Antibiofilm activity of the biosurfactant and organic acids against foodborne pathogens at different temperatures, times of contact, and concentrations

Comparative Assessment of the Antibacterial and Antibiofilm Actions of Benzalkonium Chloride, Erythromycin, and L(+)-Lactic Acid against Raw Chicken Meat Campylobacter spp. Isolates

Campylobacter spp. are significant zoonotic agents, which cause annually millions of human cases of foodborne gastroenteritis worldwide. Their inclusion in biofilms on abiotic surfaces seems to play a pivotal role in their survival outside of the host, growth, and spread. To successfully mitigate the risks that arise with these bacteria, it is crucial to decrease their prevalence within the food production chain (from farm to the table), alongside the successful treatment of the resulting illness, known as campylobacteriosis. For this, the use of various antimicrobial agents remains actively in the foreground. A general-purpose biocide and cationic surfactant (benzalkonium chloride; BAC), a widely used macrolide antibiotic (erythromycin; ERY), and a naturally occurring organic acid (L(+)-lactic acid; LA) were comparatively evaluated in this work for their potential to inhibit both the planktonic and biofilm growth of 12 selected Campylobacter spp. (of which, seven were C. jejuni and five were C. coli) raw chicken meat isolates, all grown in vitro as monocultures. The inhibitory action of LA was also studied against four mixed-culture Campylobacter biofilms (each composed of three different isolates). The results showed that the individual effectiveness of the agents varied significantly depending on the isolate, growth mode (planktonic, biofilm), intercellular interactions (monocultures, mixed cultures), and the growth medium used (with special focus on blood presence). Thus, BAC exhibited minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and minimum biofilm inhibitory concentrations (MBICs) that ranged from 0.5 to 16 μg/mL. Interestingly enough, these values varied widely from 0.25 to 1024 μg/mL for ERY. Concerning LA, the MICs, MBCs, and MBICs varied from 1024 to 4096 μg/mL, with mixed-culture biofilm formation always being more difficult to suppress when compared to biofilm monocultures. In addition, it was evident that intercellular interactions encountered within mixed-culture Campylobacter biofilms significantly influenced both the population dynamics and the tolerance of each consortium member to acid exposure. Overall, the findings of this study provide useful information on the comparative effectiveness of three well-known antimicrobial agents for the control of Campylobacter spp. under various growth modes (i.e., planktonic, biofilm, monocultures, mixed cultures) that could potentially be encountered in food production and clinical settings.

An insight into the utilization of microbial biosurfactants pertaining to their industrial applications in the food sector

Microbial biosurfactants surpass synthetic alternatives due to their biodegradability, minimal toxicity, selective properties, and efficacy across a wide range of environmental conditions. Owing to their remarkable advantages, biosurfactants employability as effective emulsifiers and stabilizers, antimicrobial and antioxidant attributes, rendering them for integration into food preservation, processing, formulations, and packaging. The biosurfactants can also be derived from various types of food wastes. Biosurfactants are harnessed across multiple sectors within the food industry, ranging from condiments (mayonnaise) to baked goods (bread, muffins, loaves, cookies, and dough), and extending into the dairy industry (cheese, yogurt, and fermented milk). Additionally, their impact reaches the beverage industry, poultry feed, seafood products like tuna, as well as meat processing and instant foods, collectively redefining each sector's landscape. This review thoroughly explores the multifaceted utilization of biosurfactants within the food industry as emulsifiers, antimicrobial, antiadhesive, antibiofilm agents, shelf-life enhancers, texture modifiers, and foaming agents.

Adhesion capacity of Salmonella Enteritidis, Escherichia coli and Campylobacter jejuni on polystyrene, stainless steel, and polyethylene surfaces

Poultry products are recognized as the main source of Salmonella and Campylobacter jejuni infections in humans, while avian pathogenic Escherichia coli may have zoonotic potential and can be transmitted from chicken meat to humans. Biofilm formation contributes to their spread through the food chain. This study aimed to compare the adhesion of Salmonella Enteritidis, E. coli, and C. jejuni strains isolated from poultry, food implicated in outbreaks, and poultry slaughterhouses on three surfaces widely used in poultry production (polystyrene, stainless steel, and polyethylene). S. Enteritidis and E. coli adhesion on the three surfaces tested were not significantly different (p > 0.05). Interestingly, the number of C. jejuni cells on stainless steel (4.51-4.67 log₁₀ CFU/cm.^-2) was significantly higher (p = 0.0004) than that on polystyrene (3.80-4.25 log₁₀ CFU/cm.^-2), but similar (p > 0.05) to that on polyethylene (4.03-4.36 log₁₀ CFU/cm.^-2). However, C. jejuni adhesion was significantly lower (p < 0.05) than S. Enteritidis and E. coli adhesion, regardless of the surface evaluated. In addition, scanning electron microscopy analyses have shown an increased irregularity of the stainless steel surface when compared to polyethylene and polystyrene. These irregularities form small spaces ideal for microbial adhesion.

Antibiofilm activity of electrochemically activated water (ECAW) in the control of Salmonella Heidelberg biofilms on industrial surfaces

Owing to its antimicrobial activity, electrochemically activated water (ECAW) is a potential alternative to chemical disinfectants for eliminating foodborne pathogens, including Salmonella Heidelberg, from food processing facilities. However, their antibiofilm activity remains unclear. This study aimed to evaluate the antibiofilm activity of ECAW against S. Heidelberg biofilms formed on stainless steel and polyethylene and to determine its corrosive capacity. ECAW (200 ppm) and a broad-spectrum disinfectant (0.2%) were tested for their antibiofilm activity against S. Heidelberg at 25 °C and 37 °C after 10 and 20 min of contact with stainless steel and polyethylene. Potentiostatic polarization tests were performed to compare the corrosive capacity of both compounds. Both compounds were effective in removing S. Heidelberg biofilms. Bacterial counts were significantly lower with ECAW than with disinfectant in polyethylene, regardless the time of contact. The time of contact and the surface significantly influenced the bacterial counts of S. Heidelberg. Temperature was not an important factor affecting the antibiofilm activities of the compounds. ECAW was less corrosive than the disinfectant. ECAW demonstrated a similar or even superior effect in the control of S. Heidelberg biofilms, when compared to disinfectants, reducing bacterial counts by up to 5 log10 CFU cm-2. The corrosion of stainless steel with ECAW was similar to that of commercial disinfectants. This technology is a possible alternative for controlling S. Heidelberg in the food production chain.

Physiological and Transcriptomic Analyses of Escherichia coli Serotype O157:H7 in Response to Rhamnolipid Treatment

Rhamnolipid (RL) can inhibit biofilm formation of Escherichia coli O157:H7, but the associated mechanism remains unknown. We here conducted comparative physiological and transcriptomic analyses of cultures treated with RL and untreated cultures to elucidate a potential mechanism by which RL may inhibit biofilm formation in E. coli O157:H7. Anti-biofilm assays showed that over 70% of the E. coli O157:H7 biofilm formation capacity was inhibited by treatment with 0.25-1 mg/mL of RL. Cellular-level physiological analysis revealed that a high concentration of RL significantly reduced outer membrane hydrophobicity. E. coli cell membrane integrity and permeability were also significantly affected by RL due to an increase in the release of lipopolysaccharide (LPS) from the cell membrane. Furthermore, transcriptomic profiling showed 2601 differentially expressed genes (1344 up-regulated and 1257 down-regulated) in cells treated with RL compared to untreated cells. Functional enrichment analysis indicated that RL treatment up-regulated biosynthetic genes responsible for LPS synthesis, outer membrane protein synthesis, and flagellar assembly, and down-regulated genes required for poly-N-acetyl-glucosamine biosynthesis and genes present in the locus of enterocyte effacement pathogenicity island. In summary, RL treatment inhibited E. coli O157:H7 biofilm formation by modifying key outer membrane surface properties and expression levels of adhesion genes.

The Effect of Different Organic Acids and Their Combination on the Cell Barrier and Biofilm of Escherichia coli

Organic acids are natural antimicrobial compounds commonly used in the food industry. In this study, acetic, lactic, butyric, citric, and malic acid at minimum inhibitory concentrations and their combinations at optimal inhibition concentrations were used to treat E. coli, and the effects on the cell barrier and biofilm of E. coli were evaluated. Acetic acid showed the highest membrane-damaging effect, while citric acid and malic acid could specifically damage the cell wall of E. coli, leading to alkaline phosphatase leakage. The RT-qPCR results showed that organic acids upregulated the membrane-protein-related genes of E. coli, and the combination of organic acids had a wider range of effects than single organic acid treatment. Moreover, organic acids inhibited the formation of E. coli biofilm and cellular activity within the biofilm. This study showed that the combination of organic acids plays a synergistic inhibitory role mainly through multiple destructive effects on the cell barrier and exhibited synergistic anti-biofilm effects. The three-three combination of acetic, lactic acid, and a third organic acid (butyric, citric, or malic) can play a better synergistic antibacterial effect than the two-pair combination of acetic and lactic acid. These findings have implications for the usage, development, and optimization of organic acid combinations.