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Background: Obesity has been reported to be associated with iron deficiency. However, few studies have investigated iron status in low adiposity. To investigate whether body adiposity was associated with altered hepatic iron status, we compared liver iron levels and markers involved in inflammation and iron absorption in obese, control, and mildly calorie restricted mice. Methods: Seven week old C57BL/6 mice were fed control (10% kcal fat, Control) or high fat (60% kcal fat, HFD) diets, or reduced amount of control diet to achieve 15% calorie restriction (CR) for 16 weeks. Hepatic non-heme iron content and ferritin protein level, and hematocrit and hemoglobin levels were determined to assess iron status. Hepatic expression of Mcp-1 and Tnf-α were measured as hepatic inflammatory markers. Hepatic hepcidin (Hamp) and Bmp6, and duodenal Dmt1, Dcyt1b, hephaestin (Heph) and ferroportin mRNA levels were measured as factors involved in regulation of iron absorption. Results: Hepatic non-heme iron and ferritin protein levels were significantly higher in the CR group compared with the Control group, and significantly lower in the HFD group. These two iron status markers showed significantly negative correlations with the amount of white adipose tissue (r = -0.689 for hepatic non-heme iron and r = -0.740 for ferritin). Hepatic Mcp-1 and Tnf-α mRNA levels were significantly lower in the CR compared with the HFD (74 and 47% lower) and showed significantly negative correlations with hepatic non-heme iron levels (Mcp-1: r = -0.557, P < 0.05; Tnf-α: r = -0.464, P < 0.05). Hepatic Hamp mRNA levels were lower in the HFD and higher in the CR groups compared with the Control group, which could be a response to maintain iron homeostasis. Duodenal Dcyt1b mRNA levels were higher in the CR group compared with the HFD group and duodenal Heph mRNA levels were higher in the CR group than the Control group. Conclusion: We showed that body adiposity was inversely correlated with liver iron status. Low inflammation levels in hepatic milieu and enhanced expression of duodenal oxidoreductases induced by calorie restriction could have contributed to higher iron status. [ABSTRACT FROM AUTHOR]

CrAssphage has been recognized as the most abundant and human-specific bacteriophage in the human gut. Consequently, crAssphage has been used as a microbial source tracking (MST) marker to monitor human fecal contamination. Many crAss-like phages (CLPs) have been recently discovered, expanding the classification into the new order Crassvirales. This study aims to assess CLP prevalence in South Korea and develop a detection system for MST applications. Thirteen CLPs were identified in six human fecal samples and categorized into seven genera via metagenomic analysis. The major head protein (MHP) displayed increased sequence similarity within each genus. Eight PCR primer candidates, designed from MHP sequences, were evaluated in animal and human feces. CLPs were absent in animal feces except for those from raccoons, which hosted genera VI, VIIa, and VIIb. CLPs were detected in 91.52% (54/59) of humans, with genus VI (38 out of 59) showing the highest prevalence, nearly double that of p-crAssphage in genus I (22 out of 59). This study highlights genus VI as a potent MST marker, broadening the detection range for CLPs. Human-specific and selectively targeted MST markers can significantly impact hygiene regulations, lowering public health costs through their application in screening liver, sewage, wastewater, and various environmental samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Gut microbiota is a diverse community of microorganisms that constantly work to protect the gut against pathogens. Salmonella stands out as a notorious foodborne pathogen that interacts with gut microbes, causing an imbalance in the overall composition of microbiota and leading to dysbiosis. This review focuses on the interactions between Salmonella and the key commensal bacteria such as E. coli , Lactobacillus , Clostridium , Akkermansia , and Bacteroides . The review highlights the role of these gut bacteria and their synergy in combating Salmonella through several mechanistic interactions. These include the production of siderophores, which compete with Salmonella for essential iron; the synthesis of short-chain fatty acids (SCFAs), which exert antimicrobial effects and modulate the gut environment; the secretion of bacteriocins, which directly inhibit Salmonella growth; and the modulation of cytokine responses, which influences the host's immune reaction to infection. While much research has explored Salmonella , this review aims to better understand how specific gut bacteria engage with the pathogen, revealing distinct defense mechanisms tailored to each species and how their synergy may lead to enhanced protection against Salmonella . Furthermore, the combination of these commensal bacteria could offer promising avenues for bacteria-mediated therapy during Salmonella -induced gut infections in the future.

Listeria monocytogenes is a foodborne pathogen that can cause deadly severe listeriosis. While systematic review and meta-analysis are powerful tools for comprehensive analysis by pooling every related study, these approaches to L.monocytogenes contamination food have yet to be studied in South Korea. We aimed to identify high-risk L.monocytogenes foods in South Korea through a prevalence survey of retail food products for the first time. A total of 13,684 samples of 59 articles were used for meta-analysis through the systematic review, and the results were synthesized using a random-effects model considering the heterogeneity. The overall pooled prevalence was 2.26 % (95 % CI: 1.44-3.52 %). Among nine food categories, meat exhibited the highest prevalence at 8.32 % (95 % CI: 4.42-12.14 %) after sample size restriction. Specifically, a post-hoc sensitivity analysis was conducted to identify the prevalence difference among subgroups and the source of heterogeneity. Intriguingly, the analysis revealed chicken as the primary contributor to the elevated prevalence of L.monocytogenes, a key factor deriving the observed heterogeneity. This study carries significant implications for public health and food safety in Korea. Furthermore, knowledge of differences in prevalence levels in various foods will be able to be used as a predictive guideline for foodborne outbreaks., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ok Kyung Koo reports financial support was provided by National Research Foundation of Korea. Ok Kyung Koo reports financial support was provided by Chungnam National University., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Campylobacter spp. constitute a significant global threat as a leading cause of foodborne illnesses, with poultry meat as a prominent reservoir for these pathogens. South Korea is known for its diverse poultry consumption habits, and continuous outbreaks make it a matter of concern to perform a meta-analysis to identify the primary source of contamination. This systematic review and meta-analysis aimed to assess and compare the prevalence of Campylobacter in various poultry and meat types while also considering the importance of environmental factors in South Korea. The meta-analysis revealed that duck meat exhibited the highest prevalence of Campylobacter , with a pooled estimate of 70.46% (95% CI: 42.80% to 88.38%), followed by chicken meat at a pooled prevalence of 36.17% (95% CI: 26.44% to 47.91%). Additionally, our analysis highlighted the predominance of C. jejuni and C. coli in South Korea. These findings underscore the importance of implementing rigorous food safety measures and establishing robust surveillance programs in the poultry industry to mitigate the risk of Campylobacter -related foodborne illnesses associated with meat consumption in South Korea.

Listeria monocytogenes is a foodborne pathogen that causes listeriosis in humans with severe symptoms. In South Korea, listeriosis had only been reported sporadically among hospitalized patients until the first foodborne outbreak occurred in 2018. In this study, a L. monocytogenes strain responsible for this outbreak (FSCNU0110) was characterized via whole genome sequencing and compared with publicly available L. monocytogenes genomes of the same clonal complex (CC). Strain FSCNU0110 belonged to multilocus sequence typing (MLST)-based sequence type 224 and CC224, and core genome MLST-based sublineage 6,178. The strain harbored tetracycline resistance gene tetM , four other antibiotic resistance genes, and 64 virulence genes, including Listeria pathogenicity island 1 (LIPI-1) and LIPI-3. Interestingly, llsX in LIPI-3 exhibited a characteristic SNP (deletion of A in position 4, resulting in a premature stop codon) that was missing among all CC224 strains isolated overseas but was conserved among those from South Korea. In addition, the tetM gene was also detected only in a subset of CC224 strains from South Korea. These findings will provide an essential basis for assessing the characteristics of CC224 strains in South Korea that have shown a potential to cause listeriosis outbreaks., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Lee, Lee, Park and Koo.)

Foodborne pathogenic bacteria in multi-species biofilms in food manufacturing facilities have been suspected to be the cause of cross-contamination leading to foodborne illness. We studied if cafeteria kitchen-associated bacterial isolates can have any protective effect on E. coli O157:H7 in biofilm against extracellular polymeric substances (EPS)-degrading enzymes and sodium hypochlorite. We investigated multi-species biofilm-forming ability and the efficacy of EPS-degrading enzymes using crystal violet assay. The susceptibility of E. coli O157:H7 to sodium hypochlorite (NaClO) was evaluated using propidium monoazide combined with quantitative PCR (PMA-qPCR). Then, a combined treatment with enzymes followed by NaClO was also tested. Most cafeteria kitchen isolates of Acinetobacter and Bacillus were able to form biofilms. Several of them showed a protective effect on E. coli O157:H7 against NaClO after forming multi-species biofilms, particularly in Acinetobacter. This protective effect on E. coli O157:H7 was also noticed after the enzyme or the combined treatment with NaClO. Our results give us an insight into the protective role of food-associated environmental bacteria for E. coli O157:H7 in biofilms against common sanitizers and warrant further study to develop effective control methods. Our study also highlights the importance of preventing contamination or biofilm formation by environmental microorganisms, eventually reducing foodborne illness., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Food poisoning outbreaks in schools can affect many students, causing physical and psychological damage and time and economic loss. Fecal indicator bacteria (FIB) have been used to monitor the contamination; however, the detection is time-consuming and confirms the contamination from all warm-blooded animals. Microbial source tracking (MST) is a molecular-based detection method that is host specific. This study aimed to evaluate MSTs and FIBs for tracing contamination in the school cafeteria. The average total aerobic count was 0.89 to 3.63 log CFU/100 cm 2 , and the faucets in the cooking area showed a significantly high aerobic count. The stove valve, faucet, and hand-washer were the most contaminated area, with a concentration of 1.90 to 6.80 log CFU/100 cm 2 from the frequent hand contact. Escherichia coli was not detected on any surfaces, and coliform was detected on five surfaces: the sink and faucet in the food preparation area, the faucet in the cooking area, the hand-washer, and the toilet seat in the restroom with 0.33 to 3.64 log CFU/100 cm 2 . Human-specific crAssphage appeared on a faucet in the food preparation area, while HF183 was not detected. The result indicates that the continuous monitoring of frequent hand-contact areas is recommended to maintain the hygiene condition in the school cafeteria., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ok Kyung Koo reports financial support was provided by National Research Foundation of Korea., (Copyright © 2022. Published by Elsevier Inc.)

CrAssphage is a novel and by far the most abundant bacteriophage in the human gut and has been proposed as a human-specific microbial source tracking (MST) marker. However, its global use as a human-specific MST marker requires validation in more extensive regions. The purpose of this study was to evaluate the specificity and abundance of the human-specific MST marker crAssphage with PCR and RT-PCR assays in human and animal feces in Korea. The prevalence of crAssphage was confirmed in 94 human feces samples (subjects: 19 to 45 years old) and 56 animal feces samples (from birds, raccoons, squirrels, weasels, deer, wild boars, hares, cats, and dogs). CrAssphage showed sensitivity of 0.39 and specificity of 1.00 in Korea, with a sequencing analysis showing that genotype II was dominant at 71.9%. The quantitative analysis showed that crAssphage is sufficiently abundant in human feces given the high concentration range of 4.26 to 8.25 log gene copies (GC)/ng in human feces. In conclusion, this study confirmed the crAssphage as a specific and abundant MST marker with which to identify human fecal contamination in Korea., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Bacterial contamination of food-contact surfaces can be a potential risk factor for food quality and safety. To evaluate the spatial and temporal variations of the potential cross-contamination routes, we conducted a biogeographical assessment of bacteria in a foodservice facility based on the diversity of microflora on each surface. To this end, we performed high-throughput amplicon sequencing of 13 food-contact and non-food contact surfaces in a foodservice facility throughout a year. The results showed that Bacillus , Acinetobacter, Streptophyta , Enterobacter , Pseudomonas , Serratia , Enhydrobacter , Staphylococcus , Paracoccus , and Lysinibacillus were the dominant genera found on the kitchen surfaces of the foodservice facility. Depending on the season, changes in Firmicute/Proteobacteria ratios were observed, and the fan becomes the main source of outdoor air contamination. The microbial flow associated with spoilage was also observed throughout food preparation. Taken together, our results would be a powerful reference to hygiene managers for improvement of food processes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lim, Kim, Sul, Kim, Kim, Kim and Koo.)

Clostridium perfringens is a major human pathogen that causes gastroenteritis via enterotoxin production and has the ability to form spores and biofilms for environmental persistence and disease transmission. This study aimed to compare the disinfectant and environmental resistance properties of C. perfringens vegetative cells and spores in planktonic and sessile conditions, and to examine the nucleotide polymorphisms and transcription under sessile conditions in C. perfringens strains isolated from meat. The sporulation rate of sessile C. perfringens TYJAM-D-66 ( cpe +) was approximately 19% at day 5, while those of CMM-C-80 ( cpe -) and SDE-B-202 ( cpe +) were only 0.26% and 0.67%, respectively, at day 7. When exposed to aerobic conditions for 36 h, TYJAM-D-66, CMM-C-80, and SDE-B-202 vegetative cells showed 1.70 log, 5.36 log, and 5.67 log reductions, respectively. After treatment with sodium hypochlorite, the survival rates of TYJAM-D-66 vegetative cells (53.6%) and spores (82.3%) in biofilms were higher than those of planktonic cells (9.23%). Biofilm- and spore-related genes showed different expression within TYJAM-D-66 (-4.66~113.5), CMM-C-80 (-3.02~2.49), and SDE-B-202 (-5.07~2.73). Our results indicate the resistance of sessile cells and spores of C. perfringens upon exposure to stress conditions after biofilm formation.

Environmental cues promote microbial biofilm formation and physiological and genetic heterogeneity. In food production facilities, biofilms produced by pathogens are a major source for food contamination; however, the pathogenesis of biofilm-isolated sessile cells is not well understood. We investigated the pathogenesis of sessile Listeria monocytogenes (Lm) using cell culture and mouse models. Lm sessile cells express reduced levels of the lap, inlA, hly, prfA, and sigB and show reduced adhesion, invasion, translocation, and cytotoxicity in the cell culture model than the planktonic cells. Oral challenge of C57BL/6 mice with food, clinical, or murinized-InlA (InlA m ) strains reveals that at 12 and 24 h post-infection (hpi), Lm burdens are lower in tissues of mice infected with sessile cells than those infected with planktonic cells. However, these differences are negligible at 48 hpi. Besides, the expressions of inlA and lap mRNA in sessile Lm from intestinal content are about 6.0- and 280-fold higher than the sessle inoculum, respectively, suggesting sessile Lm can still upregulate virulence genes shortly after ingestion (12 h). Similarly, exposure to simulated gastric fluid (SGF, pH 3) and intestinal fluid (SIF, pH 7) for 13 h shows equal reduction in sessile and planktonic cell counts, but induces LAP and InlA expression and pathogenic phenotypes. Our data show that the virulence of biofilm-isolated Lm is temporarily attenuated and can be upregulated in mice during the early stage (12-24 hpi) but fully restored at a later stage (48 hpi) of infection. Our study further demonstrates that in vitro cell culture assay is unreliable; therefore, an animal model is essential for studying the pathogenesis of biofilm-isolated bacteria.

Bacteria can form biofilms, complex microbial communities protected from environmental stress, on food contact surfaces. Brassicaceae plant has been shown to contain bioactive compounds with antimicrobial activities. The objective of this study was to evaluate the synergistic effects of Brassicaceae species and proteinase K against E. coli O157:H7 biofilm. We determined the minimum biofilm inhibitory concentration, the fractional inhibitory concentration indexes, and the synergistic inhibitory effect of Raphanus sativus var. longipinnatus, R. sativus, and Brassica oleracea var. acephala extracts with proteinase K on E. coli O157:H7. The biofilm showed a 49% reduction with 2 mg/mL R. sativus. The combination of proteinase K 25 µg/mL significantly increased the effect of 2 mg/mL R. sativus var. longipinnatus and the combined treatment yielded up to 2.68 log reduction on stainless steel coupons. The results showed that the combination of R. sativus var. longipinnatus extract and proteinase K could serve as an anti-biofilm agent with synergistic effects for inhibiting E. coli O157:H7 biofilm on stainless steel surfaces.

Insufficient and ineffective cleaning practices can cause food residues to remain in kitchen and can facilitate bacterial attachment and persistence by protective films. The present study investigated the survival of five major foodborne pathogens on stainless steel coupons, in the presence of cooked rice, whole eggs, and soymilk. Foodborne pathogens showed different survival rates by desiccation and disinfection depending on food residues. Overall, the pathogens showed stronger survival than the control at 0.13-3.97 log CFU/coupon with 5% residues, and at 0.75-5.29 log CFU/coupon with 50% residues. Staphylococcus aureus was not affected by the food residue with showing the least difference in concentration, while Escherichia coli O157:H7 showed the most significant increase by food residue. The cells with cooked rice were observed using FE-SEM, and demonstrated bacterial binding or embedment. All results suggest that food safety can be practically ensured by food residue types and appropriate cleaning and disinfectants., Competing Interests: Conflict of interestThe authors declare no conflict of interest., (© The Korean Society of Food Science and Technology 2019.)

Escherichia coli O157:H7 is one of the most important pathogens worldwide. In this study, three different kinds of enzymes, DNase I, proteinase K and cellulase were evaluated for inhibitory or degrading activity against E. coli O157:H7 biofilm by targeting extracellular DNA, proteins, and cellulose, respectively. The cell number of biofilms formed under proteinase K resulted in a 2.43 log CFU/cm 2 reduction with an additional synergistic 3.72 log CFU/cm 2 reduction after NaClO post-treatment, while no significant reduction occurred with NaClO treatment alone. It suggests that protein degradation could be a good way to control the biofilm effectively. In preformed biofilms, all enzymes showed a significant reduction of 16.4-36.7% in biofilm matrix in 10-fold diluted media (p < 0.05). The sequential treatment with proteinase K, cellulase, and NaClO showed a significantly higher synergistic inactivation of 2.83 log CFU/cm 2 compared to 1.58 log CFU/cm 2 in the sequence of cellulase, proteinase K, and NaClO (p < 0.05). It suggests that the sequence of multiple enzymes can make a significant difference in the susceptibility of biofilms to NaClO. This study indicates that the combination of extracellular polymeric substance-degrading enzymes with NaClO could be useful for the efficient control of E. coli O157:H7 biofilms.

Bacteria can survive and persist in food processing environments by attachment and biofilm formation and transfer to food products, causing serious foodborne illness. In this study, we investigated natural substances that belong to the family Brassicaceae to determine whether they have potential anti-attachment activities against Escherichia coli O157:H7. The inhibition of biofilm formation was evaluated by crystal violet and resazurin assays at different stages of biofilm formation (initial attachment, biofilm formation, and after biofilm development) of E. coli O157:H7. The sessile cells were reduced to a range of 13.8-31.3% by young radish, radish, radish sprout, red cabbage, and kale extracts, and the viability was reduced to between 5.83 and 51.5%. The radical scavenging activities and the presence of polyphenolic compounds were compared. The presence of phenolic compounds such as gallic acid, caffeic acid, and phenylethyl ITC in the Brassicaceae family verified the potential use as a natural anti-biofilm substituent against E. coli O157:H7., (© The Korean Society of Food Science and Technology 2019.)

Clostridium perfringens is one of the leading causes of food poisoning worldwide. The aims of this study were to investigate the presence of C. perfringens in food supplied to school cafeterias, to assess the presence of toxin genes in the isolates, and to investigate the biofilm formation and antibiotic susceptibility of the isolates. A total of 30 C. perfringens strains (12.9%) from 232 samples of beef, pork, chicken, and duck meat were isolated. Toxin genes, including cpa, cpe, cpb2, and netB, were detected, while the cpb, etx, iap and tpeL genes were absent. Biofilm formation was analyzed, and all the isolates were able to form biofilm. Antibiotic resistance was observed against penicillin (97%), lincomycin (20%), bacitracin (97%), oxytetracycline (73%), trimethoprim (7%), gentamicin (10%), tetracycline (93%), erythromycin (83%), ampicillin (100%), amikacin (7%), and streptomycin (3%). In conclusion, the results showed that students are exposed to a potentially high risk of food poisoning by C. perfringens; therefore, precaution is required for these types of catering services., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The purpose of this study was to characterize the microbial community in ground pork using molecular approaches. Forty six ground pork products were purchased from local stores in the north central area of South Korea. Aerobic plate counts varied 4.23 ± 5.14 × 10(5) CFU/g with the range between 5.00 × 10(3) and 1.85 × 10(6) CFU/g for ground pork samples. Four ground meat samples were further processed for metagenomic analysis. Pseudomonas species was the most relative abundant with a wide range occurring (1.72 to 77.7%) as part of the microbial genera in ground pork. Bacteria such as Carnobacterium, Yersinia, Photobacterium were also identified in ground pork. Despite the prominence of certain genera across all samples there was still extensive microbial diversity among ground pork products that originated from different slaughter houses and were processed in different markets. Such diversity indicates that designing interventions to extend shelf life may be hampered by the extensive variability in the microbial consortia associated with pork products. However, this diversity may be useful for developing microbial traceability signatures unique to a slaughter house or a particular market.

Salmonella infections are reported as the second most common pathogen caused foodborne disease in the United States, and several Salmonella serovars can colonize in the intestinal tracts of poultry. Reducing Salmonella in poultry is crucial to decrease the incidence of salmonellosis in humans. In this study, we evaluated the immune response of chicken macrophage cells (HD-11) and effects of bacteriophage P22 against the extra- and intracellular S. Typhimurium LT2. Four treatments, (1) HD-11 cells as control, (2) HD-11 cells with LT2, (3) HD-11 cells with LT2 and P22, and (4) HD-11 cells with P22, were administered, and IL-8 responses of HD-11 cells were measured using an ELISA. Also, four cytokine (IL-4, IL-8, IL-10, and IFN-γ) gene expression levels in the presence of LT2 and/or P22 were quantified by qRT-PCR. We found that P22 lysed the extra- and intracellular LT2, which adhered and were taken up by the HD-11 cells. The ELISA indicated that HD-11 cells produced significantly higher IL-8 cytokine levels in the supernatant during the intracellular lyses of LT2 by P22 (P < 0.05). The IL-8 expression levels measured by qRT-PCR also exhibited similar results with the IL-8 production based on ELISA measurements., (© 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.)

In this study we assessed the use of acridine orange as an alternative to optical density to quantify the growth of Lactobacillus bulgaricus ATCC 7517. The growth of bacteria in Lactobacillus de Man Rogosa Sharpe (MRS) medium was measured by both acridine orange (AO) and optical density (OD) measurements for 24 h. The relationship between both methods was compared via correlation analysis. The doubling time of bacteria based on the values of OD600 and AO obtained during 24 h growth were also calculated. The result shows strong correlation of cell growth between OD600 and AO during the first 10 hours of growth, but the correlation was less strong when analyzing the data from 0 to 24 hours. Growth rates, generation time and lag time were also similar. This study indicates that AO could be used in place of OD to prepare growth curves of Lactobacillus bulgaricus during the exponential phase of growth, and to compare growth rates, generation times or lag times.

Contamination by Listeria monocytogenes has been a constant public health threat for the ready-to-eat (RTE) meat industry due to the potential for high mortalities from listeriosis. Lactic acid bacteria (LAB) have shown protective action against various pathogenic bacteria. The aim of this study was to evaluate the antilisterial activity of a combination of three LAB strains (Lactiguard®) on L. monocytogenes. The combination of the LAB was inhibitory to L. monocytogenes inoculated onto frankfurters not containing lactate/diacetate after 8weeks of refrigerated storage (0.6 log reduction compared to L. monocytogenes only control), and when a cell free extract (CFS) of the LAB was added with LAB even more inhibition was obtained (1.2 log reduction compared with L. monocytogenes only). In frankfurters containing lactate/diacetate the LAB and the LAB plus CFS were more effective in reducing growth of L. monocytogenes after 8 weeks of refrigerated storage (2 and 3.3 log reductions respectively)., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The study was conducted to evaluate the attachment of three lactic acid bacteria (LAB) strains and their combination in a cocktail, to stainless steel coupons from a deli slicer, and their ability to inhibit the attachment of Listeria monocytogenes. In a previous study, three LAB strains, Pediococcus acidilactici, Lactobacillus amylovorus, and Lactobacillus animalis, were isolated from ready-to-eat meat and exhibited antilisterial effect. In the study reported here, hydrophobicity tests were determined according to the method of microbial adhesion to solvent. The attachment of the cells was evaluated on stainless steel coupons from deli slicers. Extracellular carbohydrates were determined with a colorimetric method. Based on these tests, L. animalis exhibited the greatest hydrophobicity (26.3%), and its adherence increased sharply from 24 to 72 h, whereas L. amylovorus yielded the lowest hydrophobicity (3.86%) and was weakly adherent. Although P. acidilactici had moderate hydrophobicity (10.1%), it adhered strongly. The attached LAB strains produced significantly (P < 0.05) higher total carbohydrates than their planktonic counterparts did, which is an important characteristic for attachment. Three conditions were simulated to evaluate the ability of the LAB cocktail (10(8) CFU/ml) to competitively exclude L. monocytogenes (10(3) CFU/ml) on the surface of the coupons. The coupons were pretreated with the LAB cocktail for 24 h prior to the addition of L. monocytogenes, simultaneously treated with the LAB cocktail and L. monocytogenes, or pretreated with L. monocytogenes 24 h prior to the addition of the LAB cocktail. The LAB cocktail was able to reduce the attachment L. monocytogenes significantly (P < 0.05). The LAB cocktail indicated potential attachment on stainless steel and bacteriostatic activity toward L. monocytogenes attached on stainless steel, which indicates a possible role for LAB as a biosanitizer in the food industry.

Visible indication based on the aggregation of colloidal nanoparticles (NPs) is highly advantageous for rapid on-site detection of biological entities, which even untrained persons can perform without specialized instrumentation. However, since the extent of aggregation should exceed a certain minimum threshold to produce visible change, further applications of this conventional method have been hampered by insufficient sensitivity or certain limiting characteristics of the target. Here we report a signal amplification strategy to enhance visible detection by introducing switchable linkers (SLs), which are designed to lose their function to bridge NPs in the presence of target and control the extent of aggregation. By precisely designing the system, considering the quantitative relationship between the functionalized NPs and SLs, highly sensitive and quantitative visible detection is possible. We confirmed the ultrahigh sensitivity of this method by detecting the presence of 20 fM of streptavidin and fewer than 100 CFU/mL of Escherichia coli.

Background: Listeria monocytogenes, an intracellular foodborne pathogen, infects immunocompromised hosts. The primary route of transmission is through contaminated food. In the gastrointestinal tract, it traverses the epithelial barrier through intracellular or paracellular routes. Strategies to prevent L. monocytogenes entry can potentially minimize infection in high-risk populations. Listeria adhesion protein (LAP) aids L. monocytogenes in crossing epithelial barriers via the paracellular route. The use of recombinant probiotic bacteria expressing LAP would aid targeted clearance of Listeria from the gut and protect high-risk populations from infection., Methodology/principal Findings: The objective was to investigate the ability of probiotic bacteria or LAP-expressing recombinant probiotic Lactobacillus paracasei (Lbp(LAP)) to prevent L. monocytogenes adhesion, invasion, and transwell-based transepithelial translocation in a Caco-2 cell culture model. Several wild type probiotic bacteria showed strong adhesion to Caco-2 cells but none effectively prevented L. monocytogenes infection. Pre-exposure to Lbp(LAP) for 1, 4, 15, or 24 h significantly (P<0.05) reduced adhesion, invasion, and transepithelial translocation of L. monocytogenes in Caco-2 cells, whereas pre-exposure to parental Lb. paracasei had no significant effect. Similarly, Lbp(LAP) pre-exposure reduced L. monocytogenes translocation by as much as 46% after 24 h. Lbp(LAP) also prevented L. monocytogenes-mediated cell damage and compromise of tight junction integrity. Furthermore, Lbp(LAP) cells reduced L. monocytogenes-mediated cell cytotoxicity by 99.8% after 1 h and 79% after 24 h., Conclusions/significance: Wild type probiotic bacteria were unable to prevent L. monocytogenes infection in vitro. In contrast, Lbp(LAP) blocked adhesion, invasion, and translocation of L. monocytogenes by interacting with host cell receptor Hsp60, thereby protecting cells from infection. These data show promise for the use of recombinant probiotics in preventing L. monocytogenes infection in high-risk populations.

Listeria adhesion protein (LAP), an alcohol acetaldehyde dehydrogenase (lmo1634), interacts with host-cell receptor Hsp60 to promote bacterial adhesion during the intestinal phase of Listeria monocytogenes infection. The LAP homologue is present in pathogens (L. monocytogenes, L. ivanovii) and non-pathogens (L. innocua, L. welshimeri, L. seeligeri); however, its role in non-pathogens is unknown. Sequence analysis revealed 98 % amino acid similarity in LAP from all Listeria species. The N-terminus contains acetaldehyde dehydrogenase (ALDH) and the C-terminus an alcohol dehydrogenase (ADH). Recombinant LAP from L. monocytogenes, L. ivanovii, L. innocua and L. welshimeri exhibited ALDH and ADH activities, and displayed strong binding affinity (K(D) 2-31 nM) towards Hsp60. Flow cytometry, ELISA and immunoelectron microscopy revealed more surface-associated LAP in pathogens than non-pathogens. Pathogens exhibited significantly higher adhesion (P<0.05) to Caco-2 cells than non-pathogens; however, pretreatment of bacteria with Hsp60 caused 47-92 % reduction in adhesion only in pathogens. These data suggest that biochemical properties of LAP from pathogenic Listeria are similar to those of the protein from non-pathogens in many respects, such as substrate specificity, immunogenicity, and binding affinity to Hsp60. However, protein fractionation analysis of extracts from pathogenic and non-pathogenic Listeria species revealed that LAP was greatly reduced in intracellular and cell-surface protein fractions, and undetectable in the extracellular milieu of non-pathogens even though the lap transcript levels were similar for both. Furthermore, a LAP preparation from L. monocytogenes restored adhesion in a lap mutant (KB208) of L. monocytogenes but not in L. innocua, indicating possible lack of surface reassociation of LAP molecules in this bacterium. Taken together, these data suggest that LAP expression level, cell-surface localization, secretion and reassociation are responsible for LAP-mediated pathogenicity and possibly evolved to adapt to a parasitic life cycle in the host.

Efficient capture of target analyte on biosensor platforms is a prerequisite for reliable and specific detection of pathogenic microorganisms in a microfluidic chip. Antibodies have been widely used as ligands; however, because of their occasional unsatisfactory performance, a search for alternative receptors is underway. Heat shock protein 60 (Hsp60), a eukaryotic mitochondrial chaperon protein is a receptor for Listeria adhesion protein (LAP) during Listeria monocytogenes infection. This paper reports application of biotinylated Hsp60 as a capture molecule for living (viable) L. monocytogenes in a microfluidic environment. Hsp60, immobilized on the surface of streptavidin-coated silicon dioxide exhibited specific capture of pathogenic Listeria against a background of other Listeria species, Salmonella, Escherichia, Bacillus, Pseudomonas, Serratia, Hafnia, Enterobacter, Citrobacter, and Lactobacillus. The capture efficiency of L. monocytogenes was 83 times greater than another Listeria receptor, the monoclonal antibody, mAb-C11E9. Additionally, the capture rate was further increased on a Hsp60-coated biochip by 60% when a dielectrophoresis force was applied for 5 min at the beginning of the final 1 h incubation step. Our data show that Hsp60 could be used for specific detection of L. monocytogenes on a biochip sensor platform.

A bifunctional alcohol/acetaldehyde dehydrogenase (AdhE) gene (adhE) was cloned from Leuconostoc mesenteroides C7 (LMC7), which is the dominant lactic acid bacterium produced during heterofermentation of kimchi. The nucleotide sequence of the DNA fragment containing putative adhE, which is 2685 bp long and encodes an 886 amino acid polypeptide, exhibits 99% homology with Leu. mesenteroides sp. cremoris. The deduced AdhE comprises two conserved domains: alcohol dehydrogenase (Adh) and acetaldehyde dehydrogenase (Aldh). Moreover, two NAD-binding sites were observed, based on the presence of the GXGXXG motif. A pADHE containing the adhE gene expressed AdhE at the translational level in Escherichia coli BL21, which was at a higher level than in E. coli DH5alpha and E. coli JM109. The AdhE of LMC7 showed Adh and Aldh activities that, when expressed in E. coli. BL21, were 7.5 and 5.7 U mg(-1) , respectively.