Quantitative risk assessment of foodborne Salmonella illness by estimating cooking effect on eggs from retail markets.

In this study, we performed a quantitative microbial risk assessment (QMRA) of Salmonella through intake of egg consumption after cooking (dry-heat, moist-heat, and raw consumption). Egg samples (n = 201) from retail markets were analyzed for the presence of Salmonella. In addition, temperature and time were investigated during egg transit, storage, and display. A predictive model was developed to characterize the kinetic behavior of Salmonella in eggs, and data on egg consumption and frequency were collected. Eventually, the data was simulated to estimate egg-related foodborne illnesses. Salmonella was not found in any of the 201 egg samples. Thus, the estimated initial contamination level was -4.0 Log CFU/g. With R2 values of 0.898 and 0.922, the constructed predictive models were adequate for describing the fate of Salmonella in eggs throughout distribution and storage. Eggs were consumed raw (1.5%, 39.2 g), dry-heated (57.5%, 43.0 g), and moist-heated (41%, 36.1 g). The probability of foodborne Salmonella illness from the consumption of cooked eggs was evaluated to be 6.8×10-10. Additionally, the probability of foodborne illness not applied cooking methods was 1.9×10-7, indicating that Salmonella can be reduced by cooking. Therefore, the risk of Salmonella infection through consumption of eggs after cooking might be low in S. Korea.

Isolation of Debaryomyces hansenii and selection of an optimal strain to improve the quality of low-grade beef rump (middle gluteal) during dry aging.

OBJECTIVE: The objective of this study was to evaluate the effect of Debaryomyces hansenii isolated from dry-aged beef on the tenderness and flavor attributes of low-grade beef during dry aging. METHODS: Five D. hansenii strains were isolated from dry-aged beef samples. The rump of low-grade beef was inoculated with individual D. hansenii isolates and subjected to dry aging for 4 weeks at 5°C and 75% relative humidity. Microbial contamination levels, meat quality attributes, and flavor attributes in the dry-aged beef were measured. RESULTS: Of the five isolates, the shear force of dry-aged beef inoculated with SMFM201812-3 and SMFM201905-5 was lower than that of control samples. Meanwhile, all five isolates increased the total free amino acid, glutamic acid, serine, glycine, alanine, and leucine contents in dry-aged beef. In particular, the total fatty acid, palmitic acid, and oleic acid contents in samples inoculated with D. hansenii SMFM201905-5 were higher than those in control samples. CONCLUSION: These results indicate that D. hansenii SMFM201905-5 might be used to improve the quality of beef during dry aging.

Salmonella Risk Assessment in Poultry Meat from Farm to Consumer in Korea.

This study predicted Salmonella outbreak risk from eating cooked poultry in various methods. The incidence of Salmonella in poultry meat and the environment from farm to home for consumption was investigated. To develop the predictive models, Salmonella growth data were collected at 4-25 °C during storage and fitted with the Baranyi model. The effects of cooking on cell counts in poultry meat were investigated. Temperature, duration, and consumption patterns were all searched. A simulation in @Risk was run using these data to estimate the probability of foodborne Salmonella disease. In farm, Salmonella was detected from only fecal samples (8.5%; 56/660). In slaughterhouses, Salmonella was detected from feces 16.0% (38/237) for chicken and 19.5% (82/420) for duck) and from carcasses of each step (scalding, defeathering, and chilling) by cross contamination. In chicken (n = 270) and duck (n = 205), Salmonella was detected in 5 chicken (1.9%) and 16 duck meat samples (7.8%). Salmonella contamination levels were initially estimated to be -3.1 Log CFU/g and -2.5 Log CFU/g, respectively. With R2 values between 0.862 and 0.924, the predictive models were suitable for describing the fate of Salmonella in poultry meat with of 0.862 and 0.924. The Salmonella was not detected when poultry meat cooks completely. However, if poultry meat contaminated with Salmonella were cooked incompletely, Salmonella remained on the food surface. The risk of foodborne Salmonella disease from poultry consumption after cooking was 3.0 × 10-10/person/day and 8.8 × 10-11/person/day in South Korea, indicating a low risk.

Reconstruction of mandibular defects in osteoradionecrosis and medication-related osteonecrosis of the jaw using fibula free flap and management of postoperative wound infections.

BACKGROUND: Complications from osteoradionecrosis (ORN) and medication-related osteonecrosis of the jaw (MRONJ) include oro-cutaneous fistulas, necrotic bone exposure, soft-tissue defects, and pathologic fractures. The fibula free flap (FFF) is a common free flap method used to reconstruct the mandible in severe cases. Recently, we have used the FFF successfully for the reconstruction of ORN and MRONJ mandibular defects. We report this method as a recommended technique for the treatment of ORN and MRONJ and the management method of postoperative infections. METHODS: Four patients who were diagnosed with ORN of the mandible and 3 patients who were diagnosed with MRONJ of the mandible were included in the study. Among the 7 patients, 3 patients also had pathologic fractures. Partial mandibulectomy and FFF reconstruction were performed at the Department of Oral and Maxillofacial Surgery, Samsung Medical Center from April 2019 to March 2021. RESULTS: All 7 patients recovered following the reconstruction of the defect by FFF. Four patients experienced infections after surgery and pus cultures were performed. All were well healed without flap damage after changing the antibiotics by consultation with infectious medicine experts. CONCLUSION: FFF is a widely used method and can provide an extensive flap to reconstruct the mandible, especially those affected by ORN or MRONJ. If an infection occurs after surgery, appropriate antibiotic changes should be made through cooperation with the infectious medicine department. Therefore, FFF is a well-established and recommended method even in cases of challenging reconstruction.

Isolation of Bacillus cereus from Soft Soybean Curd and the Kinetic Behavior of B. cereus Isolates at Changing Temperatures.

ABSTRACT: In this study, Bacillus cereus was isolated from soft soybean curds, and a dynamic model was developed to describe the kinetic behavior of these isolates during transfer and storage. B. cereus isolates recovered from soft soybean curds were inoculated into soft soybean curd, and the levels were determined during storage at 10 to 30°C. The B. cereus counts were fitted to the Baranyi model to calculate maximum growth rate (µmax) and lag-phase duration (LPD). These kinetic parameters were then analyzed with a polynomial equation to evaluate the effects of temperature on the kinetic parameters. The developed model was validated with observed values, and the differences between predicted and observed values were determined by calculating the root mean square error (RMSE). A dynamic model was then developed with a combination of primary and secondary models to describe B. cereus growth under changing temperature conditions. B. cereus was detected in two soft soybean curd samples (5.1%) at 0.7 log CFU/g. The µmax was -0.04 to 0.47 log CFU/g/h, and the ln(LPD) was 3.94 to 0.04 h, depending on the storage temperature. The model performance was appropriate with a 0.216 RMSE and accurately described the kinetic behavior of B. cereus in soft soybean curd samples. These results suggest that B. cereus can contaminate soft soybean curds and that the models developed with the B. cereus isolates are useful for describing the kinetic behavior of B. cereus in soft soybean curd.

High Prevalence of Listeria monocytogenes in Smoked Duck: Antibiotic and Heat Resistance, Virulence, and Genetics of the Isolates.

This study aimed at determining the genetic and virulence characteristics of the Listeria monocytogenes from smoked ducks. L. monocytogenes was isolated by plating, and the isolated colonies were identified by PCR. All the obtained seven L. monocytogenes isolates possessed the virulence genes (inlA, inlB, plcB, and hlyA) and a 385 bp actA amplicon. The L. monocytogenes isolates (SMFM2018 SD 1-1, SMFM 2018 SD 4-1, SMFM 2018 SD 4-2, SMFM 2018 SD 5-2, SMFM 2018 SD 5-3, SMFM 2018 SD 6-2, and SMFM 2018 SD 7-1) were inoculated in tryptic soy broth (TSB) containing 0.6% yeast extract at 60°C, followed by cell counting on tryptic soy agar (TSA) containing 0.6% yeast extract at 0, 2, 5, 8, and 10 min. We identified five heat resistant isolates compared to the standard strain (L. monocytogenes ATCC13932), among which three exhibited the serotype 1/2b and D-values of 5.41, 6.48, and 6.71, respectively at 60°C. The optical densities of the cultures were regulated to a 0.5 McFarland standard to assess resistance against nine antibiotics after an incubation at 30°C for 24 h. All isolates were penicillin G resistant, possessing the virulence genes (inlA, inlB, plcB, and hlyA) and the 385-bp actA amplicon, moreover, three isolates showed clindamycin resistance. In conclusion, this study allowed us to characterize L. monocytogenes isolates from smoked ducks, exhibiting clindamycin and penicillin G resistance, along with the 385-bp actA amplicon, representing higher invasion efficiency than the 268-bp actA, and the higher heat resistance serotype 1/2b.

Erratum to: Description of Kinetic Behavior of Pathogenic Escherichia coli in Cooked Pig Trotters under Dynamic Storage Conditions Using Mathematical Equations.

[This corrects the article DOI: 10.5851/kosfa.2020.e64.].

Contamination of Clostridium perfringens in soy sauce, and quantitative microbial risk assessment for C. perfringens through soy sauce consumption.

The objective of this study was to conduct QMRA (quantitative microbial risk assessment) of Clostridium perfringens through soy sauce consumption. Four hundred and ninety soy sauce samples from markets were analyzed to detect C. perfringens. Temperature and time were also measured during transportation and display of soy sauce. A primary model was developed by fitting the Weibull model to the C. perfringens cell counts in soy sauce at 7-35°C, and δ (the time needed to decrease 1 log CFU/ml) and ρ (curve shape) were calculated. The parameters were analyzed, using the Exponential model (secondary model) as a function of temperature. The consumption amount and percentage of soy sauce were surveyed, and a dose-response model was searched. Using all collected data, a simulation model was prepared in the @RISK program to estimate the probability of C. perfringens foodborne illness by soy sauce consumption. C. perfringens were negative in 490 samples. Thus, the initial contamination level was estimated to be -2.9 log CFU/ml. The developed predictive models showed that C. perfringens cell counts decreased during transportation and display. The average consumption amounts, and the percentage of soy sauce were 7.81 ml and 81.2%, respectively. The simulation showed that the probability of C. perfringens foodborne illness by consumption of soy sauce was 1.7 × 10-16 per person per day. Therefore, the risk of C. perfringens by consumption of soy sauce is low in Korea.

Lactobacillus fermentum SMFM2017-NK4 Isolated from Kimchi Can Prevent Obesity by Inhibiting Fat Accumulation.

This study evaluated the anti-obesity effects of lactic acid bacteria. Thirty-one lactic acid bacteria were examined in vitro for their ability to inhibit α-glucosidase activity, lipase activity, and 3T3-L1 cell differentiation. Four selected lactic acid bacteria were administered to obese C57BL/6J mice models for 8 weeks. The degree of improvement in obesity was determined by weight gain and serum biochemical analysis. The expression levels of genes (Fas and Cpt-2) related to obesity in the liver were analyzed by quantitative reverse transcription (qRT)-PCR. In addition, antioxidant protein levels (SOD-2, CAT, and GPx-1) in the liver were evaluated. The lactic acid bacteria-treated groups (PPGK1, LFNK3, LPNK2, and LFNK4) showed lower weight increase rate than the control group. The total cholesterol (T-chol), triglyceride (TG), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels in the blood serum of the LFNK4 group were the lowest among other groups, compared to the control group. The expression levels of lipid metabolism-related genes (Fas and Cpt-2) in the liver of the LFNK4 group were lower in Fas and higher in Cpt-2 than in the control group. The antioxidant protein expression levels (SOD-2, CAT, and GPx-1) in the liver tissue were also higher in the LFNK4 group. These results indicate that L. fermentum SMFM2017-NK4 has anti-obesity effects.

Development of a Selective Agar for Improving Campylobacter jejuni Detection in Food.

BACKGROUND: Campylobacter jejuni is a major gastroenteritis-causing foodborne pathogen. However, it is difficult to isolate when competing bacteria or cold-damaged cells are present. OBJECTIVE: Herein, a medium (Campylobacter selective agar, CSA) was developed and supplemented with catalase, L-serine, L-cysteine, and quercetin for the selective detection of C. jejuni in food. METHOD: The C. jejuni-detection efficiency in media broth and chicken tenders was evaluated. The pathogen was enumerated on modified charcoal-cefoperazone-deoxycholate agar (mCCDA), CSA supplemented with 4 µM catalase (CSA-C4), 8 µM catalase (CSA-C8), 20 mM L-serine (CSA-S20) or 50 mM L-serine (CSA-S50), and mCCDA supplemented with 0.5 mM L-cysteine (mCCDA-LC0.5), 1 mM L-cysteine (mCCDA-LC1), 40 µM quercetin (mCCDA-Q40) or 320 µM quercetin (mCCDA-Q320). The detection efficiency was then evaluated by counting colonies on the selective agar media. Quantitative assessment was also performed using chicken and duck carcasses. RESULTS: The C. jejuni detection efficiencies were higher (P < 0.05) in the groups CSA-C4 or CSA-C8, and CSA-S20 or CSA-S50, than mCCDA, and the detection efficiencies were maintained even in the presence of Acinetobacter baumannii, a competing bacterium. In the quantitative test, CSA-C8 and CSA-S50 demonstrated higher C. jejuni-detection efficiencies than mCCDA (control). CONCLUSIONS: Therefore, CSA-C8 and CSA-S50 improved the detection efficiency of C. jejuni in poultry products by promoting the recovery of cold-damaged cells. HIGHLIGHTS: When using CSA-C8 or CSA-S50 developed in this study for detection of C. jejuni in food, detection efficiency was higher than mCCDA.

Antimicrobial activity of fermented Maillard reaction products, novel milk-derived material, made by whey protein and Lactobacillus rhamnosus and Lactobacillus gasseri on Clostridium perfringens.

OBJECTIVE: The objective of this study was to evaluate the antimicrobial effects of fermented Maillard reaction products made by milk proteins (FMRPs) on Clostridium perfringens (C. perfringens), and to elucidate antimicrobial modes of FMRPs on the bacteria, using physiological and morphological analyses. METHODS: Antimicrobial effects of FMRPs (whey protein plus galactose fermented by Lactobacillus rhamnosus [L. rhamnosus] 4B15 [Gal-4B15] or Lactobacillus gasseri 4M13 [Gal-4M13], and whey protein plus glucose fermented by L. rhamnosus 4B15 [Glc-4B15] or L. gasseri 4M13 [Glc-4M13]) on C. perfringens were tested by examining growth responses of the pathogen. Iron chelation activity analysis, propidium iodide uptake assay, and morphological analysis with field emission scanning electron microscope (FE-SEM) were conducted to elucidate the modes of antimicrobial activities of FMRPs. RESULTS: When C. perfringens were exposed to the FMRPs, C. perfringens cell counts were decreased (p<0.05) by the all tested FMRPs; iron chelation activities by FMRPs, except for Glc-4M13. Propidium iodide uptake assay indicate that bacterial cellular damage increased in all FMRPs-treated C. perfringens, and it was observed by FE-SEM. CONCLUSION: These results indicate that the FMRPs can destroy C. perfringens by iron chelation and cell membrane damage. Thus, it could be used in dairy products, and controlling intestinal C. perfringens.

Identification of Pathogenic Variations in Seafood Vibrio parahaemolyticus Isolates by Comparing Genome Sequences.

ABSTRACT: An investigation of the pathogenic characteristics of isolates of Vibrio parahaemolyticus was conducted by identifying the pathogenic tdh gene and then performing adherence and cytotoxicity assays. Genome sequences of the seafood isolates were analyzed using the Illumina HiSeq 2500 platform. The isolated strains were then mapped by comparing the genomes to the reference genome, and variations in the nucleotide sequences and amino acids were identified with the CLC Genomics Workbench program. The tdh gene was identified in four isolates of V. parahaemolyticus, of which three-SMFM201809-CPC7-3, SMFM201809-CF8-2, and SMFM201809-CF8-3-showed high cytotoxicity and differences in cell adhesion. These isolates were selected to identify virulence factors and genomic variations. All three isolates had the same virulence factors, such as adherence, secretion system, and toxin. In addition, amino acid variants were identified in the regions of type IV pilus, T3SS1 and T3SS1 secreted effectors, and thermolabile hemolysin. These results indicate that variations in amino acids found in regions related to adherence and cytotoxicity result in differences in adhesion efficiency and cytotoxicity; therefore, the isolates with these variations may cause more serious foodborne illness compared with other strains.

Synthesis of nitrogen-doped carbon nanodots to destroy bacteria competing with Campylobacter jejuni in enrichment medium, and development of a monoclonal antibody to detect C. jejuni after enrichment.

The objective of this study was to develop a method with improved sensitivity for Campylobacter jejuni detection in foods. Nitrogen-doped carbon nanodots (N-CNDs) were synthesized and added to an enrichment medium (Bolton broth) at a concentration of 10 mg/mL. A light-emitting diode (LED) at a wavelength of 425 nm was used to irradiate the N-CNDs-supplemented enrichment medium to induce an exothermic reaction for 1 h. Additionally, a monoclonal antibody specific to C. jejuni NCTC11168 was developed using hybridoma cells to aid detection. The C. jejuni detection capabilities of N-CNDs-supplemented enrichment medium and the conventional Bolton broth enrichment, were compared using duck samples. C. jejuni in the enrichment was detected with the monoclonal antibody based-indirect enzyme-linked immunosorbent assay (ID-ELISA). The N-CNDs-supplemented enrichment medium showed a better C. jejuni detection capability than the conventional Bolton broth enrichment. Additionally, data from ID-ELISA showed excellent detection efficiency and a shortened detection time in the N-CNDs-supplemented enrichment medium after LED irradiation at 425 nm. These results indicate that 1-h LED irradiation at 425 nm to Bolton broth supplemented with the N-CNDs increased the detection efficiency and shortened the detection time with the monoclonal antibody for C. jejuni in food.

Description of Kinetic Behavior of Pathogenic Escherichia coli in Cooked Pig Trotters under Dynamic Storage Conditions Using Mathematical Equations.

A dynamic model was developed to predict the Escherichia coli cell counts in pig trotters at changing temperatures. Five-strain mixture of pathogenic E. coli at 4 Log CFU/g were inoculated to cooked pig trotter samples. The samples were stored at 10°C, 20°C, and 25°C. The cell count data was analyzed with the Baranyi model to compute the maximum specific growth rate (µ max) (Log CFU/g/h) and lag phase duration (LPD) (h). The kinetic parameters were analyzed using a polynomial equation, and a dynamic model was developed using the kinetic models. The model performance was evaluated using the accuracy factor (A f), bias factor (B f), and root mean square error (RMSE). E. coli cell counts increased (p<0.05) in pig trotter samples at all storage temperatures (10°C-25°C). LPD decreased (p<0.05) and µ max increased (p<0.05) as storage temperature increased. In addition, the value of h0 was similar at 10°C and 20°C, implying that the physiological state was similar between 10°C and 20°C. The secondary models used were appropriate to evaluate the effect of storage temperature on LPD and µ max. The developed kinetic models showed good performance with RMSE of 0.618, B f of 1.02, and A f of 1.08. Also, performance of the dynamic model was appropriate. Thus, the developed dynamic model in this study can be applied to describe the kinetic behavior of E. coli in cooked pig trotters during storage.

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.

Influence of milk microbiota on Listeria monocytogenes survival during cheese ripening.

This study aimed to compare the three strains of Listeria monocytogenes survival in raw milk cheese and pasteurized milk cheese and to suggest the effect of milk microbiota on survival. L. monocytogenes cell counts decreased in all cheese as ripening time increased, and the survival rate was different for the strains of L. monocytogenes. Furthermore, L. monocytogenes survived longer in raw milk cheese than in pasteurized milk cheese. The difference of bacterial survival in each cheese was independent of Aw or the Lactobacillus spp. populations in cheeses; there was no difference in Aw or Lactobacillus spp. populations in all cheeses. The richness of microbiota in raw milk was little higher than in pasteurized milk, and five phyla (Chloroflexi, Cyanobacteria, Deinococcus-Thermus, Lentisphaerae, and Verrucomicrobia) were present only in raw milk. Also, organic acid-producing bacteria were presented more in pasteurized milk compared with raw milk; thus, the growth of L. monocytogenes was slower in pasteurized milk. In conclusion, differences in the microbial community of milk can affect the growth of L. monocytogenes. Making cheese using raw milk is a risk of L. monocytogenes infection; thus, efforts to prevent growth of L. monocytogenes such as the use of appropriate food additives are required.

Quantitative microbial risk assessment for Clostridium perfringens foodborne illness following consumption of kimchi in South Korea.

The purpose of this study was to conduct a risk assessment for Clostridium perfringens foodborne illness via kimchi consumption in South Korea. Prevalence of C. perfringens in kimchi, kimchi consumption amount and frequency, and distribution conditions (time and temperature) from manufacture to the home were determined. C. perfringens initial contamination level was estimated using Beta distribution [Beta (6, 79)]. Potential C. perfringens cell counts during distribution were predicted using the Weibull model (primary models, R 2 = 0.923-0.953) and a polynomial model [(δ = 1/(0.2385 + (- 0.0307 × Temp) + (0.0011 × Temp2)), R 2 = 0.719]. Average daily consumption data was assessed using Gamma distribution [1.0444, 91.767, RiskShift (0.16895), RiskTruncate (0, 1078)]. The mean risk of C. perfringens-associated foodborne illness following kimchi consumption was found to be 1.21 × 10-17. These results suggest that the risk of C. perfringens foodborne illness from kimchi consumption, under current conditions, can be considered to be very low in S. Korea.

Anti-Inflammatory Effect of a Peptide Derived from the Synbiotics, Fermented Cudrania tricuspidata with Lactobacillus gasseri, on Inflammatory Bowel Disease.

The objective of this study was to evaluate the effects of peptides derived from synbiotics on improving inflammatory bowel disease (IBD). Five-week-old male C57BL/6 mice were administered with dextran sulfate sodium (DSS) via drinking water for seven days to induce IBD (IBD group). The mice in the IBD group were orally administered with PBS (IBD-PBS-positive control), Lactobacillus gasseri 505 (IBD-Pro), fermented powder of CT extract with L. gasseri 505 (IBD-Syn), ß-casein: LSQSKVLPVPQKAVPYPQRDMP (IBD-Pep 1), or α s2-casein: VYQHQKAMKPWIQPKTKVIPYVRYL (IBD-Pep 2) (both peptides are present in the synbiotics) for four more days while inducing IBD. To confirm IBD induction, the weights of the animals and the disease activity index (DAI) scores were evaluated once every two days. Following treatment of probiotics, synbiotics, or peptides for 11 days, the mice were sacrificed. The length of the small and large intestines was measured. The expression of the proinflammatory cytokines IL-1ß, IL-6, TNF-α, and COX-2 in the large intestine was measured. Large intestine tissue was fixed in 10% formalin and stained with hematoxylin and eosin for histopathological analysis. The body weights decreased and DAI scores increased in the IBD group, but the DAI scores were lower in the IBD-Pep 2 group than those in the IBD group treated with PBS, Pro, Syn, or Pep 1. The lengths of the small and large intestines were shorter in the IBD group than in the group without IBD, and the expression levels of the proinflammatory cytokines were lower (p < 0.05) in the IBD-Pep 2 group than those in the IBD-PBS-positive control group. In addition, histopathological analysis showed that IBD was ameliorated in the Pep 2-treated group. These results indicate that Pep 2 derived from α s2-casein was effective in alleviating IBD-associated inflammation. Thus, we showed that these peptides can alleviate inflammation in IBD.

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.

Akkermansia muciniphila Prevents Fatty Liver Disease, Decreases Serum Triglycerides, and Maintains Gut Homeostasis.

The objective of this study was to elucidate the effect of intestinal Akkermansia muciniphila bacteria on fatty liver disease. Five-week-old C57BL/6N mice were administered either phosphate-buffered saline (PBS; control) or A. muciniphila at 108 to 109 CFU/ml, and were fed either a 45% fat diet (high-fat diet [HFD]) or a 10% fat diet (normal diet [ND]) for 10 weeks. After 10 weeks, the mice were euthanized, and blood and tissue samples, including adipose tissue, cecum, liver, and brain, were immediately collected. Biochemical and histological analyses were conducted, and the expression levels of related factors were compared to determine the antiobesity effects of Akkermansia muciniphila The gut microbiome was analyzed in fecal samples. Oral administration of A. muciniphila significantly (P < 0.05) lowered serum triglyceride (TG) and alanine aminotransferase (ALT) levels in obese mice. Compared to the non-A. muciniphila-treated group, the expression of SREBP (regulator of TG synthesis in liver tissue) was decreased in the A. muciniphila-treated group. The expression of IL-6 in the liver of obese mice was decreased following the administration of A. muciniphila Furthermore, alterations in the ratio of Firmicutes to Bacteroidetes and the decrease in bacterial diversity caused by the HFD were restored upon the administration of A. muciniphila These results indicate that A. muciniphila prevents fatty liver disease in obese mice by regulating TG synthesis in the liver and maintaining gut homeostasis.IMPORTANCE This study investigated the effect of Akkermansia muciniphila on fatty liver disease. Although some research about the effects of A. muciniphila on host health has been published, study of the relationship between A. muciniphila administration and fatty liver, as well as changes in the gut microbiota, has not been conducted. In this study, we demonstrated that A. muciniphila prevented fatty liver disease by regulation of the expression of genes that regulate fat synthesis and inflammation in the liver.