In 2015, the CDC reported on an outbreak and recall that occurred in 2014 – And, then a death certificate landed in my inbox.
On July 19, 2014, a packing company in California, Wawona Packing Co., voluntarily recalled certain lots of stone fruits, including whole peaches, nectarines, plums, and pluots, because of concern about contamination with Listeria monocytogenes based on internal company testing. On July 31, the recall was expanded to cover all fruit packed at their facility during June 1–July 17.
In early August 2014, a two-enzyme pulsed-field gel electrophoresis (PFGE) pattern shared by three L. monocytogenes isolates from stone fruit associated with the recall was uploaded to PulseNet, the national molecular subtyping network for foodborne disease surveillance. Four human isolates with isolation dates during the period May 8–July 8, 2014 (Illinois, Massachusetts, and South Carolina) and August 28 (Minnesota) were identified that had PFGE patterns indistinguishable from isolates from company A stone fruit.
Samples of stone fruits from Wawona Packing Co. collected after the recall yielded an additional 31 L. monocytogenes isolates, 22 of which were indistinguishable from the initial isolates by PFGE; three other PFGE patterns were identified that did not match any isolates from clinical specimens collected during May 1–August 31. Whole-genome sequencing (WGS) analysis by whole-genome multilocus sequence typing showed that isolates from the Massachusetts and Minnesota patients were highly related (<10 allele differences and <10 high-quality single nucleotide polymorphism differences) to the isolates from recalled stone fruits, whereas the Illinois and South Carolina isolates were not.
A review of the standardized Listeria Initiative exposure questionnaire for the Massachusetts patient showed that organic nectarine consumption was recorded, although the form does not specifically ask about stone fruit consumption. A subsequent interview using a questionnaire with questions about stone fruits indicated that the patient consumed nectarines and peaches purchased from stores that sold Wawona Packing Co. stone fruit. Traceback using receipts and shopper card data indicated the patient’s family purchased recalled fruit.
Strong evidence linked the Massachusetts case to recalled stone fruit, including food exposure interviews, receipt and shopper card data, and WGS results showing very high genetic relatedness between the patient’s isolate and isolates from nectarines.
Republished with permission from Bill Marler and Marler Clark. Copyright (c) Marler Clark LLP, PS. All rights reserved.