International Specialty Supply
Supplying Sprout Companies Throughout the World
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International Specialty Supply Supplying Sprout Companies Throughout the World
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820 East 20th Street Cookeville, TN 38501 USA 931 526 1106
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Alfalfa Sprouts Arizona, California, Colorado, and New Mexico, February-April 2001 February 6, 2002 On March 12, 2001, the California
Department of Health Services (CDHS) identified a cluster of Salmonella
Kottbus isolates with indistinguishable pulsed-field gel electrophoresis (PFGE)
patterns. During February 1--May 1, CDHS identified 23 patients with S.
Kottbus infections in several California counties and an additional patient from
Arizona. This report summarizes the results of the investigation of this
outbreak, which identified cases in four states and implicated alfalfa sprouts
produced at a single facility. The median age of
case-patients was 36 years (range: 9--72 years); 16 patients (67%) were female.
Twenty-one patients developed an acute diarrheal illness, and three patients had
urinary tract infections. Three patients were hospitalized. Using a standardized
questionnaire, a matched case-control study was conducted. A case was defined as
culture-confirmed S. Kottbus infection with onset after January 2001 in a
California resident with an isolate having the outbreak PFGE pattern. The first
10 reported California patients were matched with two controls by age group,
sex, and city prefix code. Fifteen (63%) of 23 patients ate alfalfa sprouts
during the week before becoming ill. A significant association was found between
eating alfalfa sprouts and illness (matched odds ratio: 5.5; 95% confidence
interval=1.2--26.1). No other food or restaurant exposure was significantly
associated with illness. Following the case-control study, 32 patients infected
with the outbreak strain of S. Kottbus were identified in California
(24), Arizona (six), Colorado (one), and New Mexico (one). A traceback
investigation identified a single sprout producer as the source of the
contaminated sprouts. Review of the sprouter's production records indicated that
a single seed lot was temporally associated with the dates of illness onset. A
culture of a sample of this seed lot yielded S. Kottbus. These seeds were
imported from Australia in November 2000, but no further information about the
distribution of this seed lot was available. Cultures from two floor drains in
the production facility also yielded S. Kottbus. Patient, seed, and
environmental isolates all had indistinguishable PFGE patterns. Although the implicated
seed lot was last used on March 29, the sprouter issued a voluntary recall of
all sprout products on April 17, and ceased all sprout production pending
further internal review of their production processes. Review of decontamination
and distribution records indicated that at least some seeds underwent heat
treatment followed by a 2,000-ppm sodium hypochlorite treatment for 15 minutes.
The U.S. Food and Drug Administration (FDA) recommends decontamination of seeds
with one or more treatments (e.g., soaking in a 20,000-ppm calcium hypochlorite
for 15 minutes) that have been approved for reduction of pathogens in seeds (1,2).
The effectiveness of alternative seed decontamination has not been established.
The sprout producers subsequently agreed to use only the FDA-recommended
20,000-ppm soak when sprout production resumed. Reported by: J
Mohle-Boetani, MD, B Werner, MD, M Polumbo, PhD, J Farrar, DVM, D Vugia, MD,
Acting State Epidemiologist, California Dept of Health Svcs. S Anderson, K
Komatsu, MPH, K Tagg, N Peterson, MD, State Epidemiologist, Arizona Dept of
Health Svcs. J Painter, DVM, S Van Dunn, MA, Div of Bacterial and Mycotic
Diseases, National Center for Infectious Diseases; K Winthrop, MD, M Beatty, MD,
EIS officers, CDC. Editorial
Note:
S.
Kottbus is a rarely reported cause of salmonellosis in the United States. During
1968--1998, a median of 42 S. Kottbus isolates were reported each year to
CDC through the Public Health Laboratory Information System (3). This was
the second outbreak of S. Kottbus since 1985 and the first outbreak
associated with sprouts. Since 1995, 15 outbreaks
of Salmonella spp. and two outbreaks of Escherichia coli O157:H7
infections associated with sprouts have been reported to CDC. Despite public
health advisories about the risks for eating raw sprouts, persons at high risk
for systemic infection continue to eat sprouts (4).
Two of the patients in this outbreak were immunocompromised, and one was a young
child. In each case, persons perceived raw sprouts as a "healthy" food
item. Sprouts may be
contaminated during seed production, germination, sprout processing, or consumer
handling and preparation (5,6). On the farm, sprouts seeds may become
contaminated through the use of untreated agricultural water, improperly
composted manure as fertilizer, excretion from domestic or wild animals, runoff
from domesticated animal production facilities, or improperly cleaned harvesting
or processing machines (5,6). The association of specific seed lots with
illness suggests that seeds are the most likely source for this and most other
sprout-related outbreaks (4).
Conditions suitable for seed sprouting also are ideal for increasing pathogenic
bacterial counts by several logs. The use of a 20,000-ppm
calcium hypochlorite soak before sprouting might reduce the risk for
sprout-related illness (4).
However, use of this high-dose soak is not completely effective, and outbreaks
continue to occur (7). Cracks and crevasses in the sprout seed may trap
pathogenic bacteria, making them inaccessible to lethal concentrations of
disinfectants (5). Because >20,000-ppm calcium hypochlorite soaks can
impair seed germination (5), alternative methods are needed to reduce the
risk for human disease following sprout consumption. In this outbreak, some of
the implicated sprouts were from seeds that had undergone a combination of heat
treatment and a 15-minute, low-dose calcium hypochlorite soak (2,000 ppm). The
subsequent outbreak suggests that this hybrid technique using a heat treatment
combined with a low-dose hypochlorite solution might not reduce adequately
pathogenic bacterial colony counts in alfalfa seeds. Reducing pathogenic
bacterial counts on seed during production and harvest could improve the
effectiveness of postharvest decontamination. Public education efforts
about the risks for eating uncooked sprouts need to be continued, particularly
among vulnerable populations (i.e., the elderly, young children, and
immunocompromised persons). CDC and FDA recommend that persons at high risk for
systemic infections not eat raw sprouts. For persons who continue to eat
sprouts, FDA recommends cooking before eating to reduce the risk for illness (8).
In response to this
outbreak, CDHS and the California Department of Education recommend that schools
stop serving uncooked sprouts to young children. Public health officials should
promote awareness of the role of raw sprout consumption in foodborne disease and
consider package labeling as a method for improving consumer awareness. In
addition, designation of sprout seed production for human consumption at seed
planting could further reduce the risk for sprout-associated outbreaks (5).
If sprout seed producers knew which sprout seed crops were dedicated for human
consumption before harvest, producers could focus on reducing potential
contamination in the field. Avoiding seed contamination in the field might
reduce the risk for consumer exposure to foodborne pathogens. References
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