.2 ± 2.2, 8.5 ± 1.5, and 4.0 ± 1.0 mg/L, respectively. After 24 h shaking (aggregation equilibrium) in the synthetic surface waters, the dispersed GO aggregated and the 3 h IC₅₀ values of GO aggregates in the three synthetic waters were 40.3 ± 6.9, 15.9 ±  2.2, and 7.5 ± 1.5 mg/L, respectively. The dispersed GO sheets wrapped E. coli cells and cut the cell membrane, resulting in the disruption of cell membrane and the cell inactivation. With increasing water hardness, the heteroaggregation between GO sheets/aggregates and E. coli cells was enhanced, resulting in the increase of toxic effect. The GO aggregates could also entrap E.coli cells while exhibited limited effect on cell membrane disruption without sharp edges, thereby causing the lower toxic effect compared with the dispersed GO sheets. These outcomes shed new light on the assessment of ecological effects of GO.

Ultrasonic exposure parameters screening in permeability of mycobacterium smegmatis cytoderm induced by cavitation based on artificial neural network identification

The low intensity ultrasound has been adopted by researchers to enhance the bactericidal effect against bacteria in vitro and in vivo. Although the mechanism is not completely understood, one dominant opinion is that the permeability increases because of acoustic cavitation. However, the relationship between ultrasonic exposure parameters and cavitation effects is not definitely addressed. In this paper, by establishing a modified artificial neural network (ANN) model between ultrasonic parameters and cavitation effects, the cavitation effects can be predicted and inversely the direction for choosing parameters can be given despite of different ultrasonic systems. Compared with the generic model, the computational results obtained by modified model are more close to experimental results with low calculation cost. It means that as an efficient solution, the validity of the new model has been proved. Although the research is of preliminary stage, the new method may have great value and significance because of reducing the experimental expense. The next step of this research is to explore an optimization method to obtain the most suitable parameters based on this identification model. We hope it can give a guideline for future applications in ultrasonic therapy.

A facile ultrasonic-aided biosynthesis of ZnO nanoparticles using Vaccinium arctostaphylos L. leaf extract and its antidiabetic, antibacterial, and oxidative activity evaluation

The synthesis of nanoparticles often result in the generation of harmful chemical pollutants. As such, many researchers have focused on developing green processes, which include the biosynthesis. In this research, ZnO nanoparticles were prepared using the leaf extract of whortleberry (Vaccinium arctostaphylos L.) via a simple ultrasonic-assisted method. The morphology, crystal size and structure, surface, thermal, and optical properties of the bio-mediated ZnO sample (ZnO_ext) were analyzed and compared with that produced without incorporating the extract (ZnO_chem). The ZnO samples were evaluated for their antidiabetic, antibacterial, as well as their sono- and photo-catalytic performances. Initially, the samples were intraperitoneal injected to alloxan-diabetic rats to examine their treatment efficiency in terms of effects on fasting blood glucose, insulin, cholesterol, high-density lipoprotein, and total triglyceride levels. The ZnO_ext showed significantly higher efficiency for improving the health status of alloxan-diabetic rats in contrast with other tested treatments, vis. ZnO_chem, insulin, and only leaf extract. In addition, both the ZnO samples were assessed against gram-negative and gram-positive bacteria and through sono- and photo-catalytic processes for removing rhodamine B, respectively. The results of this study indicated that not only the ZnO_ext sample was pollution free, it also exhibited higher potentials for treating diabetic rats, bacterial decontamination, and also oxidative removal of organic compounds under the influences of ultrasound and UV irradiations when compared with ZnO_chem sample.

Characterization of CuO-bacterial cellulose nanohybrids fabricated by in-situ and ex-situ impregnation methods

The aim of this research was to fabricate CuO-bacterial cellulose (BC) nanohybrids by two in-situ synthesis methods including sonochemical and precipitation methods. The ex-situ synthesized nanohybrid was also prepared by immersing BC pellicles in commercial CuO dispersion. FT-IR analysis confirmed the formation of real nanohybrid by occurring new interactions between CuO-NPs and BC. XRD results approved no disruption effect of nanohybrid formation on the crystallinity index of BC nanofibers. FE-SEM results indicated the formation of small sized NPs attached to the inner space of BC network at in-situ synthesized nanohybrids. But agglomerated NPs precipitated on the surface of BC layer was observed for ex-situ synthesized sample. In spite of higher loading capacity of ex-situ method, the in-situ synthesized nanohybrids exhibited lower release rate of NPs into the water. The antibacterial activity of ex-situ synthesized nanohybrid against S.aureus and E.coli bacteria was more than both of in-situ synthesized samples.

Comparison of high and low molecular weight chitosan as in-vitro boosting agent for photodynamic therapy against Helicobacter pylori using methylene blue and endoscopic light

BACKGROUND

We reported in a previous study that photodynamic therapy (PDT) of Helicobacter pylori(H. pylori) could potentiate bactericidal effect by adding chitosan. As a next step, we compared the bactericidal effects of low molecular weight (LMW) combined with Photodynamic Therapy to high molecular weight (HMW) chitosan.

METHOD

To perform PDT to kill H. pylori, we used endoscopic light as light source, methylene blue (MB) as a photosensitizer and chitosan (310-375, 50-190 kDa). We evaluated bacterial removal rate and its membrane damage by ethidium bromide monoazide PCR method (EMA q-PCR). 8-oxo-2'-dexoyguanosine by ELISA was measured for oxidative stress.

RESULTS

At a chitosan concentration of ≤0.05%, the killing effect did not differ between the two molecular weights, and 100% bacterial removal rate was observed at a light energy ≥ 6.23 mJ/cm² powers under 0.02% MB. After 15 min irradiation, LMW chitosan with high concentration of MB (0.004%) showed highest killing effects, which were consistent with the results of EMA q-PCR but not with the level of 8-OHdG. Bactericidal effects of LMW chitosan plus PDT using 0.002 and 0.004% MB for 15 min irradiation were significantly higher than those using HMW chitosan plus PDT.

CONCLUSION

We found that PDT using methylene blue with LMW chitosan to kill H. pylori exerted greater bactericidal effects through bacterial membrane damage than PDT with HMW chitosan. These results suggest that it would be better to choose LMW chitosan to enhance the effect of PDT for clinical application, even at a very low concentration of PS.

Slightly acidic electrolyzed water disrupts biofilms and effectively disinfects Pseudomonas aeruginosa

INTRODUCTION

Biofilm formation is an important issue in the healthcare industry, but conventional disinfectants are not effective for biofilms formed in the hospital environment and on medical instruments. In this study, aim at determine the effectiveness of slightly acidic electrolyzed water (SAEW) on biofilm removal and the disinfection of biofilm-forming Pseudomonas aeruginosa.

METHODS

Mucoid and non-mucoid strains were used for biofilm formation. Biofilms were incubated with SAEW and the reduction in biofilm volume was determined based on the optical density. Furthermore, to investigate the mechanism underlying the effects of SAEW, a biofilm was produced with alginate and structural changes in response to incubation with SAEW were observed by fluorescence microscopy. The minimum bactericidal chlorine concentration of SAEW for P. aeruginosa cells was evaluated.

RESULTS

The amounts of alginate and biofilm decreased by 99.9% and 56.8% immersed by 30 ppm of SAEW at 25 °C for 10 min. The effectiveness of SAEW increased as the temperature increased, and the biofilm volume was reduced by 85.4% at 45 °C. Furthermore, 30 ppm SAEW completely disinfected P. aeruginosa in the biofilm, even for immersion at 15 °C for 5 min.

CONCLUSION

Our results suggest that SAEW, a low-cost and safe chlorine disinfectant, is a useful disinfectant for biofilm-forming bacteria.

Physical, morphological, antimicrobial and release properties of novel MgO-bacterial cellulose nanohybrids prepared by in-situ and ex-situ methods

MgO-bacterial cellulose (BC) nanohybrids were fabricated by in-situ synthesis of nanoparticles (NPs) within BC network via two methods (the sonochemical and wet chemical). The ex-situ synthesized nanohybrid was prepared by immersing BC pellicles in the commercial MgO dispersion. The occurrence of new interactions between MgO-NPs and nanofibers was approved by Fourier transform infrared spectroscopy (FT-IR) spectra. X-ray diffraction (XRD) results indicated that the crystallinity index of nanofibers decreased after the formation of nanohybrid by the sonochemical in-situ method. The results of the field emission scanning electron microscopy (FE-SEM) indicated the formation of the small-sized NPs attached to the inner space of BC network at the in-situ synthesized nanohybrids. However, the agglomerated NPs precipitated on the surface of BC layer were observed for the ex-situ synthesized sample. The loading capacity of the ex-situ method was higher than that of the in-situ methods; but after 24 h, MgO releasing for in-situ and ex-situ synthesized nanohybrids was recorded about 16% and 28%, respectively. The antibacterial activity of the ex-situ synthesized nanohybrid against S. aureus and E. coli bacteria was more than those of both in-situ synthesized samples.

Effects of in vitro gastrointestinal digestion and colonic fermentation on a rosemary (Rosmarinus officinalis L) extract rich in rosmarinic acid

The potential phytochemical losses occurring throughout the sequential steps of in-vitro gastrointestinal digestion and colonic fermentation of a rosemary aqueous extract were investigated. Crude (CE), digested (DE) and fermented (FE) extracts were characterized in terms of their phenolic profile and biological activities. Rosmarinic acid was the phytochemical that underwent the most significate transformation during digestion and fermentation, which amounted to 60% compared to the 26% degradation of the total phenolics. Overall, the simulated digestion step decreased the antioxidant activity estimated by DPPH, ABTS, FRAP, ORAC and TBARS assays. Both CE and DE did not present antiproliferative potential, however, FE exhibited a pronounced cytotoxic activity (GI50 = 116 µg/mL) against HeLa cells. CE and DE showed to be moderate inhibitors of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S. aureus (MSSA), S. aureus, Listeria monocytogenes, whilst the FE acted as a moderate inhibitor of MRSA and MSSA.

Proteomic changes in EHEC O157:H7 under catechin intervention

Catechin exhibits antimicrobial activity against various microorganisms, such as EHEC O157:H7. This study reports the bactericidal effect of catechin on EHEC O157:H7 in simulated human gastrointestinal environment and the underlying antibacterial mechanism. Bacteriostasis test results showed that the minimum bactericidal concentration of catechin for EHEC O157:H7 was 5 g/L. The bactericidal effect of catechin in the gastrointestinal juice became more significant with increased culture time, and catechin exhibited a synergistic effect with bile salt in inhibiting EHEC O157:H7. Changes in the profile of protein expression in EHEC O157:H7 in response to catechin intervention were investigated. Two-dimensional electrophoresis identified 34 proteins with significantly altered expression. A total of 2 and 12 proteins were upregulated and downregulated, respectively. However, 20 proteins disappeared. No new protein was expressed compared with the control. Hence, catechin intervention resulted in diverse changes in the expression of proteins associated with cell structure and genetic information processing. Catechin could cause the disappearance of certain proteins or the destruction of certain peptides. These processes lead to the inhibition of EHEC O157: H7 cells.

Maternal intrapartum antibiotic treatment continues to exert a bactericidal effect on the umbilical cord and peripheral venous blood of newborn infants

AIM

It is unclear whether maternal intrapartum antibiotic treatment (IAT) continues to exert a bactericidal effect on common pathogens in neonates. We studied the in vitro bactericidal effect of IAT on the cord and peripheral venous blood of newborn infants.

METHODS

Umbilical cord and peripheral venous blood from newborn infants born at Kaplan Medical Center, Israel, from April to October 2014 were studied for serum bactericidal titres against Group B Streptococcus (GBS) and Escherichia coli (E. coli) strains. We studied 60 samples of umbilical cord blood and 18 samples of peripheral venous blood from 60 newborn infants whose mothers received IAT. The controls were 10 samples of cord blood from mothers without IAT.

RESULTS

Cord blood exerted a bactericidal effect against 98% of GBS isolates but only 8% of E.coli isolates. Peripheral blood exerted a bactericidal effect against GBS in 94% of cases, but not against E. coli. No bactericidal effect was seen in the blood from the controls.

CONCLUSION

We found a continued bactericidal effect of umbilical cord blood and neonatal peripheral blood from newborn infants of IAT-treated mothers, mainly against GBS, but rarely against E. Coli. These findings may assist clinicians treating at-risk infants exposed to IAT.

Capsular bag irrigation using 0.025% povidone-iodine in balanced salt solution PLUS for the treatment of postoperative endophthalmitis

We examined the effectiveness and adverse events of using balanced salt solution (BSS) PLUS containing 0.025% povidone-iodine, a non-oculotoxic concentration, for capsular bag irrigation in a case of endophthalmitis mainly involving the anterior chamber. A 57-year-old female underwent cataract surgery and developed hypopyon on day 3 after surgery, with mainly anterior chamber inflammation. The capsular bag was irrigated with BSS PLUS containing 0.025% povidone-iodine. Gram-negative rods were detected from the anterior chamber fluid. Post-procedural visual acuity was 24/20. In a case, endophthalmitis was resolved and there were no adverse events. With the recent increase in multidrug-resistant bacteria, use of 0.025% povidone-iodine in BSS PLUS for anterior chamber irrigation is expected to be useful.

Experimental study on the influence of low-frequency and low-intensity ultrasound on the permeability of the Mycobacterium smegmatis cytoderm and potentiation with levofloxacin

Tuberculosis is an infectious disease caused by the bacterium M. tuberculosis. The aim of this study was to investigate the bactericidal effect and underlying mechanisms of low-frequency and low-intensity ultrasound combined with levofloxacin treatment against M. smegmatis (a surrogate of M. tuberculosis). As part of this study, M. smegmatis was continuously irradiated with low frequency ultrasound (42kHz) using several different doses whereby both intensity (0.138, 0.190 and 0.329W/cm²) and exposure time (5, 15 and 20min) were varied. Flow cytometric analyses revealed that the permeability of M. smegmatis increased following ultrasound exposure. The survival rate, structure and morphology of bacteria in the lower-dose (I_SATA=0.138W/cm² for 5min) ultrasound group displayed no significant differences upon comparison with the untreated group. However, the survival rate of bacteria was significantly reduced and the bacterial structure was damaged in the higher-dose (I_SATA=0.329W/cm² for 20min) ultrasound group. Ultrasound irradiation (0.138W/cm²) was subsequently applied to M. smegmatis in combination with levofloxacin treatment for 5min. The results demonstrated that the bactericidal effect of ultrasonic irradiation combined with levofloxacin is higher compared to ultrasound alone or levofloxacin alone.

In vitro antibacterial activity of fosfomycin combined with other antimicrobials against KPC-producing Klebsiella pneumoniae

The increasing prevalence of KPC-producing Klebsiella pneumoniae (KPC-Kp) strains poses a serious threat to patients. Therapeutic options are limited to colistin, fosfomycin, tigecycline and selected aminoglycosides. Although the combination of fosfomycin with other antimicrobials is recommended, data regarding possible synergistic activity in vitro and in vivo appear inconsistent. Here we report that five drug combinations (fosfomycin combined with imipenem, ertapenem, tigecycline, colistin or amikacin) had a significant additive effect against 136 KPC-Kp strains in an in vitro chequerboard assay. In addition, time-kill assays revealed that fosfomycin enhanced the bactericidal activity of the five other antimicrobial agents. Moreover, owing to its persistent bactericidal effect, the combination of fosfomycin plus amikacin is an effective therapeutic candidate for infections by KPC-producing organisms.

Enhancement of bactericidal activity against group B streptococci with reduced penicillin susceptibility by uptake of gentamicin into cells resulting from combination with β-lactam antibiotics

Combined effects of penicillin (PEN) and gentamicin (GM) against Streptococcus agalactiae, i.e. group B streptococci (GBS), are known to occur, but synergy has not been examined in strains with reduced PEN susceptibility, usually called PEN-resistant GBS (PRGBS). We therefore studied combined effects of β-lactam antibiotics and GM in cultures of 3 PRGBS strains belonging to serotype Ia or III that were isolated from Japanese adults with invasive infections. Killing kinetics were determined at 2-h intervals from 0 to 6 h after exposure to ampicillin (AMP) or cefotaxime (CTX) combined with GM. Concentrations of GM in bacterial cells were measured by liquid chromatography-tandem mass spectrometry. Morphologic changes after exposure to agents were observed by transmission electron microscopy. Combining AMP or CTX with GM synergistically increased bactericidal activity against PRGBS beyond that of either β-lactam alone. GM concentrations in bacterial cells increased 5- to 8-fold when GM was combined with AMP or CTX. Electron microscopically, bacterial cells showed aggregates of strands and ribosomal damage most likely reflecting enhanced GM uptake into bacterial cells. This uptake appeared to result from cell wall damage caused by β-lactam antibiotics. This study suggests that combining β-lactam antibiotics with GM might be useful against severe PRGBS infection.

An exception to the rule "no association between antibiotic resistance and decreased disinfectant microbicidal efficacy": Orthophthalaldehyde (OPA) and Pseudomonas aeruginosa isolated from ICU and paraplegic patients

BACKGROUND

Antibiotic resistance and decreased susceptibility to disinfectants are not usually associated in microorganisms, but we have found an exception to this rule: P. aeruginosa versus orthophthalaldehyde (OPA).

METHODS

Bactericidal effect of OPA was measured at 10 minutes on endodoncy files contaminated with an ATCC strain (control) or 206 strains of P. aeruginosa recently isolated from 206 ICU and paraplegic patients in a tertiary university hospital, in two consecutive years.

RESULTS

Differences in bactericidal effect of OPA were found between the strains isolated each year (decreased susceptibility in the first period), but in both years the statistical differences (p < 0.05) were maintained according to whether the strains were "susceptible" to antibiotics, "resistant" (to one family of antibiotics) or "multi-resistant" (resistant to more than one family of antibiotics), exhibiting a reduction in their OPA susceptibility in parallel to an increase of their antibiotic resistance. In contrast, there were no differences depending on the type of sample (sputum, urine, faeces, pharynx) or of patient (paraplegic or ICU: adult, newborn, burn). Finally we selected 15 strains with an OPA effect below 3.5 log10 at 10 minutes and repeated the study with an OPA exposure of 15 minutes. In these conditions OPA showed a total bactericidal effect on these P. aeruginosa strains.

CONCLUSIONS

There was an association between antibiotic resistance and decreased OPA susceptibility. This normally does not require an increase in disinfection time, but, for endoscope disinfection or instruments from colonized/infected patients with resistant/multiresistant P. aeruginosa, we consider it better to use 15 min of OPA. Regular tests (e.g., once every 12 months) with germ-carriers, should be performed to assess ecological changes in susceptibility to high level disinfectants and must include not only ATCC strains, but also recently isolated microorganisms with different antibiotic sensitivities (susceptible, resistant and multi-resistant).

Ag loaded WO3 nanoplates for efficient photocatalytic degradation of sulfanilamide and their bactericidal effect under visible light irradiation

Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO3 nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO3 nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO3 nanoplates using a photo-reduction method to generate WO3/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO3 and WO3/Ag composites was conducted under visible light irradiation. The results show that WO3/Ag composites performed much better than pure WO3 where the highest removal rate was 96.2% in 5h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO3, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2h under visible light irradiation for all three WO3/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO3/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process.

Nanostructured poly (lactic acid) electrospun fiber with high loadings of TiO2 nanoparticles: Insights into bactericidal activity and cell viability

Researchers have been looking for modifying surfaces of polymeric biomaterials approved by FDA to obtain nanofeatures and bactericidal properties. If modified, it would be very interesting because the antibiotic administration could be reduced and, therefore, the bacterial resistance. Here, we report the electrospinning of poly (lactic acid) (PLA) with high loadings of titanium dioxide nanoparticles (TiO₂, 1-5wt%) and their bactericidal properties. TiO₂ nanoparticles have been recognized for a long time for their antibacterial, low cost and self-cleaning properties. However, their ability to reduce bacteria functions when used in polymers has not been well studied to date. In this context, we aimed here to generate nanostructured PLA electrospun fiber-TiO₂ nanoparticle composites for further evaluation of their bactericidal activity and cell viability. TEM and SEM micrographs revealed the successful electrospinning of PLA/TiO₂ and the generation of polymer-TiO₂ nanostructures. When increasing the TiO₂ concentration, we observed a proportional increase in the nanoparticle density along the fiber and surface. The nanostructured PLA/TiO₂ nanofibers showed no mammalian cell toxicity and, most importantly, possessed bactericidal activity with higher TiO₂ loads. Such results suggest that the present PLA electrospun fiber-TiO₂ nanoparticle composites should be further studied for a wide range of biomedical applications.

The bactericidal effect of an ionizer under low concentration of ozone

BACKGROUND

Several mechanisms have been suggested for the bactericidal action of ionizers including electrical phenomena, effects of negative and positive ions and electrostatic repulsion. Negative and positive ions have indeed been shown to have bactericidal effects. In addition, since ozone is generated along with ions, these may contribute to the bacterial killing. In this study, we used a newly developed ionizer, which generates a relatively low concentration of ozone, to determine whether its effect on bacterial cells were due to ions or ozone, and, if ions, how the ions exerted their effects.

RESULTS

The effect of ions on bacterial killing was compared with that of the ozone produced using an ion trap to remove the ions. The ionizer had the ability to kill the bacteria, and ion capture dramatically reduced its bactericidal effect, indicating that the ozone generated had little or no bactericidal effect under these conditions, and the ions produced were responsible for almost all the bacterial killing. Operation of the ionizer increased the level of 8-oxo-dG, a marker of oxidative DNA damage, and decreased aconitase activity, which is known to be sensitive to ROS. The ionizer further affected the adenylate energy charge of bacterial cells. Removal of the ions with the ion trap greatly reduced all these effects.

CONCLUSION

These results indicate that negative and positive ions generated by the ionizer are responsible for inducing oxidative stress and so reducing bacterial survival.

Microbicidal effects of plain soap vs triclocarban-based antibacterial soap

The aim of this study was to determine the bactericidal effects of plain and antibacterial soap. The bactericidal effects of plain and antibacterial soap containing 0.3% triclocarban were examined against 10 Gram-positive and 10 Gram-negative bacterial strains after exposure at 22°C and 40°C for 20 s. Gram-negative bacteria were more susceptible to both soaps than Gram-positive bacteria. However, with one exception (Enterococcus faecalis ATCC 19433 at 40°C), there was no significant difference between the effects of medicated and non-medicated soap at either temperature. Triclocarban in soap does not lead to a meaningful reduction in bacterial levels during use.

Bactericidal Effect of Strong Acid Electrolyzed Water against Flow Enterococcus faecalis Biofilms

INTRODUCTION

This study evaluated the bactericidal effect of strong acid electrolyzed water (SAEW) against flow Enterococcus faecalis biofilm and its potential application as a root canal irrigant.

METHODS

Flow E. faecalis biofilms were generated under a constant shear flow in a microfluidic system. For comparison, static E. faecalis biofilms were generated under a static condition on coverslip surfaces. Both the flow and static E. faecalis biofilms were treated with SAEW. Sodium hypochlorite (NaOCl, 5.25%) and normal saline (0.9%) were included as the controls. Bacterial reductions were evaluated using confocal laser scanning microscopy and the cell count method. Morphological changes of bacterial cells were observed using scanning electron microscopy.

RESULTS

The confocal laser scanning microscopic and cell count results showed that SAEW had a bactericidal effect similar to that of 5.25% NaOCl against both the flow and static E. faecalis biofilms. The scanning electron microscopic results showed that smooth, consecutive, and bright bacteria surfaces became rough, shrunken, and even lysed after treated with SAEW, similar to those in the NaOCl group.

CONCLUSIONS

SAEW had an effective bactericidal effect against both the flow and static E. faecalis biofilms, and it might be qualified as a root canal irrigant for effective root canal disinfection.

Proteomic Analysis to Elucidate the Antibacterial Action of Silver Ions Against Bovine Mastitis Pathogens

Silver ions act as a powerful, broad-spectrum antimicrobial agent and are known to kill over 650 different kinds of pathogens. We investigated the protein expression pattern and identity after silver ion treatment in Escherichia coli and Staphylococcus aureus, which are primarily responsible for the majority of bovine mastitis cases using proteomics. Two-dimensional electrophoresis showed that silver ion treatment significantly reduced 5 spot's density in E. coli and S. aureus, respectively. We identified 10 proteins (alkyl hydroperoxide reductase C22 subunit, phosphoglucomutase, fructose-1-phosphate kinase, putative carbamoyl transferase, alpha-galactosidase, carbamate kinase, ornithine transcarbamoylase, fumarate hydratase class II, alcohol dehydrogenase, and conserved hypothetical protein) by matrix-assisted laser desorption ionization time of flight (MALDI-TOF). These results demonstrated that silver ions have bactericidal effects through energy deprivation, inhibition of DNA replication, and accumulation of oxidants in bovine mastitis pathogens and suggested that silver ions can be applied for the treatment of bovine mastitis.

Macrobrachium rosenbergii mannose binding lectin: synthesis of MrMBL-N20 and MrMBL-C16 peptides and their antimicrobial characterization, bioinformatics and relative gene expression analysis

Mannose-binding lectin (MBL), an antimicrobial protein, is an important component of innate immune system which recognizes repetitive sugar groups on the surface of bacteria and viruses leading to activation of the complement system. In this study, we reported a complete molecular characterization of cDNA encoded for MBL from freshwater prawn Macrobrachium rosenbergii (Mr). Two short peptides (MrMBL-N20: (20)AWNTYDYMKREHSLVKPYQG(39) and MrMBL-C16: (307)GGLFYVKHKEQQRKRF(322)) were synthesized from the MrMBL polypeptide. The purity of the MrMBL-N20 (89%) and MrMBL-C16 (93%) peptides were confirmed by MS analysis (MALDI-ToF). The purified peptides were used for further antimicrobial characterization including minimum inhibitory concentration (MIC) assay, kinetics of bactericidal efficiency and analysis of hemolytic capacity. The peptides exhibited antimicrobial activity towards all the Gram-negative bacteria taken for analysis, whereas they showed the activity towards only a few selected Gram-positive bacteria. MrMBL-C16 peptides produced the highest inhibition towards both the Gram-negative and Gram-positive bacteria compared to the MrMBL-N20. Both peptides do not produce any inhibition against Bacillus sps. The kinetics of bactericidal efficiency showed that the peptides drastically reduced the number of surviving bacterial colonies after 24 h incubation. The results of hemolytic activity showed that both peptides produced strong activity at higher concentration. However, MrMBL-C16 peptide produced the highest activity compared to the MrMBL-N20 peptide. Overall, the results indicated that the peptides can be used as bactericidal agents. The MrMBL protein sequence was characterized using various bioinformatics tools including phylogenetic analysis and structure prediction. We also reported the MrMBL gene expression pattern upon viral and bacterial infection in M. rosenbergii gills. It could be concluded that the prawn MBL may be one of the important molecule which is involved in antimicrobial mechanism. Moreover, MrMBL derived MrMBL-N20 and MrMBL-C16 peptides are important antimicrobial peptides for the recognition and eradication of viral and bacterial pathogens.

Comparison of disinfection effect of pressurized gases of CO2, N2O, and N2 on Escherichia coli

Based on the production of gas bubbles with the support of a liquid film-forming apparatus, a device inducing contact between gas and water was used to inactivate pathogens for water disinfection. In this study, the inactivation effect of CO2 against Escherichia coli was investigated and compared with the effects of N2O and N2 under the same pressure (0.3-0.9 MPa), initial concentration, and temperature. The optimum conditions were found to be 0.7 MPa and an exposure time of 25 min. Under identical treatment conditions, a greater than 5.0-log reduction in E. coli was achieved by CO2, while 3.3 log and 2.4 log reductions were observed when N2O and N2 were used, respectively. Observation under scanning electron microscopy and measurement of bacterial cell substances by UV-absorbance revealed greater cell rupture of E. coli following treatment with CO2 than when treatment was conducted using N2O, N2 and untreated water. The physical effects of the pump, acidified characteristics and the release of intracellular substances caused by CO2 were bactericidal mechanism of this process. Overall, the results of this study indicate that CO2 has the disinfection potential without undesired by-product forming.