Virulence gene- and pandemic group-specific marker profiling of clinical Vibrio parahaemolyticus isolates

Abstract

Vibrio parahaemolyticus is a halophilic bacterium capable of causing food- and waterborne gastroenteritis, wound infections, and septicemia in humans. The organism has recently received increasing attention, as the emergence of a new clone, V. parahaemolyticus O3:K6, has resulted in the first documented pandemic spread of V. parahaemolyticus. We used microarray analyses to explore the presence of known virulence factors and genetic markers thought to be specific for V. parahaemolyticus O3:K6 and its clonal derivatives. Analyses of 48 human clinical isolates collected between 1997 and 2005 revealed that the V. parahaemolyticus chromosome 2 type III secretion system is not specifically associated with pandemic strains and can be found in tdh-negative (i.e., Kanagawa-negative) clinical isolates. These results highlight the genetic dynamism of V. parahaemolyticus and aid in refining the genetic definition of the pandemic group members.

FIG. 1.

Targeted V. parahaemolyticus T3SS2 gene cluster. (A) Genetic organization of the 11 targeted T3SS2 genes (gray arrows) that reside within the 80-kb pathogenicity island on chromosome 2 of V. parahaemolyticus strain RIMD2210633 (17). The locus spanning VPA1334 to VPA1368 is shown with the T3SS2 gene designations listed above each gray arrow. A scale line showing the position (in base pairs) from the chromosome 2 origin of replication can be found below the gene cluster map. (B) BLAST comparison of V. parahaemolyticus T3SS2 genes with known T3SS genes in other bacteria. *, BLAST comparison with V. cholerae non-O1/non-O139 AM-19226 (9); †, BLAST comparison with bacterial systems with known and established T3SSs.

FIG. 2.

Representative confirmatory microarray hybridization profiles of randomly amplified clinical V. parahaemolyticus isolates. Probes targeting (row 1, left to right) VP1657, VP1667, VP1670, and VP1680; (row 2) VP1690, VP1696, negative control, and negative control; (row 3) TL, TDH, TRH, and TRH; (row 4) ToxRS/new, ORF8, VPF/R2, and HU-α; (row 5) VPA1335, VPA1338, VPA1339, and VPA1341; (row 6) VPA1342, VPA1346, VPA1349, and VPA1354; and (row 7) VPA1355, VPA1362, VPA1367, and the unrelated hybridization-positive control are shown. The strain identification number and corresponding serotype are found under each panel.