The Bactericidal Effect of a Combination of Food-Grade Compounds and their Application as Alternative Antibacterial Agents for Food Contact Surfaces

Current status of development and biomedical applications of peptide-based antimicrobial hydrogels

Microbial contamination poses a serious threat to human life and health. Through the intersection of material science and modern medicine, advanced bionic hydrogels have shown great potential for biomedical applications due to their unique bioactivity and ability to mimic the extracellular matrix environment. In particular, as a promising antimicrobial material, the synthesis and practical biomedical applications of peptide-based antimicrobial hydrogels have drawn increasing research interest. The synergistic effect of peptides and hydrogels facilitate the controlled release of antimicrobial agents and mitigation of their biotoxicity while achieving antimicrobial effects and protecting the active agents from degradation. This review reports on the progress and trends of researches in the last five years and provides a brief outlook, aiming to provide theoretical background on peptide-based antimicrobial hydrogels and make suggestions for future related work.

Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on stainless steel by synergistic effects of tap water-based neutral electrolyzed water and lactic acid

Contaminated food contact surface is one of the most important transmission routes for foodborne pathogens. Stainless steel is one such food-contact surface that is widely used in food-processing environments. The present study aimed to evaluate the synergistic antimicrobial efficacy of a combination of tap water-based neutral electrolyzed water (TNEW) and lactic acid (LA) against the foodborne pathogens Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on stainless steel. The results revealed that simultaneous treatment with TNEW (ACC of 4.60 mg/L) and 0.1% LA (TNEW-LA) for 5 min resulted in 4.99-, 4.34-, and >5.4- log CFU/cm² reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes on stainless steel, respectively. Of these, 4.00-, 3.57-, and >4.76-log CFU/cm² reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively were exclusively attributed to the synergistic action of the combined treatments after factoring out the reductions due to individual treatments. Furthermore, five mechanistic investigations revealed that the key mechanisms underlying the synergistic antibacterial effect of TNEW-LA were reactive oxygen species (ROS) production, cell membrane damage resulting from membrane lipid oxidation, DNA damage, and inactivation of intracellular enzymes. Overall, our findings suggest that the TNEW-LA combination treatment could be effectively used in the sanitization of food processing environments, especially the food contact surfaces, to control major pathogens and enhance food safety.

Antimicrobial potential of the Mayan medicine plant Matayba oppositifolia (A. Rich.) Britton against antibiotic-resistant priority pathogens

ETHNOPHARMACOLOGICAL RELEVANCE

The bark of Matayba oppositifolia (A. Rich.) Britton (commonly known as "huaya" or "palo huacax") is commonly utilized in traditional Mayan medicine for treating diarrhea and for canker and other sores.

AIM OF THE STUDY

The aim of this study was to investigate the in-vitro antimicrobial activity of M. oppositifolia bark extracts against drug-susceptible and -resistant ESKAPE-E pathogens. In addition, the phytochemical composition of the best antibacterial extract was analyzed.

MATERIALS AND METHODS

The bark extracts were prepared with different solvents, including water, n-hexane, ethyl acetate and methanol. These were tested against ESKAPE-E (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp., including Escherichia coli) strains using Resazurin Microtiter Assay. In addition, the composition of the most active extract was analyzed by GC-MS.

RESULTS

The aqueous and organic bark extracts showed activity on drug-susceptible and -resistant ESKAPE-E microbes (MIC = 1000-31.25 μg/mL). The n-hexane bark extract was more active against the superbugs carbapenem-resistant K. pneumoniae (MIC = 500-31.25 μg/mL) and A. baumannii (MIC = 250-125 μg/mL). The GC-MS analysis of this extract allowed the identification of 12 phytochemicals as the potential antibacterial compounds. The major compounds identified were palmitic acid (1), friedelan-3-one (2) and 7-dehydrodiosgenin (3).

CONCLUSION

The present study reveals the strong in-vitro antibacterial activity of the n-hexane extract from the bark of M. oppositifolia and demonstrates the potential of natural products as a source of antibacterial compounds or phytomedicines that are specifically effective against drug-resistant ESKAPE-E bugs. Additionally, our investigation contributes to the ethnopharmacological knowledge and reappraisal of Mayan medicinal flora, as well as supports the traditional use of the bark of the medicinal plant M. oppositifolia for the treatment of infectious diseases.

Susceptibility of Salmonella serotypes isolated from meat and meat contact surfaces to thermal, acidic, and alkaline treatments and disinfectants

The present study was conducted to evaluate the response of 29 Salmonella isolates to exposure to thermal (60°C for 2 min), acidic (pH 2.9 for 30 min), and alkaline (pH 11 for 60 min) treatments and investigate the susceptibility of the isolates and their biofilms to disinfectants. The reductions of Salmonella isolates populations subjected to each treatment were analyzed according to their isolation source, serotype, antibiotic resistance pattern, and biofilm formation ability. Median reductions for all of Salmonella isolates populations after thermal, acidic, and alkaline treatments were 1.8, 2.1, and 0.7 log CFU/ml, respectively. The isolates behavior under stress conditions were not related to their isolation source, serotype, or biofilm formation ability. The median reduction after alkaline treatment in non-MDR (multidrug- resistant) isolates populations was significantly (p < .05) higher than MDR isolates. The median reduction in biofilms of moderate biofilm producers by disinfectants was significantly (p < .05) higher than that of strong biofilm producers. In conclusion, Salmonella isolates showed the highest susceptibility to acidic treatment and MDR isolates were more resistant to alkaline treatment than non-MDR ones. The current study also revealed that the strong biofilm producer isolates were more resistant to disinfectants than moderate biofilm producers. This study facilitated the understanding of the relationship between Salmonella characteristics (isolation source, serotype, antibiotic resistance pattern, and biofilm formation ability) and its susceptibility to thermal, acidic, and alkaline treatments and disinfectants. The findings are helpful for the prevention and control of Salmonella.

Controlling of Mycobacterium by Natural Degradant-Combination Models for Sequestering Mycolic Acids in Karish Cheese

Degradation of the mycobacterial complex containing mycolic acids (MAs) by natural bioactive compounds is essential for producing safe and value-added foods with therapeutic activities. This study aimed to determine the degradation efficiency of natural organic acid extracts (i.e., citric, malic, tartaric, and lactic), quadri-mix extract from fruits and probiotics (i.e., lemon, apple, grape, and cell-free supernatant of Lactobacillus acidophilus), and synthetic pure organic acids (i.e., citric, malic, tartaric, and lactic), against MA in vitro in phosphate buffer solution (PBS) and Karish cheese models. The degradation effect was evaluated both individually and in combinations at different concentrations of degradants (1, 1.5, and 2%) and at various time intervals (0, 6, 12, 24, and 48 h). The results show that MA degradation percentage recorded its highest value at 2% of mixed fruit extract quadri-mix with L. acidophilus and reached 99.2% after 48 h both in PBS and Karish cheese, unlike other treatments (i.e., citric + malic + tartaric + lactic), individual acids, and sole extracts at all concentrations. Conversely, organic acid quadri-mix revealed the greatest MA degradation% of 95.9, 96.8, and 97.3% at 1, 1.5, and 2%, respectively, after 48 h. Citric acid was more effective in MA degradation than other acids. The fruit extract quadri-mix combined with L. acidophilus-fortified Karish cheese showed the highest sensorial characteristics; hence, it can be considered a novel food-grade degradant for MA and could be a promising biocontrol candidate against Mycobacterium tuberculosis (Mtb) in food matrices.

Synergistic antimicrobial effect and mode of action of palmarosa oil-loaded nanoemulsion and citric acid against Pectobacterium carotovorum

The synergistic antimicrobial activity of palmarosa oil (Cymbopogon martini, PO)-loaded nanoemulsion (PO-NE) and citric acid (CA) against Pectobacterium, the major pathogen for soft-rot disease, was evaluated. The combination of PO-NE and CA (PO-NE + CA) significantly improved the storage stability of PO-NE at 30 °C. Compared to the anti-Pectobacterium activity of alone, PO-NE + CA reduced the minimum inhibitory concentration (MIC) by 1/4 and 1/2, respectively. Bactericidal efficacy of PO-NE + CA against P. carotovorum PCC3 was similar of PO-NE alone in the MIC in time-kill kinetic assay. PO-NE treatment mainly influenced membrane integrity, while CA treatment strongly stimulated intracellular ATP depletion. This synergistic combination effectively reduced the use of PO-NE, imparting a strong flavor note without sacrificing the antimicrobial efficacy against Pectobacterium.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01217-6.

Combined Biocidal Effect of Gaseous Ozone and Citric Acid on Acinetobacter baumannii Biofilm Formed on Ceramic Tiles and Polystyrene as a Novel Approach for Infection Prevention and Control

Acinetobacter baumannii is a prominent emerging pathogen responsible for a variety of hospital-acquired infections. It can contaminate inanimate surfaces and survive in harsh environmental conditions for prolonged periods of time in the form of biofilm. Biofilm is difficult to remove with only one method of disinfection, so combined disinfection methods and biocidal active substances are needed for biofilm eradication. Additionally, having in mind ecological demands, legislators are more prone using fewer toxic substances for disinfection that produce less solid waste and hazardous disinfection byproducts. Gaseous ozone and citric acid are natural biocidal compounds, and the purpose of this study was to determine their combined biocidal effects on A. baumannii biofilm formed on ceramics and polystyrene. Twenty-four-hour A. baumannii biofilm formed on ceramic tiles and polystyrene was exposed to different combinations of disinfection protocols with 25 ppm of gaseous ozone for 1 h exposure time and 15% citric acid for 10 min exposure. The total number of bacteria was counted afterwards and expressed as CFU/cm2. The determined disinfection protocols of A. baumannii biofilm with combined citric acid and gaseous ozone caused reduction of 2.8 to 5.89 log10 CFU (99.99% inhibition rate) of total viable bacteria for each method, with the citric acid–ozone–citric acid disinfection protocol being most successful in eradication of viable bacteria on both ceramics and polystyrene. In conclusion, gaseous ozone and citric acid showed good combined biocidal effects on A. baumannii biofilm and successfully reduced early A. baumannii biofilm from ceramic and polystyrene surfaces. The given combination of active substances can be a good option for eco-friendly disinfection of hospital inanimate surfaces from A. baumannii biofilm contamination with prior mechanical cleaning.

Probiotic Characteristics and Antimicrobial Potential of a Native Bacillus subtilis Strain Fa17.2 Rescued from Wild Bromelia sp. Flowers

In the present study, we identified the Bacillus subtilis strain annotated Fa17.2 isolated from Bromelia flower inflorescences collected from the subtropical humid mesothermal region, Santo Domingo de Los Tsachilas Province, Ecuador. The probiotic capacity and antimicrobial potential against four foodborne pathogens were assessed. The cell culture of Fa17.2 is highly resistant to synthetic gastric acid (pH 2.5, 3.0, and 3.5), bile salts (0.3%), tolerating different sodium chloride concentrations (1, 3, and 5%), and growth conditions (15 °C and 45 °C), suggesting its potential probiotic features. The isolate showed no antibiotic resistance and was considered safe as no hemolysis was detected on sheep blood agar. The optimum medium for bacterial growth and the release of antimicrobial compounds was MRS with 10% glucose. The active components released in the neutralized crude extract (NCE) were insensitive to organic solvents, surfactants, and nonproteolytic enzymes and sensitive to proteolytic enzymes suggesting their proteinaceous nature. The antimicrobial activity was enhanced by heat and maintained active over a wide range of pH (2.0–8.0). Moreover, the crude extract (CE) showed inhibitory activity against several Gram-negative and Gram-positive bacteria. The molecular weight of partially purified precipitated bacteriocin-like substances (BLISs) was about 14 kDa in 20% Tricine-SDS-PAGE. The CE obtained from Fa17.2 inhibits the growth of four foodborne pathogens, Staphylococcus aureus, Escherichia coli, Kosaconia cowanii, and Shigella dysenteriae, which implies its potential as an antimicrobial producer strain.

Impact of Drying Regimes and Different Coating Layers on Carboxymethyl Cellulose Cross-Linked with Citric Acid on Cotton Thread Fibers for Wound Dressing Modification

The oldest preservation techniques used are drying techniques, which are employed to remove moisture and prevent microorganisms’ growths, prolonging a material’s shelf life. This study evaluates the effects of drying methods on carboxymethyl cellulose (CMC) + citric acid (CA) coating layers on cotton threads. For this reason, cotton threads were washed and then coated with different layers of CMC cross-linked with CA, followed by drying using an oven (OD), infrared (IR), and a combination of oven + IR (OIR) drying methods at 65 °C. Our investigations revealed that CMC + CA yields a pliable biopolymer. The differences in drying regimes and coating layers of CMC + CA have a significant effect on the coated cotton thread strength and absorption capability. The study concluded that the IR drying regime is more effective to dry a single-layered cotton thread with a single layer of CMC + CA coating to enhance desirable properties for wound dressing modification.

Lactiplantibacillus plantarum subsp. plantarum and Fructooligosaccharides Combination Inhibits the Growth, Adhesion, Invasion, and Virulence of Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen responsible for many food outbreaks worldwide. This study aimed to investigate the single and combined effect of fructooligosaccharides (FOS) and Lactiplantibacillus plantarum subsp. plantarum CICC 6257 (L. plantarum) on the growth, adhesion, invasion, and virulence of gene expressions of Listeria monocytogenes 19112 serotype 4b (L. monocytogenes). Results showed that L. plantarum combined with 2% and 4% (w/v) FOS significantly (p < 0.05) inhibited the growth of L. monocytogenes (3-3.5 log10 CFU/mL reduction) at the incubation temperature of 10 °C and 25 °C. Under the same combination condition, the invasion rates of L. monocytogenes to Caco-2 and BeWo cells were reduced more than 90% compared to the result of the untreated group. After L. plantarum was combined with the 2% and 4% (w/v) FOS treatment, the gene expression of actin-based motility, sigma factor, internalin A, internalin B, positive regulatory factor A, and listeriolysin O significantly (p < 0.05) were reduced over 91%, 77%, 92%, 89%, 79%, and 79% compared to the result of the untreated group, respectively. The inhibition level of the L. plantarum and FOS combination against L. monocytogenes was higher than that of FOS or L. plantarum alone. Overall, these results indicated that the L. plantarum and FOS combination might be an effective formula against L. monocytogenes.

Antimicrobial and Antiviral (SARS-CoV-2) Potential of Cannabinoids and Cannabis sativa: A Comprehensive Review

Antimicrobial resistance has emerged as a global health crisis and, therefore, new drug discovery is a paramount need. Cannabis sativa contains hundreds of chemical constituents produced by secondary metabolism, exerting outstanding antimicrobial, antiviral, and therapeutic properties. This paper comprehensively reviews the antimicrobial and antiviral (particularly against SARS-CoV-2) properties of C. sativa with the potential for new antibiotic drug and/or natural antimicrobial agents for industrial or agricultural use, and their therapeutic potential against the newly emerged coronavirus disease (COVID-19). Cannabis compounds have good potential as drug candidates for new antibiotics, even for some of the WHO's current priority list of resistant pathogens. Recent studies revealed that cannabinoids seem to have stable conformations with the binding pocket of the Mpro enzyme of SARS-CoV-2, which has a pivotal role in viral replication and transcription. They are found to be suppressive of viral entry and viral activation by downregulating the ACE2 receptor and TMPRSS2 enzymes in the host cellular system. The therapeutic potential of cannabinoids as anti-inflammatory compounds is hypothesized for the treatment of COVID-19. However, more systemic investigations are warranted to establish the best efficacy and their toxic effects, followed by preclinical trials on a large number of participants.

Durability Assessment of a Plasma-Polymerized Coating with Anti-Biofilm Activity against L. monocytogenes Subjected to Repeated Sanitization

Biofilm formation on food-contact surfaces is a matter of major concern causing food safety and spoilage issues to this sector. The aim of this study was to assess the durability of the anti-biofilm capacity of a plasma-polymerized coating composed of a base coating of (3-aminopropyl)triethoxysilane (APTES) and a functional coating of acrylic acid (AcAc). Coated and uncoated AISI 316 stainless steel (SS) plates were subjected to five sanitization cycles with sodium hypochlorite (0.05%) and peracetic acid (0.5%). The effectiveness of the coating for the inhibition of multi-strain Listeria monocytogenes biofilm formation was confirmed using a three-strain cocktail, which was grown on the SS plates at 12 °C for 6 days. Compared to the uncoated SS, relative biofilm productions of 14.6% on the non-sanitized coating, 27.9% on the coating after sanitization with sodium hypochlorite, and 82.3% on the coating after sanitization with peracetic acid were obtained. Morphological and physicochemical characterization of the coatings suggested that the greater anti-biofilm effectiveness after sanitization with sodium hypochlorite was due to the high pH of this solution, which caused a deprotonation of the carboxylic acid groups of the functional coating. This fact conferred it a strong hydrophilicity and negatively charged its surface, which was favorable for preventing bacterial attachment and biofilm formation.

Advances of peptides for antibacterial applications

In the past few decades, peptide antibacterial products with unique antibacterial mechanisms have attracted widespread interest. They can effectively reduce the probability of drug resistance of bacteria and are biocompatible, so they possess tremendous development prospects. This review provides recent research and analysis on the basic types of antimicrobial peptides (including poly (amino acid)s, short AMPs, and lipopeptides) and factors to optimize antimicrobial effects. It also summarizes the two most important modes of action of antimicrobial peptides and the latest developments in the application of AMPs, including antimicrobial agent, wound healing, preservative, antibacterial coating and others. Finally, we discuss the remaining challenges to improve the antibacterial peptides and propose prospects in the field.

Chemical characterization of the polar antibacterial fraction of the ethanol extract from Rosmarinus officinalis

Rosmarinus officinalis L. has been widely used as a spice to extend the shelf life of foods. Most studies in the literature indicate that its essential oil is its major antibacterial component. In this study, a polar fraction from rosemary exhibited considerably stronger antibacterial activity against Bacillus subtilis than its essential oil. Guided by rapid characterization of the chemical compositions based on UPLC-Orbitrap-MS/MS, further investigation resulted in the isolation and identification of sixteen compounds. Among them, two new and six known compounds were identified in rosemary for the first time. Most isolated compounds exhibited significant antibacterial activities with minimum inhibitory concentration values of 2-128 μg/mL; however, these activities were weaker than that of the polar fraction. Thus, the polar fraction demonstrated a promising potential to serve as a food additive, as an alternative to the essential oil, because of its stronger antibacterial activity.

Plants and Lactic Acid Bacteria Combination for New Antimicrobial and Antioxidant Properties Product Development in a Sustainable Manner

In this study, nutraceuticals based on antimicrobial ingredients (Artemisia absinthium water extract and essential oil (EO), Lactobacillus uvarum LUHS245 strain cultivated in a whey media, and blackcurrants juice (BCJ) preparation by-products were developed. In addition, two texture forming agents for nutraceutical preparations were tested (gelatin and agar). The developed nutraceutical ingredients showed antimicrobial properties: Artemisia absinthium EO (concentration 0.1%) inhibited methicillin-resistant Staphylococcus aureus, Enterococcus faecium, Bacillus cereus, Streptococcus mutans, Staphylococcus epidermidis, and Pasteurella multocida; LUHS245 strain inhibited 14 from the 15 tested pathogenic strains; and BCP inhibited 13 from the 15 tested pathogenic strains. The best formulation consisted of the Artemisia absinthium EO, LUHS245, and BCP immobilised in agar and this formulation showed higher TPC content (by 2.1% higher), as well as higher overall acceptability (by 17.7% higher), compared with the formulation prepared using gelatin.