Notes from the Field: Outbreak of Listeriosis Associated with Consumption of Packaged Salad — United States and Canada, 2015–2016

Abstract

allele median (min-max) di erence at node 0-16 alleles di erent U.S. patient isolate U.S. salad isolate Canadian patient isolate Canadian salad isolate FIGURE. Phylogenetic tree by whole-genome multilocus sequence typing (wgMLST) of Listeria monocytogenes isolates* from patients and salad products with indistinguishable pulsed-field gel electrophoresis patterns-United States and Canada, † July 5, 2015-January 31, 2016 * By wgMLST, clinical and food isolates from the United States and Canada were closely related because they differed by a median of three alleles, with a range of 0-16 alleles. † 19 patients from nine U.S. states and six patients from Canada.

Nutrition and listeriosis during pregnancy: a systematic review

“…These focused solely on case–control and cohort studies to allow a comparison of nutritional exposures in cases compared with controls. We note important findings from the broader listeriosis outbreak literature including confirmation of high-risk foods reported here such as soft cheeses ( 42 ) , smoked fish ( 43 ) , processed meats ( 44 ) , ready-to-eat vegetables ( 45 , 46 ) and pâté ( 47 ) . We also highlight that this broader outbreak literature aids in identification of high-risk foods that were not significantly associated with listeriosis in the limited identified literature on case–control and cohort studies in pregnancy, such as rockmelon or cantaloupe ( 48 ) .…”

“…These foods are well documented as being associated with outbreaks in the past which have included pregnant women ( 48 ) . Where foods identified as high risk from population outbreaks such as vegetables ( 45 , 46 ) were not significantly associated with listeriosis here ( 10 ) , the authors also comment on potential limited power to detect significant associations. This supports the inclusion of these foods in current population recommendations for minimising listeriosis ( 8 ) .…”

A clade of Listeria monocytogenes serotype 4b variant strains linked to recent listeriosis outbreaks associated with produce from a defined geographic region in the US

“…This supports the assessment that this group may represent an emerging risk, having been responsible for four independent listeriosis events within less than 2 years, making further evaluation of this group as well as other 4bV strains critical. Furthermore, the association of this group of strains with atypical clinical cases, observed in otherwise healthy children [3, 47], gives cause for further concern and the need for more detailed characterization of these strains.…”

Risk Factors and Level of Listeria monocytogenes Contamination of Raw Pork in Retail Markets in China

“…A total of 256 cases of listeriosis were reported from 1964 to 2013 in China, involved 48 perinatal women, 86 neonatal and 122 non-perinatal women and more sporadic cases of listeriosis were reported in recent years ( Wu et al, 2008 ; Zhou et al, 2010 ; Sun et al, 2016 ). Listeriosis outbreaks have been reported in many countries including Japan, the United States and Europe ( European Food Safety Authority, 2011 ; Miya et al, 2015 ; Self et al, 2016 ). Human infections caused by L. monocytogenes have become a global health concern.…”