Hydrogen sulfide inhibits gene expression associated with aortic valve degeneration by inducing NRF2-related pro-autophagy effect in human aortic valve interstitial cells.

Aortic valve stenosis (AS) is the most common valvular heart disease but there are currently no effective medical treatments that can delay disease progression due to a lack of knowledge of the precise pathophysiology. The expression of sulfide: quinone oxidoreductase (SQOR) and nuclear factor erythroid 2-related factor 2 (NRF2) was decreased in the aortic valve of AS patients. However, the role of SQOR and NRF2 in the pathophysiology of AS has not been found. We investigated the effects of hydrogen sulfide (H2S)-releasing compounds on diseased aortic valve interstitial cells (AVICs) to explain the cellular mechanism of SQOR and elucidate the medical value of H2S for AS treatment. Sodium hydrosulfide (NaHS) treatment increased the expression of SQOR and NRF2 gene and consequently induced the NRF2 target genes, such as NAD(P)H quinone dehydrogenase 1 and cystathionine γ-lyase. In addition, NaHS dose-dependently decreased the expression level of fibrosis and inflammation-related genes (MMP9, TNF-α, IL6) and calcification-related genes (ALP, osteocalcin, RUNX2, COL1A1) in human AVICs. Furthermore, NaHS activated the AMPK-mTOR pathway and inhibited the PI3K-AKT pathway, resulting in a pro-autophagy effect in human AVICs. An NRF2 inhibitor, brusatol, attenuated NaHS-induced AMPK activation and decreased the autophagy markers Beclin-1 and LC3AB, suggesting that the mechanism of action of H2S is related to NRF2. In conclusion, H2S decreased gene expression levels related to aortic valve degeneration and activated AMPK-mTOR-mediated pro-autophagy function associated with NRF2 in human AVICs. Therefore, H2S could be a potential therapeutic target for the development of AS treatment.

Probiotics-Mediated Bioconversion and Periodontitis.

Novel bioactive metabolites have been developed through a bioconversion of dairy products or other foods using probiotics isolated from dairy products or other fermented foods. These probiotics-mediated bioconversion (PMB) metabolites show antioxidant, anti-inflammatory, antimicrobial, epithelial barrier, and anticancer activities. In addition, the effect of PMB metabolites in periodontitis is recently reported in several studies. Periodontitis is a chronic inflammatory disease caused by infections, and the tooth support tissue is destroyed. Common treatments for periodontitis include scaling and root planning with systemic antibiotics. However, the overuse of antibiotics has led to the emergence of drug-resistant microorganisms and disturbs the beneficial bacteria, including lactobacilli in the oral cavity. For this reason, PMB metabolites, such as fermented milk, have been suggested as substitutes for antibiotics to reduce periodontitis. This paper reviews the recent studies on the correlation between periodontitis and PMB metabolites and classifies the efficacy of major PMB metabolites for periodontitis. The review suggests that PMB is effective for periodontitis, and further studies are needed to confirm the therapeutic effect of PMB metabolites on periodontitis.

Upregulation of Low-Density Lipoprotein Receptor of the Steroidogenesis Pathway in the Cumulus Cells Is Associated with the Maturation of Oocytes and Achievement of Pregnancy.

The maturation of the oocyte is influenced by cumulus cells (CCs) and associated with pregnancy rate, whereas the influencing factors have not been completely elucidated in the CCs. In this study, we identified new regulators of CCs for high-quality oocytes and successful pregnancies during assisted reproductive techniques. CCs were collected from cumulus-oocyte complexes (COCs) in young (≤33 years old) and old (≥40 years old) women undergoing intracytoplasmic sperm injection (ICSI) procedures. We screened for factors differentially expressed between young vs. old CCs and pregnancy vs. non-pregnancy using whole mRNA-seq-next-generation sequencing (NGS). We characterized the transcriptome of the CCs to identify factors critical for achieving pregnancy in IVF cycles. Women in the young and old pregnancy groups exhibited the up- and downregulation of multiple genes compared with the non-pregnancy groups, revealing the differential regulation of several specific genes involved in ovarian steroidogenesis in CCs. It was shown that the low-density lipoprotein (LDL) receptor to the steroidogenesis pathway was upregulated in CCs with higher maturity rates of oocytes in the pregnancy group. In conclusion, a higher pregnancy rate is related to the signaling pathway of steroidogenesis by the LDL receptor in infertile women undergoing IVF procedures.

Effects of Advanced Glycation End Products on Differentiation and Function of Osteoblasts and Osteoclasts.

BACKGROUND: Risk of fragility fractures increases in patients with diabetes mellitus, independent of bone mineral density. In the present study, the effects of advanced glycation end products (AGEs) on differentiation and function of osteoblasts and osteoclasts were investigated. METHODS: AGEs and 25 mM glucose were administered to marrow-derived macrophages and MCT3T3-E1 cells. The effects of AGEs on osteoclast differentiation was investigated using tartrate-resistant acid phosphatase (TRAP) assay. The effects of AGEs on osteoblast differentiation was investigated using alkaline phosphatase (ALP) activity and bone nodule formation assays. Expression of osteoclast-specific and osteoblast-specific genes and effects on cell signaling pathways associated with cell differentiation were analyzed using reverse transcription polymerase chain reaction and western blotting. RESULTS: AGEs significantly decreased TRAP-positive multinucleated cell formation in receptor activator of nuclear factor-κB ligand-induced marrow-derived macrophages in a dose-dependent manner. AGEs suppressed the expression of osteoclast-specific genes, JNK, p38, AKT, intercellular adhesion molecule 1, and lymphocyte function-associated antigen 1 in marrow-derived macrophages. AGEs decreased ALP activity and showed a tendency to decrease bone nodule formation in MC3T3-E1 cells. AGEs suppressed the expression of osteoblast-specific genes, lysyl hydroxylase and lysyl oxidase in MC3T3-E1 cells. CONCLUSION: AGEs suppressed differentiation and function of osteoclasts and osteoblasts, and collagen cross-linking activity. It suggests that AGE may induce bone fragility through low bone turnover and deterioration of bone quality.

Effect of Neprilysin Inhibition for Ischemic Mitral Regurgitation after Myocardial Injury.

Angiotensin receptor neprilysin inhibitor (ARNI) treatment reduces functional mitral regurgitation (MR) to a greater extent than angiotensin receptor blocker (ARB) treatment alone, but the mechanism is unclear. We evaluated the mechanisms of how ARNI has an effect on functional MR. After inducing functional MR by left circumflex coronary artery occlusion, male Sprague Dawley rats (n = 31) were randomly assigned to receive the ARNI LCZ696, the ARB valsartan, or corn oil only (MR control). Excised mitral leaflets and left ventricle (LV) were analyzed, and valvular endothelial cells were evaluated focusing on molecular changes. LCZ696 significantly attenuated LV dilatation after 6 weeks when compared with the control group (LV end-diastolic volume, 461.3 ± 13.8 µL versus 525.1 ± 23.6 µL; p < 0.05), while valsartan did not (471.2 ± 8.9 µL; p > 0.05 to control). Histopathological analysis of mitral leaflets showed that LCZ696 strongly reduced fibrotic thickness compared to the control group (28.2 ± 2.7 µm vs. 48.8 ± 7.5 µm; p < 0.05). Transforming growth factor-ß and downstream phosphorylated extracellular-signal regulated kinase were also significantly lower in the LCZ696 group. Consequently, excessive endothelial-to-mesenchymal transition (EndoMT) was mitigated in the LCZ696 group compared to the control group and leaflet area was higher (11%) in the LCZ696 group than in the valsartan group. Finally, the MR extent was significantly lower in the LCZ696 group and functional improvement was observed. In conclusion, neprilysin inhibitor has positive effects on LV reverse remodeling and also attenuates fibrosis in MV leaflets and restores adaptive growth by directly modulating EndoMT.

Intestinal Clostridioides difficile Can Cause Liver Injury through the Occurrence of Inflammation and Damage to Hepatocytes.

This study investigated if intestinal Clostridioides difficile (CD) causes liver injury. Four-week-old male C3H/HeN mice were treated with phosphate-buffered solution (control), CD, diethylnitrosamine (DEN) to induce liver injury with PBS (DEN+PBS), and DEN with CD (DEN+CD) for nine weeks. After sacrifice, livers and mesenteric lymph nodes (MLNs) were removed and bacterial translocation, transcriptomes, and proteins were analysed. CD was found in 20% of MLNs from the control and DEN+PBS groups, in 30% of MLNs from the CD group, and in 75% of MLNs from the DEN+CD groups, which had injured livers. Also, CD was detected in 50% of the livers in the DEN+CD group with CD-positive MLNs. Elevated IL-1ß, HB-EGF, EGFR, TGF-α, PCNA, DES, HMGB1, and CRP expressions were observed in the CD and DEN+CD groups as compared to the control and DEN+PBS groups. Protein levels of IL-6 and HMGB1 were higher in the CD and DEN+CD groups than in the control and DEN+PBS groups. These results indicate that intestinal CD can initiate and aggravate liver injury, and the mechanism of pathogenesis for liver injury should be investigated in further studies.

The role of Pseudomonas aeruginosa DesB in pathogen-host interaction.

Pseudomonas aeruginosa, commonly found in environments, can cause chronic lung disease in immunocompromised patients. In previous study, an aerobic desaturase (DesB) in P. aeruginosa exerted considerable effects on virulence factor production. The objective of this study was to analyze the role of DesB on the virulence traits of P. aeruginosa in the host. For the in vitro experiments, cells and supernatants from wild-type (WT) P. aeruginosa and its desB mutant were collected. The diluted cells were added to the A549 cell monolayer in order to determine cell viability, invasion ability, and/or immune response. For the in vivo experiments, 6-week-old ICR mice were infected with 6-7 log CFU bacterial cells using endotracheal intubation. The ratio of lung weight to body weight and survival rate of each bacterial strain in the lung were measured. The histopathology of lung tissue was also studied. desB mutants exhibited lower cytotoxicity in A549 cells. In addition, more pro-inflammatory cytokines and chemokines were present in desB mutant-treated. In the lungs of mouse model, WT survived longer than desB mutant, and the WT migrated from the lung to the liver and spleen. The results suggest that P. aeruginosa DesB affects the pathogenicity of the organism in the host.

Association Between Functional Activity of Mitochondria and Actin Cytoskeleton Instability in Oocytes from Advanced Age Mice.

Mitochondrial dysfunction is strongly associated with the oocyte quality and aging, wherein the aged oocytes are related to the actin cytoskeleton integrity; however, whether this integrity is associated with mitochondrial dysfunction in oocytes from aged mice remains unclear. In the present study, we investigated the relationship between mitochondrial dysfunction and actin cytoskeleton instability in oocytes from the aged mice. We performed comparable analysis of mitochondrial motility between young, 1.5 µM cytochalasin B (CB)-treated young oocytes, and aged oocytes by confocal live imaging. Moreover, we analyzed the relationships between mitochondrial motility and maturation ratios, including ATP production ratio of the young, CB-treated young, and aged oocytes. Actin cytoskeleton instability in the aged oocytes and CB-treated young oocytes led to a significant decrease in the mitochondrial motility and low ATP productive ratios compared to those in the young group. Our data suggest that the actin cytoskeleton instability is presumably the primary cause for the loss of mitochondrial function in the aged murine oocytes.

Asymptomatic Clostridium perfringens Inhabitation in Intestine Can Cause Inflammation, Apoptosis, and Disorders in Brain.

Clostridium perfringens (CP) is a foodborne pathogen. The bacterium can also inhabit human gut without symptoms of foodborne illness. However, the clinical symptoms of long-term inhabitation have not been known yet. Therefore, the objective of this study was to elucidate the relationship between intestinal CP and other internal organs. Phosphate-buffered saline (PBS) and CP were orally injected into 5-week-old (YOUNG) and 12-month-old C57BL6/J (ADULT) mice. Gene expression levels related to inflammation (tumor necrosis factor-α [TNF-α], interleukin [IL]-1ß, and IL-6) and oxidative stress (superoxide dismutase [SOD]1, SOD2, SOD3, glutathione reductase [GSR], glutathione peroxidase [GPx]3, and catalase [CAT]) responses were evaluated in the brain, small intestine, and liver. In addition, apoptosis-related (BCL2-associated X [BAX]1 and high-mobility group box-1 [HMGB1]) and brain disorder-related genes (CCAAT-enhancer-binding protein [C/EBP]-ß, C/EBPδ, C/EBP homologous protein [CHOP], and amyloid precursor protein [APP]) as brain damage markers were examined. The protein expressions in the brain were also measured. Gene expression levels of inflammation and oxidative stress responses were higher (p < 0.05) in brains of CP-YOUNG and CP-ADULT mice, compared with PBS-YOUNG and PBS-ADULT, and the gene expression levels were higher (p < 0.05) in brains of CP-ADULT mice than CP-YOUNG mice. Apoptosis-related (BAX1 and HMGB1) and brain disorder-related genes (C/EBPß, C/EBPδ, CHOP, and APP) were higher (p < 0.05) in brains of CP-challenged mice, compared with PBS-challenged mice. Even oxidative stress response (GPx and SOD2), cell damage-related (HMGB1), and ß-amyloid proteins were higher (p < 0.05) in brains of CP- than in PBS-challenged mice. C/EBP protein was higher (p < 0.05) in CP-YOUNG, compared with PBS-YOUNG mice. However, these clinical symptoms were not observed in small intestine and liver. These results indicate that although asymptomatic intestinal CP do not cause foodborne illness, their inhabitation may cause brain inflammation, oxidative stress, apoptosis, and cell damage, which may induce disorders, especially for the aged group.

Role of Pseudomonas aeruginosa DesB in Adaptation to Osmotic Stress.

Proper membrane fluidity is maintained by adjusting the ratio of saturated fatty acids to unsaturated fatty acids (UFAs), and the control of membrane fluidity plays an important role in bacterial adaptation to stress. Adaptability to these stresses involves survival and colonization of bacteria, thus contributing to bacterial contamination in food. UFAs are synthesized by FabAB- and Des-mediated pathways in Pseudomonas aeruginosa. Therefore, in this study, the roles of UFA-synthesizing proteins of P. aeruginosa in resistance to stresses were examined. The growth and transcription levels of wild-type (WT) P. aeruginosa PAO1 and its mutants were compared. The growth of all strains was inhibited by exposure to 0.5 or 1.0 M sodium chloride, but it was not affected by oxidative or pH stress. In particular, growth was impaired more substantially in the desB mutant than in the WT strain and other mutants, suggesting that DesB has a role in response to salt stress. A comparative transcriptional analysis showed that genes involved in the synthesis of osmoprotectants (trehalose, N-acetylglutaminylglutamine amide, and hydrophilin) were highly expressed in WT P. aeruginosa in response to high salt, but they were rarely expressed in the desB mutant. Furthermore, decreases in osmoprotectant production by the desB mutant were partially complemented by the addition of betaine. These results indicate that P. aeruginosa DesB contributes to adaptation to high salinity by positively regulating the synthesis of osmoprotectants.

Prevalence, Serotype Diversity, Genotype and Antibiotic Resistance of Listeria monocytogenes Isolated from Carcasses and Human in Korea.

This study investigated the prevalence of Listeria monocytogenes in slaughterhouses, and determined serovars and genotypes, and antibiotic resistance of the isolates obtained from slaughterhouses and humans in Korea. Two hundred ninety samples were collected from feces (n=136), carcasses [n=140 (cattle: n=61, swine: n=79)], and washing water (n=14) in nine slaughterhouses. Eleven human isolates were obtained from hospitals and the Korea Center for Disease Control and Prevention. Listeria monocytogenes was enriched and identified, using polymerase chain reaction (PCR) and 16S rRNA sequencing. Serovars and presence of virulence genes were determined, and genetic correlations among the isolates were evaluated by the restriction digest patterns of AscI. Antibiotic resistance of L. monocytogenes isolates were examined against 12 different antibiotics. Of 290 slaughterhouse samples, 15 (5.17%) carcass samples were L. monocytogenes positive. Most L. monocytogenes isolates possessed all the virulence genes, while polymorphisms in the actA gene were found between carcass and human isolates. Serovars 1/2a (33.3%) and 1/2b (46.7%) were the most frequent in carcass isolates. Genetic correlations among the isolates from carcass and clinical isolates were grouped within serotypes, but there were low geographical correlations. Most L. monocytogenes isolates were antibiotic resistant, and some strains showed resistance to more than four antibiotics. These results indicate that L. monocytogenes are isolated from carcass and human in Korea, and they showed high risk serotypes and antibiotic resistance. Therefore, intensive attentions are necessary to be aware for the risk of L. monocytogenes in Korea.

Pathogenic Escherichia coli and Salmonella Can Survive in Kimchi during Fermentation.

The survival of Escherichia coli and Salmonella strains during diced white radish kimchi fermentation was studied. Kimchi batches inoculated with the pathogens were fermented at 4, 15, and 25°C for 42 to 384 h. Cell counts of E. coli and Salmonella were enumerated on E. coli-coliform count plates and xylose lysine deoxycholate agar, respectively. Baranyi (primary model) and polynomial (secondary model) models, validated by root mean square error, were used to describe the kinetic behavior of the pathogens. In the primary model, both the death phase shoulder ( E. coli: 208.18 to 8.25 h, 4 to 25°C; Salmonella: 79.91 to 0.97 h, 4 to 25°C) and bacterial cell counts (log CFU per gram per hour) decreased with increasing temperature ( P < 0.05) (death rate: E. coli: -0.02 to -0.09, 4 to 25°C; Salmonella: -0.01 to -0.10, 4 to 25°C), the results being equally significant in the secondary model. The root mean square error (0.480 to 0.485) showed that the model performance was good. The fermentation temperature and time are the critical factors that control pathogenic E. coli and Salmonella in kimchi.

Microbiological safety of processed meat products formulated with low nitrite concentration - A review.

Nitrite plays a major role in inhibiting the growth of foodborne pathogens, including Clostridium botulinum (C. botulinum) that causes botulism, a life-threatening disease. Nitrite serves as a color-fixing agent in processed meat products. However, N-nitroso compounds can be produced from nitrite, which are considered as carcinogens. Thus, consumers desire processed meat products that contain lower concentrations (below conventional concentrations of products) of nitrite or no nitrite at all, although the portion of nitrite intake by processed meat consumption in total nitrite intake is very low. However, lower nitrite levels might expose consumers to risk of botulism poisoning due to C. botulinum or illness caused by other foodborne pathogens. Hence, lower nitrite concentrations in combination with other factors such as low pH, high sodium chloride level, and others have been recommended to decrease the risk of food poisoning. In addition, natural compounds that can inhibit bacterial growth and function as color-fixing agents have been developed to replace nitrite in processed meat products. However, their antibotulinal effects have not been fully clarified. Therefore, to have processed meat products with lower nitrite concentrations, low pH, high sodium chloride concentration, and others should also be applied together. Before using natural compounds as replacement of nitrite, their antibotulinal activities should be examined.

Serotyping and Genotyping Characterization of Pathogenic Escherichia coli Strains in Kimchi and Determination of Their Kinetic Behavior in Cabbage Kimchi During Fermentation.

This study determined the serotyping and genotyping properties of Escherichia coli strains isolated from kimchi and various raw vegetables used for kimchi preparation. In addition, the kinetic behavior of E. coli strains in kimchi during fermentation was also determined using a predictive microbiological model. The study results revealed that E. coli isolated from napa cabbage (3.3%; 1/30) was enterohemorrhagic E. coli (O6:H34), and eight typical colonies isolated from kimchi (15%; 6/40) were enteropathogenic E. coli (H8, H8, H12, H34, H30, O20:H39, H39, and H12). The genetic correlation of the strains did not show close genetic correlations. On the other hand, the kinetic behavior of E. coli strains in kimchi during fermentation using a predictive Baranyi model (primary model) and a polynomial equation (secondary model), followed by validation by calculating root mean square error (RMSE), revealed that the pathogenic E. coli cell counts increased (with RMSE of 0.280 in growth curve) in the early stage of fermentation and decreased (with RMSE of 0.920 in death curve) thereafter depending on fermentation temperature. Therefore, this finding indicated that pathogenic E. coli isolated from kimchi and related vegetables underwent proliferation at the beginning of fermentation, which decreased thereafter. Thus, these results of this study suggest intake of sufficiently fermented kimchi to prevent potential foodborne illness due to pathogenic E. coli.

icaA Gene of Staphylococcus aureus Responds to NaCl, Leading to Increased Biofilm Formation.

The objective of this study was to elucidate the role of the icaA gene in biofilm formation of Staphylococcus aureus exposed to NaCl. The icaA-deletion mutant of S. aureus ATCC 13565 was constructed with the temperature-sensitive plasmid pIMAY. Microtiter plate assays were performed to confirm biofilm formation for both the wild type and the mutant at 0% (control), 2, 4, and 6% NaCl. The microtiter plate assay revealed that biofilm formation by the wild type increased ( P < 0.05) as NaCl concentration increased, but biofilm formation of the mutant was not affected by NaCl concentration. Biofilm formation by the mutant was lower ( P < 0.05) than that by the wild type. These results indicate that icaA plays an important role in biofilm formation by S. aureus when the pathogen is exposed to NaCl.

Effect of Gene actA on the Invasion Efficiency of Listeria monocytogenes, as Observed in Healthy and Senescent Intestinal Epithelial Cells.

Listeria monocytogenes can asymptomatically inhabit the human intestine as a commensal bacterium. However, the mechanism by which L. monocytogenes is able to inhabit the intestine without pathogenic symptoms remains unclear. We compared the invasion efficiency of L. monocytogenes strains with the 268- and 385-bp-long actA gene. Clinical strains SMFM-CI-3 and SMFM-CI-6 with 268-bp actA isolated from patients with listeriosis, and strains SMFM-SI-1 and SMFM-SI-2 with the 385-bp gene isolated from carcasses, were used for inoculum preparation. The invasion efficiency of these strains was evaluated using Caco-2 cells (intestinal epithelial cell line), prepared as normal and healthy cells with tightened tight junctions and senescent cells with loose tight junctions that were loosened by adriamycin treatment. The invasion efficiency of L. monocytogenes strains with the 268-bp-long actA gene was 1.1-2.6-times lower than that of the strains with the 385-bp-long gene in normal and healthy cells. However, the invasion efficiency of both types of strains did not differ in senescent cells. Thus, L. monocytogenes strains with the 268-bp-long actA gene can inhabit the intestine asymptomatically as a commensal bacterium, but they may invade the intestinal epithelial cells and cause listeriosis in senescent cells.

Kinetic Behavior of Campylobacter jejuni in Beef Tartare at Cold Temperatures and Transcriptomes Related to Its Survival.

This study was conducted to examine the kinetic behavior of Campylobacter jejuni in raw beef tartare by using mathematical models and to identify genes related to C. jejuni survival at cold temperatures. C. jejuni was inoculated onto beef tartare samples, stored at 4, 10, 15, 25, and 30°C, plated on modified charcoal-cefoperazone-deoxycholate agar, and enumerated. The survival data was fitted to the Weibull model to calculate delta (δ), which is the time required for the first 1-log reduction of the cells. The Davey model was then fitted to the δ to evaluate the effect of temperature. To evaluate the performance of the developed model, the root mean square error (RMSE) was calculated by comparing the observed data with the predicted data. The mRNA was extracted from samples stored at 4 and 30°C under aerobic and anaerobic conditions, and the expression of oxidative stress response and stress response genes was evaluated. C. jejuni survived in beef tartare longer at 4°C (δ = 657.1 ± 79.6 min) than at other temperatures (9.7 ± 11.2 to 465.7 ± 139.3°C) even under aerobic conditions. The RMSE (0.475) suggested that the developed model was appropriate to describe the kinetic behavior of C. jejuni. Quantitative real-time PCR results revealed that oxidative stress and stress response genes were related to C. jejuni survival at cold temperatures, even under aerobic conditions. These results indicate that the model will be useful for describing the kinetic behavior of C. jejuni in beef tartare and that this pathogen can survive at cold temperatures because of the expression of the sodB, katA, and clpP genes.

Evaluation on Antimicrobial Activity of Psoraleae semen Extract Controlling the Growth of Gram-Positive Bacteria.

This study investigated bacterial growth-inhibitory effect of 69 therapeutic herbal plants extracts on 9 bacterial strains using a disc diffusion assay. Especially, the antimicrobial activity of Psoraleae semen, which showed different activity on pathogenic Gram-positive and Gram-negative bacteria, was evaluated by MIC (minimal inhibition concentration) and biofilm formation assay. The effect of Psoraleae semen extract on bacterial cell membranes was examined by measurement of protein leakage (optical density at 280 nm) and scanning electron microscope (SEM). No clear zone was formed on discs containing Gram-negative bacteria, but Gram-positive bacteria exhibited clear zones. The MICs of Psoraleae semen extract were 8 µg/mL for Streptococcus mutans, and 16 µg/mL for Enterococci and Staphylococcus aureus. In addition, biofilm formation was inhibited at concentration 8-16 µg/mL. Protein leakage values and SEM images revealed that cell membranes of Gram-positive bacteria were impaired following exposure to the extract. Further, the extract inhibited the growth of Listeria monocytogenes in sausages. These results indicate that Psoraleae semen extract could be utilized as a natural antimicrobial agent against Gram-positive bacteria.

Effects of low NaNO2 and NaCl concentrations on Listeria monocytogenes growth in emulsion-type sausage.

OBJECTIVE: The objective of this study was to evaluate the effect of combinations of NaNO2 and NaCl concentrations on Listeria monocytogenes (L. monocytogenes) growth in emulsion-type sausage. METHODS: Emulsion-type sausages formulated with different combinations of NaNO2 (0 and 10 ppm) and NaCl (1.00%, 1.25%, and 1.50%) were inoculated with a five-strain L. monocytogenes mixture, and stored at 4°C, 10°C, and 15°C, under aerobic or vacuum conditions. L. monocytogenes cell counts were measured at appropriate intervals, and kinetic parameters such as growth rate and lag phase duration (LPD) were calculated using the modified Gompertz model. RESULTS: Growth rates increased (0.004 to 0.079 Log colony-forming unit [CFU]/g/h) as storage temperature increased, but LPD decreased (445.11 to 8.35 h) as storage temperature and NaCl concentration increased. The effect of combinations of NaCl and low-NaNO2 on L. monocytogenes growth was not observed at 4°C and 10°C, but it was observed at 15°C, regardless of atmospheric conditions. CONCLUSION: These results indicate that low concentrations of NaNO2 and NaCl in emulsion-type sausage may not be sufficient to prevent L. monocytogenes growth, regardless of whether they are vacuum-packaged and stored at low temperatures. Therefore, additional techniques are necessary for L. monocytogenes control in the product.

Invited review: Microbe-mediated aflatoxin decontamination of dairy products and feeds.

Aspergillus flavus, Aspergillus parasiticus, and Aspergillus nomius contaminate corn, sorghum, rice, peanuts, tree nuts, figs, ginger, nutmeg, and milk. They produce aflatoxins, especially aflatoxin B1, which is classified as a Group 1 carcinogen by the International Agency for Research on Cancer. Many studies have focused on aflatoxin removal from food or feed, especially via microbe-mediated mechanisms-either adsorption or degradation. Of the lactic acid bacteria, Lactobacillus rhamnosus GG efficiently binds aflatoxin B1, and a peptidoglycan in the bacterium cell wall plays an important role. This ability of L. rhamnosus GG should be applied to the removal of aflatoxin B1. Aflatoxin can be removed using other aflatoxin-degrading microorganisms, including bacterial and fungal strains. This review explores microbe-associated aflatoxin decontamination, which may be used to produce aflatoxin-free food or feed.