Lethality Prediction for Escherichia Coli O157:H7 and Uropathogenic E. coli in Ground Chicken Treated with High Pressure Processing and Trans-Cinnamaldehyde

Bioactive Compounds from Plant Origin as Natural Antimicrobial Agents for the Treatment of Wound Infections

The rising prevalence of drug-resistant bacteria underscores the need to search for innovative and nature-based solutions. One of the approaches may be the use of plants that constitute a rich source of miscellaneous compounds with a wide range of biological properties. This review explores the antimicrobial activity of seven bioactives and their possible molecular mechanisms of action. Special attention was focused on the antibacterial properties of berberine, catechin, chelerythrine, cinnamaldehyde, ellagic acid, proanthocyanidin, and sanguinarine against Staphylococcus aureus, Enterococcus spp., Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa. The growing interest in novel therapeutic strategies based on new plant-derived formulations was confirmed by the growing number of articles. Natural products are one of the most promising and intensively examined agents to combat the consequences of the overuse and misuse of classical antibiotics.

Advances, Applications, and Comparison of Thermal (Pasteurization, Sterilization, and Aseptic Packaging) against Non-Thermal (Ultrasounds, UV Radiation, Ozonation, High Hydrostatic Pressure) Technologies in Food Processing

Nowadays, food treatment technologies are constantly evolving due to an increasing demand for healthier and tastier food with longer shelf lives. In this review, our aim is to highlight the advantages and disadvantages of some of the most exploited industrial techniques for food processing and microorganism deactivation, dividing them into those that exploit high temperatures (pasteurization, sterilization, aseptic packaging) and those that operate thanks to their inherent chemical–physical principles (ultrasound, ultraviolet radiation, ozonation, high hydrostatic pressure). The traditional thermal methods can reduce the number of pathogenic microorganisms to safe levels, but non-thermal technologies can also reduce or remove the adverse effects that occur using high temperatures. In the case of ultrasound, which inactivates pathogens, recent advances in food treatment are reported. Throughout the text, novel discoveries of the last decade are presented, and non-thermal methods have been demonstrated to be more attractive for processing a huge variety of foods. Preserving the quality and nutritional values of the product itself and at the same time reducing bacteria and extending shelf life are the primary targets of conscious producers, and with non-thermal technologies, they are increasingly possible.

Effect of plant-derived antimicrobials against multidrug-resistant Salmonella Heidelberg in ground Turkey

Salmonella Heidelberg (SH) is a highly invasive human pathogen for which turkeys can serve as reservoir hosts. Colonization of turkeys with SH may result in potential contamination and is a greater challenge to prevent in comminuted products. Antimicrobial efficacy of 3 GRAS-status plant-derived antimicrobials (PDAs), lemongrass essential oil (LG), citral (CIT), and trans-cinnamaldehyde (TC), against SH in ground turkey, a comminuted product implicated in several outbreaks, was evaluated in this study. Ground turkey samples inoculated with ∼3.50 log₁₀ CFU/g of a three-strain SH cocktail were treated with either LG, CIT, or TC at either 0.5, 1, or 2% (vol/wt). Samples were stored at 4°C, and bacterial enumeration was performed on d 0, 1, 3, and 5. Appropriate controls were included alongside all treatments. Fluorescence microscopy was performed to evaluate the direct impact of the PDAs against SH in vitro. Appearance and aroma difference testing of raw patties was also performed for select treatments with trained sensory panelists. Treatment with 2% TC yielded a 2.5 log₁₀ CFU/g reduction by d 1 and complete reduction by d 5 (P < 0.05). By d 3, 2% CIT and 2% LG resulted in SH reduction of at least 1.7 log₁₀ CFU/g (P < 0.05). Addition of 1% TC resulted in reduction of at least 1.8 log₁₀ CFU/g by d 3 (P < 0.05). Participants could distinguish PDA-treated raw patties by aroma. Most participants (7/11) could not distinguish patties treated with 0.5% TC based on appearance. Microscopic images indicate that all PDAs resulted in disruption of the SH membrane. Results of the present study indicate that the three tested PDAs, LG, CIT, and TC are effective against SH in ground turkey, indicating their potential use as interventions to mitigate Salmonella contamination in comminuted turkey products.

The Inclusion of the Food Microstructural Influence in Predictive Microbiology: State-of-the-Art

Predictive microbiology has steadily evolved into one of the most important tools to assess and control the microbiological safety of food products. Predictive models were traditionally developed based on experiments in liquid laboratory media, meaning that food microstructural effects were not represented in these models. Since food microstructure is known to exert a significant effect on microbial growth and inactivation dynamics, the applicability of predictive models is limited if food microstructure is not taken into account. Over the last 10-20 years, researchers, therefore, developed a variety of models that do include certain food microstructural influences. This review provides an overview of the most notable microstructure-including models which were developed over the years, both for microbial growth and inactivation.

Synthesis of Escherichia coli OmpA Oral Nanoparticles and Evaluation of Immune Functions against the Major Etiologic Agent of Cow Mastitis

Escherichia coli is a major etiologic agent of cow mastitis, a condition that results in huge economic losses. There is a lack of an oral vaccine for cow mastitis. Previous studies have confirmed that the outer membrane protein A (OmpA) of E. coli is immunogenic and can be used for vaccine design. In the present study, OmpA was encapsulated into nanoparticles (NP-OmpA) for an oral vaccine for cow mastitis. Methods: OmpA was purified with Ni-NTA flow resin and encapsulated with chitosan (CS) to prepare NP-OmpA nanoparticles. The gastrointestinal tract was simulated in vitro (PBS, pH 1.2) to measure the protein release rate. The optimal preparation conditions for NP-OmpA were determined by analyzing the concentrations of OmpA and CS, magnetic mixing speed, mixing time, and the ratio of tripolyphosphate (TPP)/CS (w/w). NP-OmpA safety was assessed by function factors and histopathological examination of livers and kidneys. The immune activity of NP-OmpA was determined using qRT-PCR to assess immune-related gene expression, leukocyte phagocytosis of Staphylococcus aureus, ELISA to evaluate antiserum titer and immune recognition of E. coli, and the organ index. The immune protection function of NP-OmpA was assessed by the protection rate of NP-OmpA to E. coli in mice, qRT-PCR for inflammation-related gene expression, assay kits for antioxidant factors, and visceral injury in the histopathological sections. Results: NP-OmpA nanoparticles had a diameter of about 700 nm, loading efficiency (LE) of 79.27%, and loading capacity (LC) of 20.31%. The release rate of NP-OmpA (0~96 h) was less than 50% in vitro. The optimal preparation conditions for NP-OmpAs were OmpA protein concentration of 2 mg/mL, CS concentration of 5 mg/mL, TPP/CS (w/w) of 1:1, magnetic mixing speed of 150 r/min, and mixing time of 15 min. Histopathological sections and clinical analytes of uric acid (UA), creatinine (Cr), alanine aminotransferase (ALT), aspartate transaminase (AST), catalase (CAT), glutathione (GSH), and malondialdehyde (MDA) showed NP-OmpA did not damage mice livers or kidneys. NP-OmpA could enhance the immune-related gene expression of IFN-γ and HSP70 in the spleen, liver, and kidney and the leukocyte phagocytosis of S. aureus. The antiserum titer (1:3200) was obtained from mice immunized with NP-OmpA, which had an immune recognition effect to E. coli. The immune protection rate of NP-OmpA was 71.43% (p < 0.05) to E. coli. NP-OmpA could down-regulate the inflammation-related gene expression of TNF-a, IL-6, and IL-10 in the spleen, liver, and kidney, and the antioxidant factors MDA and SOD in the liver, and reduce injury in the liver and kidney of mice induced by E. coli. Conclusions: A novel NP-OmpA nanoparticle was encapsulated, and the optimal preparation conditions were determined. The NP-OmpA was safe and had good immune functions. They are expected to induce a response that resists infection with the major etiologic agent (E. coli) of cow mastitis.

Modeling the effect of simultaneous use of allyl isothiocyanate and cinnamaldehyde on high hydrostatic pressure inactivation of Uropathogenic and Shiga toxin-producing Escherichia coli in ground chicken

BACKGROUND

A combination of high-pressure processing (HPP) and antimicrobials is a well-known approach for enhancing the microbiological safety of foods. However, few studies have applied multiple antimicrobials simultaneously with HPP, which could be an additional hurdle for microbial inactivation. The present study applied a full factorial design to investigate the impact of HPP (225-325 MPa; 10-20 min), allyl isothiocyanate (AITC) (0.3-0.9 g kg^-1 ) and trans-cinnamaldehyde (tCinn) (1.0-2.0 g kg^-1 ) on the inactivation of Shiga toxin-producing Escherichia coli (STEC) O157:H7 and uropathogenic E. coli (UPEC) in ground chicken meat.

RESULTS

The regulatory requirement of 5-log reduction was achieved at 305 MPa, 18 min, 0.8 g kg^-1 AITC and 1.7 g kg^-1 tCinn for STEC O157:H7 and at 293 MPa, 16 min, 0.6 g kg^-1 AITC and 1.6 g kg^-1 tCinn for UPEC, as specified by response surface analysis and verified via experiments. The surviving population was eliminated by post-treatment storage of 9 days at 10 °C. The developed linear regression models showed r²  > 0.9 for the E. coli inactivation. The developed dimensionless non-linear regression models covered a factorial range slightly wider than the original experimental limit, with probability P_r  > F (< 0.0001).

CONCLUSION

Simultaneous use of AITC and tCinn reduced not only the necessary concentration of each compound, but also the intensity of high-pressure treatments, at the same time achieving a similar level of microbial inactivation. STEC O157:H7 was found to be more resistant than UPEC to the HPP-AITC-tCinn stress. The developed models may be applied in commercial application to enhance the microbiological safety of ground chicken meat. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Effect of corn starch coating incorporated with nanoemulsion of Zataria multiflora essential oil fortified with cinnamaldehyde on microbial quality of fresh chicken meat and fate of inoculated Listeria monocytogenes

The present study compared the effects of corn starch coatings incorporated with Zataria multiflora essential oil (ZEO) and cinnamaldehyde (CIN) in conventional, nanoemulsion (NZEO) and fortified nanoemulsion (NZEOC) forms, on specific spoilage microorganisms of chicken meat and on the fate of inoculated Listeria monocytogenes during 20 days storage at 4 ± 1 °C. Based on the results of GC-MS analysis of ZEO, carvacrol (36.62%) was the most important compound of essential oil. Samples coated with the starch solution containing nanoemulsions had better antimicrobial activities than conventional forms. Also, NZEOC treatment had the best antimicrobial properties at the end of storage with the following results: Total viable count (7.96 log₁₀ CFU/g), Psychrotrophic count (7.29 log₁₀ CFU/g), Lactic acid bacteria (6.51 log₁₀ CFU/g), Enterobacteriaceae count (6.98 log₁₀ CFU/g), Mold and yeast count (5.16 log₁₀ CFU/g) and inoculated L. monocytogenes (6.51 log₁₀ CFU/g). Furthermore, the addition of CIN-ZEO during nanoemulsion formation (NZEOC) increased the antimicrobial properties of the samples compared to individual addition of NZEO and CIN (NZEO + CIN) to the starch solution. Therefore, corn starch coating containing NZEOC is recommended as a natural preservative to enhance the microbial stability of poultry meat.

Inactivation of foodborne pathogens by the synergistic combinations of food processing technologies and food-grade compounds

There is a need to develop food processing technologies with enhanced antimicrobial capacity against foodborne pathogens. While considering the challenges of adequate inactivation of pathogenic microorganisms in different food matrices, the emerging technologies are also expected to be sustainable and have a minimum impact on food quality and nutrients. Synergistic combinations of food processing technologies and food-grade compounds have a great potential to address these needs. During these combined treatments, food processes directly or indirectly interact with added chemicals, intensifying the overall antimicrobial effect. This review provides an overview of the combinations of different thermal or nonthermal processes with a variety of food-grade compounds that show synergistic antimicrobial effect against pathogenic microorganisms in foods and model systems. Further, we summarize the underlying mechanisms for representative combined treatments that are responsible for the enhanced microbial inactivation. Finally, regulatory issues and challenges for further development and technical transfer of these new approaches at the industrial level are also discussed.

Survival Evaluation of Salmonella and Listeria monocytogenes on Selective and Nonselective Media in Ground Chicken Meat Subjected to High Hydrostatic Pressure and Carvacrol

High pressure processing (HPP) and treatment with the essential oil extract carvacrol had synergistic inactivation effects on Salmonella and Listeria monocytogenes in fresh ground chicken meat. Seven days after HPP treatment at 350 MPa for 10 min, Salmonella treated with 0.75% carvacrol was reduced to below the detection limit (1 log CFU/g) at 4°C and was reduced by ca. 6 log CFU at 10°C. L. monocytogenes was more sensitive to these imposed stressors, remaining below the detection limit during storage at both 4 and 10°C after HPP treatment at 350 MPa for 10 min following treatment with 0.45% carvacrol. However, pressure-injured bacterial cells may recover and lead to an overestimation of process lethality when a selective medium is used without proper justification. For HPP-stressed Salmonella, a 1- to 2-log difference was found between viable counts on xylose lysine Tergitol 4 agar and aerobic plate counts, but no significant difference was found for HPP-stressed L. monocytogenes between polymyxin-acriflavine-lithium chloride-ceftazidime-esculin-mannitol (PALCAM) agar and aerobic plate counts. HPP-induced bacterial injury and its recovery have been investigated by comparing selective and nonselective agar plate counts; however, few investigations have addressed this issue in the presence of essential oil extracts, taking into account the effect of high pressure and natural antimicrobial compounds (e.g., carvacrol) on bacterial survival in various growth media. Use of selective media may overestimate the efficacy of bacterial inactivation in food processing evaluation and validation studies, and the effects of various media should be systematically investigated.

Modeling the Survival of Escherichia coli O157:H7 Under Hydrostatic Pressure, Process Temperature, Time and Allyl Isothiocyanate Stresses in Ground Chicken Meat

Shiga toxin-producing Escherichia coli O157:H7 (STEC) is a common contaminant in meat and poultry. We investigated the use of non-thermal high pressure processing (HPP), with or without allyl isothiocyanate (AITC) essential oil, to kill STEC in ground chicken meat. Temperature was found an important factor affecting the inactivation of STEC in addition to pressure and process time. A full factorial experiment design (4 factors × 2 levels) was used to facilitate and evaluate the effect of pressure (250–350 MPa), operation temperature (−15–4°C), AITC concentration (0.05–0.15%, w/w), and pressure-holding time (10–20 min) on the inactivation of STEC. A linear model (a polynomial equation) was developed to predict/describe those four parameters’ impact on E. coli O157:H7 survival (R² = 0.90), as well as a dimensionless non-linear model. Both types of models were validated with data obtained from separate experimental points. The dimensionless model also demonstrated that it may predict the lethality (defined as the log CFU/g reduction of STEC before and after treatment) reasonably well with some factors set slightly outside the design ranges (e.g., a wider application than the linear model). The results provide important information regarding STEC survival as affected by HPP (e.g., pressure, time and temperature) and AITC. With the addition of AITC, the hydrostatic pressure may be lowered to the 250–350 MPa level. Regulatory agencies and food industry may use those models for STEC risk assessment in ground chicken meat. A storage test (at 4 and 10°C, 10 days) after HPP+AITC treatment indicated that AITC may continue depressing or killing the pressure-damaged cells.