In recent years, probiotics have attracted public attention and transformed the social perception of microorganisms, convening a beneficial role/state on human health. With aging, the immune system, body physiology, and intestinal microbiota tend to change unfavorably, resulting in many chronic conditions. The immune-mediated disorders can be linked to intestinal dysbiosis, consequently leading to immune dysfunctions and a cluster of conditions such as asthma, autoimmune diseases, eczema, and various allergies. Probiotic bacteria such as Lactobacillus and Bifidobacterium species are considered probiotic species that have a great immunomodulatory and anti-allergic effect. Moreover, recent scientific and clinical data illustrate that probiotics can regulate the immune system, exert anti-viral and anti-tumoral activity, and shields the host against oxidative stress. Additionally, microbiota programming by probiotic bacteria can reduce and prevent the symptoms of respiratory infections and ameliorate the neurological status in humans. This review describes the most recent clinical findings, including safe probiotic therapies aiming to medicate respiratory infections, allergies, cancer, and neurological disorders due to their physiological interconnection. Subsequently, we will describe the major biological mechanism by which probiotic bacteriotherapy expresses its anti-viral, anti-allergic, anticancer, and neuro-stimulatory effects.

Biocides are currently considered the first line of defense against foodborne pathogens in hospitals or food processing facilities due to the versatility and efficiency of their chemical active ingredients. Understanding the biological mechanisms responsible for their increased efficiency, especially when used against foodborne pathogens on contaminated surfaces and materials, represents an essential first step in the implementation of efficient strategies for disinfection as choosing an unsuitable product can lead to antibiocide resistance or antibiotic–biocide cross-resistance. This review describes these biological mechanisms for the most common foodborne pathogens and focuses mainly on the antipathogen effect, highlighting the latest developments based on in vitro and in vivo studies. We focus on biocides with inhibitory effects against foodborne bacteria (e.g., Escherichia spp., Klebsiella spp., Staphylococcus spp., Listeria spp., Campylobacter spp.), aiming to understand their biological mechanisms of action by looking at the most recent scientific evidence in the field.

The Campylobacter genus is the leading cause of human gastroenteritis, with the consumption of contaminated poultry meat as the main route of infection. Probiotic bacteria, such as Lactobacillus , Bacillus , Escherichia coli Nissle, and Bifidobacterium species, have a great immunomodulatory capacity and exhibit antipathogenic effects through various molecular mechanisms. Reducing Campylobacter levels in livestock animals, such as poultry, will have a substantial benefit to humans as it will reduce disease transmissibility through the food chain. Moreover, probiotic-based strategies might attenuate intestinal inflammatory processes, which consequently reduce the severity of Campylobacter disease progression. At a molecular level, probiotics can also negatively impact on the functionality of various Campylobacter virulence and survival factors (e.g., adhesion, invasion), and on the associated colonization proteins involved in epithelial translocation. The current review describes recent in vitro , in vivo , and preclinical findings on probiotic therapies, aiming to reduce Campylobacter counts in poultry and reduce the pathogen's virulence in the avian and human host. Moreover, we focused in particular on probiotics with known anti- Campylobacter activity seeking to understand the biological mechanisms involved in their mode of action.

Staphylococcus aureus, Streptococcus pyogenes and Enterococcus faecalis can colonize the tooth root canals, adhere to dentin walls, and frequently cause periodontitis in dogs. Bacterial periodontal diseases are common in domesticated pets, causing severe oral cavity inflammation and a strong immune response. This study investigates the antioxidant effect of a natural antimicrobial mixture (Auraguard—Ag) on the ability of S. aureus, S. pyogenes and E. faecalis to infect primary canine oral epithelial cells as well as its impact on their virulence factors. Our data show that a concentration of 0.25% Ag is sufficient to inhibit the growth of all three pathogens, whereas a concentration of 0.5% will become bactericidal. The sub-inhibitory concentration of 0.125% Ag reveals that the antimicrobial mixture can significantly reduce biofilm formation and exopolysaccharide production. The impact on these virulence factors was further translated into a significantly reduced ability to infect primary canine oral epithelial cells and restore epithelial tight junctions, with no impact on the epithelial cell viability. The post-infection inflammatory cytokines (IL-1β and IL-8) and the COX-2 mediator were also reduced both in mRNA and protein expression levels. The oxidative burst, detected upon infection, was also decreased in the presence of Ag, as our results show a significant decrease in H2O2 released by the infected cells. We show that inhibition of either NADPH or ERK activity will result in a downregulation of COX-2 expression and lower levels of H2O2 in infected cells. Conclusively, our study shows that natural antimicrobials reduce pro-inflammatory events, post infection, through an antioxidative mechanism that involves the downregulation of the COX-2 mediator via the inactivation of ERK in the absence of H2O2. As a result, they significantly reduce the risk of secondary bacterial infections and host oxidative stress caused by Staphylococcus aureus, Streptococcus pyogenes and Enterococcus faecalis accumulation in biofilms in an in vitro canine oral infection model.

Farm biosecurity management includes a set of practical measures used to prevent and limit the spread of infections to humans and animals. Infections, predominantly caused by zoonotic agents, often occur due to a lack of safety standards monitoring on farms, but also because of the use of inappropriate antimicrobial products leading to bacterial resistance, tolerance to biocides and the emergence antimicrobial-resistant germs. To date, research was mainly focused on studying the antimicrobial resistance in bacterial biofilms and the mechanisms involved in their occurrence. At molecular level, the limited diffusion of biocides in the biofilm matrix, enzyme-mediated resistance, genetic adaptation, efflux pumps, and levels of metabolic activity inside the biofilm are some of the investigated biological mechanisms which can promote antimicrobial resistance in biofilms were also investigated. Interventions, based on the identification of novel antimicrobial compounds, that would exclude the occurrence of bacterial tolerance, including essential oils (oregano, cloves), organic acids (tannic & oleic acid) and natural plant compounds (e.g. alkaloids, flavonoids, tannins and coumarins) were also extensively studied and reviewed given their effectiveness against pathogen-produced biofilms. The aim of this review was emphasize the importance of biosecurity and farm management practices and to assess their impact on bacterial biofilm formation. Furthermore, we present the recent intervention strategies aimed at reducing and combating the formation of bacterial biofilms in livestock farms.

Nematopsis messor infections severely impact on shrimp’s health with devastating economic consequences on shrimp farming. In a shrimp primary intestinal cells (SGP) model of infection, a sub-inhibitory concentration (0.5%) of natural antimicrobials (Aq) was able to reduce the ability of N. messor to infect (p < 0.0001). To prevent N. messor infection of SGP cells, Aq inhibits host actin polymerization and restores tight junction integrity (TEER) and the expression of Zo-1 and occluding. The oxidative burst, caused by N. messor infection, is attenuated by Aq through the inhibition of NADPH-produced H2O2. Simultaneous to the reduction in H2O2 released, the activity of catalase (CAT) and superoxide dismutase (SOD) were also significantly increase (p < 0.0001). The antimicrobial mixture inactivates the ERK signal transduction pathway by tyrosine dephosphorylation and reduces the expression of DCR2, ALF-A, and ALF-C antimicrobial peptides. The observed in vitro results were also translated in vivo, whereby the use of a shrimp challenge test, we show that in N. messor infected shrimp the mortality rate was 68% compared to the Aq-treated group where the mortality rate was maintained at 14%. The significant increase in CAT and SOD activity in treated and infected shrimp suggested an in vivo antioxidant role for Aq. In conclusion, our study shows that Aq can efficiently reduce N. messor colonization of shrimp’s intestinal cells in vitro and in vivo and the oxidative induced cellular damage, repairs epithelial integrity, and enhances gut immunity.

Increasing the abundance of probiotic bacteria in the gut requires either direct dietary supplementation or the inclusion of feed additives able to support the growth of beneficial commensal bacteria. In crustaceans, the increased presence of probiotic-like bacteria in the gut, including of Faecalibacterium prausnitzii (F. prausnitzii), will guarantee a positive health status and a gut environment that will ensure enhanced performance. The aim of this study was to investigate if a mixture of organic acids, AuraAqua (Aq) can stimulate the growth and the anti-pathogenic efficacy of F. prausnitzii through a combination of in vitro and ex vivo models. The results showed that 0.5% Aq was able to improve the growth rate of F. prausnitzii in vitro and in an ex vivo shrimp gut model. Moreover, we were able to demonstrate that Aq increases butyrate production and cellulose degradation in culture or in the shrimp gut model. The growth-stimulating effect of Aq also led to an improved and anti-pathogenic effect against Vibrio parahaemolyticus in a co-culture experiment with shrimp gut primary epithelial cells (SGP). In conclusion, our work demonstrates that Aq can stimulate the growth of F. prausnitzii, increase the production of short-chain fatty acid (SCFA) butyrate, improve substrate digestion, and prevent V. parahaemolyticus invasion of SGP cells.

The objective of this work was to investigate, for the first time, the antioxidant effect of a mixture of natural antimicrobials in an Enterocytozoon hepatopenaei (EHP) shrimp-gut model of infection and the biological mechanisms involved in their way of action. The study approach included investigations, firstly, in vitro, on shrimp-gut primary (SGP) epithelial cells and in vivo by using EHP-challenged shrimp. Our results show that exposure of EHP spores to 0.1%, 0.5%, 1%, and 2% AuraAqua (Aq) significantly reduced spore activity at all concentrations but was more pronounced after exposure to 0.5% Aq. The Aq was able to reduce EHP infection of SGP cells regardless of cells being pretreated or cocultured during infection with Aq. The survivability of SGP cells infected with EHP spores was significantly increased in both scenarios; however, a more noticeable effect was observed when the infected cells were pre-exposed to Aq. Our data show that infection of SGP cells by EHP activates the host NADPH oxidases and the release of H2O2 produced. When Aq was used during infection, a significant reduction in H2O2 was observed concomitant with a significant increase in the levels of CAT and SOD enzymes. Moreover, in the presence of 0.5% Aq, the overproduction of CAT and SOD was correlated with the inactivation of the NF-κB pathway, which, otherwise, as we show, is activated upon EHP infection of SGP cells. In a challenge test, Aq was able to significantly reduce mortality in EHP-infected shrimp and increase the levels of CAT and SOD in the gut tissue. Conclusively, these results show, for the first time, that a mixture of natural antimicrobials (Aq) can reduce the EHP-spore activity, improve the survival rates of primary gut-shrimp epithelial cells and reduce the oxidative damage caused by EHP infection. Moreover, we show that Aq was able to stop the H2O2 activation of the NF-κB pathway of Crustins, Penaeidins, and the lysozyme, and the CAT and SOD activity both in vitro and in a shrimp challenge test.