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.ResultsTen 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.ConclusionOur 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.

Production of G protein‐coupled receptors in an insect‐based cell‐free system

“…In this context cell‐free protein synthesis (CFPS) offers a promising alternative to conventional in vivo expression systems. This holds particularly true for difficult‐to‐express proteins as well as posttranslationally modified proteins (Dondapati et al, ; Fenz et al, ) and toxic proteins (Bechlars et al, ). The potential to circumvent cytotoxic effects, together with the open nature of CFPS that enables the simple addition of ligands, co‐factors, and chaperones, are outstanding criteria for the improved synthesis of active GPCRs (Klammt et al, ; Schwarz et al, ).…”

Phenotypic and Genotypic Characterization of Veterinary Vibrio cincinnatiensis Isolates

“…We investigated the German strains for this phenotype; however, only two out of ten strains showed an intermediate resistance level (Table 4) and the remaining strains were sensitive. Similar investigation on V. cholerae non-O1, non-O139 [37], V. vulnificus [22], and V. parahaemolyticus [38] had revealed that a significant number of strains exhibited serum resistance under these conditions.…”

Genetic and virulence characterisation of Vibrio parahaemolyticus isolated from Indian coast

“…The existence of a second copy of tdh or mutations in the promoter needs to be further determined. Similarly, the low haemolytic activity of clinical as well as environmental tdh − trh + isolates was not surprising as both contain the trh2 allele (Additional file 1: Figure S4), which exhibit reduced hemolysis, not due to reduced gene expression, rather, owing to the differences in the amino acid molecular conformation and binding capacity of RBC by the trh2 product [50,51]. Further, the tdh-trh + environmental isolate K23 transcribed the genes vopC, vopA and vopL encoding effectors that promote invasion and modulate host cell behaviour, making it a possible pathogen.…”