Etiologic and molecular characteristics of Vibrio parahaemolyticus strains isolated from diarrheal patients in Shenzhen, in 2007 - 2008

Abstract

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. 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). 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. 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.