• Journal of Microbiology and Biotechnology
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• v.31 no.5
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• pp.710-716
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• 2021

A risk analysis of Shiga toxin (Stx)-encoding bacteriophage was carried out by confirming the transduction phage to non-Stx-producing Escherichia coli (STEC) and subsequent expression of the Shiga toxin genes. The virulence factor stx1 was identified in five phages, and both stx1 and stx2 were found in four phages from a total of 19 phage isolates with seven non-O157 STEC strains. The four phages, designated as ϕNOEC41, ϕNOEC46, ϕNOEC47, and ϕNOEC49, belonged morphologically to the Myoviridae family. The stabilities of these phages to temperature, pH, ethanol, and NaClO were high with some variabilities among the phages. The infection of five non-STEC strains by nine Stx-encoding phages occurred at a rate of approximately 40%. Non-STEC strains were transduced by Stx-encoding phage to become lysogenic strains, and seven convertant strains had stx1 and/or stx2 genes. Only the stx1 gene was transferred to the receptor strains without any deletion. Gene expression of a convertant having both stx1 and stx2 genes was confirmed to be up to 32 times higher for Stx1 in 6% NaCl osmotic media and twice for Stx2 in 4% NaCl media, compared with expression in low-salt environments. Therefore, a new risk might arise from the transfer of pathogenic genes from Stx-encoding phages to otherwise harmless hosts. Without adequate sterilization of food exposed to various environments, there is a possibility that the toxicity of the phages might increase.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.80-86
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• 2010

This paper describes the development result of S-band Transmitter of STSAT-3 by satellite research center(SaTReC), KAIST. STSAT-3 has two kinds of communication channels, S- band for Telemetry & Command and X-band for mission payload. S-band Transmiiter(STX) consist of modulator, frequency synthesizer, power amp and DC/DC converter. The modulation scheme of STX is FSK(Frequency Shift Keying). The interface between spacecraft OBC and STX is RS-422. The STX is based on modular design. The RF output power of STX is 1.5W(31.7dBm) and BER of STX is under 1E-5. The Test of STX is completed successfully such as functional Test and environmental(vibration, thermal vacuum) Test.

• Korean Journal of Microbiology
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• v.44 no.3
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• pp.203-211
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• 2008

Rapid detection-method for Shiga toxin type 1 that was produced from Shiga toxin-producing Escherichia coli (STEC) was developed by two-step ultra-rapid real-time (URRT) PCR. The specific primers were deduced from 80 bp stable region of stx type 1 (stxl) gene among various informations of STEC strains. URRT PCR is a microchip-based real-time PCR using 6 ${\mu}l$ of reaction volume with extremely short denaturation step and annealing/extension step (1 sec, 3 sec, respectively) in each cycle of PCR. Using the stx1-specific URRT PCR, 35 cycled PCR were finished in time of 6 min and 38 see, also measured 7 min and 28 see including melting temperature (Tm) analysis. The detection-limit of stxl-specific URRT-PCR was estimated until 3 colony forming units / PCR with products with stable Tm at $81.42{\pm}0.34^{\circ}C$. In the applications to various STEC strains and contaminated genomic DNAs, stx1-specific URRT-PCR were tested and shown that it would be expected an useful method for the rapid detection of stx1-coded STEC strains.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.2
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• pp.212-218
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• 2006

Changes of paralytic shellfish poison (PSP) contents, toxicity and toxin composition with pH and storing periods at different temperature in toxic blue mussel, Mytilus edulis, were tested by using fluorometric HPLC method. Toxicity at pH 3 was the highest as 14.1 MU/g $(100\%)$ and showed 12.9 MU/g $(92.1\%)$ at pH 5, 9.0 MU/g $(63.8\%)$ at pH 7, 3.6 MU/g $(25.5\%)$ at pH 9 and 0.8 MU/g $(5.7\%)$ at pH 10 which suggested PSP was unstable at alkaline conditions. The decrease in toxicity during storage days was depend on pH and temperature. The toxicity markedly decreased until during the first S day storage $(19.9\~65.3\%)$ at all pH (3, 5, 7, 9) and temperature (30, 5, $-20^{\circ}C$), but, slightly decreased after then till to 30 days. C group toxin (C1 and C2) was the major components and other toxins such as GTX 1,2,3,4, STX and dcSTX were detected. Among the 8 toxins, GTX1,4, dcSTX and STX were firstly decreased according to the decreasing the toxicity at all processing conditions. The toxicity in blue mussel (14.1 MU/g) were able to remove by heating over 10 minutes at pH higher than 7.

• Journal of Microbiology and Biotechnology
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• v.25 no.9
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• pp.1460-1466
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• 2015

In this study, the prevalence of Shiga toxin-producing Escherichia coli (STEC) was investigated among raw meat or meat products from slaughterhouses and retail markets in South Korea, and their potential for antibiotic resistance and virulence was further analyzed. A total of 912 raw meats, including beef, pork, and chicken, were collected from 2008 to 2009. E. coli strains were frequently isolated in chicken meats (176/233, 75.9%), beef (102/217, 42.3%), and pork (109/235, 39.2%). Putative STEC isolates were further categorized, based on the presence or absence of the Shiga toxin (stx) genes, followed by standard O-serotyping. Polymerase chain reaction assays were used to detect the previously defined virulence genes in STEC, including Shiga toxins 1 and Shiga toxin 2 (stx1 and 2), enterohemolysin (ehxA), intimin (eaeA), STEC autoagglutination adhesion (saa), and subtilase cytotoxin (subAB). All carried both stx1 and eae genes, but none of them had the stx2, saa, or subAB genes. Six (50.0%) STEC isolates possessed the ehxA gene, which is known to be encoded by the 60-megadalton virulence plasmid. Our antibiogram profiling demonstrated that some STEC strains, particularly pork and chicken isolates, displayed a multiple drug-resistance phenotype. RPLA analysis revealed that all the stx1-positive STEC isolates produced Stx1 only at the undetectable level. Altogether, these results imply that the locus of enterocyte and effacement (LEE)-positive strains STEC are predominant among raw meats or meat products from slaughterhouses or retail markets in Korea.

• Korean Journal of Veterinary Service
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• v.32 no.3
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• pp.241-249
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• 2009

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains can cause broad spectrum of human disease, including diarrhea, hemorrhagic colitis, and the life-threatening hemolytic uremic colitis (HUS). We examined 868 samples was taken from bovine feces and carcass from January to December 2008 in Seoul. Twenty two (9.5%) shiga toxin -producing Escherichia coli were isolated from the 230 of bovine feces, and two (0.31%) were isolated from the 638 of carcasses. Serotype of E. coli isolates were O157 (10, 41.6%), O26 (10, 41.6%), O111 (1, 4.2%) and UT (3, 12.6%). In PCR, the isolates displayed three different stx gene combination (stx1 [2, 8.4%]), stx2 [3, 12.6%] and stx1 and stx2 [19,87.5%]). The eaeA and hlyA gene were found in 11 (45.8%) of the 24 strains. Saa gene was present only one strains (4.2%). Toxin typing using reverse passive latex agglutination test showed the same result in VT 1. But it showed different result in VT 2. In antimicrobial susceptibility test, all isolates were sensitive to amikacin, amoxicillin/clavulanic acid, ciprofloxacin and colistin. Eighteen strains (75.0%) of 24 isolates showed the multi-resistant patterns with over 3 drugs. PFGE was performed after the genomic DNA of twenty four isolates was digested with Xba I. the 24 isolates showed 7 (A~G) PFGE type.

• Korean Journal of Veterinary Research
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• v.46 no.2
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• pp.135-142
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• 2006

Shiga toxin (stx) producing Escherichia coli (STEC) causes various clinical signs in animal and human. In this study, 255 fecal samples from calves showing diarrhea were collected from cattle farms in Chonnam province during the period from January 2005 to July 2005. Twenty six STEC (10%) were isolated from 255 fecal samples by PCR. The isolates displayed three different stx combinations (stx1 [69%], stx1 and stx2 [15%], and stx2 [38%]). The isolates were further studied for virulence associated genes and antimicrobial resistance to define the virulence properties. Intimin (eaeA), enterohemolysin (hlyA), and lipopolysaccharide (rfbE) virulence genes were detected in 6 (23%), 7 (26%), and 1 (3.8%) of the isolates, respectively, by PCR. One isolate possessing rfbE gene was typed as E. coli 0157 : H7 by agglutination test with O and H antisera. All 26 isolates showed susceptibility to amikacin (100%) and the majority of isolates showed high susceptibility to gentamicin (88.5%) and chloramphenicol (73.1%). But all isolates were resistant to penicillin. These results may provide the basic knowledge to establish strategies for the treatment and prevention of enteric disease in calves.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.364-372
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• 1995

On the outbreak of paralytic shellfish poisoning in April 1993 in most of shellfish harvesting areas in Jinhae Bay, Korea, to clarify the toxin production of causative organism Alexandrium species, 19 axenic clonal isolates established from the benthic resting cysts in three different stations of those culture grounds were subjected to PSP toxin analysis by HPLC. Individual toxin content per cell was highly variable among the strains isolated from a sampling area and originated from an individual cyst. Average toxin contents in those areas revealed higher values of 54-70 fmol/cell. Toxin profiles included C1/C2(epiGTX8/GTX8), GTX1/GTX4 and neoSTX as the major components, and GTX2/GTX3, GTX5, C4, dcSTX and STX as the minor or sporadic ones. neoSTX on the dominant toxins showed not only most diverse compositional changes comprising $5-54 mol\%$ ranges but also no detection on the half of the strains examined, which were implicated in arising of heterogeneity with a genetic trait within a geographical region. When average toxin composition was compared, carbamate toxins comprised large proportions of $57\%,\;54\%\;and\;67\%$ as total toxin in St. 1, St. 2 and St. 4, respectively. These results suggested that an extensive paralytic shellfish toxification in Jinhae Bay could be largely due to the production of highly potent carbamate toxins in the causative dinoflagellate Alexandrium species.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.6
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• pp.553-558
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• 2011

This paper describes the development and test result of S-band Transmitter flight model(FM) of STSAT-3 by satellite research center(SaTReC), KAIST. The communication sub-system of STSAT-3 is consist of two different frequency band channels, S-band for Telemetry & Command and X-band for mission data. S-band Transmitter(STX) functionally made of modulator, frequency synthesizer, power amp and DC/DC converter. The transmission data is modulated by FSK(Frequency Shift Keying) and the interface between spacecraft sub-module and STX is RS-422 standard method. The FM STX is based on modular design. The RF output power of STX is 1.5W(31.7dBm) and BER of STX is under $1{\times}10^{-5}$ which meets the specification respectively. The FM STX is delivered Spacecraft Assembly, Integration and Test(AIT) level through the completion of functional Test and environmental(vibration, thermal vacuum) Test successfully.

• Journal of Food Hygiene and Safety
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• v.29 no.4
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• pp.316-321
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• 2014

The aim of study was to investigate the virulence profile of Escherichia coli O157:H7 bacteriophages isolated from sewage and livestock stools. Among 23 E. coli O157:H7 bacteriophages, 14 strains were isolated from sewage and 9 were from animal stools collected from 10 livestock farms in Korea. For each bacteriophage DNA sample, the presence of stx1, stx2, eae, aafII, ial, elt, estI, estII, astA, afa, and cnf was examined by polymerase chain reaction. The detection rate of eae, stx2, estI, astA, and ial was 100%, 69.6%, 13.0%, 13.0%, 8.7%, respectively. While all E. coli O157:H7 bacteriophages isolated from stools carried eae+stx2, stx2+eae, eae+astA, eae, stx2+eae+estI, eae+estI, stx2+eae+ial, and eae+ial were observed in bacteriophages isolated from sewage. As several plasmid-carrying virulence factors (estI, astA, and ial) were found in E. coli O157:H7 bacteriophages obtained from sewage and stools, the microbial safety of bacteriophages should be investigated in further study.