Published Date: 2006-11-03 00:00:00
Subject: PRO/AH/EDR> Salmonellosis, serotype Typhimurium - USA (multistate) (03)
Archive Number: 20061103.3152
SALMONELLOSIS, SEROTYPE TYPHIMURIUM - USA (MULTISTATE) (03)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Fri, 3 Nov 2006
From: ProMED-mail <email@example.com>
Source: Food Production Daily [edited]
USA health officials investigating a salmonella
outbreak that infected 171 people across 19
States believe fresh produce may have been the
cause of the spread. Tomatoes and lettuce, which
many of the people affected more commonly ate,
are the early suspects believed to be responsible
for hospitalizing 11 people with salmonella
poisoning since the first reports of the illness on 1 Sep 2006.
Researchers from the CDC, in collaboration with
state departments of health and the FDA, have
been testing and interviewing victims to
determine the exact source of the salmonella
outbreak. No link has yet been made to any retailer, restaurant or food firm.
Tomatoes are particularly susceptible to
contamination as salmonella can form during
flowering and grow inside as the fruit develops,
rendering external washing useless.
Risk of infection from the most recent outbreak
is now considered small, the CDC has said,
following few new cases being detected.
Dr. David Acheson, FDA chief medical officer,
said the contaminated fresh food had likely now
been either eaten or thrown away. The agency is
not advising the public to avoid any types of food as a result.
There have been 9 salmonella outbreaks involving
tomatoes since 1990, while officials estimate
there are 1.4 million cases of salmonellosis, the
illness caused by the bacteria, in the USA every year.
[Byline: George Reynolds]
Date: 2 Nov 2006
From: Brent Barrett <firstname.lastname@example.org>
Source: CIDRAP (Center for Infectious Disease
Research And Policy) News [edited]
Tomatoes suspected in Salmonella outbreak
Federal investigators have turned up few solid
leads in a Salmonella outbreak that has sickened
171 people in 19 states, but some food safety
experts are suggesting that contaminated tomatoes
and infected food service workers might have played a role.
The Centers for Disease Control and Prevention
(CDC), in a press release yesterday, said DNA
fingerprinting revealed that _Salmonella enterica
serotype Typhimurium_ caused the outbreak. The
organism typically causes fever and nonbloody
diarrhea that resolves in a week. Of 73 patients
for whom the CDC has clinical data, 14 (19
percent) were hospitalized; no deaths have been reported.
The CDC said the outbreak appears to be over: "At
this time, few new cases are being detected, and
there is little evidence of continuing risk to
the public." The agency said the hunt for the
source of the outbreak may take days to weeks.
The New York Times reported yesterday that the
CDC detected the outbreak 2 weeks ago through a
national database that identifies patterns in
foodborne illness reports. The CDC said cases in
the outbreak have been reported since 1 Sep
. Most of the states affected are in the eastern half of the nation.
Carlota Medus, PhD, an epidemiologist with the
Minnesota Department of Health in St. Paul, said
samples from 14 patients in Minnesota matched the
outbreak strain on pulsed-field gel
electrophoresis (PFGE). She said most of the
Minnesota cases occurred between 12 Sep 
and 13 Oct . Minnesota, like some of the
other states involved in the outbreak, noticed
the pattern and contacted the CDC.
Medus said a case-control study in Minnesota
suggests the contamination source may be
tomatoes, adding that 5 cases appear to be linked
to the same fast-food restaurant. "Our study is
pretty small, though. It would be nice to have
more supporting information, so it's a little too soon to say," she said.
Salmonella bacteria are found in the intestines
of animals and can contaminate raw fruits and
vegetables that have been in contact with impure
water, animal manure, or an infected food
handler. Symptoms of infection usually begin from
12 to 36 hours after a person consumes
contaminated food. Most cases infection resolve
without medical treatment, but the pathogen can
cause serious and sometimes fatal illness in
children, elderly people, and those with weak immune systems.
Jack Guzewich, RS, MPH, director of emergency
coordination and response in the Food and Drug
Administration (FDA) Center for Food Safety and
Applied Nutrition (CFSAN), said _S. Typhimurium_
is the most common strain found in humans and
that the CDC usually sees about 5 to 10 cases
each month; the numbers usually peak in September
and October. "It is found in many places in the
food supply, but most often in poultry," he said.
Foodborne disease expert Craig W. Hedberg, PhD,
an associate professor of environmental health
sciences at the University of Minnesota School of
Public Health in Minneapolis, called the outbreak
fairly significant in its size and scope. "This
outbreak is most likely due to tomatoes, and many
cases were probably exposed through restaurants,"
he said, though health officials have not linked
the outbreak to a specific product, restaurant, or store.
David Acheson, MD, chief medical officer for the
FDA's CFSAN, told the Associated Press yesterday
that if fresh tomatoes are to blame in the
outbreak, it will be more difficult to trace the
original source of the contamination than it was
in the recent Escherichia coli O157:H7 outbreak
linked to fresh spinach. "You can get a lot of
information from looking at a bag. You don't get
that information from looking at a tomato," he told the AP.
During the summer of 2004, three Salmonella
outbreaks were traced to contaminated Roma
tomatoes. The outbreak sickened 561 people in 18
states and one Canadian province, the CDC said in
an April 2005 article in Morbidity and Mortality Weekly Report.
Hedberg said a major concern in
restaurant-related outbreaks of salmonellosis is
the role of infected food handlers in spreading
the disease. He said food service workers can
become ill from eating the contaminated product
and then expose customers to the disease when
they are still shedding the organism and don't use proper hygiene practices.
Medus was the lead author of a study in the
August  issue of the Journal of Food
Protection that tracked the role of food service
workers in restaurant-related Salmonella
outbreaks in Minnesota between 1995 and 2004.
Investigators found that 12 percent (129 of
1,033) food workers tested positive for
Salmonella. About half of those who tested
positive reported no recent gastrointestinal
illness. Bacterial shedding lasted about 30 days
in the workers who reported symptoms, but
averaged only 3 days in those who didn't.
The authors concluded that the duration of
Salmonella outbreaks in restaurants suggests an
ongoing contamination reservoir, and that
infected food workers are a likely source of disease transmission.
Hedberg, a coauthor of the report, said infected
food workers, as secondary transmission sources,
can increase the size and duration of the
outbreaks. "Restaurants should be stepping up
surveillance for illnesses in their food
workers," he said, adding that restaurants should
make sure that food workers who have
gastrointestinal illnesses are evaluated and treated.
Guzewich said the FDA depends on the CDC and
state and local health investigators to consider
food workers as the possible source of
contamination. "This investigation would be no
exception," he said, adding that Massachusetts
evaluated the food workers involved in its cases,
and all tested negative for Salmonella infection.
31 Oct 2006 CDC press release on Salmonella outbreak
8 Apri 2005, MMWR article "Outbreaks of
Salmonella Infections Associated with Eating Roma
Tomatoes�United States and Canada, 2004"
August 2006 Journal of Food Protection article
"Salmonella outbreaks in restaurants in
Minnesota, 1995 through 2003: evaluation of the
role of infected foodworkers"
CIDRAP overview of salmonellosis
[Byline: Lisa Schnirring]
[There is still no 'smoking tomato' here, but as
mentioned in the 1st posting above, salmonellae
can survive inside the ripening tomato, as shown
experimentally in the following paper: Guo X,
Chen J, Brackett RE and Beuchat LR: Survival of
Salmonellae on and in Tomato Plants from the Time
of Inoculation at Flowering and Early Stages of
Fruit Development through Fruit Ripening. Appl
Environl Microbiol 2001;67: 4760-64.
"The fate of salmonellae applied to tomato plants
was investigated. 5 _Salmonella_ serotypes were
used to inoculate tomato plants before and after
fruits set, either by injecting stems with
inoculum or brushing flowers with it. Ripe tomato
fruits were subjected to microbiological
analysis. Peptone wash water, homogenates of stem
scar tissues, and homogenates of fruit pulp were
serially diluted and plated on bismuth sulfite
agar before and after enrichment. Presumptive
_Salmonella_ colonies were confirmed by
serological tests, PCR assay using HILA2 primers,
and enterobacterial repetitive intergenic consensus PCR.
Of 30 tomatoes harvested from inoculated plants,
11 (37 percent) were positive for _Salmonella_.
Of the _Salmonella_-positive tomatoes, 43 and 40
percent, respectively, were from plants receiving
stem inoculation before and after flower set. 2
of 8 tomatoes produced from inoculated flowers
contained_Salmonella_. Higher percentages of
surface (82 percent) and stem scar tissue (73
percent) samples, compared to pulp of
_Salmonella_-positive tomatoes (55 percent),
harbored the pathogen. Of the 5 serotypes in the
inoculum, Montevideo was the most persistent,
being isolated from tomatoes 49 days after
inoculation, and Poona was the most dominant,
being present in 5 of 11 _Salmonella_-positive
tomatoes. Results suggest that _Salmonella_ cells
survive in or on tomato fruits from the time of
inoculation at flowering through fruit ripening.
Tomato stems and flowers are possible sites at
which Salmonella may attach and remain viable
during fruit development, thus serving as routes
or reservoirs for contaminating ripened fruit." - Mod.LL]