A Korean Nationwide Surveillance Study for Non-Typhoidal Salmonella Isolated in Humans and Food Animals from 2006 to 2008: Extended-Spectrum beta-Lactamase, Plasmid-Mediated AmpC beta-Lactamase, and Plasmid-Mediated Quinolone Resistance qnr Genes / 대한임상미생물학회지

BACKGROUND: The emergence of non-typhoidal Salmonella (NTS) with decreased susceptibilities to fluoroquinolone, ampicillin, or ceftriaxone has been reported worldwide. However, current surveillance studies of resistance among NTS in Korea are limited. Thus, the antimicrobial susceptibilities; resistance mechanisms such as extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and molecular epidemiologic characteristics were investigated in the present study. METHODS: National Institute of Health and National Veterinary Research and Quarantine Service collected NTS strains from 219 clinical and 293 non-clinical specimens from 2006 to 2008. The antimicrobial susceptibilities were determined using the Clinical and Laboratory Standards Institute disk diffusion test. ESBL, PABL, and qnr genotyping were performed using PCR and nucleotide sequencing. Pulsed-field gel electrophoresis was used for the molecular epidemiologic study. RESULTS: The resistance to ampicillin in clinical and non-clinical NTS was 49% and 18 to 47%, respectively. The resistance rates to trimethoprim-sulfamethoxazole in clinical and non-clinical NTS were 8% and 0 to 41%, respectively. The rates to extended-spectrum cephalosporin were 0 to 1%. One CTX-M-15-producing isolate and four CMY-2-producing isolates were detected. Notably, PFGE analysis showed four isolates carrying bla CMY-2, including one non-clinical strain had high clonality. Although the rate of ciprofloxacin resistance was very low, two qnrS1-carrying NTS strains were detected in non-clinical specimens. CONCLUSION: The resistance rates to ampicillin in both clinical and non-clinical NTS were high, while those to trimethoprim-sulfamethoxazole varied depending on the specimen. NTS strains harboring CTX-M-15-type ESBL or CMY-2-type PABL were detected even though the resistance rates to cephalosporins were very low. Four NTS strains carrying the blaCMY-2-gene implied zoonotic infection. Continuous effort to minimize transfer of resistance genes in NTS is necessary.

Detection and Characterization of Integrons in Nontyphoid Salmonella Clinical Isolates

BACKGROUND: Nontyphoid Salmonella (NTS) is a leading cause of human food-borne enteritiS. It has been known that integron, a naturally occurring gene capture and expression element, plays an important role in the development and dissemination of multidrug-resistance. In this study, we investigated the prevalences and molecular characteristics of integrons in NTS clinical strains. MATERIALS AND METHODS: Between 1995-96 and 2000-03, a total 261 NTS clinical strains comprising 39 serotypes were collected from clinical specimens. All strains were serotyped, and the MICs of ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim were determined by agar dilution method. Integrons were detected by PCR amplification of integrase genes, and gene cassettes were determined by PCR and sequencing. Conjugation experiments were performed using E. coli J53 as a recipient. The clonal relationship was analyzed by pulsed-field gel electrophoresis (PFGE). RESULTS: Of the 261 strains tested, class 1 integrons were present in 21 strains (8.0%). Class 2 and class 3 integrons were not found. The integron-positive rate was higher in S. Typhimurium (24.2% [8/33]) than in S. Enteritidis (2.0% [3/153]). Overall rates of antimicrobial resistance were higher in integron-positive strains. dhfr12-orfF-aadA2 gene cassette was detected in 5 strains, aadA2 in 4 strains, dhfr17-orfF-aadA5 in 2 strains, and addA1 in 1 strain. Ten integron-positive transconjugants were successfully selected. Among 8 integron-positive strains of S. Typhimurium, 7 had similar PFGE patterns. CONCLUSION: This study suggests that integrons are already playing a significant role in antimicrobial resistance in NTS. Continuous monitoring is needed to detect the emergence and spread of integron-mediated antimicrobial resistance.

Detection and Characterization of Integrons in Nontyphoid Salmonella Clinical Isolates

BACKGROUND: Nontyphoid Salmonella (NTS) is a leading cause of human food-borne enteritiS. It has been known that integron, a naturally occurring gene capture and expression element, plays an important role in the development and dissemination of multidrug-resistance. In this study, we investigated the prevalences and molecular characteristics of integrons in NTS clinical strains. MATERIALS AND METHODS: Between 1995-96 and 2000-03, a total 261 NTS clinical strains comprising 39 serotypes were collected from clinical specimens. All strains were serotyped, and the MICs of ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim were determined by agar dilution method. Integrons were detected by PCR amplification of integrase genes, and gene cassettes were determined by PCR and sequencing. Conjugation experiments were performed using E. coli J53 as a recipient. The clonal relationship was analyzed by pulsed-field gel electrophoresis (PFGE). RESULTS: Of the 261 strains tested, class 1 integrons were present in 21 strains (8.0%). Class 2 and class 3 integrons were not found. The integron-positive rate was higher in S. Typhimurium (24.2% [8/33]) than in S. Enteritidis (2.0% [3/153]). Overall rates of antimicrobial resistance were higher in integron-positive strains. dhfr12-orfF-aadA2 gene cassette was detected in 5 strains, aadA2 in 4 strains, dhfr17-orfF-aadA5 in 2 strains, and addA1 in 1 strain. Ten integron-positive transconjugants were successfully selected. Among 8 integron-positive strains of S. Typhimurium, 7 had similar PFGE patterns. CONCLUSION: This study suggests that integrons are already playing a significant role in antimicrobial resistance in NTS. Continuous monitoring is needed to detect the emergence and spread of integron-mediated antimicrobial resistance.

Molecular Genetic Characterization of Shiga Toxin-producing E. coli Isolated from Diarrhea Patients and Cattle in Gwangju Area, Korea

Shiga toxin-producing Escherichia coli (STEC) can cause a broad spectrum of human illness ranging from symptom-free to hemolytic uremic syndrom (HUS). Associations between known or putative virulence factors of STEC and diseases in human were investigated. PCR analyses showed that 33 (78.6%) isolates carried an ehxA enterohemolysin gene and 6 (14.3%) isolates possessed an saa autoaggutinating adhesin gene, and 31 (73.8%) isolates carried an eae intimin gene (7 isolates with type beta, 16 with type gamma, and 3 with type epsilon). Twenty-nine (69%) isolates from patients carried eae+, ehxA+, saa- (genotype A) and 68 (86%) isolates from asymptomatic outbreaks and 4 (36%) isolates from bovine possessed eae-, ehxA+, saa+ (genotype C). Neither the bundle-forming pilus gene nor the enteropathogenic E. coli adherence factor plasmid was found. In HEp-2 cell adherence assay, isolates carrying eae gene exhibited a localized adherence phenotype, the other isolates carrying saa showed LC (loose clusters of bacteria) and IS (isolated bacteria). In conclusion, most STEC isolated from cattle feces in Gwangju, Korea showed characteristics different from those isolated from patients. But these results may be useful information for pathogenesis judgement of STEC.

A Case of Emetic Toxin Producing Bacillus cereusStrains Isolated from Outbreak / 대한임상미생물학회지

Bacillus cereus causes two types of gastrointestinal diseases: emesis and diarrhea. It produces one emetic toxin and nine different enterotoxins. In March 2008, eight of a family became sick after eating slices of raw fish. We isolated emetic toxin producing B. cereus from the stools of 6 patients and 2 subclincal humans. In this study, the presence of enterotoxin genes, such as those of haemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe), B. cereus enterotoxin T (BceT), enterotoxin FM (EntFM), cytotoxin K (cytK) and cereulide were assayed by polymerase chain reaction (PCR) methods. Their enterotoxin activities were assayed using the BCET- RPLA, Tecra ELISA kit and Hep-2 vacuole activity. Bacterial isolates were subtyped by pulsed-field gel electrophoresis (PFGE). This study demonstrates the emetic toxin-producing stains of B. cereus in clinical specimens, for the first time in the Republic of Korea.

Surveillance of Stool Samples for the Presence of Enterobacter sakazakii among Korean People

PURPOSE: Enterobacter sakazakii (E. sakazakii) infections are an important cause of life-threatening meningitis, septicemia, and necrotizing enterocolitis in infants. Dried infant formula milk is an important vehicle for E. sakazakii infection. E. sakazakii was isolated in Korea from dried infant formula milk. Although E. sakazakii infection of infants may occur in Korea, its prevalence has not yet been documented. Therefore, we determined the prevalence of E. sakazakii and documented symptoms. MATERIALS AND METHODS: Between March and October 2006, 1,146 stool samples were collected from patients at Uijeongbu St. Mary's Hospital. Each fecal swab was dissolved in 10mL of buffered peptone solution, and enriched culture was streaked onto Druggan-Forsythe-Iversen (DFI) agar. Presumptive E. sakazakii colonies that exhibited a blue-green color during culture on DFI medium were selected. The identity of colonies that developed yellow pigment during culture on TSA was determined using the Vitek system and PCR. RESULTS: We isolated 4 E. sakazakii strains whose 16S rRNA sequence alignments had a similarity of 99% with those of 3 E. sakazakii ATCC strains. CONCLUSION: This is the first report on isolation of E. sakazakii from stool samples and to document the symptoms of Korean patients.

National Early Warning System Construction for Timely Surveillance of Foodborne Disease Outbreaks-PulseNet Korea

Foodborne illnesses and big outbreaks have been increased because of the widespread of lunch distribution at school, mass production of food products, and international food trades. It is important to find the origin of contamination by various pathogens in an early stage of the outbreaks for the disease control and prevention. For the purpose of construction of the early warning system, Korea National Institute of Health (KNIH) inaugurated PulseNet Korea in 2005. The organization of PulseNet Korea consists of KNIH as a center and the participating laboratories including Korea Food & Drug Administration (KFDA), National Veterinary Research & Quarantine Station (NVRQS), and regional Institutes of Health & Environment. PulseNet Korea has focused on training researchers from participating laboratories as well as playing an important role in PulseNet International. In this review, PulseNet Korea construction is introduced as a national early warning system for timely surveillance of foodborne diseases.

Enterotoxigenic Escherichia coli Outbreak in a High School

BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) has been well known pathogen as a cause of travelers' diarrhea. Nowadays, however, ETEC is also increasingly recognized as the cause of foodborne or waterborne outbreaks. We investigated an outbreak of a high school in Gwangju metropolitan city to trace the source of infection and the mode of transmission of ETEC. MATERIALS AND METHODS: All symptomatic persons were interviewed and filled out the questionnaires. We surveyed their clinical symptoms and the foods that they ate. We checked the facilities of the school, dinning room and water supply system. Microbiologic examination were carried out on above symptomatic persons and many environmental specimens. All gathered samples were examined in Gwangju city Health & Environment Research Institute. ETEC isolates were submitted to Korea Center for Disease Control and Prevention (KCDC) for Pulsed-field gel electrophoresis (PFGE). We also requested water quality analysis of water samples to Waterworks Research Institute. RESULTS: The 39 students and one sibling who visited and ate school meal showed symptoms. All staffs and cooks showed no symptom. Among 51 stool specimens, ETEC was isolated from 19 (18: students, 1:cook). ETEC was also isolated from specimens from a purifier and a water tap of the dinning room and water tank (underground water). In PFGE test, isolates from 18 persons showed identical pattern, but the PFGE patterns from water were different. Isolates of water samples showed different PFGE patterns even within the same sample. Investigation of the water distribution system revealed that contaminated underground water had been supplied to the dinning room and students of the school were exposed to it. CONCLUSION: This is the outbreak of ETEC infection occurred in a high school. Besides students, ETEC was also isolated from water samples. Considering some epidemiologic features, we suspect the mode of transmission may be waterborne despite the inconsistent PFGE results.

National Early Warning System Construction for Timely Surveillance of Foodborne Disease Outbreaks-PulseNet Korea

Foodborne illnesses and big outbreaks have been increased because of the widespread of lunch distribution at school, mass production of food products, and international food trades. It is important to find the origin of contamination by various pathogens in an early stage of the outbreaks for the disease control and prevention. For the purpose of construction of the early warning system, Korea National Institute of Health (KNIH) inaugurated PulseNet Korea in 2005. The organization of PulseNet Korea consists of KNIH as a center and the participating laboratories including Korea Food & Drug Administration (KFDA), National Veterinary Research & Quarantine Station (NVRQS), and regional Institutes of Health & Environment. PulseNet Korea has focused on training researchers from participating laboratories as well as playing an important role in PulseNet International. In this review, PulseNet Korea construction is introduced as a national early warning system for timely surveillance of foodborne diseases.

Enterotoxigenic Escherichia coli Outbreak in a High School

BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) has been well known pathogen as a cause of travelers' diarrhea. Nowadays, however, ETEC is also increasingly recognized as the cause of foodborne or waterborne outbreaks. We investigated an outbreak of a high school in Gwangju metropolitan city to trace the source of infection and the mode of transmission of ETEC. MATERIALS AND METHODS: All symptomatic persons were interviewed and filled out the questionnaires. We surveyed their clinical symptoms and the foods that they ate. We checked the facilities of the school, dinning room and water supply system. Microbiologic examination were carried out on above symptomatic persons and many environmental specimens. All gathered samples were examined in Gwangju city Health & Environment Research Institute. ETEC isolates were submitted to Korea Center for Disease Control and Prevention (KCDC) for Pulsed-field gel electrophoresis (PFGE). We also requested water quality analysis of water samples to Waterworks Research Institute. RESULTS: The 39 students and one sibling who visited and ate school meal showed symptoms. All staffs and cooks showed no symptom. Among 51 stool specimens, ETEC was isolated from 19 (18: students, 1:cook). ETEC was also isolated from specimens from a purifier and a water tap of the dinning room and water tank (underground water). In PFGE test, isolates from 18 persons showed identical pattern, but the PFGE patterns from water were different. Isolates of water samples showed different PFGE patterns even within the same sample. Investigation of the water distribution system revealed that contaminated underground water had been supplied to the dinning room and students of the school were exposed to it. CONCLUSION: This is the outbreak of ETEC infection occurred in a high school. Besides students, ETEC was also isolated from water samples. Considering some epidemiologic features, we suspect the mode of transmission may be waterborne despite the inconsistent PFGE results.

An outbreak of inapparent non-O157 enterohemorrhagic escherichia coli infection / 대한내과학회지

BACKGROUND: No outbreak of Enterohemorrhagic Escherichia coli (EHEC) infection has occurred as a group in Korea. On July 2004, an outbreak of EHEC infection occurred in an elementary school in Gwangju metropolitan city. Epidemic investigation was undertaken to track the source of infection and the mode of transmission of EHEC. METHODS: All students and staffs of the elementary school were interviewed and completed questionnaires. We surveyed their clinical symptoms and the foods that they ate. Microbiologic examinations were also carried out on the above school-related persons and many environmental specimens. We also investigated the facilities of the school, some suppliers of food materials, and other associated institutions. All the EHEC-positive persons were isolated in 5 hospitals and tested everyday for verotoxin until they turned out to be negative twice in succession, and their family were also interviewed and tested for EHEC. Pulsed-field gel electrophoresis (PFGE) was performed to find out the genetic relationship between isolates. RESULTS: Of the 1,643 school-related persons, 77 persons (4.7%) were positive for EHEC. Most of them were asymptomatic. All the isolated strains were non-O157 EHEC. Serotype O91 was the most frequent serotype (68 isolates), and the isolates revealing O91 serotypes showed identical PFGE patterns. The school meal was significantly associated with this outbreak (relative risk=13.29, p=0.00). CONCLUSIONS: This is the first EHEC outbreak occurred as a group in Korea, All the isolated strains were non-O157 serotypes and the mode of transmission was most likely by school meal.

Prevalence of Salmonella Serovars Isolated from Domestic Residents and Overseas Travelers in Korea, 2004~2005

Salmonella is a communicable enteric pathogen commonly found in foodborne diseases. We showed the prevalence of S. enterica serovars from domestic residents and overseas travelers. In 2004-2005 years, Weltevreden, Anatum, and Tallahassee were predominant Salmonella serovars from overseas travelers, but Enteritidis, Typhimurium, and Typhi were major Salmonella serovars from domestic residents. In order to analyze the trends of prevalence and distribution of the serovars, Salmonella surveillance with an international study is essential for the disease control and prevention.

Rapid Serological Identification for Monophasic Salmonella Serovars with a hin Gene: Specific Polymerase Chain Reaction

Salmonellosis is one of the most common food born diseases in Korea. However, it takes more than 8 days and many expensive antiserums are used for the identification of Salmonella serovars since the microorganism easily undergoes phase variation. According to the data that 65.5% of Salmonella isolates in 2000~2004 year had monophasic flagella, we have developed a rapid serological identification method using a hin gene-specific polymerase chain reaction (PCR) for monophasic Salmonella isolates that does not require the time-consuming phase conversion experiments. Using our new method, 'hin specific PCR-based serological test', we could identify serovars of monophasic Salmonella in 4 days. For the purpose of rapid identification of salmonella serovars collected from outbreaks and sporadic cases, hin specific PCR-based serological tests will be a fast and efficient method.

A study on epidemiological characteristics and control methods of EHEC infection in Korea / 한국역학회지

E. coli is a bacterium that is commonly found in the gut of humans and warm-blooded animals. Most strains of E. coli are harmless. But some strains such as Enterohaemorrhagic E. coli(EHEC), can cause severe food borne disease. It is transmitted to humans primarily through consumption of contaminated foods, such as raw or undercooked ground meat. There is no widely agreed definition of when a shiga-toxin producing E. coli is considered to be an EHEC. But in Korea, the word "EHEC", "STEC", "VTEC" are often used as same meaning, which refer to the E.coli those producing shiga-toxin. We suggest the term STEC refers to those E. coli produce one or more shiga-toxins(stx), and the term EHEC refers only to STEC that cause a clinical illness. EHEC infection were designated as the class 1 notifiable disease in Korea in 2000. Although EHEC/STEC cases were not common in Korea, the number of STEC infection cases reported has increased since 2001. From 2001 to 2004, the number of STEC infection cases in Korea were 11, 8, 52, 118 respectively. These cases included 17 due to E. coli O157, 136 due to E. coli, serogroup non-O157, and 15 due to E. coli that were not serogrouped. The most common serotype implicated is E. coli O91 without virulent factor and clinical symptoms. But those cases involve in one epidemic in primary school in 2004. STEC infections in Korea occur in all age groups, with the highest frequencies in children less than 5 years old. Healthy cattle are the main animal reservoir for STEC and they harbor the organism as part of the bowel flora. The proportion of STEC in E. coli in animal feces was examined by using stool samples from 283 Korean beef cattle on 27 farms, 169 milk cattle on 28 frams, 455 swine on 50 farms. As determined by culture and toxin assay, the proportion of STEC was 25.8%(16 STEC/62 E. coli) in milk cattle, 18.8%(19 STEC/101 E.coli) in Korean beef cattle, 14.0%(25 STEC/178 E. coli) in swine. Effective surveillance of EHEC/STEC in humans is essential in order to protect the public health. EHEC infection is notifiable in many countries including USA, Japan, and Belgium, Finland, Italy, Netherlands, and the United Kingdom(UK), have sentinel systems. England, Wales, and Scotland have comprehensive national laboratory reporting schemes for STEC. And there has been an increase in the number of reported cases and outbreaks during the past decades in many countries Prevention of STEC infection requires control measures at all stages of surveillace, investigations and special pathogen tracing such as PulseNet.

Antibiotic Resistance and Genetic Analysis of Shigella sonnei Strains Isolated in South Korea and Japan

A total of 35 strains of Shigella sonnei, 21 strains isolated in South Korea from 2000 to 2001 and 14 strains isolated in Japan from 2001 and 2002 were analyzed for antimicrobial susceptibility, plasmid profile and molecular epidemiology. Using polymerase chain reaction (PCR) method, the strains were tested for the presence of virulence genes. And then reversed passive latex agglutination(RPLA) test was used to determine if the strain was Shiga-toxin producing. Their random amplified polymorphic DNA (RAPD) patterns were examined. Pulsed-field gel electrophoresis (PFGE) patterns were also analyzed. Most strains showed multiple resistance to more than four antimicrobial agents, i.e., tetracycline, erythromycin, streptomycin and vancomycin. All South Korea strains were susceptible to chloramphenicol and gentamicin, while all Japan strains were susceptible to kanamycin and cefoperazone. The antibiogram could be classified into 6 groups. By PCR, ipaH gene was detected from all strains, but set1A and set1B genes were not. Sen and ial genes were detected from 19 strains (54.3 %). Especially, stx gene was positive in 11 of the 35 strains by PCR method but not confirmed by RPLA method. The strains were differentiated into 12 groups by plasmid profile and 6 arbitrary groups (a to f) by RAPD analysis. The isolates could be grouped into 5 (A to E) PFGE patterns including 3 subgroups A-1, A-2 and A-3. Type A was the major type (82.9 %).

Characterization of Resistance Plasmid of Shigella sonnei Isolates from the Outbreak at Cheju Island in 2000

A large outbreak of Shigella sonnei gastrointestinal infections occurred at Cheju Island in Korea from May to August 2000. We selected 54 strains which were isolated from the primary treatment failure cases in the outbreak, and characterized the resistance-determining region of the R-plasmid. The 54 strains showed same antimicrobial resistance patterns; resistance against ampicillin, streptomycin, tetracycline, and trimethoprim-sulfamethoxazole. The resistance to ampicillin, streptomycin, and tetracycline were mediated by a conjugable plasmid of about 80 kb size, but the trimethoprim- sulfamethoxazole resistance was not transferred by this plasmid. The R-determining region of the plasmid was cloned and characterized. The 8,384 bp sequences contained resistance genes in the following order:strA, strB, tetR, tetA, and sul1. Fifty four isolates harbored the same sized plasmid and showed same ribotyping patterns, which suggested the clonal spread of S. sonnei in the outbreak.

Characterization of Resistance Plasmid of Shigella sonnei Isolates from the Outbreak at Cheju Island in 2000

A large outbreak of Shigella sonnei gastrointestinal infections occurred at Cheju Island in Korea from May to August 2000. We selected 54 strains which were isolated from the primary treatment failure cases in the outbreak, and characterized the resistance-determining region of the R-plasmid. The 54 strains showed same antimicrobial resistance patterns; resistance against ampicillin, streptomycin, tetracycline, and trimethoprim-sulfamethoxazole. The resistance to ampicillin, streptomycin, and tetracycline were mediated by a conjugable plasmid of about 80 kb size, but the trimethoprim- sulfamethoxazole resistance was not transferred by this plasmid. The R-determining region of the plasmid was cloned and characterized. The 8,384 bp sequences contained resistance genes in the following order:strA, strB, tetR, tetA, and sul1. Fifty four isolates harbored the same sized plasmid and showed same ribotyping patterns, which suggested the clonal spread of S. sonnei in the outbreak.

Epidemiology of Salmonella enterica Serotype Typhi Infections in Korea for Recent 9 Years: Trends of Antimicrobial Resistance

The aim of this study is to characterize the epidemiological features of typhoid fever, categorized as class 1 notifiable disease in Korea and to analyze the recent change of antimicrobial resistance of Salmonella enterica serotype Typhi isolated nationwide. We retrospectively analyzed the 1,692 culture-proven cases from 1992 to 2000, using the data of the Korean National Institute of Health. The overall incidence of culture-proven typhoid fever was 0.41 per 100,000 population. It occurred all over the country, but the southeastern part of Korean peninsula had the higher incidence rate than other areas. There were several outbreaks suspected, of which two outbreaks were confirmed. The resistance rate against chloramphenicol showed mild increase, but the ampicillin, trimethoprim/sulfamethoxazole, kanamycin, or nalidixic acid resistance remained at the similar levels for the past 9 yr. There were 21 (1.3%) multidrug-resistant (MDR) strains isolated since 1992, and the number of those has increased. Two strains resistant to ciprofloxacin were first identified in Korea.

A Study of Virulence Factors and Pathogenicity of Vibrio parahaemolyticus Isolated from Diarrheal Patients and Environmental Sources in Gyeongbuk Province

BACKGROUND: V. parahaemolyticus, an important seafood-borne pathogen, is the causative agent of gastroenteritis in humans. In this study, the occurrence and distribution of the thermostable hemolysin (tdh) gene and the tdh-related hemolysin (trh) gene were investigated, and as many as 72 different O:K serovar combinations were determined from diarrheal patients and environmental sources in Gyeongbuk provinceas during the 2000-2001. METHODS: A total of 50 strains of V. parahaemolyticus isolated from diarrheal patients and environmental sources were analyzed for the tdh gene and trh gene. The strains were analyzed for kanagawa phenomenon (KP) with the wagatsuma blood agar medium test. Furthermore, the strains belonging to O and K serotypes were determined. DNA sequence determination of the tdh gene were verified using GenBank and analyzed. RESULTS: In the KP experiments of V. parahaemolyticus, 80% of the strains isolated from diarrheal patients showed positive, but all of the strains isolated from environment sources were negative The distribution of O and K serotypes were O3:K29, O3:K6, and O3:K31, atc. isolated from diarrheal patients, and O2:K28, O3:K29, and 04:K34 atc. isolated from environmental sources. As for the tdh and trh gene of V. parahaemolyticus, the tdh gene was detected from 88.0% of diarrheal patients and 16.0% of environmental sources. The trh gene was not detected from diarrheal patients and 8.0 % of environmental sources, whereas all urease positive strains possessed the trh gene. The DNA sequence of tdh gene were verified using GenBank and analyzed the difference, tdh nucleotide sequence was found among the V. parahaemolyticus. CONCLUSION: V. parahaemolyticus is distributed with high frequency in the environmental sources such as sea water, fishes and shellfishes sampled at the Gyeongbuk coastal area, and the O3:K6 strains producing TDH were confirmed, which is prevalent throughout the world, from diarrheal patients. Thus, it is very important to establish a measure to prevent food poisoning by V. parahaemolyticus.

A Study of Virulence Factors and Pathogenicity of Vibrio parahaemolyticus Isolated from Diarrheal Patients and Environmental Sources in Gyeongbuk Province

BACKGROUND: V. parahaemolyticus, an important seafood-borne pathogen, is the causative agent of gastroenteritis in humans. In this study, the occurrence and distribution of the thermostable hemolysin (tdh) gene and the tdh-related hemolysin (trh) gene were investigated, and as many as 72 different O:K serovar combinations were determined from diarrheal patients and environmental sources in Gyeongbuk provinceas during the 2000-2001. METHODS: A total of 50 strains of V. parahaemolyticus isolated from diarrheal patients and environmental sources were analyzed for the tdh gene and trh gene. The strains were analyzed for kanagawa phenomenon (KP) with the wagatsuma blood agar medium test. Furthermore, the strains belonging to O and K serotypes were determined. DNA sequence determination of the tdh gene were verified using GenBank and analyzed. RESULTS: In the KP experiments of V. parahaemolyticus, 80% of the strains isolated from diarrheal patients showed positive, but all of the strains isolated from environment sources were negative The distribution of O and K serotypes were O3:K29, O3:K6, and O3:K31, atc. isolated from diarrheal patients, and O2:K28, O3:K29, and 04:K34 atc. isolated from environmental sources. As for the tdh and trh gene of V. parahaemolyticus, the tdh gene was detected from 88.0% of diarrheal patients and 16.0% of environmental sources. The trh gene was not detected from diarrheal patients and 8.0 % of environmental sources, whereas all urease positive strains possessed the trh gene. The DNA sequence of tdh gene were verified using GenBank and analyzed the difference, tdh nucleotide sequence was found among the V. parahaemolyticus. CONCLUSION: V. parahaemolyticus is distributed with high frequency in the environmental sources such as sea water, fishes and shellfishes sampled at the Gyeongbuk coastal area, and the O3:K6 strains producing TDH were confirmed, which is prevalent throughout the world, from diarrheal patients. Thus, it is very important to establish a measure to prevent food poisoning by V. parahaemolyticus.