Epidemiological Characteristics of Field Tick-Borne Pathogens in Gwang-ju Metropolitan Area, South Korea, from 2014 to 2018

ObjectivesThe importance of tick-borne diseases is increasing because of climate change, with a lack of long-term studies on tick-borne pathogens in South Korea. To understand the epidemiological characteristics of tick-borne diseases, the monthly distribution of field ticks throughout the year was studied in South Korea between May 2014 and April 2018 in a cross sectional study.MethodsThe presence of various tick-borne pathogens (Rickettsia species, Borrelia species, Anaplasma phagocytophilum) was confirmed by using polymerase chain reaction, to provide information for a prevention strategy against tick-borne pathogenic infections, through increased understanding of the relationship between seasonal variation and risk of infection with Rickettsia species. This was performed using logistic regression analysis (SPSS 20, IBM, USA) of the data obtained from the study.ResultsDuring the study period there were 11,717 ticks collected and 4 species identified. Haemapysalis longicornis was the most common species (n = 10,904, 93.1%), followed by Haemapysalis flava (n = 656, 5.6%), Ixodes nipponensis (n = 151, 1.3%), and Amblyomma testudinarium (n = 6, 0.05%) The results of this cross-sectional study showed that Haemapysalis flava carried a higher risk of transmission of Rickettsia species than other tick species (p < 0.05).ConclusionIn conclusion, due attention should be paid to preventing tick-borne infections in humans whilst engaged in outdoor activities in Spring and Autumn, particularly in places where there is a high prevalence of ticks.

Epidemiological Characteristics of Rodents and Chiggers with Orientia Tsutsugamushi in the Republic of Korea

A survey of rodents and chiggers associated with Orientia tsutsugamushi was conducted in a rural region of the Republic of Korea (Korea) between 2014 and 2018. Overall Apodemus agrarius 15.2% had the highest seropisitive for O. tsutsugamushi, followed by Myodes regulus 11.4%. Monthly risk factors using logistic regression analysis were not associated with O. tsutsugamushi infections in rodents. The overall prevalence rate of O. tsutsugamushi among chiggers was 0.3%. The chigger (Leptotrombidium scutellare) and monthly (October) risk factors were associated with O. tsutsugamushi human infections (P<0.05). Orientia tsutsugamushi infections are endemic in rodents in Korea and people, for example, soldiers who are active outdoors, must employ preventive measures, especially during October (P<0.05). When there are many reports of O. tsutsugamushi infections in Korea. The Boryong strain 85.7% (2/14) was the most common strain detected in chiggers, followed by the Shimokoshi 7.1% (1/14) and Karp 7.1% strains.

Profile of Antimicrobial Resistance of Staphylococcus aureus and Molecular Epidemiologic Characterization of Methicillin-resistant Staphylococcus aureus (MRSA) Isolated from Hands of People Using Multitude Facilities

BACKGROUND: The purpose of this study was to investigate perception of hand hygiene and actual hand washing practices of people who used public facilities as well as the presence of indicator bacteria and food-borne pathogens on their hands. Data from this study will be used as a tool for public education and provide basic information on the potential risk for the spread of infectious disease by hands. MATERIALS AND METHODS: Sixty S. aureus and 15 methicillin-resistant S. aureus (MRSA) were recovered from 500 swab samples from hands of people in public places, including super markets and amusement facilities in Gwangju Metropolitan City during February to May 2011. Using conventional methods and the Vitek system, all of the isolates were confirmed as Staphylococcus auerus (S. aureus). Antimicrobial susceptibility was determined by performing disk diffusion testing according to the Clinical Laboratory Standard Institute guidelines. The minimum inhibition concentrations (MICs) of MRSA isolates were tested using E-test strips. To confirm the MRSA, polymerase chain reaction (PCR) for the S. aureus-specific gene and mecA gene was performed. Gene detection using PCR, SCCmec typing, Panton-Valentine Leukocidin (PVL), and Multilocus sequence typing (MLST) were performed on all isolates of MRSA. RESULTS: Of 60 S. aureus isolates, 48 (80%) harbored at least one type of enterotoxin gene: two, three, four, and five types of enterotoxin gene were found in 16 (26.7%), seven (11.7%), 10 (16.7%), and eight (13.3%) isolates, respectively. The most prevalent antimicrobial resistance observed in the S. aureus isolates was to penicillin (92%, 55/60), followed by erythromycin (35%, 21/60), oxacillin (32%, 19/60), and ampicillin (23%, 14/60). No resistance was observed against vancomycin, clindamycin, linazolid, rifampin, imipenem, trimethoprim/sulfamethoxazole, and telithromycin. In this study, based on molecular characterization of MRSA isolates, all MRSA, except for one isolate, belonged to ST72 and SCCmec type IV. Eleven of 15 (78.6%) MRSA were ST72:SCCmecIV:t324. CONCLUSIONS: In this study, we detected serious pathogens, including S. aureus and MRSA, from swab samples of peoples' hands. Most S. aureus isolates harbored the enterotoxin gene and the types of MRSA isolated in this study were community-associated MRSA, indicating the importance of washing hands for public health.

Comparison of Clinical Manifestations of RSV, Rhinovirus and Bocavirus Infections in Children with Acute Wheezing / 소아알레르기및호흡기학회지

PURPOSE: The purpose of this study was to compare clinical manifestations of human bocavirus (hBoV), respiratory syncytial virus (RSV), and human rhinovirus (hRV) in children with acute wheezing. METHODS: We retrospectively investigated 549 virus-positive throat swabs obtained between January 2006 and December 2008 from pediatric inpatients with acute respiratory tract disease at Kwangju Christian Hospital. Among them, 109 patients, who had lower respiratory tract infections with wheezing, were enrolled in this study. The medical records of patients with positive results were reviewed for clinical data. RESULTS: The mean age of the patients with RSV was 7.15 months, 15.66 months in those with hRV, and 15.04 months in those with hBoV. The mean fever duration and frequency of patients with fever was 2.43 days and 47.9% for RSV, 2.86 days and 51.7% for hRV, and 3.75 days and 69.6% for hBoV. The frequency of patients with acute otitis media was 20.8% in the RSV, 20.7% in the hRV, and 13.0% in the hBoV groups. The frequency of lung infiltration on chest X-ray was 12.5% in the RSV, 20.7% in the hRV, and 47.8% in the hBoV groups. CONCLUSION: We compared the clinical manifestations of respiratory viral infections in infants and children with wheezing. However, further surveillance will be necessary to clarify the clinical manifestations of the viruses.

Recurrent Wheezing After Human Bocavirus Lower Respiratory Tract Illnesses in Early Life / 소아알레르기및호흡기학회지

PURPOSE: Excluding RSV, the relationship between bronchiolitis caused by viruses and the development of wheezing and atopy in childhood has not been well studied. We studied this relationship in children who had bronchiolitis caused by human bocavirus before 2 years of age. METHODS: We retrospectively investigated 2,430 throat swab obstained between January 2005 and December 2007 from pediatric in-patients with acute respiratory tract disease at the Kwangju Christian Hospital. Human bocavirus was detected in 112 patients. A total of 61 patients less than 2 years of age were finally enrolled in this study. Patients were followed up between April and June of 2008. We measured the frequency of wheezing and atopic status using (allergy skin-prick tests, CAP tests and MAST tests). RESULTS: Of the 61 patients, 16 (26.2%) had recurrent wheezing. Of these 16 patients, 8 (13.1%) had Infrequent wheezing (1-2 wheezing episodes) and 8 (13.1%) had frequent wheezing (3 and over wheezing episodes). Of the total 61 patients, 18 (29.5%) completed allergy tests. Of the 18 patients, 10 (55.6%) were sensitized to at least 1 allergen. Recurrent wheezing was significantly associated with the severity of bronchiolitis (mild vs. moderate vs. severe; 9.1% vs. 22.2% vs. 66.7%). CONCLUSION: Human bocavirus-induced bronchiolitis in childhood are an independent risk factor for development of wheezing in childhood and may be associated with an increased risk of allergic sensitization. The most important risk factor for recurrent wheezing is the severity of lower respiratory tract illnesses.

Surveillance of Legionella Contamination on Water Supply Systems of Public Utilizing Facilities in Gwangju, Korea

Legionella is a pathogenic bacteria associated to aquatic habit of natural and artificial environments. Clinical cases of legionellosis have been reported in Korea but there is a lack of information about the incidence of this bacterium on environmental sources. Thus, we investigated the contamination of Legionella on water supply systems in Gwangju, Korea, including cooling towers, public baths, hospitals and fountains. Legionella spp. were detected from 81 samples (16.9%) out of 480 samples collected and the major species of Legionella isolates was identified to L. pneumophila serogroup (sg) 1 (n=33). The result of PFGE pattern analysis for L. pneumophila sg 1 isolates was discriminated into 11 pulsotypes. In dendrogram of PFGE, the clusters of isolates from cooling tower were quite different from those derived from hot water system of public bath. Surveillance for 4 sentinel public baths showed that their water supply systems had been contaminated with Legionella spp. and L. pneumophila sg 5 or sg 6 was the major isolate. The similarity of its PFGE patterns was 92.3%, 96.6%, respectively. Thus, PFGE may be a useful tool in molecular epidemiology studies, and the monitor and control for water supply systems of public utilizing facilities will be able to provide a resolution for the reduction of Legionella infection.

Surveillance of Legionella Contamination on Water Supply Systems of Public Utilizing Facilities in Gwangju, Korea

Legionella is a pathogenic bacteria associated to aquatic habit of natural and artificial environments. Clinical cases of legionellosis have been reported in Korea but there is a lack of information about the incidence of this bacterium on environmental sources. Thus, we investigated the contamination of Legionella on water supply systems in Gwangju, Korea, including cooling towers, public baths, hospitals and fountains. Legionella spp. were detected from 81 samples (16.9%) out of 480 samples collected and the major species of Legionella isolates was identified to L. pneumophila serogroup (sg) 1 (n=33). The result of PFGE pattern analysis for L. pneumophila sg 1 isolates was discriminated into 11 pulsotypes. In dendrogram of PFGE, the clusters of isolates from cooling tower were quite different from those derived from hot water system of public bath. Surveillance for 4 sentinel public baths showed that their water supply systems had been contaminated with Legionella spp. and L. pneumophila sg 5 or sg 6 was the major isolate. The similarity of its PFGE patterns was 92.3%, 96.6%, respectively. Thus, PFGE may be a useful tool in molecular epidemiology studies, and the monitor and control for water supply systems of public utilizing facilities will be able to provide a resolution for the reduction of Legionella infection.

The Distribution of Seropositivities for Human Immunodeficiency Virus and, Syphilis and the Gonorrhea Positive Rates in Gwangju (2002-2006)

BACKGROUND: The epidemic of human immunodeficiency virus (HIV) or sexually transmitted infections (STIs) is an important public health issue in the worldwide. Therefore, we investigated the trends of the seroprevalence of HIV and, syphilis and the gonorrhea positive rates in Gwangju from 2002 to 2006. MATERIALS AND METHODS: The results of laboratory tests for HIV, syphilis and gonorrhea were collected from five public health centers and 19 hospitals in Gwangju. The number of tested patients from 2002 to 2006 was 348,202 cases for HIV, 80,115 cases for syphilis and, 103,548 cases for gonorrhea. RESULTS: HIV/AIDS infections have rapidly increased at public health centers and hospitals. Especially, most of newly HIV-infected people were patients on ambulatory care/hospitalization, and they were also found via preoperation tests and according to the clinical symptoms. The gonorrhea positive rates have gradually decreased by year while the syphilis infection rates have slightly increased from 2002 to 2006. CONCLUSIONS: We have to determine the reasons why HIV and syphilis infections, but not gonorrhea, have increases simultaneously by the year. These results should be helpful to create a more effective STD prevention policy and the treatment guidelines for the people in Gwangju in the near future.

The Distribution of Seropositivities for Human Immunodeficiency Virus and, Syphilis and the Gonorrhea Positive Rates in Gwangju (2002-2006)

BACKGROUND: The epidemic of human immunodeficiency virus (HIV) or sexually transmitted infections (STIs) is an important public health issue in the worldwide. Therefore, we investigated the trends of the seroprevalence of HIV and, syphilis and the gonorrhea positive rates in Gwangju from 2002 to 2006. MATERIALS AND METHODS: The results of laboratory tests for HIV, syphilis and gonorrhea were collected from five public health centers and 19 hospitals in Gwangju. The number of tested patients from 2002 to 2006 was 348,202 cases for HIV, 80,115 cases for syphilis and, 103,548 cases for gonorrhea. RESULTS: HIV/AIDS infections have rapidly increased at public health centers and hospitals. Especially, most of newly HIV-infected people were patients on ambulatory care/hospitalization, and they were also found via preoperation tests and according to the clinical symptoms. The gonorrhea positive rates have gradually decreased by year while the syphilis infection rates have slightly increased from 2002 to 2006. CONCLUSIONS: We have to determine the reasons why HIV and syphilis infections, but not gonorrhea, have increases simultaneously by the year. These results should be helpful to create a more effective STD prevention policy and the treatment guidelines for the people in Gwangju in the near future.

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.

Distribution of Group A Rotavirus Genotypes Circulating in Gwangju, Korea

To determine the distribution of rotavirus strain genotypes in Gwangju, Korea, we performed reverse-transcription polymerase chain reaction and nucleotide sequencing analysis using the 115 rotavirus EIA positive stool specimens collected from December 2006 through April 2007. The most predominant genotype was confirmed as G1P[8] (53.9%), followed by G3P[8] (29.6%), G4P[6] (8.7%), G2P[4] (4.3%) and G9P[8] (1.7%). A special attention is drawn to the unusual findings of the genotypes G11P[25] and G12P[9] during this study period. In order to investigate the phylogenetic relationships among the same or different genotypes, the nucleotide sequences of rotavirus circulating in Korea and the foreign countries were analyzed using MegAlign and Clustal X programme. The G11P[25] strain identified in this study showed the highest nucleic acid similarity with G11 /CUK1 /2006 /Korea (99.2%) and P[25] /Dhaka /2001 /BGD (98.7%). Meanwhile, the G12P[9] strain detected in this study shared 99.4~99.5% nucleotide homology with the reference strain G12P[9] /CP1030 /2004 /Japan. This incidence of new rotavirus genotypes in our area illustrates the large diversity of rotavirus strains found worldwide. Therefore, the epidemiological surveillance of rotavirus may need to be continued in a wide geographic area.

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

Shiga toxin-producing Escherichia coli (STEC) strains are commensal bacteria in cattle and cause food borne disease in human. We analyzed the isolation rate of STEC in stool specimens of patients with diarrhea and in fecal samples of cattle in Gwangju, Korea. STEC strains were detected from 33 (0.19%) out of 17,148 patients with diarrhea while there has been a progressive increase in the incidence rate from 0.07% in 2004 to 0.33% in 2008. We investigated serotypes, shiga toxin genes, and antimicrobial resistance patterns of the 44 STEC isolates from human and cattle sources. The 33 STEC isolates from human belonged to 14 O serotypes including O157, O26 and O111. The 11 isolates from cattle belonged to 11 O serotypes. PCR detection for stx genes showed that 12 (27.3%) isolates carried stx1 genes, 20 (45.5%) possessed stx2 genes, and 12 (27.3%) carried both stx1 and stx2. Of the 33 STEC isolates from human, 25 strains (76%) were resistant to one or more antibiotics. High level of resistance to tetracycline (73%) was most common, followed by ticarcillin and ampicillin (64%). But none of the 33 isolates from human were resistant to amikacin, cefazolin, cefepime, cefotetan, cefotaxime, ciprofloxacin, or imipenem. The 5 strains (45%) of the 11 isolates from cattle were resistant to at least one or three antibiotics but most of the isolates were sensitive to the 16 antibiotics employed in this survey. In conclusion, toxin types and serotypes of STEC isolated from human and cattle were diverse, and non-O157 STEC was also observed to be a greater proportion of STEC isolates. According to a specific comparison solely based on the toxin types and serotypes, most of the STEC strains isolated from cattle feces in Gwangju, Korea showed characteristics different from those isolated from patients. Therefore, laboratory surveillance is required to detect and carefully monitor the potentially hypervirulent STEC not only in human and cattle but also in other animals.

Characterization of Respiratory Viral Infection in Children in Gwangju

BACKGROUND: This investigation was to perform the epidemiological surveillance and genetic analysis on respiratory viral agents from children with acute respiratory infections in Gwangju. MATERIALS AND METHODS: For this study, 3,695 specimens obtained from patients with acute respiratory infections were collected by collaboration with pediatric hospitals in Gwangju between 2005 and 2007. Specimens were screened for 8 respiratory viruses including influenza viruses (IFV), human rhinoviruses (HRV), human coronaviruses (HCoV), adenoviruses (ADV), parainfluenza viruses (PIV), human enteroviruses (HEV), respiratory synthitial viruses (RSV) and human bocaviruses (HBoV). Respiratory viruses were detected using multiplex (RT) PCR with viral specific primers. RESULTS: Out of 3,695 specimens, the ratio of virus detection was 24.9% (919). Overall, HRV (35.5%) and IFV (34.9%) were the most common viruses found, followed by HBoV (14.8%), HCoV (10.6%), RSV (3.7%), ADV (3.4%), PIV (3.2%) and HEV (3.0%). In addition, multiple infections were detected in 80 patients (8.7%). When the prevalence was analyzed according to season, HBoV, IFV and HCoV showed two epidemic points in late spring and early winter. ADV, HRV, RSV PIV and HEV, however, were all found to have only one epidemic point, with RSV being most common during winter and the others being most prominent during spring. CONCLUSIONS: Through this epidemiological surveillance, the respiratory viruses prevalent in children in Gwangju area were investigated. We strongly recommend the development of nationwide policy for the management of prevalent respiratory virus that includes long term collection of data and samples, vaccine development and prevention education of the misuse of antibiotics.

Characterization of Respiratory Viral Infection in Children in Gwangju

BACKGROUND: This investigation was to perform the epidemiological surveillance and genetic analysis on respiratory viral agents from children with acute respiratory infections in Gwangju. MATERIALS AND METHODS: For this study, 3,695 specimens obtained from patients with acute respiratory infections were collected by collaboration with pediatric hospitals in Gwangju between 2005 and 2007. Specimens were screened for 8 respiratory viruses including influenza viruses (IFV), human rhinoviruses (HRV), human coronaviruses (HCoV), adenoviruses (ADV), parainfluenza viruses (PIV), human enteroviruses (HEV), respiratory synthitial viruses (RSV) and human bocaviruses (HBoV). Respiratory viruses were detected using multiplex (RT) PCR with viral specific primers. RESULTS: Out of 3,695 specimens, the ratio of virus detection was 24.9% (919). Overall, HRV (35.5%) and IFV (34.9%) were the most common viruses found, followed by HBoV (14.8%), HCoV (10.6%), RSV (3.7%), ADV (3.4%), PIV (3.2%) and HEV (3.0%). In addition, multiple infections were detected in 80 patients (8.7%). When the prevalence was analyzed according to season, HBoV, IFV and HCoV showed two epidemic points in late spring and early winter. ADV, HRV, RSV PIV and HEV, however, were all found to have only one epidemic point, with RSV being most common during winter and the others being most prominent during spring. CONCLUSIONS: Through this epidemiological surveillance, the respiratory viruses prevalent in children in Gwangju area were investigated. We strongly recommend the development of nationwide policy for the management of prevalent respiratory virus that includes long term collection of data and samples, vaccine development and prevention education of the misuse of antibiotics.

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.

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.

Epidemiological Study of Viral Diarrhea in Gwangju Area During 2000~2002

There are well known infectious diarrheal disease including viral disease such as HuCVs (Human caliciviruses), rotaviruses, enteric adenoviruses and astroviruses. We performed surveillance of infectious diarrheal disease in this study for providing the information for regional prevalence of infectious diarrheal disease and establish basement of diagnostic scheme for these infectious diarrheal disease. For the study, 3,400 stool specimens collected from 10 hospitals in Gwangju from April 2000 to March 2002 were used in investigation for the detection of infectious diarrheal disease. For group A rotaviruses, enteric adenoviruses and astrovirus, we carried out antigen capturing ELISA and RT-PCR with specific primers reacting RNA dependent RNA polymerase gene of HuCVs is used for the detection of RNA of HuCVs. As a results, we detected viral antigen or genome from 537 out of 3,400 specimens (15.8%). 443 out of 537 (82.5%) were confirmed as rotaviruses antigen positively, and 14 (2.6%) and 3 (0.8%) samples were antigen positive to enteric adenoviruses and astroviruses, respectively. We detected HuCV genome from 73 (13.6%) samples by specific amplification. We found that predominantly causative virus is rotavirus in Gwangju but HuCVs take major portion of viral agents causing diarrhea considering the age and seasonal distribution of specimens. Prevalence of adenoviruses and astroviruses are very low compared with worldwide situation. While the infection of rotavirus is limited to young infant under 2 years old, infection of HuCV has wide age distribution. These results suggest that existence of various strains of HuCVs and low rate of cross-protection among distinct antigenic group make it difficult to form immunity in older age. This epidemiological information relating to various diarrheic viruses is first reported in Gwangju, therefore it could provide present prevalence of viral agents causing gastroenteritis and backgrounds to establishment of protection viral diarrhea and development.

Investigation of Outbreak caused by Shigella flexneri

BACKGROUND: Most of the shigellosis outbreak in Korea was caused by Shigella sonnei since late 1990's. In contrast, outbreak by Shigella flexneri were rare since late 1990's. Currently, we experienced the shigellosis outbreak by S.flexneri and described the results of investigation. METHODS: We recruited employees from company "A" who had a meal at least once at the company's cafeteria from Dec 23th, 2002 to Dec 26th, 2002. We surveyed the symptoms, food items, and history of travel of eligible persons and their family members. For the microbiological examination, we collected specimen from eligible persons and their family. Collected specimens were cultured for bacteriologic agents and viruses. Epidemiological relationship among the isolates were analyzed by pulsed field gel electrophoresis (PFGE). RESULTS: Among the eligible persons, one hundred ten were symptomatic (110/258, 42,6%). Eighty- two were confirmed bacteriologically. Day of symptom onset showed a unipolar pattern. Diarrhea was the most common symptom among the symptomatic patients (110/110, 100%). The other symptoms included abdominal pain (81.8%), tenesmus (70.0%), headache (63.6%), nausea (61.8%), febrile sense (59.1%), and vomiting (24.5%). Lunch on 24th Dec was the most significant risk factor of the outbreak (RR=6.46, 3.56< or =95% CI< or =11.75). All isolates of the outbreak has the same pattern on PFGE analysis and the PFGE pattern was not similar compared with other S.flexneri isolates from Korea. CONCLUSION: This is the largest and unique outbreak by S.flexneri since 2000 in Korea. The outbreak has the same origin according to the PFGE pattern and epidemic characteristics. Considering rarity of S.flexneri among shigellosis in Korea, surveillance for S.flexneri should be enhanced.

Investigation of Outbreak caused by Shigella flexneri

BACKGROUND: Most of the shigellosis outbreak in Korea was caused by Shigella sonnei since late 1990's. In contrast, outbreak by Shigella flexneri were rare since late 1990's. Currently, we experienced the shigellosis outbreak by S.flexneri and described the results of investigation. METHODS: We recruited employees from company "A" who had a meal at least once at the company's cafeteria from Dec 23th, 2002 to Dec 26th, 2002. We surveyed the symptoms, food items, and history of travel of eligible persons and their family members. For the microbiological examination, we collected specimen from eligible persons and their family. Collected specimens were cultured for bacteriologic agents and viruses. Epidemiological relationship among the isolates were analyzed by pulsed field gel electrophoresis (PFGE). RESULTS: Among the eligible persons, one hundred ten were symptomatic (110/258, 42,6%). Eighty- two were confirmed bacteriologically. Day of symptom onset showed a unipolar pattern. Diarrhea was the most common symptom among the symptomatic patients (110/110, 100%). The other symptoms included abdominal pain (81.8%), tenesmus (70.0%), headache (63.6%), nausea (61.8%), febrile sense (59.1%), and vomiting (24.5%). Lunch on 24th Dec was the most significant risk factor of the outbreak (RR=6.46, 3.56< or =95% CI< or =11.75). All isolates of the outbreak has the same pattern on PFGE analysis and the PFGE pattern was not similar compared with other S.flexneri isolates from Korea. CONCLUSION: This is the largest and unique outbreak by S.flexneri since 2000 in Korea. The outbreak has the same origin according to the PFGE pattern and epidemic characteristics. Considering rarity of S.flexneri among shigellosis in Korea, surveillance for S.flexneri should be enhanced.