Evolutionary clade affects resistance of Clostridium difficile spores to Cold Atmospheric Plasma

Clostridioides difficile as a Potential Pathogen of Importance to One Health: A Review

Clostridioides difficile (basonym Clostridium) is a bacterial enteropathogen associated with cases of C. difficile infection that can result in pseudomembranous colitis, rapid fluid loss, and death. For decades following its isolation, C. difficile was thought to be a solely nosocomial pathogen, being isolated from individuals undergoing antimicrobial therapy and largely affecting elderly populations. More recently, C. difficile spores have been identified in the broader environment, including in food-producing animals, soil, and food matrices, in both ready-to-eat foods and meat products. Furthermore, evidence has emerged of hypervirulent ribotypes (RTs), such as RT078, similar to those cultured in asymptomatic carriers, also being identified in these environments. This finding may reflect on adaptations arising in these bacteria following selection pressures encountered in these niches, and which occurs due to an increase in antimicrobial usage in both clinical and veterinary settings. As C. difficile continues to adapt to new ecological niches, the taxonomy of this genus has also been evolving. To help understand the transmission and virulence potential of these bacteria of importance to veterinary public health, strategies applying multi-omics-based technologies may prove useful. These approaches may extend our current understanding of this recognized nosocomial pathogen, perhaps redefining it as a zoonotic bacterium. In this review, a brief background on the epidemiological presentation of C. difficile will be highlighted, followed by a review of C. difficile in food-producing animals and food products. The current state of C. difficile taxonomy will provide evidence of Clade 5 (ST11/RT078) delineation, as well as background on the genomic elements linked to C. difficile virulence and ongoing speciation. Recent studies applying second- and third-generation sequencing technologies will be highlighted, and which will further strengthen the argument made by many throughout the world regarding this pathogen and its consideration within a One Health dimension.

Technologies to decontaminate bacterial biofilm on hospital surfaces: a potential new role for cold plasma?

Healthcare-associated infections (HCAIs) are a major challenge and the near patient surface is important in harbouring causes such as methicillin-resistant Staphylococcus aureus (MRSA) and Clostridioides difficile. Current approaches to decontamination are sub-optimal and many studies have demonstrated that microbial causes of HCAIs may persist with onward transmission. This may be due to the capacity of these microbes to survive in biofilms on surfaces. New technologies to enhance hospital decontamination may have a role in addressing this challenge. We have reviewed current technologies such as UV light and hydrogen peroxide and also assessed the potential use of cold atmospheric pressure plasma (CAPP) in surface decontamination. The antimicrobial mechanisms of CAPP are not fully understood but the production of reactive oxygen and other species is believed to be important. CAPP systems have been shown to partially or completely remove a variety of biofilms including those caused by Candida albicans, and multi-drug-resistant bacteria such as MRSA. There are some studies that suggest promise for CAPP in the challenge of surface decontamination in the healthcare setting. However, further work is required to define better the mechanism of action. We need to know what surfaces are most amenable to treatment, how microbial components and the maturity of biofilms may affect successful treatment, and how would CAPP be used in the clinical setting.

A Cold Plasma Technology for Ensuring the Microbiological Safety and Quality of Foods

Changing consumers’ taste for chemical and thermally processed food and preference for perceived healthier minimally processed alternatives is a challenge to food industry. At present, several technologies have found usefulness as choice methods for ensuring that processed food remains unaltered while guaranteeing maximum safety and protection of consumers. However, the effectiveness of most green technology is limited due to the formation of resistant spores by certain foodborne microorganisms and the production of toxins. Cold plasma, a recent technology, has shown commendable superiority at both spore inactivation and enzymes and toxin deactivation. However, the exact mechanism behind the efficiency of cold plasma has remained unclear. In order to further optimize and apply cold plasma treatment in food processing, it is crucial to understand these mechanisms and possible factors that might limit or enhance their effectiveness and outcomes. As a novel non-thermal technology, cold plasma has emerged as a means to ensure the microbiological safety of food. Furthermore, this review presents the different design configurations for cold plasma applications, analysis the mechanisms of microbial spore and biofilm inactivation, and examines the impact of cold plasma on food compositional, organoleptic, and nutritional quality.

Presence of Clostridioides difficile in cattle feces, carcasses, and slaughterhouses: Molecular characterization and antibacterial susceptibility of the recovered isolates

The aims of this study were to isolate and identify Clostridioides difficile from cattle feces and carcasses, and slaughterhouse samples, and to determine the molecular characteristics and antibacterial susceptibility of the recovered isolates. A total of 220 samples, including 100 cattle fecal samples, 100 cattle carcass surface samples, and 20 slaughterhouse samples were used as the study material. In total, 12 (5.45%) samples, including 11 (11%) cattle fecal samples and 1 (5%) slaughterhouse sample, were found to be positive for C. difficile. On the other hand, all of the carcass samples were negative for C. difficile. A total of 11 (91.66%) isolates, including 10 fecal isolates and 1 slaughterhouse wastewater isolate, were found to be positive for the presence of the toxin genes tcdA and tcdB, whilst 1 fecal isolate was found to be negative for both genes. In addition, 3 different ERIC-PCR profiles were identified in the 11 fecal isolates. The ERIC-PCR profile of the slaughterhouse wastewater isolate was found to be similar to one of the ERIC-PCR profiles obtained from the fecal isolates. All of the isolates were resistant to ciprofloxacin and levofloxacin. Considering that the agent is a spore-forming bacterium shed in feces, the detection of C. difficile isolates of different genotypes, some carrying toxin genes, suggests that feces and slaughterhouse wastewater carrying this bacterium may pose a risk for the contamination of carcasses. The current study revealed that hygiene conditions should be performed to the maximum extent in slaughterhouses.

Assessment of mutations induced by cold atmospheric plasma jet treatment relative to known mutagens in Escherichia coli

The main bactericidal components of cold atmospheric plasma (CAP) are thought to be reactive oxygen and nitrogen species (RONS) and UV-radiation, both of which have the capacity to cause DNA damage and mutations. Here, the mutagenic effects of CAP on Escherichia coli were assessed in comparison to X- and UV-irradiation. DNA damage and mutagenesis were screened for using a diffusion-based DNA fragmentation assay and modified Ames test, respectively. Mutant colonies obtained from the latter were quantitated and sequenced. CAP was found to elicit a similar mutation spectrum to X-irradiation, which did not resemble that for UV implying that CAP-produced RONS are more likely the mutagenic component of CAP. CAP treatment was also shown to promote resistance to the antibiotic ciprofloxacin. Our data suggest that CAP treatment has mutagenic effects that may have important phenotypic consequences.

One Health approach to Clostridioides difficile in Japan

Clostridioides difficile infections (CDIs) are predominantly a healthcare-associated illness in developed countries, with the majority of cases being elderly and hospitalize patients who used antibiotic therapy. Recently, the incidence of community-associated CDIs (CA-CDIs) in younger patients without a previous history of hospitalization or antibiotic treatment has been increasing globally. C. difficile is sometimes found in the intestine of many animals, such as pigs, calves, and dogs. Food products such as retail meat products and vegetables sometimes contain C. difficile. C. difficile has also been isolated from several environments such as compost manure, rivers, and soils. Yet, direct transmission of C. difficile from animals, food products, and environments to humans has not been proven, although these strains have similar molecular characteristics. Therefore, it has been suggested that there is a relationship between CA-CDIs and C. difficile from animals, food products, and the environment. To clarify the importance of the presence of C. difficile in several sources, characterization of C. difficile in these sources is required. However, the epidemiology of C. difficile in animals, food products, and the environment is not well studied in Japan. This review summarizes recent trends of CDIs and compares the molecular characteristics of C. difficile in Japanese animals, food products, and the environment. The prevalence trends of C. difficile in Japan are similar to those in the rest of the world. Therefore, I recommend using a One Health approach to CDI surveillance, monitoring, and control.

The recent emergence of a highly related virulent Clostridium difficile clade with unique characteristics

OBJECTIVES

Clostridium difficile is a major global human pathogen divided into five clades, of which clade 3 is the least characterized and consists predominantly of PCR ribotype (RT) 023 strains. Our aim was to analyse and characterize this clade.

METHODS

In this cohort study the clinical presentation of C. difficile RT023 infections was analysed in comparison with known 'hypervirulent' and non-hypervirulent strains, using data from the Netherlands national C. difficile surveillance programme. European RT023 strains of diverse origin were collected and whole-genome sequenced to determine the genetic similarity between isolates. Distinctive features were investigated and characterized.

RESULTS

Clinical presentation of C. difficile RT023 infections show severe infections akin to those seen with 'hypervirulent' strains from clades 2 (RT027) and 5 (RT078) (35%, 29% and 27% severe CDI, respectively), particularly with significantly more bloody diarrhoea than RT078 and non-hypervirulent strains (RT023 8%, other RTs 4%, p 0.036). The full genome sequence of strain CD305 is presented as a robust reference. Phylogenetic comparison of CD305 and a further 79 previously uncharacterized European RT023 strains of diverse origin revealed minor genetic divergence with >99.8% pairwise identity between strains. Analyses revealed distinctive features among clade 3 strains, including conserved pathogenicity locus, binary toxin and phage insertion toxin genotypes, glycosylation of S-layer proteins, presence of the RT078 four-gene trehalose cluster and an esculinase-negative genotype.

CONCLUSIONS

Given their recent emergence, virulence and genomic characteristics, the surveillance of clade 3 strains should be more highly prioritized.

Inactivation kinetics of Bacillus cereus spores by Plasma activated water (PAW)

In recent years, plasma activated water has attracted more attention as a new disinfectant. The purpose of this study was to explore impact of variation of different treatment conditions on the inactivation kinetics of Bacillus cereus spores by PAW. All survival curves showed that the number of spores has decreased rapidly at first, followed by tailing results from the reduction inactivation rate. A linear and two nonlinear models (Weibull and Log-logistic model) were fitted to these data, and Log-logistic model fitted the inactivation of the B. cereus spores best. B. cereus spores in 10⁶ CFU/mL was reduced by 1.62-2.96 log CFU/mL by PAW at 55 °C due to the reactive species generated in PAW. Elevated temperature, lower initial spore concentration, lower bovine serum albumin content, and smaller activation volume of PAW considerably enhanced PAW inactivation of B. cereus spores. These results provide an approach to evaluate the inactivation efficacy of different treatment conditions for PAW.

Adaptation of host transmission cycle during Clostridium difficile speciation

Bacterial speciation is a fundamental evolutionary process characterized by diverging genotypic and phenotypic properties. However, the selective forces that affect genetic adaptations and how they relate to the biological changes that underpin the formation of a new bacterial species remain poorly understood. Here, we show that the spore-forming, healthcare-associated enteropathogen Clostridium difficile is actively undergoing speciation. Through large-scale genomic analysis of 906 strains, we demonstrate that the ongoing speciation process is linked to positive selection on core genes in the newly forming species that are involved in sporulation and the metabolism of simple dietary sugars. Functional validation shows that the new C. difficile produces spores that are more resistant and have increased sporulation and host colonization capacity when glucose or fructose is available for metabolism. Thus, we report the formation of an emerging C. difficile species, selected for metabolizing simple dietary sugars and producing high levels of resistant spores, that is adapted for healthcare-mediated transmission.

The State of Research on Antimicrobial Activity of Cold Plasma

Microbiological contamination is a big challenge to the food industry, medicine, agriculture, and environmental protection. For this reason, scientists are constantly looking for alternative methods of decontamination, which ensure the effective elimination of unwanted biological agents. Cold plasma is a new technology, which due to its unique physical and chemical properties becomes a point of interest to a growing group of researchers. The previously conducted experiments confirm its effective action, e.g. in the disinfection of skin wounds, air, and sewage treatment, as well as in food preservation and decontamination. The reactive compounds present in the plasma: high-energy electrons, ionized atoms and molecules, and UV photons are the key factors that cause an effective reduction in the number of microorganisms. The mechanism and effectiveness of the cold plasma are complex and depend on the process parameters, environmental factors and the type and properties of the microorganisms that are to be killed. This review describes the current state of knowledge regarding the effectiveness of the cold plasma and characterizes its interaction with various groups of microorganisms based on the available literature data.

Characterization of Efficiency and Mechanisms of Cold Atmospheric Pressure Plasma Decontamination of Seeds for Sprout Production

The consumption of fresh fruit and vegetable products has strongly increased during the past few decades. However, inherent to all minimally processed products is the short shelf life, and the risk of foodborne diseases, which have been increasingly related to such products in many parts of the world. Because of the favorable conditions for the growth of bacteria during the germination of seeds, sprouts are a frequent source for pathogenic bacteria, thus highlighting the need for seed decontamination to reduce the risk of foodborne illness. Consequently, this study focused on cold atmospheric pressure plasma (CAPP) treatment of artificially inoculated seeds in a diffuse coplanar surface barrier discharge to determine the inactivation efficiency for relevant foodborne pathogens and fungal spores. Plasma treatment of seeds resulted in a highly efficient reduction of microorganisms on the seed surface, while preserving the germination properties of seeds, at least for moderate treatment times. To characterize the mechanisms that contribute to microbial inactivation during plasma treatment, an experimental setup was developed to separate ultraviolet light (UV) and other plasma components. The combination of bacterial viability staining with confocal laser scanning microscopy was used to investigate the impact of ozone and other reactive species on the bacterial cells in comparison to UV. Further characterization of the effect of CAPP on bacterial cells by atomic force microscopy imaging of the same Escherichia coli cells before and after treatment revealed an increase in the surface roughness of treated E. coli cells and a decrease in the average height of the cells, which suggests physical damage to the cell envelope. In conclusion, CAPP shows potential for use as a decontamination technology in the production process of sprouts, which may contribute to food safety and prolonged shelf life of the product.

Clostridium difficile colitis and zoonotic origins-a narrative review

Clostridium difficile is a major cause of hospital-associated diarrhoea, and in severe cases leads to pseudomembranous colitis and toxic megacolon. The frequency of C. difficile infection (CDI) has increased in recent decades, with 453 000 cases identified in 2011 in the USA. This is related to antibiotic-selection pressure, disruption of normal host intestinal microbiota and emergence of antibiotic-resistant C. difficile strains. The burden of community-acquired CDI has been increasingly appreciated, with disease identified in patients previously considered low-risk, such as young women or patients with no prior antibiotic exposure. C. difficile has been identified in livestock animals, meat products, seafood and salads. It has been postulated that the pool of C. difficile in the agricultural industry may contribute to human CDI. There is widespread environmental dispersal of C. difficile spores. Domestic households, turf lawns and public spaces are extensively contaminated, providing a potential reservoir for community-acquired CDI. In Australia, this is particularly associated with porcine-derived C. difficile UK PCR ribotype 014/020. In this article, the epidemiological differences between hospital- and community-acquired CDI are discussed, including some emerging evidence for community-acquired CDI being a possible zoonosis.

Bacterial spore inactivation induced by cold plasma

Cold plasma has emerged as a non-thermal technology for microbial inactivation in the food industry over the last decade. Spore-forming microorganisms pose challenges for microbiological safety and for the prevention of food spoilage. Inactivation of spores induced by cold plasma has been reported by several studies. However, the exact mechanism of spore deactivation by cold plasma is poorly understood; therefore, it is difficult to control this process and to optimize cold plasma processing for efficient spore inactivation. In this review, we summarize the factors that affect the resistance of spores to cold plasma, including processing parameters, environmental elements, and spore properties. We then describe possible inactivation targets in spore cells (e.g., outer structure, DNA, and metabolic proteins) that associated with inactivation by cold plasma according to previous studies. Kinetic models of the sporicidal activity of cold plasma have also been described here. A better understanding of the interaction between spores and cold plasma is essential for the development and optimization of cold plasma technology in food the industry.

Effects of atmospheric pressure plasma jet operating with DBD on Lavatera thuringiaca L. seeds' germination

The paper presents the results of an experiment on the effect of pre-sowing stimulation of seeds with atmospheric pressure plasma jet operating with dielectric barrier discharge (DBD plasma jet) on the process of germination of Thuringian Mallow (Lavatera thuringiaca L.). Five groups of seeds characterized by a different exposure times (1, 2, 5, 10 and 15 minutes) as well as untreated seeds—control were used. Pre-sowing plasma stimulation of seeds improved germination parameters such as: germination capacity and germination energy for all tested groups relative to control. The highest germination parameters were obtained for seeds stimulated with plasma for the exposure times of 2 and 5 min. The analysis of the contact surface angle indicated the decrease of its’ mean values upon seed stimulation while no statistical effects were observed. Analysis of the SEM scans revealed the increase in seed pattern intensity which could be attributed to removing of the surface parts of cuticle possibly covered with wax upon short time—2 and 5 min plasma treatment. Such a phenomenon can act similarly to mechanical scarification of seeds. Longer exposure of seeds to plasma resulted in affecting the deeper zone of cuticle and damage or fracture of some parts of the cuticle. Lower germination parameters of seeds upon longer exposure times to plasma may indicate mechanical damage of the seeds.

Application of High Pressure with Homogenization, Temperature, Carbon Dioxide, and Cold Plasma for the Inactivation of Bacterial Spores: A Review

Formation of highly resistant spores is a concern for the safety of low-acid foods as they are a perfect vehicle for food spoilage and/or human infection. For spore inactivation, the strategy usually applied in the food industry is the intensification of traditional preservation methods to sterilization levels, which is often accompanied by decreases of nutritional and sensory properties. In order to overcome these unwanted side effects in food products, novel and emerging sterilization technologies are being developed, such as pressure-assisted thermal sterilization, high-pressure carbon dioxide, high-pressure homogenization, and cold plasma. In this review, the application of these emergent technologies is discussed, in order to understand the effects on bacterial spores and their inactivation and thus ensure food safety of low-acid foods. In general, the application of these novel technologies for inactivating spores is showing promising results. However, it is important to note that each technique has specific features that can be more suitable for a particular type of product. Thus, the most appropriate sterilization method for each product (and target microorganisms) should be assessed and carefully selected.

Medical applications of nonthermal atmospheric pressure plasma in dermatology

Plasma is an ionized gas that consists of positively and negatively charged particles, neutral atoms, and photons. Recent developments in plasma sources have made it possible to generate room-temperature plasma in the "open air", thus enabling the application of plasma in vivo. Using nonthermal plasma, active agents can be efficiently delivered to target cells without creating thermal damage. Also known as cold atmospheric pressure plasma (CAP), nonthermal atmospheric pressure plasma offers innovative medical applications. In this context, it has also gained wide attention in the field of dermatology. The complex and variable mixture of active agents in plasma - predominantly reactive oxygen and nitrogen species (ROS, RNS) - can control or trigger complex biochemical reactions, achieving the desired effects in a dose-dependent manner. The objective of the present review is to present potential applications of plasma in dermatology and analyze its potential mechanisms of action.

Innovative non-thermal plasma disinfection process inside sealed bags: Assessment of bactericidal and sporicidal effectiveness in regard to current sterilization norms

In this work, we developed a device capable to generate a non-thermal plasma discharge inside a sealed bag. The aim of this study was to assess the effectiveness of the oxygen, nitrogen and argon plasma sterilization on Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis spores according to the NF EN 556 Norm. Moreover the bag integrity which is a critical key to maintain the sterile state of items after the end of the process was verified by Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectrometry (XPS) analyses. After plasma treatments, the bacterial counting showed a 6 log reduction of P. aeruginosa and S. aureus in 45 min and 120 min respectively whatever the gas used and a 4 log reduction of B. subtilis spores in 120 min with only oxygen plasma. These results were confirmed by Scanning Electron Microscopy (SEM) observations showing altered bacteria or spores and numerous debris. Taking into account the studied microorganisms, the oxygen plasma treatment showed the highest efficiency. FTIR and XPS analyses showed that this treatment induced no significant modification of the bags. To conclude this non-thermal plasma sterilization technique could be an opportunity to sterilize heat and chemical-sensitive medical devices and to preserve their sterile state after the end of the process.