Etiologic and molecular characteristics of Vibrio parahaemolyticus strains isolated from diarrheal patients in Shenzhen, in 2007-2008 / 中华流行病学杂志

Objective To study the infection status and the molecular characteristics of Vibrio parahaemolyticus isolated from diarrheal patients in Shenzhen, in 2007 to 2008 and to provide evidence for the prevention and control of diarrheal diseases caused by Vibrio parahaemolyticus. Methods More than 80 fecal specimens from four sentinel surveillance hospitals were collected and cultured each month. A total of 361 isolates of Vibrio parahaemolyticus were sero-typed and examined by real-time PCR for the presence of two major virulence genes, tdh and trh. Of 361 strains, 60 O3: K6 strains isolated from six suspected outbreaks in August, 2007 and in September, 2008 were typed by pulsed-field gel electrophoresis (PFGE). Results 4384 stool samples were detected in four sentinel surveillance hospitals and with 361 Vibrio parahaemolyticus strains isolated that belonged to 28 serotypes. Serotype O3:K6, O4:K8 and O1:KUT accounted for 67.90%, 7.50% and 6.10%, respectively. Of 361 strains, 337 strains belonged to tdh + trh- , 11 strains were tdh-trh- and 13 strains were tdh + trh +. The most prevalent serotype which caused diarrheal diseases was tdh + trh-in Shenzhen. The 60 isolates were discriminated into twenty different PFGE patterns, which belonged to three clones. Among the 60 isolates, most of the PFGE patterns of isolates from the suspected outbreak locations were identical and some strains isolated from different year were different. Conclusion Vibrio parahaemolyticus isolates in Shenzhen were dominated by O3:K6 strains. Most of these isolates carried tdh gene and few carried trh gene. Meanwhile, the identical patterns of isolates from 6 suspected outbreaks locations demonstrated that Vibrio parahaemolyticus outbreaks occurred in July 2007 and in September 2008 in Shenzhen. However, the dominated strains' PFGE patterns were different each year, indicating that the sources of Vibrio parahaemolyticus had a multiplex nature and the multiplex sources such as water, sea food and pickled products should be integrated monitored. Laboratory based surveillance of diarrheal diseases could contribute in establishing early warning system for the better prevention and control of diarrheal diseases.

Analysis of pulsed-field gel electrophoresis molecular subtyping of Shigella strains in Shenzhen / 中华预防医学杂志

<p><b>OBJECTIVE</b>To analyze the genetic relations of Shigella isolated from Shenzhen in 2001-2006 and develop primary molecular subtyping surveillance network of Shigella.</p><p><b>METHODS</b>Chromosomal DNAs from 55 isolated in agarose were digested with the restriction enzyme Xba I, and then were analyzed by pulsed-field gel electrophoresis. Pulsed-field gel electrophoresis (PFGE) patterns were clustered using BioNumerics software.</p><p><b>RESULTS</b>All 41 distinctive PFGE patterns were identified among 55 strains. 32 strains belonged to one cluster. Differences were observed in other strains.</p><p><b>CONCLUSION</b>Both genetic-related clones and non-related clones of Shigella existed in Shenzhen. The development of PFGE molecular subtyping surveillance network would contribute to the active surveillance, outbreak investigation and source tracking for Shigellosis.</p>

Application of pulsed-field gel electrophoresis in a food-borne outbreak of Salmonella serotype Muenchen infection / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate the application of pulsed-field gel electrophoresis (PFGE) in food-borne outbreak.</p><p><b>METHODS</b>Pathogens were isolated and further characteristics identified by traditional methods. The strains isolated were carried out with molecular typing with using PFGE. PFGE was performed by Laboratory Directions for molecular subtyping of Salmonella by PFGE (CDC, USA) and the results of PFGE were analyzed by BioNumerics soft.</p><p><b>RESULTS</b>Totally 14 Salmonella serotype Muenchen strains were isolated from 19 patients, 3 of 9 suspicious foods were positive for S. muenchen and 7 strains were isolated from 18 cooks. The biochemistry characterization and antimicrobial susceptibility of all the strains isolated were the same. 23 S. muenchen isolates were all shown indistinguishable by PFGE.</p><p><b>CONCLUSION</b>PFGE should play a key role in identifying the outbreak-associated isolates and distinguishing them from unrelated sporadic isolates. It might also demonstrate that the genetic fingerprints of serotype Muenchen isolates derived from patients were indistinguishable from those derived from drinks. PFGE might provide precise information on bacterial food-borne pathogens, promptly identify the source of infection, and effectively prevent from spreading. It should be one of the early warning method on controlling outbreak of the food-borne disease.</p>

Molecular subtyping of Vibrio cholerae isolates by pulsed-field gel electrophoresis in Shenzhen from 1993 / 中华流行病学杂志

<p><b>OBJECTIVE</b>To determine the genetic relationships between different Vibrio cholerae isolates in Shenzhen from 1993 to 2002.</p><p><b>METHODS</b>Chromosomal DNA from 60 isolates was digested in seakem gold agrose with restriction enzyme Not I and plugs were then analyzed by pulsed-field gel electrophoresis. Pulsed-field gel electrophoresis (PFGE) patterns of V. cholerae isolates were clustered using BioNumerics software.</p><p><b>RESULTS</b>39 distinctive PFGE patterns were identified with each pattern having 20 to 30 bands. Most PFGE patterns were divided into cluster A or cluster B.</p><p><b>CONCLUSION</b>The closely related pandemic clone clusters of V. cholerae strains did exist in Shenzhen. PFGE of V. cholerae could be used for active surveillance and tracking for cholerae.</p>