Inhibition of Salmonella enterica serovar Typhimurium by combined carvacrol and potassium sorbate in vitro and in tomato paste

Synergistic inhibition of Salmonella Typhimurium and Staphylococcus aureus in apple jam by cinnamaldehyde and potassium sorbate

The objective of this study was to evaluate the antimicrobial effectiveness of cinnamaldehyde (CIN) and potassium sorbate (P.S.), alone and in combination, against Salmonella Typhimurium and Staphylococcus aureus in vitro and in apple jam. Antimicrobial activity in vitro was investigated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), time-kill assay and determination of fractional inhibitory concentration index. CIN MIC and MBC was 312 μg/mL. P.S. MIC and MBC were 2500 and 5000 μg/mL, respectively, against S. Typhimurium; and 10,000 and 20,000 μg/mL, respectively, against S. aureus. The compounds combined exhibited a synergistic effect (FIC < 0.5), inhibiting S. Typhimurium growth after 12 h and S. aureus after 24 h. The effect of CIN and P.S., at sub-inhibitory concentrations, against bacterial strains in apple jam was evaluated during storage. Physicochemical and sensory analyses were also performed. No cultivable S. Typhimurium or S. aureus cells were recovered in apple jam supplemented with CIN + P.S. on the third day of storage. The addition of CIN and P.S. did not affect the physicochemical properties and sensory evaluation showed a score above 7.0. CIN and P.S. association at sub-inhibitory concentrations was effective in controlling foodborne pathogens and improved the shelf life of apple jam.

Biogenic silver nanoparticles and cinnamaldehyde as an effective sanitizer for fresh sweet grape tomatoes

This study evaluated the antibacterial activity of cinnamaldehyde (CIN) and biogenic silver nanoparticles (BioAgNP), alone and in combination, against Escherichia coli, Salmonella Typhimurium, and Staphylococcus aureus in vitro. Their sanitation activities on fresh sweet grape tomatoes were also evaluated. CIN and BioAgNP inhibited the growth of the tested bacteria, and at low concentrations, their combinations presented a synergistic effect. In the sanitization of fresh sweet grape tomatoes, CIN (156 µg/mL) combined with BioAgNP (31.25 µM) at subinhibitory concentrations inhibited the growth of E. coli after only 5 min of contact. Exposed samples showed no growth of E. coli during their shelf life. The combination of these compounds did not change significantly (p > 0.05) the physicochemical properties of sweet grape tomatoes and showed that CIN combined with BioAgNP could represent an effective method for decontaminating fruits and vegetables. This combination has great potential for application in the prevention of foodborne diseases.

Synergistic antibacterial activity of carvacrol loaded chitosan nanoparticles with Topoisomerase inhibitors and genotoxicity evaluation

The increasing prevalence of antibiotic resistant bacteria is a significant healthcare crisis with substantial socioeconomic impact on global community. The development of new antibiotics is both costly and time-consuming prompting the exploration of alternative solutions such as nanotechnology which represents opportunities for targeted drug delivery and reduced MIC. However, concerns have arisen regarding genotoxic effects of nanoparticles on human health necessitating an evaluation of nanoparticle induced DNA damage. This study aimed to investigate the antibacterial potential of already prepared, characterized chitosan nanoparticles loaded with carvacrol and their potential synergism with Topoisomerase II inhibitors against S. aureus, E. coli and S. typhi using agar well diffusion, microdilution and checkerboard method. Genotoxicity was assessed through comet assay. Results showed that both alone and drug combinations of varying concentrations exhibited greater zones of inhibition at higher concentrations. Carvacrol nanoparticles combined with ciprofloxacin and doxorubicin significantly reduced MIC compared to the drugs used alone. The MIC50 values for ciprofloxacin were 35.8 µg/ml, 48.74 µg/ml, 35.57 µg/ml while doxorubicin showed MIC50 values of 20.79 µg/ml, 34.35 µg/ml, 25.32 µg/ml against S. aureus, E. coli and S. typhi respectively. The FICI of ciprofloxacin and doxorubicin with carvacrol nanoparticles found ≤ 0.5 Such as 0.44, 0.44,0.48 for ciprofloxacin and 0.45, 0.45, 0.46 for doxorubicin against S. aureus, E. coli and S. typhi respectively revealed the synergistic effect. The analysis of comet assay output images showed alteration of DNA at high concentrations. Our results suggested that carvacrol nanoparticles in combination with Topoisomerase inhibitors may prevent and control the emergence of resistant bacteria with reduced dose.

Antimicrobial effect of sorbic acid-loaded chitosan/tripolyphosphate nanoparticles on Pseudomonas aeruginosa

Sorbic acid-loaded chitosan/tripolyphosphate nanoparticles (SANs) have previously been shown to exert both antibacterial and antioxidant effects on Chinese sausage. In this study, the minimum inhibitory concentrations (MICs) of SANs against two Pseudomonas aeruginosa strains were determined. The blank control group (BC) served as the negative control, while the chitosan/tripolyphosphate nanoparticles (CTNs) group and free sorbic acid (SA) group served as the positive controls. Tests conducted under five different pH conditions (5/6/7/8/9) revealed that the SANs exhibited a good bacteriostatic effect against P. aeruginosa. Variations in the metabolism, cell membrane or cell wall integrity, and morphology of P. aeruginosa were measured to evaluate the effects of SANs on their intracellular and extracellular components. The MIC of SANs for the two P. aeruginosa strains was determined to be 150 μg/mL. SANs delayed the growth of P. aeruginosa and severely damaged both its inner and outer cell membranes. The heteromorphism of the bacteria as observed by field emission scanning electron microscopy (FESEM), verified the aforementioned results. The results showed SANs could effectively inhibit the growth of P. aeruginosa and exert antibacterial ability in a wider range of acid-base environments. This study broadens the application of SANs in food processing and provides experimental basis.

Quantitative proteomic analysis provides insight into the survival mechanism of Salmonella typhimurium under high-intensity ultrasound treatment

The survival mechanism of Salmonella treated with high-intensity ultrasound (HIU) should be explored to further enhance the bactericidal efficacy of HIU. In this study, culturable Salmonella was reduced by applying HIU. Electron microscope imaging revealed that HIU caused the disintegration of cell structure and leakage of intracellular substances. For the Salmonella after the HIU treatment, key enzymes of the tricarboxylic acid [TCA] cycle were significantly downregulated, which led to a reduced ATP content (45.25%-75.00%), although ATPase activity was augmented by 33.82%-60.64% in the Salmonella. Accordingly, surviving Salmonella could have tolerated the stress of HIU by upregulating their environmental sensing (two-component system), chemotaxis (bacterial chemotaxis), substance uptake (ABC transporter), and ATP production (oxidative phosphorylation). Therefore, synergistically blocking the ATP production, signal transduction, or substance intake of Salmonella offer promising potential strategies to improve the bactericidal effect of HIU in industrial food processing.

Synergistic activity of Stryphnodendron adstringens and potassium sorbate against foodborne bacteria

Stryphnodendron adstringens is a medicinal plant that has a broad spectrum of action, including antibacterial activity. The aim of the present study was to evaluate the effect of S. adstringens alone and in combination with potassium sorbate (PS) against foodborne bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined and, for most of the bacteria tested, the crude extract (CE), aqueous fraction (AQF), and ethyl-acetate fraction (EAF) of S. adstringens had a MIC and MBC ranging from 500 to ≥ 1000 µg/mL. The AQF and EAF showed greater activity against S. aureus strains (MIC = 125 to 250 µg/mL; MBC = 500 to 1000 µg/m). Quantitative cell viability was determined and was observed reductions ranging from 3.0 to 5.8 log10 CFU/ml.The combination of S. adstringens and PS against seven S. aureus isolates was determined by the checkerboard method at neutral and acid pH. In a neutral medium, the AQF + PS combination presented synergistic or additive interactions against six S. aureus strains. The combination of EAF + PS resulted in additive interactions against four bacterial isolates. In an acidic medium, the AQF + PS combination was synergistic or additive against all S. aureus, while EAF + PS presented the same effect against six S. aureus strains S. adstringens showed important antibacterial effects against foodborne S. aureus strains. Moreover, the combination of S. adstringens fractions and PS improved the antibacterial activity compared to the compounds utilized individually. The combined use of these compounds may be an alternative to reduce bacterial food contamination and improve food safety.

Application and Effects of Ohmic-Vacuum Combination Heating on the Quality Factors of Tomato Paste

Ohmic-vacuum combination heating is a common method used in the food industry as a concentration process. In the present study, an OH-VC combination heating system was developed for producing tomato paste at temperatures of 70, 80, and 90 °C and pressure of 0.3, 0.5, and 0.7 bar and electric field of 1.82, 2.73, and 3.64 V/cm using a central composite design. The effects of heating conditions on the quality and sensory evaluation of tomato paste were also evaluated. Each combination of temperature, pressure, and the electric field was quantified for specific energy consumption, energy efficiency, and productivity. A decrease of 35.08% in the amount of acid ascorbic and lycopene content 19.01%, using conventional heating compared to ohmic-vacuum heating under optimized conditions, was attained. The results also highlighted an increase in the amount of HMF (69.79%) and PME (24.33%) using conventional heating compared to ohmic-vacuum heating under optimized conditions. Ascorbic acid, lycopene, titratable acidity, productivity, energy efficiency was higher than conventional heating; on the other hand, HMF, PME, pH, SEC were lower than conventional heating at the applied OH-VC process. No significant effects between OH-VC and conventional heating on the TSS were observed. In addition, OH-VC heating was highly efficient in the inhibition of bacterial growth. Further, a minor effect on the sensory properties of tomato paste with OH-VC heating compared to the conventional treatment. The obtained results indicate a strong potential for an OH-VC combination heating system as a rapid-heating, high-efficiency alternative for saving electrical energy consumption and preserving nutritional value.

Destruction of the cell membrane and inhibition of cell phosphatidic acid biosynthesis inStaphylococcus aureus: an explanation for the antibacterial mechanism of morusin

Morusin from mulberry inhibits the growth ofS. aureusby destroying its cell membrane and further moderating the phosphatidic acid biosynthesis pathway.