Epidemiological Analysis of Shiga Toxin-producing E. coli Isolated in Gwangju, Korea, by Pulse-field Gel Electrophoresis

In Gwangju, Korea, over the last 4 years, human gastrointestinal infection caused by shiga toxin-producing E. coli (STEC) increased. The aim of this study was to ascertain the genetic relatedness of STEC strains by pulsed-field gel electrophoresis (PFGE), as no data on the molecular epidemiology of STEC in Gwangju has yet been published. The PFGE banding patterns were defined for 62 of the 67 STEC strains isolated from cattle and human. There were 11 clonal types in the 11 STEC strains of cattle origin. Among the 11 STEC strains from asymptomatic person, four O91 strains were 100% similarity in band profiles. In the STEC strains isolated from diarrhea patients, same serogroups were grouped to the same cluster; O111 stains were 89.5% similarity, O157 strains 80%, O26 strains 81.5%, and O103 strains 91% similarity, respectively. In conclusion, this is the first report that a large collection of STEC strains from Korea has been analyzed, and a high degree of diversity was observed among the strains analyzed by this technique. PFGE analysis revealed that the strains isolated from human and cattle were closely related within serotypes, and it was useful for epidemiological analysis of STEC. The importance and usefulness of active laboratory surveillance of STEC such as PFGE should be recommended.

Molecular Epidemiological Characteristics of Vibrio parahaemolyticus Isolated from Diarrheal Patients in Jeonnam, Korea

To investigate the occurrence and distribution of serotype, specific virulence genes, and pulse field gel electrophoresis (PFGE) patterns in Vibrio parahaemolyticus isolates from Jeonnam, Korea, we tested 87 strains which were identified with V. parahaemolyticus from diarrheal episode patients in 2005. In this study, 16 different O:K serotype combinations of V. parahaemolyticus were determined. The distributions of O and K serotypes were O4:K68 (51.72%), O1:K70 (18.39%), O3:K6 (5.74%), O1:K68 (4.60%) and O3:K57 (4.60%) respectively. Serotype O4:K68 was the regional dominant specific serotype of V. parahaemolyticus in Sinan of Jeonnam, Korea. For the detection of thermostable direct hemolysin (tdh) and TDH-related hemolysin (trh) gene of V. parahaemolyticus, PCR was performed. The tdh gene was detected in all of the V. parahaemolyticus isolates from diarrheal patients, but trh gene was not detected. Analysis of PFGE patterns of 30 V. parahaemolyticus isolates showed 3 groups and 20 types. Among 14 O4:K68 serotypes which were isolated in Sinan, PFGE patterns of 12 strains were closely related (100%), but 2 strains were related by 58.3% and 45.4%, respectively. Also two strains of O1:K4 serotype in Gurye and two strains of O3:K6 serotype in Yeosu were closely related (100%), respectively. Although serotypes (O1:K4, O1:K70, O3:K6 and O4:K68) were different, PFGE patterns were related for more than 80.9%. Therefore, the epidemiological surveillance of V. parahaemolyticus is required by PFGE typing scheme as a further diagnostic tool.

Establishment of a bovine leukemia virus-free dairy herd in Korea

In view of the high prevalence rate of bovine leukemia virus (BLV)infections in cattle over the entire country, a large dairy farm in Chungnam province was chosen and 'test and segregate' program was instituted. On July 1999, ELISA test was performed on 491 animals on the farm and only 163 cattle (139 adult cows, 18 female and 6 male calves)were BLV-seronegative. From February 2000 through April 2004, the seronegative group was placed in barns 1,500 to 2,000 m from seropositive group and thereafter tested at 3-to 5-month intervals by ELISA. Animals seroconverted in consecutive tests were removed from the seronegative group immediately after the detection of anti-BLV antibodies. The changes in management were aimed at preventing iatrogenic transfer of blood between cattle. Replacement heifers imported from other countries and calves born at the farm were repeatedly tested by ELISA, and only seronegative animals were introduced into the group. As of April 2004, there were 311 cattle in the BLV seronegative group of the farm. Twent y four cows of the initial 139 adult cows were seroconverted in 2000, and no seropositive animals were found since February 2001. Follow up of the group, from which all seropositive cattle were moved to a separate location, revealed no recurrence of BLV infection for three years. The approach in the present study might be valuable for Korean producers who would like to move toward a BLV-negative status.