Biofilm of Escherichia coli O157:H7 on cantaloupe surface is resistant to lauroyl arginate ethyl and sodium hypochlorite

Antibacterial mechanism of vanillin against Escherichia coli O157: H7

Vanillin, a plant-derived antimicrobial volatile substance, has potential microbial control applications in the food industry. However, the effect of vanillin on the food-borne pathogen Escherichia coli (E. coli) O157:H7 has not been well studied. This study aims to explore the antibacterial mechanism of vanillin against E. coli O157:H7. The minimum inhibitory concentration (MIC) and antibacterial effect of vanillin were determined by microdilution. Scanning electron microscopy (SEM) was used to observe the damage of vanillin to the cell membrane, while cell membrane potential and the leakage of nucleic acid protein were measured to explore the effect of vanillin on the membrane system. Confocal laser scanning and intracellular adenosine triphosphate (ATP) concentration determination were utilized to investigate the effects of vanillin on the energy, life, and death of E. coli. Finally, transcriptome sequencing was conducted to investigate the gene expression differences induced by vanillin treatment. The results showed that vanillin treatment effectively controlled E. coli O157:H7 with an MIC of 2 mg/mL. After treatment, damage to the membrane system, depolarization of the membrane, and leakage of nucleic acid and protein were observed. Meanwhile, vanillin treatment caused decreased ATP content and cell death. Transcriptome analysis showed that vanillin treatment significantly affected the expression of genes involved in cell membrane formation, tricarboxylic acid (TCA) cycling pathway, and oxidative phosphorylation pathway in E. coli O157:H7. In conclusion, membrane damage and energy metabolism disruption are important mechanisms of vanillin's inhibitory effect on E. coli O157:H7. This study provides new insights into the molecular reaction mechanism of vanillin against E. coli O157:H7, highlighting its potential as an antibacterial substance for preventing E. coli contamination in the food industry.

Lauric arginate ethyl ester: An update on the antimicrobial potential and application in the food systems

Lauric arginate ethyl ester (LAE), a cationic surfactant with low toxicity, displays excellent antimicrobial activity against a broad range of microorganisms. LAE has been approved as generally recognized as safe (GRAS) for widespread application in certain foods at a maximum concentration of 200 ppm. In this context, extensive research has been carried out on the application of LAE in food preservation for improving the microbiological safety and quality characteristics of various food products. This study aims to present a general review of recent research progress on the antimicrobial efficacy of LAE and its application in the food industry. It covers the physicochemical properties, antimicrobial efficacy of LAE, and the underlying mechanism of its action. This review also summarizes the application of LAE in various foods products as well as its influence on the nutritional and sensory properties of such foods. Additionally, the main factors influencing the antimicrobial efficacy of LAE are reviewed in this work, and combination strategies are provided to enhance the antimicrobial potency of LAE. Finally, the concluding remarks and possible recommendations for the future research are also presented in this review. In summary, LAE has the great potential application in the food industry. Overall, the present review intends to improve the application of LAE in food preservation.

Control Measurements of Escherichia coli Biofilm: A Review

Escherichia coli (E. coli) is a common pathogen that causes diarrhea in humans and animals. In particular, E. coli can easily form biofilm on the surface of living or non-living carriers, which can lead to the cross-contamination of food. This review mainly summarizes the formation process of E. coli biofilm, the prevalence of biofilm in the food industry, and inhibition methods of E. coli biofilm, including chemical and physical methods, and inhibition by bioactive extracts from plants and animals. This review aims to provide a basis for the prevention and control of E. coli biofilm in the food industry.

Inactivation of Polymicrobial Biofilms of Foodborne Pathogens Using Epsilon Poly-L-Lysin Conjugated Chitosan Nanoparticles

A mixed culture (polymicrobial) biofilm provides a favorable environment for pathogens to persist in the food processing environment and to contaminate food products. Inactivation and eradication of such biofilms from food processing environments are achieved by using harsh disinfectants, but their toxicity and environmentally hostile characteristics are unsustainable. This study aims to use food-grade natural nanoparticulated antimicrobials to control mixed-culture biofilms. Chitosan, a natural broad-spectrum antimicrobial biopolymer (polysaccharide) from crustaceans, was derivatized to produce chitosan nanoparticles (ChNP) as a carrier for another broad-spectrum antimicrobial agent, ε-poly-L-lysine (PL), to synthesize ChNP-PL conjugate. The antimicrobial activity of ChNP and ChNP-PL was tested against mixed-culture biofilms. ChNP-PL (~100 nm) exhibited a synergistic antimicrobial and anti-biofilm effect against mono or mixed-culture biofilms of five foodborne pathogens, including Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica serovar Enteritidis, Escherichia coli O157:H7, and Pseudomonas aeruginosa. ChNP-PL treatment prevented biofilm formation by mono or mixed cultures of L. monocytogenes, P. aeruginosa, and E. coli O157:H7, and bacterial counts were either below the detection limit or caused 3.5–5 log reduction. ChNP-PL also inactivated preformed biofilms. In monoculture biofilm, ChNP-PL treatment reduced L. monocytogenes counts by 4.5 logs, S. Enteritidis by 2 logs, E. coli by 2 logs, and S. aureus by 0.5 logs, while ChNP-PL had no inhibitory effect on P. aeruginosa. In vitro mammalian cell-based cytotoxicity analysis confirmed ChNP-PL to have no deleterious effect on intestinal HCT-8 cell line. In conclusion, our results show ChNP-PL has strong potential to prevent the formation or inactivation of preformed polymicrobial biofilms of foodborne pathogens.

Physics Comes to the Aid of Medicine-Clinically-Relevant Microorganisms through the Eyes of Atomic Force Microscope

Despite the hope that was raised with the implementation of antibiotics to the treatment of infections in medical practice, the initial enthusiasm has substantially faded due to increasing drug resistance in pathogenic microorganisms. Therefore, there is a need for novel analytical and diagnostic methods in order to extend our knowledge regarding the mode of action of the conventional and novel antimicrobial agents from a perspective of single microbial cells as well as their communities growing in infected sites, i.e., biofilms. In recent years, atomic force microscopy (AFM) has been mostly used to study different aspects of the pathophysiology of noninfectious conditions with attempts to characterize morphological and rheological properties of tissues, individual mammalian cells as well as their organelles and extracellular matrix, and cells’ mechanical changes upon exposure to different stimuli. At the same time, an ever-growing number of studies have demonstrated AFM as a valuable approach in studying microorganisms in regard to changes in their morphology and nanomechanical properties, e.g., stiffness in response to antimicrobial treatment or interaction with a substrate as well as the mechanisms behind their virulence. This review summarizes recent developments and the authors’ point of view on AFM-based evaluation of microorganisms’ response to applied antimicrobial treatment within a group of selected bacteria, fungi, and viruses. The AFM potential in development of modern diagnostic and therapeutic methods for combating of infections caused by drug-resistant bacterial strains is also discussed.

The attachment process and physiological properties of Escherichia coli O157:H7 on quartz

Background

Manure application and sewage irrigation release many intestinal pathogens into the soil. After being introduced into the soil matrix, pathogens are commonly found to attach to soil minerals. Although the survival of mineral-associated Escherichia coli O157:H7 has been studied, a comprehensive understanding of the attachment process and physiological properties after attachment is still lacking.

Results

In this study, planktonic and attached Escherichia coli O157:H7 cells on quartz were investigated using RNA sequencing (RNA-seq) and the isobaric tagging for relative and absolute quantitation (iTRAQ) proteomic method. Based on the transcriptomic and proteomic analyses and gene knockouts, functional two-component system pathways were required for efficient attachment; chemotaxis and the Rcs system were identified to play determinant roles in E. coli O157:H7 attachment on quartz. After attachment, the pyruvate catabolic pathway shifted from the tricarboxylic acid (TCA) cycle toward the fermentative route. The survival rate of attached E. coli O157:H7 increased more than 10-fold under penicillin and vancomycin stress and doubled under alkaline pH and ferric iron stress.

Conclusions

These results contribute to the understanding of the roles of chemotaxis and the Rcs system in the attachment process of pathogens and indicate that the attachment of pathogens to minerals significantly elevates their resistance to antibiotics and environmental stress, which may pose a potential threat to public health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-020-02043-8.

Salmonella, Listeria monocytogenes, and Indicator Microorganisms on Hass Avocados Sold at Retail Markets in Guadalajara, Mexico

Hass avocados may become contaminated with Salmonella and Listeria monocytogenes at the farm and the packing facility or later during transportation and at retail. In Mexico, avocados are frequently sold in bulk at retail markets, where they are stored at room temperature for several hours or days and exposed to potential sources of microorganisms. These conditions may favor the entry, adhesion, survival, and biofilm formation of Salmonella and L. monocytogenes. The aim of this study was to determine the occurrence of Salmonella, L. monocytogenes, and other Listeria species and the levels of indicator microorganisms on the surface of avocados sold at retail markets. A total of 450 samples (Persea americana var. Hass) were acquired from retail markets located in Guadalajara, Mexico. One group of 225 samples was evaluated for the presence of Salmonella and for enumeration of aerobic plate counts, yeasts and molds, Enterobacteriaceae, coliforms, and Escherichia coli. The other 225 samples were processed for isolation of L. monocytogenes and other Listeria species. Microbial counts (log CFU per avocado) were 4.3 to 9.0 for aerobic plate counts, 3.3 to 7.1 for yeasts and molds, 3.3 to 8.2 for Enterobacteriaceae, 3.3 to 8.4 for coliforms, and 3.3 to 6.2 for E. coli. Eight samples (3.5%) were positive for Salmonella. Listeria spp. and L. monocytogenes were detected in 31 (13.8%) and 18 (8.0%) of 225 samples, respectively. Listeria innocua, Listeria welshimeri, and Listeria grayi were isolated from 7.6, 1.3, and 0.9% of samples. These results indicate that avocados may carry countable levels of microorganisms and could be a vehicle for transmission of Salmonella and L. monocytogenes.

Development of an Arginine Anchored Nanoglobule with Retrograde Trafficking Inhibitor (Retro-2) for the Treatment of an Enterohemorrhagic Escherichia coli Outbreak

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) or Shiga toxin-producing E. coli (STEC) is known to cause sporadic and epidemic gastrointestinal infections with several incidences of outbreaks. Antibiotic-based therapy further worsens the condition by facilitating the release of Shiga toxins (Stx) and lipopolysaccharides (LPS). Hence, there is an urgent need to develop an antibiotic-free, safe, and effective therapeutic intervention for the treatment of EHEC infections. We proposed a novel therapeutic strategy to address this clinical problem-kill, capture, and inhibit. We aimed to formulate and characterize lauroyl arginate ethyl ester (LAE) and Retro-2 loaded self-nano emulsifying drug delivery systems (SNEDDS). Retro-2 is a recently developed novel class of molecule, which can selectively inhibit retrograde transport of Stx. In this paper, we first carried out preformulation studies of Retro-2, followed by the development of SNEDDS forming arginine anchored nanoglobules (AR-NG), characterization of LPS binding to AR-NG, and finally evaluation of activity against EHEC. Retro-2 showed extremely poor solubility at all gastrointestinal pH values, susceptibility to acidic environments, and good permeability. The positively charged AR-NG spontaneously formed a globule size of 102.8 ± 1.9 nm with a surface charge of +52.15 ± 3 mV and increased the solubility of Retro-2. Further, binding and aggregation of LPS and AR-NG were confirmed by particle size, polydispersity index, zeta potential, fluorescent intensity, turbidity analysis, and a limulus amebocyte lysate (LAL) test. Additionally, a significant reduction in LPS induced TNF-α was observed in AR-NG treated macrophages. Thus, in this paper, we demonstrate a very promising and innovative therapeutic approach based on the "kill (E. Coli), capture (released LPS), and inhibit (transport of Stx)" concept.

Disinfectant Resistance Profiles and Biofilm Formation Capacity of Escherichia coli Isolated from Retail Chicken

Disinfectant resistance and biofilm formation capacity are two important characteristics that contribute to the persistence of microorganisms in food processing environments and contamination of food products. This study investigated the susceptibility of 510 Escherichia coli isolates against 5 disinfectants and the prevalence of 10 disinfectant-resistant genes in these isolates. The biofilm formation capacity of 194 isolates was determined, and the correlation between disinfectant resistance and biofilm formation was analyzed. The minimal inhibitory concentrations (MICs) of cetyltrimethylammonium bromide (CTAB), benzalkonium chloride (BC), cetylpyridinium chloride, and chlorhexidine (CHX) against isolates were 32-512, 16-256, 32-256, and 2-32 mg/L, respectively. The MICs of triclosan against 88.43% of isolates were 8-1,024 mg/L, while the MICs for the rest of isolates exceed 2,048 mg/L. The presence of ydgE, ydgF, and qacF genes was significantly correlated with the CHX resistance of E. coli isolates, while the presence of qacF and qacEΔ1 genes was significantly correlated with CTAB and BC resistance, respectively. The biofilm formation capacity (adjusted optical density value) was positively correlated with BC resistance (r = 0.201, p < 0.01) and showed no correlation with other disinfectants. The presence of sugE(p) was positively correlated with biofilm formation, while four genes were negatively correlated with biofilm formation. This study provides useful data on disinfectant resistance and biofilm formation capacity of E. coli contaminating poultry products, which could be helpful in guiding proper disinfectant usage and establishing effective biofilm eradication strategy in food industry.