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Foodborne diseases continue to be a significant public health issue, despite improvements in food safety management systems, foodborne surveillance, better diagnostic tools, and better sanitation practices [...]

Listeria monocytogenes is an opportunistic pathogen that affects specific groups of individuals, with a high mortality rate. The control of L. monocytogenes in dairy industries presents particular challenges, as this bacterium is capable of adhering and forming biofilms, as well as thriving at refrigerated temperatures, which enables it to persist in harsh environments. The consumption of dairy products has been linked to sporadic cases and outbreaks of listeriosis, and L. monocytogenes is frequently detected in these products in retail stores. Moreover, the bacterium has been shown to persist in dairy-processing environments. In this work, we review the main characteristics of L. monocytogenes and listeriosis, and highlight the factors that support its persistence in processing environments and dairy products. We also discuss the main dairy products involved in outbreaks of listeriosis since the early 1980s, and present control measures that can help to prevent the occurrence of this pathogen in foods and food-processing environments.

The applications of microalgae biomass have been widely studied worldwide. The classical processes used in outdoor cultivations of microalgae, in closed or open photobioreactors, occur in the presence of bacteria. Understanding how communication between cells occurs through quorum sensing and evaluating co-cultures allows the production of microalgae and cyanobacteria to be positively impacted by bacteria, in order to guarantee safety and profitability in the production process. In addition, the definition of the effects that occur during an interaction, promotes insights to improve the production of biomolecules, and to develop innovative products. This review presents the interactions between microalgae and bacteria, including compounds exchanges and communication, and addresses the development of new pharmaceutical, cosmetic and food bioproducts from microalgae based on these evaluations, such as prebiotics, vegan skincare products, antimicrobial compounds, and culture media with animal free protein for producing vaccines and other biopharmaceutical products. The use of microalgae as raw biomass or in biotechnological platforms is in line with the fulfillment of the 2030 Agenda related to the Sustainable Development Goals (SDGs).

Quorum sensing is a cell-cell communication mechanism mediated by chemical signals that leads to differential gene expression in response to high population density. Salmonella is unable to synthesize the autoinducer-1 (AI-1), N-acyl homoserine lactone (AHL), but is able to recognize AHLs produced by other microorganisms through SdiA protein. This study aimed to evaluate the fatty acid and protein profiles of Salmonella enterica serovar Enteritidis PT4 578 throughout time of cultivation in the presence of AHL. The presence of N-dodecanoyl-homoserine lactone (C12-HSL) altered the fatty acid and protein profiles of Salmonella cultivated during 4, 6, 7, 12 and 36 h in anaerobic condition. The profiles of Salmonella Enteritidis at logarithmic phase of growth (4 h of cultivation), in the presence of C12-HSL, were similar to those of cells at late stationary phase (36 h). In addition, there was less variation in both protein and fatty acid profiles along growth, suggesting that this quorum sensing signal anticipated a stationary phase response. The presence of C12-HSL increased the abundance of thiol related proteins such as Tpx, Q7CR42, Q8ZP25, YfgD, AhpC, NfsB, YdhD and TrxA, as well as the levels of free cellular thiol after 6 h of cultivation, suggesting that these cells have greater potential to resist oxidative stress. Additionally, the LuxS protein which synthesizes the AI-2 signaling molecule was differentially abundant in the presence of C12-HSL. The NfsB protein had its abundance increased in the presence of C12-HSL at all evaluated times, which is a suggestion that the cells may be susceptible to the action of nitrofurans or that AHLs present some toxicity. Overall, the presence of C12-HSL altered important pathways related to oxidative stress and stationary phase response in Salmonella.

Our work demonstrated a dynamic yet stable microbial ecosystem during cheese production using an endogenous starter culture. This was observed across several distinct producers and was marked by genomic evidence of continued phage-bacterium interactions, such as the presence of bacterial defense mechanisms. Microbial starter cultures are used in the production of many cheeses around the world, such as Parmigiano-Reggiano, in Italy, Époisses, in France, and Canastra, in Brazil, providing many of the unique features of these cheeses. Bacteriophages (phages) are ubiquitous and well known to modulate the structure of bacterial communities, and recent data indicate that cheeses contain a high abundance of naturally occurring phages. Here, we analyze the viral and bacterial metagenomes of Canastra cheese: a traditional artisanal Brazilian cheese produced using an endogenous starter culture and raw milk. Over 1,200 viral operational taxonomic units were recovered using both isolated viral-like particles and complete metagenomic DNA. Common viral families identified included Siphoviridae and Myoviridae , with 40% of putative phage genomes unidentified at the family level of classification. We observed very high phage diversity, which varied greatly across different cheese producers, with 28% of phage genomes detected in only one producer. Several metagenome-assembled genomes were recovered for lactic acid-producing bacteria, as well as nonstarter bacterial species, and we identified several phage-bacterium interactions, at the strain level of resolution, varying across distinct cheese producers. We postulate that at least one bacterial strain detected could be endogenous and unique to the Canastra cheese-producing region in Brazil and that its growth seems to be modulated by autochthonous phages present in this artisanal production system. This phage-host relationship is likely to influence the fermentation dynamics and ultimately the sensorial profile of these cheeses, with implications for other similar cheese production systems around the world. IMPORTANCE Our work demonstrated a dynamic yet stable microbial ecosystem during cheese production using an endogenous starter culture. This was observed across several distinct producers and was marked by genomic evidence of continued phage-bacterium interactions, such as the presence of bacterial defense mechanisms. Furthermore, we provide evidence of unique microbial signatures for each individual cheese producer studied in the region, a fact that may have profound consequences on product traceability. This was the first effort to describe and understand the bacteriophage composition and ecological dynamics within the Brazilian Canastra cheese production system. The study of this prototypical backslopping production system provides a solid background for further mechanistic studies of the production of many cheeses around the world.

This study aims to clarify the use of Limosilactobaillus reuteri (Lmb. reuteri) in dairy products, emphasizing its main characteristics and limitations through a comprehensive literature review. Lmb. reuteri, previously classified as Lactobacillus reuteri, is a lactic acid bacterium (LAB) generally present in the gastrointestinal tracts of humans and other animals, such as sheep, chickens, and rodents. Lmb. reuteri was reclassified as part of the genus Limosilactobacillus in April 2020, reflecting advancements in biomolecular research that identified distinct metabolic and biochemical characteristics among strains. This species is an important producer of reuterin, an antimicrobial compound facilitated through glycerol fermentation via specific enzymatic pathways. In addition, selected strains of Lmb. reuteri can be considered probiotic bacteria with numerous health benefits and that lead to well-being improvements. It is consistently related to improvements in gut health, immune function enhancement, and cholesterol reduction. Furthermore, its application in dairy products has gained prominence and is increasingly reported in the literature due to its technological and sensory benefits. Despite the challenges of its incorporation into the dairy matrix, largely due to the need to supplement these products, it has already demonstrated significant effects on several dairy products’ technological, sensory, and quality characteristics. Future research should address challenges like strain-specific efficacy and regulatory hurdles for the application of Lmb. reuteri in foods.

Brazilian artisanal cheeses have recently gained significant commercial prominence and consumer favor, primarily due to their distinctive sensory attributes and cultural and historical appeal. Many of these cheeses are made with raw milk and undergo a relatively short ripening period, sometimes ranging from 4 to 8 days, though it is usually shorter than the period stated by law. Moreover, there is insufficient evidence regarding the efficacy of a short ripening period in reducing certain zoonotic foodborne pathogens, such as Brucella spp., Coxiella burnetiid, and Mycobacterium bovis (as part of the Mycobacterium tuberculosis complex). Additionally, a literature analysis revealed that the usual ripening conditions of Brazilian artisanal cheeses made with raw milk may be inefficient in reducing the levels of some hazardous bacterial, including Brucella spp., Listeria monocytogenes, coagulase-positive Staphylococcus, Salmonella, and Coxiella burnetti, to the acceptable limits established by law, thus failing to ensure product safety for all cheese types. Moreover, the assessment of the microbiological safety for this type of cheese should be broader and should also consider zoonotic pathogens commonly found in bovine herds. Finally, a standardized protocol for evaluating the effectiveness of cheese ripening must be established by considering its peculiarities.

Staphylococcus spp. present a dual role in cheese production as some species are pathogenic, while others bring beneficial characteristics. Coagulase-positive staphylococci (CoPS), particularly Staphylococcus aureus, are of concern due to their ability to produce enterotoxins linked to foodborne outbreaks. These toxins, encoded by staphylococcal enterotoxin (SE) genes, cause gastroenteritis, especially vomiting. Many members of the genus harbor a plethora of virulence genes and are able to form biofilms. The prevalence of antibiotic-resistant strains, including methicillin-resistant S. aureus (MRSA), complicates control. In contrast, some members of the coagulase-negative staphylococci (CoNS) group, such as Staphylococcus carnosus, Staphylococcus condimenti, Staphylococcus equorum, Staphylococcus piscifermentans, Staphylococcus succinus, and Staphylococcus xylosus, contribute to ripening, influencing flavor and texture. Some are even considered safe and studied for their ability to inhibit pathogens. Expression of enterotoxin genes in Staphylococcus, particularly S. aureus, is influenced by environmental factors and can be regulated by different mechanisms including quorum sensing. Understanding gene expression in conditions found during cheese production and ripening can help in formulating effective interventions. Risks posed by enterotoxin-producing Staphylococcus in cheese are evident, with numerous outbreaks reported worldwide. Moreover, several species present risks to both animal and human health. Effective control measures include adherence to microbiological criteria in foods, animal health monitoring, good manufacturing practices (GMP), temperature control, proper ripening conditions and hygiene. This review compiles and discusses existing knowledge on CoPS and CoNS in cheeses, providing a framework for evaluating their risks and benefits and guiding future studies in cheese microbiology.

This study evaluated the antagonistic activity of the cell-free supernatant of ATCC 9595 ( -CFS) against , a major foodborne pathogen, that represents a challenge to food safety, due to its remarkable tolerance to environmental stresses and strong biofilm-forming ability. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of -CFS against were defined as 31.25 and 62.5 mg/mL, respectively. Time-kill assays revealed dose- and time-dependent bactericidal effects. At sub-MICs, -CFS significantly reduced biofilm formation, disrupted preformed biofilms and decreased cell viability (80.3-96.7%), effects that were confirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and fluorescence microscopy. Transmission electron microscopy showed cell wall damage, cytoplasmic leakage, and morphological alterations consistent with bactericidal effects. Additionally, exposure to 1x and 2x MIC of -CFS induced reactive oxygen species (ROS) accumulation, indicating oxidative stress as part of the mechanism by which -CFS exerts its antimicrobial activity. Gene expression analysis revealed upregulation of stress and virulence-associated genes ( , , , , , , , and ) upon exposure to 0.5x MIC suggesting a complex cross-talk network between adaptive mechanisms and environmental stresses. Although initiates a stress response, it appears unable to counteract the damage induced by -CFS, resulting in cell death. These findings highlight the antimicrobial and anti-biofilm properties of -CFS against . Given its in vitro efficacy, -CFS emerges as a promising biocontrol agent to improve food safety by mitigating the persistence of in food processing settings.

Bacteria coordinate gene expression in a cell density-dependent manner in a communication process called quorum sensing (QS). The expression of virulence factors, biofilm formation and enzyme production are QS-regulated phenotypes that can interfere in human health. Due to this importance, there is great interest in inhibiting QS, comprising an anti-virulence strategy. This work aimed to evaluate the effect of selected phenolic compounds on the inhibition of QS-regulated phenotypes in Pseudomonas aeruginosa PAO1, using concentrations that do not interfere in bacterial growth. This is one of the main premises for studying the effect of compounds on QS. Firstly, an in-silico study with the LasR and RhlR proteins of P. aeruginosa by molecular docking of 82 phenolic compounds was performed. Then, a screening with 13 selected phenolic compounds was performed, using biosensor strains P. aeruginosa lasB-gfp and P. aeruginosa rhlA-gfp , which emit fluorescence when the QS system is activated. From this assay, eight compounds were selected and evaluated for inhibition of pyocyanin, rhamnolipids, proteases, elastase, and motility. The compounds variably inhibited the evaluated virulence factors. The greatest inhibitions were observed for swarming motility, achieving inhibition rates of up to 50% for baicalein (500 µM) and curcumin (50 µM). Notably, curcumin showed satisfactory inhibition for all phenotypes even at lower concentrations (12.5 to 50 µM) compared to the other compounds (125 to 500 µM). Four compounds - rosmarinic acid, baicalein, curcumin, and resveratrol - were finally tested against biofilm formation observed by optical microscopy. This study demonstrated that phenolic compounds exhibit strong in silico binding to P. aeruginosa LasR and RhlR proteins and variably inhibit QS-regulated phenotypes in vitro. Although no biofilm inhibition was observed, future studies combining compounds and exploring molecular mechanisms are recommended. These findings highlight the biotechnological potential of phenolic compounds for future applications in the food, clinical, and pharmaceutical fields.