title: Characterization of trh2 harbouring Vibrio parahaemolyticus strains isolated in Germany.
abstract: BACKGROUND
  Vibrio parahaemolyticus is a recognized human enteropathogen. Thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH) as well as the type III secretion system 2 (T3SS2) are considered as major virulence factors. As tdh positive strains are not detected in coastal waters of Germany, we focused on the characterization of trh positive strains, which were isolated from mussels, seawater and patients in Germany.
  
  
  RESULTS
  Ten trh harbouring V. parahaemolyticus strains from Germany were compared to twenty-one trh positive strains from other countries. The complete trh sequences revealed clustering into three different types: trh1 and trh2 genes and a pseudogene Ψtrh. All German isolates possessed alleles of the trh2 gene. MLST analysis indicated a close relationship to Norwegian isolates suggesting that these strains belong to the autochthonous microflora of Northern Europe seawaters. Strains carrying the pseudogene Ψtrh were negative for T3SS2β effector vopC. Transcription of trh and vopC genes was analyzed under different growth conditions. Trh2 gene expression was not altered by bile while trh1 genes were inducible. VopC could be induced by urea in trh2 bearing strains. Most trh1 carrying strains were hemolytic against sheep erythrocytes while all trh2 positive strains did not show any hemolytic activity. TRH variants were synthesized in a prokaryotic cell-free system and their hemolytic activity was analyzed. TRH1 was active against sheep erythrocytes while TRH2 variants were not active at all.
  
  
  CONCLUSIONS
  Our study reveals a high diversity among trh positive V. parahaemolyticus strains. The function of TRH2 hemolysins and the role of the pseudogene Ψtrh as pathogenicity factors are questionable. To assess the pathogenic potential of V. parahaemolyticus strains a differentiation of trh variants and the detection of T3SS2β components like vopC would improve the V. parahaemolyticus diagnostics and could lead to a refinement of the risk assessment in food analyses and clinical diagnostics.
authors: Federal Institute for Risk Assessment, Department of Biological Safety, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs, Berlin, Germany.
authors: Silke
authors: S
authors: Bechlars
authors: Federal Institute for Risk Assessment, Department of Biological Safety, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs, Berlin, Germany.
authors: Claudia
authors: C
authors: Jäckel
authors: Federal Institute for Risk Assessment, Department of Biological Safety, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs, Berlin, Germany.
authors: Susanne
authors: S
authors: Diescher
authors: Federal Institute for Risk Assessment, Department of Biological Safety, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs, Berlin, Germany.
authors: Doreen A
authors: DA
authors: Wüstenhagen
authors: Federal Institute for Risk Assessment, Department of Biological Safety, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs, Berlin, Germany.
authors: Stefan
authors: S
authors: Kubick
authors: Federal Institute for Risk Assessment, Department of Biological Safety, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs, Berlin, Germany.
authors: Ralf
authors: R
authors: Dieckmann
authors: Federal Institute for Risk Assessment, Department of Biological Safety, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs, Berlin, Germany.
authors: Eckhard
authors: E
authors: Strauch
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000138:chemical synthesis / Q000235:genetics*; D002474:Cell-Free System / Q000737:chemistry; D004912:Erythrocytes / Q000473:pathology; D005399:Fishes / Q000382:microbiology; D005838:Genotype; D005858:Germany; D006460:Hemolysin Proteins / Q000138:chemical synthesis / Q000235:genetics*; D006461:Hemolysis; D006801:Humans; D060885:Multiplex Polymerase Chain Reaction; D009664:Norway; D012756:Sheep / Q000097:blood / Q000382:microbiology; D014736:Vibrio parahaemolyticus / Q000235:genetics* / Q000302:isolation & purification* / Q000472:pathogenicity; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D037521:Virulence Factors