Sterilization of hydrogen peroxide resistant bacterial spores with stabilized chlorine dioxide

Chlorine Dioxide: Friend or Foe for Cell Biomolecules? A Chemical Approach

This review examines the role of chlorine dioxide (ClO₂) on inorganic compounds and cell biomolecules. As a disinfectant also present in drinking water, ClO₂ helps to destroy bacteria, viruses, and some parasites. The Environmental Protection Agency EPA regulates the maximum concentration of chlorine dioxide in drinking water to be no more than 0.8 ppm. In any case, human consumption must be strictly regulated since, given its highly reactive nature, it can react with and oxidize many of the inorganic compounds found in natural waters. Simultaneously, chlorine dioxide reacts with natural organic matter in water, including humic and fulvic acids, forming oxidized organic compounds such as aldehydes and carboxylic acids, and rapidly oxidizes phenolic compounds, amines, amino acids, peptides, and proteins, as well as the nicotinamide adenine dinucleotide NADH, responsible for electron and proton exchange and energy production in all cells. The influence of ClO₂ on biomolecules is derived from its interference with redox processes, modifying the electrochemical balances in mitochondrial and cell membranes. This discourages its use on an individual basis and without specialized monitoring by health professionals.

Effect of Stable Chlorine Dioxide and Vacuum-Packing Treatments on the Physicochemical and Volatile Flavor Properties of Pike Eel (Muraenesox cinereus) during Chilled Storage

The effects of vacuum-packaging and stable chlorine dioxide treatments on the quality of pike-eel fillets were investigated during chilled storage for a period of up to 10 days. The results reveal that the sensory scores, total volatile basic nitrogen (TVB-N) content, total viable count (TVC), malondialdehyde (MDA) content, and the myofibrillar protein (MP) content of pike-eel fillets with different packing treatments all decreased significantly over 10 days of storage. However, the vacuum-packaging and stable chlorine dioxide pretreatment showed positive effects on the protein stability of pike-eel samples. Compared with the simple packaging (SP) and vacuum packing (VP) treatments, the combination treatments (CP) significantly inhibited the rapid increases in the TVB-N content, TVC values, and MDA content. Moreover, the comparative stability in the MP and its carbonyl content were maintained. Furthermore, our volatile organic compounds (VOCs) analysis confirmed that the combined packaging treatments significantly hindered protein and lipid oxidation, inhibited the growth of spoilage bacteria, and maintained the volatile flavors of pike-eel samples during chilled storage.

Inactivation of Spores and Vegetative Forms of Clostridioides difficile by Chemical Biocides: Mechanisms of Biocidal Activity, Methods of Evaluation, and Environmental Aspects

Clostridioides difficile infections (CDIs) are the most common cause of acquired diseases in hospitalized patients. Effective surface disinfection, focused on the inactivation of the spores of this pathogen, is a decisive factor in reducing the number of nosocomial cases of CDI infections. An efficient disinfection procedure is the result of both the properties of the biocidal agent used and the technology of its implementation as well as a reliable, experimental methodology for assessing the activity of the biocidal active substance based on laboratory models that adequately represent real clinical conditions. This study reviews the state of knowledge regarding the properties and biochemical basis of the action mechanisms of sporicidal substances, with emphasis on chlorine dioxide (ClO₂). Among the analyzed biocides, in addition to ClO₂, active chlorine, hydrogen peroxide, peracetic acid, and glutaraldehyde were characterized. Due to the relatively high sporicidal effectiveness and effective control of bacterial biofilm, as well as safety in a health and environmental context, the use of ClO₂ is an attractive alternative in the control of nosocomial infections of CD etiology. In terms of the methods of assessing the biocidal effectiveness, suspension and carrier standards are discussed.

Bactericidal efficiency and photochemical mechanisms of micro/nano bubble-enhanced visible light photocatalytic water disinfection

Microbial contamination of water in the form of highly-resistant bacterial spores can cause a long-term risk of waterborne disease. Advanced photocatalysis has become an effective approach to inactivate bacterial spores due to its potential for efficient solar energy conversion alongside reduced formation of disinfection by-products. However, the overall efficiency of the process still requires significant improvements. Here, we proposed and evaluated a novel visible light photocatalytic water disinfection technology by its close coupling with micro/nano bubbles (MNBs). The inactivation rate constant of Bacillus subtilis spores reached 1.28 h^-1, which was 5.6 times higher than that observed for treatment without MNBs. The superior performance for the progressive destruction of spores' cells during the treatment was confirmed by transmission electron microscopy (TEM) and excitation-emission matrix (EEM) spectra determination. Experiments using scavengers of reactive oxygen species (ROSs) revealed that H₂O₂ and •OH were the primary active species responsible for the inactivation of spores. The effective supply of oxygen from air MNBs helped accelerate the hole oxidation of H₂O₂ on the photocatalyst (i.e. Ag/TiO₂). In addition, the interfacial photoelectric effect from the MNBs was also confirmed to contribute to the spore inactivation. Specifically, MNBs induced strong light scattering, consequently increasing the optical path length in the photocatalysis medium by 54.8% at 700nm and enhancing light adsorption of the photocatalyst. The non-uniformities in dielectricity led to a high-degree of heterogeneity of the electric field, which triggered the formation of a region of enhanced light intensity which ultimately promoted the photocatalytic reaction. Overall, this study provided new insights on the mechanisms of photocatalysis coupled with MNB technology for advanced water treatment.

Evaluation of Stabilized Chlorine Dioxide in Terms of Antimicrobial Activity and Dentin Bond Strength

BACKGROUND

Antimicrobial agents are recommended for disinfection of the cavity following mechanical dental caries removal prior to application of restorative material. There is limited information about stabilized chlorine dioxide (ClO2) as a cavity disinfectant.

OBJECTIVE

The objective of this study is to determine the antimicrobial activity and effect on dentin bond strength of ClO2 compared to chlorhexidine digluconate (CHX), sodium hypochlorite (NaOCl) and ethanolic propolis extract (EPE).

METHODS

Antimicrobial activities of agents against oral pathogens (Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans, Lactobacillus acidophilus, Lactobacillus casei, Candida albicans, and Saccharomyces cerevisiae) and analyses of EPE were examined. Seventy-five mandibular third molars were sectioned, prepared and divided into five subgroups (n=15/group). Cavity disinfectants (2% CHX, 2.5% NaOCl, 30% EPE, 0.3% ClO2) were applied to etched dentin prior to adhesive and composite build-up. Shear bond strength (SBS) was evaluated with a universal testing machine at a crosshead speed of 0.5 mm/min. The SBS data were analyzed with one-way analysis of variance (ANOVA) and Tukey's post-hoc test (p <0.05). The failure modes were evaluated with a stereomicroscope.

RESULTS

It was determined that the compared disinfectants were showed different inhibition zone values against oral pathogens. ClO2 exhibited the highest antimicrobial activity, followed by CHX, NaOCI and EPE, respectively. No statistically significant difference was observed in the SBS values between the disinfectant treated groups and control group. The failure modes were predominantly mixed.

CONCLUSION

The use of 0.3% stabilized ClO2 as a cavity disinfectant agent exhibited high antimicrobial activity against oral pathogens and no adverse effects on SBS to etched dentin.

Nucleic Acid Extraction and Sequencing from Low-Biomass Synthetic Mars Analog Soils for In Situ Life Detection

Recent studies regarding the origins of life and Mars-Earth meteorite transfer simulations suggest that biological informational polymers, such as nucleic acids (DNA and RNA), have the potential to provide unambiguous evidence of life on Mars. To this end, we are developing a metagenomics-based life-detection instrument which integrates nucleic acid extraction and nanopore sequencing: the Search for Extra-Terrestrial Genomes (SETG). Our goal is to isolate and sequence nucleic acids from extant or preserved life on Mars in order to determine if a particular genetic sequence (1) is distantly related to life on Earth, indicating a shared ancestry due to lithological exchange, or (2) is unrelated to life on Earth, suggesting convergent origins of life on Mars. In this study, we validate prior work on nucleic acid extraction from cells deposited in Mars analog soils down to microbial concentrations (i.e., 10⁴ cells in 50 mg of soil) observed in the driest and coldest regions on Earth. In addition, we report low-input nanopore sequencing results from 2 pg of purified Bacillus subtilis spore DNA simulating ideal extraction yields equivalent to 1 ppb life-detection sensitivity. We achieve this by employing carrier sequencing, a method of sequencing sub-nanogram DNA in the background of a genomic carrier. After filtering of carrier, low-quality, and low-complexity reads we detected 5 B. subtilis reads, 18 contamination reads (including Homo sapiens), and 6 high-quality noise reads believed to be sequencing artifacts.

Biological and medical applications of plasma-activated media, water and solutions

Non-thermal atmospheric pressure plasma has been proposed as a new tool for various biological and medical applications. Plasma in close proximity to cell culture media or water creates reactive oxygen and nitrogen species containing solutions known as plasma-activated media (PAM) or plasma-activated water (PAW) - the latter even displays acidification. These plasma-treated solutions remain stable for several days with respect to the storage temperature. Recently, PAM and PAW have been widely studied for many biomedical applications. Here, we reviewed promising reports demonstrating plasma-liquid interaction chemistry and the application of PAM or PAW as an anti-cancer, anti-metastatic, antimicrobial, regenerative medicine for blood coagulation and even as a dental treatment agent. We also discuss the role of PAM on cancer initiation cells (spheroids or cancer stem cells), on the epithelial mesenchymal transition (EMT), and when used for metastasis inhibition considering its anticancer effects. The roles of PAW in controlling plant disease, seed decontamination, seed germination and plant growth are also considered in this review. Finally, we emphasize the future prospects of PAM, PAW or plasma-activated solutions in biomedical applications with a discussion of the mechanisms and the stability and safety issues in relation to humans.

Correlation of Conformational Changes and Protein Degradation with Loss of Lysozyme Activity Due to Chlorine Dioxide Treatment

Chlorine dioxide (ClO₂) is a potent oxidizing agent used for the treatment of drinking water and decontamination of facilities and equipment. The purpose of this research is to elucidate the manner in which ClO₂ destroys proteins by studying the effects of ClO₂ on lysozyme. The degree of enzyme activity lost can be correlated to the treatment time and levels of the ClO₂ used. Lysozyme activity was drastically reduced to 45.3% of original enzyme activity when exposed to 4.3 mM ClO₂ in the sample after 3 h. Almost all activities were lost in 3 h after exposure to higher ClO₂ concentrations of up to 16.8 and 21.9 mM. Changes in protein conformation and amount as a result of ClO₂ treatment were determined using the Raman spectroscopy and gel electrophoresis. Raman shifts and the alteration of spectral features observed in the ClO₂-treated lysozyme samples are associated with loss of the α-helix secondary structure, tertiary structure, and disulfide bond. Progressive degradation of the denatured lysozyme by increasing levels of chlorine dioxide was also observed in gel electrophoresis. Hence, ClO₂ can effectively cause protein denaturation and degradation resulting in loss of enzyme activity.

Bacillus pumilus SAFR-032 Genome Revisited: Sequence Update and Re-Annotation

Bacillus pumilus strain SAFR-032 is a non-pathogenic spore-forming bacterium exhibiting an anomalously high persistence in bactericidal environments. In its dormant state, it is capable of withstanding doses of ultraviolet (UV) radiation or hydrogen peroxide, which are lethal for the vast majority of microorganisms. This unusual resistance profile has made SAFR-032 a reference strain for studies of bacterial spore resistance. The complete genome sequence of B. pumilus SAFR-032 was published in 2007 early in the genomics era. Since then, the SAFR-032 strain has frequently been used as a source of genetic/genomic information that was regarded as representative of the entire B. pumilus species group. Recently, our ongoing studies of conservation of gene distribution patterns in the complete genomes of various B. pumilus strains revealed indications of misassembly in the B. pumilus SAFR-032 genome. Synteny-driven local genome resequencing confirmed that the original SAFR-032 sequence contained assembly errors associated with long sequence repeats. The genome sequence was corrected according to the new findings. In addition, a significantly improved annotation is now available. Gene orders were compared and portions of the genome arrangement were found to be similar in a wide spectrum of Bacillus strains.