Published Date: 2006-09-04 00:00:00
Subject: PRO/AH/EDR> E. coli VTEC non-O157, lettuce - USA (UT)
Archive Number: 20060904.2521
E. COLI VTEC NON-O157, LETTUCE - USA (UTAH)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Thu 30 Aug 2006
From: ProMED-mail <firstname.lastname@example.org>
Source: Monterey Herald [edited]
Utah health officials say Salinas Valley lettuce may be responsible
for an _E. coli_ outbreak in their state in June 2006 that sickened
73 people, including 3 who developed kidney failure. The announcement
comes just 2 days after federal and state regulators began inspecting
local lettuce fields, plants and coolers in response to an increase
in lettuce-related _E. coli_ outbreaks over the past decade.
The iceberg lettuce was served in salads from a Wendy's restaurant in
North Ogden, Utah, which catered a teachers' conference at a junior
Just where between field and fork the lettuce was contaminated is
unknown, Utah health officials said.
In the past decade, said the FDA, more than 400 people nationwide
have been sickened in leafy-produce-related _E. coli_ outbreaks,
including 2 people who died. Investigations into these outbreaks,
often done weeks and months after they occur, rarely reveal how or
when the lettuce is tainted. In response, federal and state
regulators this week began the unprecedented monitoring of the local
[California - Mod.LL] industry, which produces at least 75 percent of
the nation's lettuce.
At least 2 women, one who ate salad at the conference and one who
didn't attend the conference but ate a hamburger with lettuce from
the same restaurant, experienced serious complications. One of the
women is now on a kidney transplant list. The other was on dialysis
for several weeks and nearly had to have her large intestine removed.
The outbreak involved _E. coli_ O121:H19, a rare form of the bacteria
that normally live in the intestines of humans and animals. Most _E.
coli_ outbreaks connected to leafy greens in the past decade have
involved the 0157:H7 strain.
Officials from the Weber-Morgan Health Department in Utah said they
narrowed their focus on the lettuce because it was the only food that
all of the sickened people ate. Wendy's International spokesman Denny
Lynch stressed on Tue, 29 Aug 2006, that the lettuce in question
wasn't tested following the outbreak. Instead, health officials are
using patients' eating histories to deduce what carried the bacteria,
he said. "There is no confirmation there was lettuce because there
was nothing to test," Lynch said.
Two days before the outbreak, Lynch said, the Wendy's in North Ogden
passed a routine health inspection "with flying colors." Once the
company learned about the outbreak, it asked the health department to
come back to the restaurant for an inspection, and nothing
inappropriate was found, he said.
[Byline: Dania Akkad]
[A map of Utah showing the location of North Ogden in the state can
be found at:
Although much attention has been paid to O157:H7 strains of _E. coli_
that (by virtue of toxin production) cause enterohemorrhagic disease
with or without hemolytic-uremic syndrome, other serotypes of _E.
coli_ have been associated with this illness as well.
_E. coli_ strains can be grouped by the presence of their O (somatic)
and H (flagellar) antigens, hence O157:H7. The toxins produced are
generally one or 2 Shiga toxins (stx1 and stx 2) as well as eae, a
protein intimin that is responsible for attachment of the organism
and mucosal effacing lesions and other virulence factors including
E-hly, espA, etp and katP.
Other _E. coli_ serogroups that have been associated with VTEC
disease include motile ones such as O26:H11 and O104:H21 and
nonmotile ones such as O111:NM (or H-). Such non-O157 isolates can be
obtained from sheep and cattle and although they cause as many as 30
percent of outbreaks of VTEC (1), appear to be somewhat less (or at
least more variably) virulent in a variety of in vivo and in vitro
assays (2-4). In analyzing the genetic and phenotypic profiles of
non-O157 groups, it has been found that they belong to their own
lineages and have unique profiles of virulence traits different from
O157 (5). The serogroups appearing to be most prominent are O26,
O111, O128, and O103 (6), the latter serotype being the implicated
strain in this outbreak.
If a laboratory is using sorbitol-MacConkey (sMAC) plates to identify
VTEC by virtue of O157's inability to ferment sorbitol, the non-O157
strains will be missed. In a 3 year pediatric study from the
University of Washington, USA (7), 1851 stool samples were processed
for sorbitol fermentation as well as toxin production by EIA, and 28
strains of O157 were found along with O103 (4 strains), O118 (2
strains), O111 (2 strains), and 3 other strains.
Clinically, the O157 infections had a higher frequency of bloody
stools, fecal leukocytes, and abdominal pain with shorter symptom
duration. Five (18 percent) of O157 infections developed HUS; none of
the non-O157 strains did. Since toxin assay did not identify all O157
strains found on sMAC plates, the investigators did not advocate
performing toxin assay alone. Non-O157 can produce hemolytic-uremic
syndrome, as demonstrated by a cluster of O121 cases associated with
a lake in Connecticut, USA (8).
Since toxin assays are not uniformly performed in many areas, and
most cases do not produce HUS, it is likely that cases due to
non-O157 strains are being missed. How frequent this phenomenon will
become over time is unclear.
1. Hussain HS, Omaye ST. Introduction to the food safety concerns of
verotoxin-producing Escherichia coli. Exp Biol Med 2003; 228: 331-2.
2. Blanco J, Blanco M, Blanco JE, et al. Verotoxin-producing
Escherichia coli in Spain: prevalence, serotypes, and virulence genes
of O157:H7 and non-O157 VTEC in ruminants, raw beef products and
humans. Exp Biol Med 2003; 228: 345- 51.
3. Law D, Kelly J. Use of heme and hemoglobin by Escherichia coli
O157 and other Shiga-toxin-producing E. coli serogroups. Infect Immun
1995; 63: 700-2.
4. Tzipori S, Wachsmuth KI, Smithers J, Jackson C. Studies in
gntobiotic piglets on non-O157:H7 Escherichia coli serotypes isolated
from patients with hemorrhagic colitis. Gastroenterology 1988; 94:
5. Schmidt H, Geitz C, Tarr PI, et al. Non-O157:H7 pathogenic
Shiga-toxin producing Escherichia coli: phenotypic and genetic
profiling of virulence traits and evidence for clonality. J Infect
Dis 1999; 179: 115-23.
6. Bettelheim KA. Role of non-O157 VTEC. Symp Ser Soc Appl Microbiol
2000; (29): 38-50S.
7. Klein EJ, Stapp JR, Calusen CR, et al. Shiga toxin-producing
Escherichia coli in children with diarrhea: a prospective
point-of-care study. J Pediatr 2002; 141: 172-7.
8. McCarthy TA, Barrett NL, Hadler JL, et al. Hemolytic-uremic
syndrome and Escherichia coli O121 at a lake in Connecticut, 1999.
Pediatrics 2001; 108: E59. - Mod.LL]