Epidemiological investigation of a foodborne outbreak in Spain associated with U.S. West Coast genotypes of Vibrio parahaemolyticus

Abstract

We describe an outbreak of seafood-associated Vibrio parahaemolyticus in Galicia, Spain in on 18th of August 2012 affecting 100 of the 114 passengers travelling on a food banquet cruise boat. Epidemiological information from 65 people was available from follow-on interviews, of which 51 cases showed symptoms of illness. The food items identified through the questionnaires as the most probable source of the infections was shrimp. This product was unique in showing a statistically significant and the highest OR with a value of 7.59 (1.52–37.71). All the nine strains isolated from stool samples were identified as V. parahaemolyticus, seven were positive for both virulence markers tdh and trh, a single strain was positive for trh only and the remaining strain tested negative for both trh and tdh. This is the largest foodborne Vibrio outbreak reported in Europe linked to domestically processed seafood. Moreover, this is the first instance of strains possessing both tdh+ and trh+ being implicated in an outbreak in Europe and that a combination of strains represent several pathogenicity groups and belonging to different genetic variants were isolated from a single outbreak. Clinical isolates were associated with a novel genetic variant of V. parahaemolyticus never detected before in Europe. Further analyses demonstrated that the outbreak isolates showed indistinguishable genetic profiles with hyper-virulent strains from the Pacific Northwest, USA, suggesting a recent transcontinental spread of these strains.

Genomic Variation and Evolution of Vibrio parahaemolyticus ST36 over the Course of a Transcontinental Epidemic Expansion

“…In addition to the environmental factors driving this expansion, the emergence and transcontinental dissemination of some particular genetic variants of V. parahaemolyti- cus are contributing to this process (15,17,(26)(27)(28). Classical typing techniques applied to the investigation of outbreaks (initially repetitive element PCR and pulsed-field gel electrophoresis and later multilocus sequence typing [MLST]) provided insights into the potential sources and origins of these new variants, documenting the first connections between populations implicated in outbreaks across large geographic distances (11,12,(29)(30)(31).…”

“…Over the last 6 years, its detection along the northeast coast of the United States has been associated with a rise in the number of cases in the region (8). In addition, ST36 was identified for the first, and only, time outside North America in the northwest of Spain, where it caused a large outbreak in 2012 (15,17). The subsequent emergence of this clone in Europe triggered concern about the potential implications of the transcontinental spreading of a second V. parahaemolyticus strain and the opportunities for a new pandemic expansion.…”

“…These 48 strains were selected on the basis of geography (representing both the Pacific and Atlantic coasts of the United States) and association with sporadic illnesses and outbreaks. Six of the ST36 strains (G25, G30, G31, G37, G36, and G35) represent the single outbreak in Galicia (northwest of Spain) in 2012 (17).…”

“…However, illnesses associated with this complex were reported along the northeast coastline of the United States in the spring of 2012 (8,15) and subsequently in the northwest of Spain in association with a large outbreak of illness in August 2012 (17). The geographic expansion of these strains caused significant economic losses in the shellfish industry in the northeast and caused the largest known food-borne Vibrio outbreak reported in Europe (17).…”

“…However, illnesses associated with this complex were reported along the northeast coastline of the United States in the spring of 2012 (8,15) and subsequently in the northwest of Spain in association with a large outbreak of illness in August 2012 (17). The geographic expansion of these strains caused significant economic losses in the shellfish industry in the northeast and caused the largest known food-borne Vibrio outbreak reported in Europe (17). A striking observation from characterization of the 2012 outbreak-associated strains, as well as previous clinical isolates of this complex from the United States, was the indistinguishable serotypes (O4:K12 or O4:Kut), pulsotypes, and STs (ST36) (15).…”