B-192. Molecular and Phylogenetic Characterization of Vibrio parahaemolyticus Carrying Pathogenicity Markers for Thermostable Direct Hemolysin (tdh), tdh-Related Hemolysin, and Type Three Secretion Systems 1 and 2

C. N. Johnson, N. F. Noriea, III, D. J. Grimes;
Univ. of Southern Mississippi, Ocean Springs, MS.

Vibrio parahaemolyticus (Vp) is a major cause of foodborne gastroenteritis in the U.S. annually, typically due to raw oyster consumption, and it has also caused several fatal wound infections. Most clinical isolates carry pathogenicity markers associated with pathogenicity in humans, such as thermostable direct hemolysin (tdh), tdh-related hemolysin, type three secretion systems (TTSSs), urease, and others. However, few environmental isolates carry these, and these are rare and not well characterized. Forty Vp isolates carrying tdh, trh, or both genes were isolated and characterized by Rep-PCR, ERIC-PCR, and TTSS-PCR. TTSS-PCR consisted of a multiplex PCR amplification of VP1669 (a YscO homolog), VPA1346 (a YopP homolog), VPA1354 (an EscU homolog), and VPA0226 (thermolabile hemolysin universally found in Vp). VP1669 is a TTSS1 component, and VPA1346 and VPA1354 are TTSS2 components. Five clinical isolates (tdh+ and/or trh+) were also analyzed. Of the 40 environmental isolates, all but 2 were VP1669+, and these were clonally unrelated. These 2 were, however, VPA1354+; thus, although they were missing the TTSS1 typically found in Vp, the presence of the TTSS2 component and at least one hemolysin may compensate for this deficiency. Eight out of 40 were VPA1354+; 3 of these 8 fell into small clusters with phylogenetically related Vp that were not VPA1354+, and the remaining 5 were unrelated to each other or to other tdh+ and/or trh+ isolates. Thus, the TTSS typically associated with clinical isolates was found in 8 heterogeneous naturally occurring tdh+/trh+ isolates, which indicates that these may have the potential to cause disease in humans if exposed. Of the 40 isolates that carried either tdh or trh, only 2 carried trh alone, and these both also carried VPA1354; one was also VP1669- and the other had a weak signal for VP1669. Surprisingly, of the 5 clinical strains tested, although all 5 carried VP1669, only one also carried VPA1354 and VPA1346, the TTSS components typically associated with clinical isolates. Additional analysis is underway, including DNA sequencing of TTSS genes and microarray analysis to identify genes globally affected by these pathogenicity factors.