• Korean Journal of Food Science and Technology
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• v.40 no.6
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• pp.712-716
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• 2008

In an effort to evaluate Salmonella food safety using combinations of preservation techniques, its viabilities when exposed to HCl, acetic acid, and the oxidative agents (hydrogen peroxide and butyl hydrogen peroxide), were analyzed using sub-lethal heat-shocked Salmonella Typhimurium at $56^{\circ}C$. 2D gel electrophoresis and MALDI-TOF MS analyses were also conducted to determine the expression and repression of proteins in heat-shocked cells. Heat-shocked S. Typhimurium evidenced a reduction of viable counts by 1-2 log CFU/mL. However, viality of non heat-shocked S. Typhimurium decreased markedly by 5-6 log CFU/mL at a pH 4 in response to acid and oxidative stresses. Sub-lethal heat treatment greatly increased the resistance of S. Typhimurium against acid and oxidant agents. As for 2D gel electrophoresis and protein identification via MALDI-TOF MS, 17 major proteins in non heat-shocked S. Typhimurium were detected, and only 13 proteins among these proteins were detected in heat-shocked S. Typhimurium. The heat shock proteins such as DnaK and small heat shock proteins were included, and may be associated with the resistance of S. typhimurium against exposure to acids and oxidants. Therefore, even though the promising hurdle technology using the combined mild treatments including heat was applied to S. Typhimurium, the proper heat treatment to reduce its crossprotection activity toward the following preservative agents might be considered.

• Korean Journal of Microbiology
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• v.20 no.2
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• pp.89-97
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• 1982

Mutants of plasmid pKM101 modified to enhance mutagenesis were induced and characterized in Salmonella typhimurium. The pKM101 mutant plasmid were transferred normally and stably maintained in cells. They had modified in their ability (i) to enhance the reversion of both point and frameshift mutations, (ii) to protect the cell against UV-irradiation and chemical mutagen treatment, (iii) of ampicillin resistance. A similar modification in enhancement of reversion was also observed in a $uvrB^-$ strains. These results indicated that mutator effect of pKM101 was coded by one plasmid gene.

• Journal of Environmental Health Sciences
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• v.35 no.5
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• pp.362-364
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• 2009

The present study was undertaken to estimate the antibacterial effect of Mume Fructus water extract (MFWE) against murine salmonellosis. At MFWE concentrations ranging from 25 to 100 ${\mu}g/ml$, the antibacterial effect was not showed on Salmonella typhimurium (S. typhimurium). On the other hand, bacteria without MFWE had a tendency to proliferate up to 8 h after incubation. Oral administration of MFWE at the dose of 40 mg/ml showed a therapeutic effect for S. typhimurium infected BALB/c mice. The mortality of MFWE-treated mice was 80% at 12 days, while that of MFWE-untreated mice was 100% at 9 days after a lethal dose of S. typhimurium infection. The results of our study strongly indicate that MFWE has potential as an effective of salmonellosis.

• Biomedical Science Letters
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• v.11 no.2
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• pp.115-119
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• 2005

A total of 28 Salmonella enterica serovar Typhimurium isolated from diseased pigs and swine carcasses between 2001 and 2003 were characterized by the antimicrobial resistance profiles, PCR for detection of S. Typhimurium DT104 and pulsed-field gel electrophoresis (PFGE) with the restriction enzyme XbaI. All but one isolate presented multidrug resistance (MDR) to more than two antibiotics tested. A total of 11 resistance profiles were observed, and two phenotypes, ST and ASSuTG, were the most common among them. Two isolates were found to be S. Typhimurium DT104 isolates by PCR, and their resistance profile did not show the DT104 typical resistance type ACSSuT, but ACSSuTGK instead. PFGE identified 11 banding patterns in dendrogram, and three main clusters (designated A to C) were represented. Interestingly, sixteen of 19S. Typhimurium isolates belonging to cluster B showed an identical band pattern.

• Korean Journal of Microbiology
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• v.48 no.2
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• pp.87-92
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• 2012

The purpose of this study was to examine the cellular response of Salmonella typhimurium exposed to tea polyphenols (TPP) extracted from Korean green tea (Camellia sinensis L.). TPP showed a dose-dependent bactericidal effect on S. typhimurium. Analysis of cell membrane fatty acids of S. typhimurium cultures treated with TPP identified unique changes in saturated and unsaturated fatty acids, while scanning electron microscopic analysis demonstrated the presence of perforations and irregular rod forms with wrinkled surfaces in cells treated with TPP. Two-dimensional polyacrylamide gel electrophoresis of soluble protein fractions from S. typhimurium cultures showed 16 protein spots increased by TPP. These up-regulated proteins including proteins involved in antioxidants and chaperons, transcript and binding proteins, energy and DNA metabolism were identified by peptide mass fingerprinting using MALDI-TOF. These results provide clues for understanding the mechanism of TPP induced stress and cytotoxicity on S. typhimurium.

• Journal of Food Hygiene and Safety
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• v.31 no.5
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• pp.342-348
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• 2016

The objective of this study was to compare the change of S. Enteritidis with S. Typhimurium populations in liquid egg products. S. Enteritidis or S. Typhimurium was inoculated into egg white and egg yolk and stored at 8, 10, 15, 25, and $35^{\circ}C$, respectively. In egg white, no growth of S. Enteritidis and S. Typhimurium was observed at 8, 10, 15, and $35^{\circ}C$, while both S. Enteritidis and S. Typhimurium in egg white stored grew more than 1 log CFU/ml after 50 hours storage at $25^{\circ}C$. In egg yolk, there was no growth of S. Enteritidis and S. Typhimurium at $8^{\circ}C$ but growth of both strains was observed at 10, 15, 25, and $35^{\circ}C$. Since growth of S. Enteritidis and S. Typhimurium was only observed in egg yolk, primary growth models for both strains were developed using modified Gompertz equation and then secondary models for lag time (LT), specific growth rate (SGR), and maximum population density (MPD) were developed as a function of temperature. At all temperatures, more rapid growth of S. Enteritidis than S. Typhimurium was observed in egg yolk, indicating the greater risk of S. Enteritidis than S. Typhimurium in egg products. In conclusion, the results indicate that temperature control less than $8^{\circ}C$ is very important to ensure safety of liquid egg products, especially liquid egg yolk.

• Journal of Microbiology
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• v.42 no.3
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• pp.216-222
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• 2004

In a previous paper, the ogdH gene that encodes 2-oxoglutarat dehydrogenase was isolated from Salmonella typhimurium. The catalytic N-terminal region in the enzyme was found to be very specific for the Salmonella species. Therefore, the aim of the present study was to detect S. typhimurium in food sources using primers designed for OGDH-l and OGDH-2 which were based on the salmonella-specific region of the ogdH gene. A simple polymerase chain reaction (PCR) detection method was developed to detect low numbers of S. typhimurium in a chicken meat microbial consortium. Using the ogdH-specific primers under stringent amplification conditions and for gene probe analysis, fewer than 100 colony-forming units (CFUs) were detectable when pure cultures were employed. When the PCR assay was run on S. typhimurium-contaminated meat contents, only the positive meat samples containing as few as 200 CFUs reacted to the assay. The method employed for sample processing is simple and it was determined to provide a sensitive means of detecting trace amounts of S. typhimurium-specific sequences in the presence of mixed meat microbial populations. When compared with six representative intestinal gram-negative bacterial strains in foods, including Vibrio parahaemolyticus, V. vulnificus, Enterobacter cloacae, E. coli O157:H7, Pseudomonas aeruginosa, and Proteus sp., S. typhimurium had a unique and distinct PCR product (796 bp). In conclusion, the two OGDH primers were found to be rapid and sensitive detectors of Salmonella spp for the PCR method.

• Korean Journal of Food Science and Technology
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• v.36 no.3
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• pp.514-517
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• 2004

O157:H7, Salmonella typhimurium, Listeria monocytogenes were treated with aqueous chlorine dioxide to elucidate effect of aqueous chlorine dioxide treatment on major food-borne pathogenic bacteria. Survival plot of E.coli O157:H7 at 5 ppm chlorine dioxide showed typical first-order rate. After 5 min of treatment, cell number decreased by 1.5 log cycle. Survival plot slope gave D value of 3.37 min. S. typhimurium and L. monocytogenes showed biphasic curve. Aqueous chlorine dioxide treatment on S. typhimurium and L. monocytogenes resulted in bactericidal effect for 5 min, and thereafter no effect was observed under experimental conditions of this study. These results suggest concentration of chlorine dioxide is more important than treatment time, and 5 ppm chlorine dioxide treatment is not sufficient for sanitizing fresh vegetables.

• Journal of Microbiology and Biotechnology
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• v.29 no.6
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• pp.962-972
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• 2019

Non-typhoidal Salmonella (NTS) is one of the most frequent causes of bacterial foodborne illnesses. Considering that the main reservoir of NTS is the intestinal tract of livestock, foods of animal origin are regarded as the main vehicles of Salmonella infection. In particular, poultry colonized with Salmonella Typhimurium (S. Typhimurium), a dominant serotype responsible for human infections, do not exhibit overt signs and symptoms, thereby posing a potential health risk to humans. In this study, comparative genomics approaches were applied to two S. Typhimurium strains, ST1539 and ST1120, isolated from a duck slaughterhouse and a pig farm, respectively, to characterize their virulence and antimicrobial resistance-associated genomic determinants. ST1539 containing a chromosome (4,905,039 bp; 4,403 CDSs) and a plasmid (93,876 bp; 96 CDSs) was phylogenetically distinct from other S. Typhimurium strains such as ST1120 and LT2. Compared to the ST1120 genome (previously deposited in GenBank; CP021909.1 and CP021910.1), ST1539 possesses more virulence determinants, including ST64B prophage, plasmid spv operon encoding virulence factors, genes encoding SseJ effector, Rck invasin, and biofilm-forming factors (bcf operon and pefAB). In accordance with the in silico prediction, ST1539 exhibited higher cytotoxicity against epithelial cells, better survival inside macrophage cells, and faster mice-killing activity than ST1120. However, ST1539 showed less resistance against antibiotics than ST1120, which may be attributed to the multiple resistanceassociated genes in the ST1120 chromosome. The accumulation of comparative genomics data on S. Typhimurium isolates from livestock would enrich our understanding of strategies Salmonella employs to adapt to diverse host animals.

• Journal of Food Hygiene and Safety
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• v.39 no.3
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• pp.273-280
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• 2024

In this study, the antibacterial activity and mechanisms of bitter orange extract, a natural antibacterial agent, were investigated, with a focus on its potential application in washing water for controlling Salmonella Typhimurium contamination of salad, a ready-to-eat food. The minimum inhibitory concentration (MIC) of bitter orange extract against S. Typhimurium was determined using the broth dilution method. Subsequently, S. Typhimurium was exposed to various concentrations of bitter orange extract (1/16 MIC-2 MIC) and growth curves were measured. Following treatment with bitter orange extract, we investigated its antibacterial mechanism by measuring intracellular reactive oxygen species (ROS) levels, alterations in membrane potential and integrity, and nucleic acid leakage in S. Typhimurium. Additionally, salads artificially contaminated with S. Typhimurium were treated with different concentrations of bitter orange extract using the dipping method for various durations to assess the reduction effect. The MIC of bitter orange extract against S. Typhimurium was 195.313 mg/L, and bacterial growth was completely inhibited at a concentration of 1 MIC. Furthermore, an increase in bitter orange extract concentration correlated with elevated intracellular ROS levels, membrane potential disruption, membrane damage, and nucleic acid release. Importantly, salads treated with bitter orange extract exhibited a significant reduction in S. Typhimurium counts compared to the control, and prolonged treatment times resulted in further reductions in bacterial counts. Bitter orange extract was more effective than sodium hypochlorite and can be used as a safer salad wash. These findings indicate the potential treatment of salads to prevent foodborne illnesses.