Phenotypic and genotypic characterization of Canadian clinical isolates of Vibrio parahaemolyticus collected from 2000 to 2009.

Vibrio parahaemolyticus is the leading bacterial cause of food-borne illness due to the consumption of contaminated seafood. The aim of the present study was to determine the population of its subtypes and establish a better understanding of the various types of V. parahaemolyticus strains that are causing human illness in Canada. The subtypes for 100 human clinical isolates of V. parahaemolyticus collected between 2000 and 2009 were determined by performing serotyping, ribotyping, pulsed-field gel electrophoresis, and multilocus sequence typing. Within this panel of strains, there was a high level of diversity (between 22 and 53 subtypes per method), but the presence of predominant clones with congruent subtypes between the various methods was also observed. For example, all 32 isolates belonging to sequence type 36 (ST36) were from serogroup O4, while 31 of them were ribotype EcoVib235-287, and 24 of the 32 were SfiI pulsed-field gel electrophoresis (PFGE) pattern VPSF1.0001. With regard to the presence of known virulence genes, 74 of the 100 isolates were PCR positive for the presence of the thermostable direct hemolysin (tdh); and 59 of these 74 strains also contained the second virulence marker, the tdh-related hemolysin (trh). The detection of trh was more predominant (81%) among the clinical isolates, and only four (4%) of the clinical isolates tested negative for the presence of both tdh and trh. This database, comprising 100 clinical isolates of V. parahaemolyticus strains from Canada, forms a baseline understanding of subtype diversity for future source attribution and other epidemiologic studies.

Identification of sulfoquinovosyl diacylglycerol as a major polar lipid in Marinococcus halophilus and Salinicoccus hispanicus and substitution with phosphatidylglycerol.

The sulfonolipid sulfoquinovosyl diacylglycerol normally associated with photosynthetic membranes was identified as a major lipid in Marinococcus halophilus, Salinicoccus hispanicus ("Marinococcus hispanicus"), and Marinococcus sp. H8 (Planococcus sp. H8). Phosphatidylglycerol and 0%-10% cardiolipin accounted for the remaining polar lipids in these moderately halophilic, Gram-positive bacteria. Negative-ion fast atom bombardment mass spectrometry was used to quantify these three polar lipids from cells grown in media containing 0.03 to 4 mol NaCl/L. All strains revealed dramatic shifts in the ratio of sulfonolipid to phospholipid dependent on the salinity of the growth media, when grown in media with low phosphate content. Highest sulfonolipid content occurred during best growth in 0.5-2 mol NaCl/L, approaching 80%-90% of the total polar lipids. It was demonstrated that growth of M. halophilus in the presence of elevated phosphate and low sulfate blocked the shift to decreased phospholipids most notably during growth in 0.5-2 mol NaCl/L, without significant influence on growth. The data suggest that in low-phosphate media the influence of NaCl concentration on growth rate (and resulting demand for phosphate by competing pathways) is the primary factor responsible for exchange between phospholipid and sulfonolipid. We conclude that sulfoquinovosyl diacylglycerol, by substitution with phospholipids, contributes to the ability of these Gram-positive cocci to adapt to changing ionic environments. A comparison of 16S rRNA established a close similarity between Planococcus sp. H8 and M. halophilus.