Multistate outbreak of Salmonella Paratyphi B variant L(+) tartrate(+) and Salmonella Weltevreden infections linked to imported frozen raw tuna: USA, March–July 2015

Abstract

Foodborne non-typhoidal salmonellosis causes approximately 1 million illnesses annually in the USA. In April 2015, we investigated a multistate outbreak of 65 Salmonella Paratyphi B variant L(+) tartrate(+) infections associated with frozen raw tuna imported from Indonesia, which was consumed raw in sushi. Forty-six (92%) of 50 case-patients interviewed ate sushi during the week before illness onset, and 44 (98%) of 45 who specified ate sushi containing raw tuna. Two outbreak strains were isolated from the samples of frozen raw tuna. Traceback identified a single importer as a common source of tuna consumed by case-patients; this importer issued three voluntary recalls of tuna sourced from one Indonesian processor. Four Salmonella Weltevreden infections were also linked to this outbreak. Whole-genome sequencing was useful in establishing a link between Salmonella isolated from ill people and tuna. This outbreak highlights the continuing foodborne illness risk associated with raw seafood consumption, the importance of processing seafood in a manner that minimises contamination with pathogenic microorganisms and the continuing need to ensure imported foods are safe to eat. People at higher risk for foodborne illness should not consume undercooked animal products, such as raw seafood.

Clinically Unreported Salmonellosis Outbreak Detected via Comparative Genomic Analysis of Municipal Wastewater Salmonella Isolates

“…For S. Java, the CDC previously reported python-implicated outbreaks with isolates with 0 to 2 SNP differences; cases from other U.S. states that fell within the same cluster were not closely genetically related (up to 24 SNPs) (20). More recently, another S. Java outbreak from tuna reported clinical isolates with 0 to 4 SNP differences (21).…”

“…While a number of recent S. Java outbreaks have been linked to domestic exposure to aquatic pets or reptiles, including turtles (26), pythons (20), and aquariums (27), many outbreaks have been associated with contaminated food (28)(29)(30). Specifically, another multistate outbreak due to contaminated frozen raw fish was reported (21), which has far-reaching implications regarding the point of contamination; fish is often consumed raw as sushi (increasing the likelihood of infection) (21), and outbreaks may extend for months as frozen fish is thawed and consumed (15).…”

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“…Fish and seafood consumption by the population is relatively high (21 kg per capita per annual) and cooking methods may vary (raw consumption or to avoid overcooking seafood), allowing the survival of bacteria. S. Weltevreden is increasingly associated with human infections and outbreaks in Southeast Asia where it appears to be an emerging foodborne pathogen [35][36][37]. It is known to be wide-spread in water-related environments, possibly due to its ability to persist and multiply in tropical aquatic environments [9,[38][39][40].…”

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“…Similarly, a study identified the contamination of a cutting board by V. parahaemolyticus from raw squid as a cause of a gastroenteritis outbreak at a food bazaar in South Korea [ 65 ]. Further, there is a heightened health risk in consuming raw seafood, as evident from previous outbreaks associated with uncooked (or undercooked) fish, oysters, abalone or sea squirt [ 66 , 67 , 68 , 69 ].…”