A recently published study led by scientists from the US Food and Drug Administration (FDA) has used whole genome sequencing (WGS) to investigate a strain of Vibrio parahaemolyticus responsible for an outbreak of food poisoning in 2010.
The outbreak occurred in Maryland and affected at least two people. The outbreak was soon linked to raw oysters eaten in local restaurants and isolates of Vibrio parahaemolyticus from the two patients and from oyster samples proved to have identical pulsed-field gel electrophoresis (PFGE) fingerprints.
However, the oysters also contained other potentially pathogenic strains of V. parahaemolyticus and so genomes from 11 isolates were sequenced by WGS. Analysis of the resulting data revealed six different “sequence types”, but the clinical isolates and four of those from oysters were all sequence type 8 (ST8) and were virtually indistinguishable, confirming oysters as the source of the outbreak.
Further analysis and comparison with data from other V. parahaemolyticus isolates showed that the ST8 strains found belonged to a clonal complex endemic in Asia, but not usually found in Maryland. The authors of the study suggest that these strains could have come to the Chesapeake Bay area – where the contaminated oysters were harvested – in ballast water from ships, or through the introduction of non-native fish.
The study is published in the journal Applied and Environmental Microbiology and can be found in full here.