title: Epidemiological evidence of lesser role of thermostable direct hemolysin (TDH)-related hemolysin (TRH) than TDH on Vibrio parahaemolyticus pathogenicity.
abstract: Vibrio parahaemolyticus carrying the tdh gene, encoding the thermostable direct hemolysin (TDH), or the trh gene, encoding the TDH-related hemolysin (TRH), are both considered virulent strains. There are, however, disproportionally fewer reports of infections caused by seafood contaminated with trh-positive strains than by seafood contaminated with tdh-positive strains. Bivalves such as clams and oysters are the major seafood varieties associated with the infections. In this study, the prevalence of strains possessing the tdh and trh genes was investigated in Japan in 74 samples collected in 2007-2008 and in 177 samples collected in 2010 of domestic bivalves, bloody clams, hen clams, short-neck clams, and rock oysters. The tdh-positive and trh-negative, tdh-negative and trh-positive, and tdh-positive and trh-positive samples represented 5.4%, 12.2%, and 4.1% of all samples collected in 2007-2008, and 5.1%, 18.6%, and 5.6% of all samples collected in 2010, respectively. As determined by polymerase chain reaction, the prevalence of tdh negative and trh positive in all samples was two to four times higher than that of tdh positive and trh negative. In the samples collected in 2010, the tdh-negative and trh-positive V. parahaemolyticus (20 samples) was more often isolated than tdh-positive and trh-negative V. parahaemolyticus (7 samples). The most common serotype of tdh-positive isolates (22 of 24 strains) was pandemic O3:K6. The trh-positive isolates (61 strains) were various serotypes including OUT:KUT. In 330 V. parahaemolyticus outbreaks and sporadic infections in Japan, most outbreaks and sporadic infections were caused by tdh-positive and trh-negative strains (89.4%). The frequencies of infections caused by tdh-negative and trh-positive, and both tdh- and trh-positive strains were 1.2% and 3.0%, respectively. This finding suggests that the virulence of trh might be less than that of tdh, although trh-positive V. parahaemolyticus frequently contaminated bivalves.
authors: 1 Akita Research Center for Public Health and Environment , Akita, Japan .
authors: Shioko
authors: S
authors: Saito
authors: Yoshito
authors: Y
authors: Iwade
authors: Eisuke
authors: E
authors: Tokuoka
authors: Tomohiro
authors: T
authors: Nishio
authors: Yoshimitsu
authors: Y
authors: Otomo
authors: Emiko
authors: E
authors: Araki
authors: Hirotaka
authors: H
authors: Konuma
authors: Hiroshi
authors: H
authors: Nakagawa
authors: Hiroyuki
authors: H
authors: Tanaka
authors: Kanji
authors: K
authors: Sugiyama
authors: Akio
authors: A
authors: Hasegawa
authors: Yoshiko
authors: Y
authors: Sugita-Konishi
authors: Yukiko
authors: Y
authors: Hara-Kudo
mesh_terms: D000818:Animals; D049893:Arcidae / Q000382:microbiology; D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D001427:Bacterial Toxins / Q000032:analysis / Q000737:chemistry / Q000633:toxicity; D049872:Bivalvia / Q000382:microbiology*; D049896:Crassostrea / Q000382:microbiology; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D006460:Hemolysin Proteins / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*; D006358:Hot Temperature; D006801:Humans; D007564:Japan / Q000453:epidemiology; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D055550:Protein Stability; D012758:Shellfish / Q000009:adverse effects* / Q000032:analysis / Q000191:economics / Q000382:microbiology; D057096:Shellfish Poisoning / Q000453:epidemiology / Q000209:etiology* / Q000382:microbiology; D014735:Vibrio Infections / Q000453:epidemiology / Q000382:microbiology; D014736:Vibrio parahaemolyticus / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity*; D014774:Virulence; D037521:Virulence Factors / Q000032:analysis* / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D037521:Virulence Factors; C088609:thermostable direct hemolysin-related hemolysin protein, Vibrio parahaemolyticus; C068489:thermostable direct hemolysin