Filamentous Phage Associated with Recent Pandemic Strains ofVibrio parahaemolyticus

Abstract

Vibrio parahaemolyticus, a halophilic gram-negative rod, causes seafood-borne gastroenteritis in humans. Infections caused by this organism have been associated with diverse serovars: 13 O serotypes and 75 K serotypes have been identified. Recent studies, however, have revealed the emergence and pandemic spread of a single serovar, O3:K6 (1-6). Strains belonging to the O3:K6 serovar abruptly appeared in India in 1996 and have since been isolated in Southeast Asian countries, from travelers at quarantine stations in Japan, and from foodborne outbreaks in the United States (1-5). This serovar accounts for more than half of the V. parahaemolyticus isolates from diarrheal patients in Japan (6). Such widespread occurrence of a single serovar of V. parahaemolyticus had not previously been reported. Since 1998, V. parahaemolyticus strains belonging to other two serovars, O4:K68 and O1:K untypeable (KUT), have also been isolated with increasing frequency from diarrheal patients (2,6,7). The genetic background of the O4:K68 and O1:KUT isolates is almost indistinguishable from that of the recent O3:K6 strains, suggesting a common origin (2,7).In a previous study, we reported on a filamentous phage that is specifically associated with the recent O3:K6 serovar strains of V. parahaemolyticus (8). This phage, f237, has several genes in common with and a similar genomic structure to another filamentous phage, CTX (9), which is known to carry the genes for cholera enterotoxin (ctxAB), the most important virulence factor of V. cholerae. Instead of ctxAB, f237 possesses a unique open reading frame, ORF8, which has no homology with other sequences in DNA databases (8). In this study, we examined the distribution of f237 in recent clinical isolates of V. parahaemolyticus.

Characterization and Analysis of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) in Pandemic and Non-Pandemic Vibrio parahaemolyticus Isolates from Seafood Sources

“…Previous studies demonstrated a strong association of filamentous phages, f237, with recent pandemic strains of V. parahaemolyticus. This phage possesses a unique ORF8 open reading frame that is found only in recent pandemic isolates, and the Zot (Zonula occludens toxin)-like toxin previously described in the V. cholerae is reported to be encoded in the ORF7 [51,52]. A match was found between the CRISPR spacer region of V. anguillarum PF7 with a zot-encoding prophage in V. anguillarum PF4, indicating the contribution of CRISPR to the phage resistance of this bacterium [53].…”

A new group of cosmopolitan bacteriophages induce a carrier state in the pandemic strain of Vibrio parahaemolyticus

“…Only three temperate phages have been associated with the pandemic strain. The temperate Inoviridae phage f237 is found integrated in most bacterial pandemic isolates providing its characteristic orf8, an open reading frame (ORF) used as a marker of pandemic strains (Nasu et al, 2000;Iida et al, 2001). Two other temperate myovirus phages were recently reported (Lan et al, 2009;Zabala et al, 2009); both belong to a fairly new group of telomeric phages.…”

Molecular characterization of thermostable direct haemolysin‐related haemolysin (TRH)‐positive Vibrio parahaemolyticus from oysters in Mangalore, India

“…Based on the sequence of this region, PCR primers were designed that specifically amplify a fragment in the pandemic strain. Further, a filamentous phage (f237) has been reported to be associated with pandemic strains of V. parahaemolyticus (Nasu et al ., 2000;Iida et al ., 2001). Genetic analysis of this phage has revealed that the sequence of eighth open reading frame (ORF8) of f237 is found only in O3:K6 pandemic strains of V. parahaemolyticus isolated after 1996 outbreak.…”