Another Leafy Green E. coli Outbreak to be Investigated

2309MLEXH-1 Closeout Summary 

Closeout Date: 11/13/2023 

Classification: Outbreak 

Vehicle: Leafy Greens

Vehicle Status: Suspected 

Exposure Type: Multistate 

On September 25th, Washington state colleagues reported a cluster of E. coli O157 to CDC with a potential connection to Hill’s Science Diet dog food. PulseNet coded the investigation and CDC’s Enteric Zoonoses Activity (EZA) investigated. By early October, eight of ten ill people reported dog exposure; seven ill people had dog exposure with pet food information available and four reported Hill’s Science Diet dog food of different varieties. Three ill people also reported pet treats containing raw or fermented goat milk, these were not tested. FDA sampling of pet food retail products were all negative for E. coli O157 and other STECS. Additional epi information and a foodborne subcluster pointed toward a potential food source and EZA transferred the response to the Foodborne Outbreak Response Team (FORT) on October 5th, and FORT deployed the NHGQ on October 6th. 

In total, there were 22 cases from 10 states (AZ, FL (2), ID, IL (6), MI, MN, ND, OR, WA (6), and WI (2)). All isolates were highly related within 0-2 alleles by cgMLST. Isolation dates ranged from September 2nd – September 25th; estimated and reported onset dates ranged from August 30th – September 22nd. Ages ranged from 9 -72 years with a median age of 19 and 50% of ill people were female. Of 20 ill people with outcome information, 11 were hospitalized and there were no reported deaths. Three ill people developed HUS. 

Illinois identified a foodborne subcluster at a local high school where students ate at a sub sandwich bar. All six lab confirmed cases from Illinois were part of this subcluster. The local health department conduced a case control study and found lettuce and provolone cheese to be statistically significant. The high school served shredded romaine lettuce. Invoices and product samples were collected and were negative however, product sampled would not have been the same product consumed by students. Additionally, one asymptomatic food handler (no onset date) was identified who was shiga toxin 2 positive by PCR. The state lab was unable to isolate shiga toxin producing organism from the food handler via culture. 

One additional subcluster was identified in North Dakota. One ill person from ND and one ill person from MN ate at Suite Shots and both had meals with romaine lettuce. Invoices were collected. Additionally, Washington was able to collect shopper records for three ill people and all three reported Taylor Farms Turkey and Cheddar Pinwheel Sandwiches prior to illness. These sandwiches used spinach and were only distributed to OR and WA. There were no other purchases in common. 

FDA reviewed invoices from the two restaurant subclusters and the three shopper records from WA. FDA did not identify any initial commonalities with romaine or spinach. Due to the ill food handler, varying signals between romaine and spinach, and decline in illness uploads, FDA did not pursue additional traceback. 

CDC closed this investigation on November 13th as an outbreak with a suspected vehicle of leafy greens. CDC will report this outbreak to NORS with NORS ID 2309MLEXH-1.

Republished with permission from Bill Marler and Marler Clark. Copyright (c) Marler Clark LLP, PS. All rights reserved.