Traceback Investigations Research Articles

A multi-state outbreak of Salmonella Saintpaul in Australia associated with cantaloupe consumption

A multi-state outbreak of Salmonella enterica serovar Saintpaul infection occurred in Australia during October 2006. A case-control study conducted in three affected jurisdictions, New South Wales, Victoria and Australian Capital Territory, included 36 cases with the outbreak-specific strain of S. Saintpaul identified by multiple locus variable-number tandem repeat analysis (MLVA) in a faecal specimen and 106 controls. Consumption of cantaloupe (rockmelon) was strongly associated with illness (adjusted OR 23.9 95%, 95% CI 5.1-112.4). S. Saintpaul, with the outbreak MLVA profile, was detected on the skin of two cantaloupes obtained from an implicated retailer. Trace-back investigations did not identify the specific source of the outbreak strain of S. Saintpaul, but multiple Salmonella spp. were detected in environmental samples from farms and packing plants investigated during the trace-back operation. Cantaloupe production and processing practices pose a potential public health threat requiring regulatory and community educational interventions.

Vibrio cholerae O1 El Tor cluster in Sydney linked to imported whitebait

Three cases of cholera in women aged 71, 72 and 84 years were notified in November 2006 in Sydney, New South Wales. This is the first reported cluster of cholera in Australia for over 30 years, and was an unusual outbreak in patients with no history of recent travel to cholera-endemic areas. A food trace-back investigation found that the only exposure common to all cases was consumption of raw whitebait imported from Indonesia. This outbreak demonstrates that the practice of eating raw whitebait does occur in Australia, albeit in the process of taste-testing uncooked fritter batter. All three patients were undergoing long-term therapy with proton-pump inhibitors, which may have contributed to their susceptibility to the disease. A review of importation practices of food from cholera-endemic regions may be required to prevent future transmission.

Traceback Identification of an Ingredient (Pork Dewlap) as the Possible Source of Listeria monocytogenes Serotype 4b Contamination in Raw Chicken Products

In surveys conducted on finished product samples from a single poultry processing plant in Spain, Listeria monocytogenes was found in 14 different uncooked products. To track contamination patterns, 77 L. monocytogenes isolates were characterized by PCR-based serotyping, pulsed-field gel electrophoresis (PFGE) restriction analysis, and PCR-based allelic analysis of the virulence gene actA. Serotyping revealed that 12 isolates (15.6%) were of the L. monocytogenes serotype 4b complex (serotype 4b or the closely related serotypes 4d and 4e). A combination of endonucleases AscI and ApaI PFGE patterns yielded 15 different pulsotypes among all 77 tested isolates. All the serotype 4b isolates belonged to one pulsotype. Sequencing of the actA gene confirmed that all serotype 4b isolates corresponded to the same allelic subtype. The subtype was recovered from five product types, but its presence was not correlated with the production line or the date of isolation, suggesting a possible association of this strain with a common ingredient. This traceback investigation established that pork dewlap, an ingredient common to all the products contaminated with this strain, was the most probable source of L. monocytogenes 4b. The same 4b strain was isolated from four samples of pork dewlap from one specific supplier. After replacement of this contaminated ingredient in the fresh products, this strain of L. monocytogenes serotype 4b was not detected. This study confirms the effectiveness of molecular subtyping to control contamination by specific strains of L. monocytogenes and the importance of testing the different ingredients added to the food products.

Outbreak of Escherichia coli O157:H7 Infections Associated with Consumption of Beef Donair

The Calgary Health Region identified an outbreak of Escherichia coli O157:H7 infection in September 2004 following a fourfold increase in laboratory reports. Clinical isolates were indistinguishable by pulsed-field gel electrophoresis (PFGE), and the PFGE pattern was unique in North America. Most affected individuals reported beef donair consumption in 10-day food histories. We conducted a matched case-control study, inspected the implicated food premises, and conducted a traceback investigation of suspect ground beef to determine the source of the outbreak and implement prevention and control measures. A total of 43 laboratory-confirmed cases were identified, with symptom onsets between 8 September and 1 October 2004. Among 26 matched case-control pairs, consumption of beef donair from one of two locations of a local restaurant chain was the only statistically significant risk factor for infection (matched odds ratio undefined; P < 0.01). No samples of the implicated ground beef were available for microbiological testing. We identified several opportunities for time-temperature abuse and other factors that may have contributed to the serving of unsafe donair meat at the implicated restaurants. This outbreak highlighted gaps in food safety policy related to beef donair and similar products in Canada. Immediately following the outbreak, the Region implemented new safe food handling requirements and a Federal/Provincial/Territorial Working Group was established to make recommendations for national food safety policies specific to these products.

Evaluating the impact of public health notification of suspected transfusion‐transmissible hepatitis C virus infection and effectiveness of lookback and traceback investigations by Canadian Blood Services in British Columbia, Canada, August 2002 through February 2005

Suspected transfusion-transmissible infections (TTIs) have been reported to public health (PH) in British Columbia (BC) since August 2002. The impact of PH notification of suspected transfusion-transmissible hepatitis C virus (TT-HCV) infection over the first 2.5 years and the effectiveness of HCV lookback (LB) and traceback (TB) investigations conducted by Canadian Blood Services (CBS) in BC were evaluated. Suspected TT-HCV cases reported to CBS in BC between August 28, 2002, and February 28, 2005, were analyzed. The incremental yield of plausible TTIs from PH-reported suspected TTIs was calculated. The effectiveness of LB and TB investigations was assessed with respect to the impact of improved anti-HCV donor screening, the number of newly recognized HCV infections, and the timeliness of initiating investigations. Nine of 553 (1.6%) investigations were initiated after PH reporting, yielding an additional 2 of 237 (i.e., 0.8%) plausible TTIs. Ninety-two percent of investigations with transfused units involved transfusions before implementing second-generation anti-HCV enzyme immunoassay (EIA) donor screening. Almost one-third of HCV-infected persons in linked investigations (i.e., LB triggered by a TB and vice versa) were newly identified. Recently tested, PH-reported cases incurred a mean delay exceeding 6 months until initiating a LB or TB investigation. PH reporting of TTIs and investigating transfusions after second-generation anti-HCV EIA donor screening identified few plausible TT-HCV infections. Many HCV-infected recipients or lapsed donors first became aware of their infection status as a result of CBS investigations. The current process of reporting suspected TTIs incurs significant time delay.

Internationally Distributed Frozen Oyster Meat Causing Multiple Outbreaks of Norovirus Infection in Australia

Between November 2003 and January 2004, outbreaks of norovirus in 3 Australian jurisdictions involving 83 cases of illness were associated with imported oyster meat. Cohort studies were conducted in 2 jurisdictions to identify relative risks of illness for the consumption of oysters. A case series was conducted in the third jurisdiction. The cohort studies conducted in the first 2 jurisdictions identified relative risks of illness of 17 (95% confidence interval, 5-51) and 35 (95% confidence interval, 5-243), respectively, for the consumption of oysters. Multiple strains of norovirus were detected in fecal specimens from 8 of 14 patients and in 1 of the 3 batches of implicated oyster meat using seminested reverse-transcriptase polymerase chain reaction methods. Traceback investigations revealed that all oyster meat was harvested from the same estuary system in Japan within the same month. These outbreaks demonstrate the potential of foodborne disease to spread internationally and the need for national and international collaboration to investigate such outbreaks. Foodborne illness related to norovirus is underestimated because of underreporting of human cases and challenges in laboratory detection of viruses in foods, both of which can delay public health action.

Two Consecutive Large Outbreaks of Salmonella enterica Serotype Agona Infections in Infants Linked to the Consumption of Powdered Infant Formula

An increase of isolation of Salmonella Agona was observed in January through February 2005 among infants in France. Case-control study, food trace-back and microbiologic investigations were promptly carried out. A total of 141 confirmed cases <12 months of age were identified. Most had diarrhea (99%; bloody 56%) and fever (75%) and 36% were hospitalized for 5 days on average and none died. In the case-control analysis, all 23 cases and none of the 23 controls had consumed powdered formula of brand A (P < 10(-5)). Active follow up of all cases showed that after the withdrawal of formula A, cases that had consumed formula A decreased rapidly, but new cases had consumed another formula (brand B). The trace-back found that 5 batches of formula B had been manufactured on the same production line as formula A. Forty-four cases were linked to formula A and 92 to formula B. All routine controls performed by the producers were negative for Salmonella. However, enhanced microbiologic investigations yielded S. Agona in one of 176 samples of formula A, in 4 of 27 tins of formula B consumed by cases and in 6 of 420 environmental swabs from the production line. All clinical, food and environmental isolates were of the same pulsed-field gel electrophoresis profile. Powdered infant formulas are not sterile products and may contain low levels of Salmonella. Routine microbiologic controls are insufficient to detect a low-grade contamination, which may cause serious illness and outbreaks among infants.

Outbreak of Salmonella enterica serotype Manhattan infection associated with meat products, France, 2005.

Between August 2005 and March 2006 in France, 69 cases of Salmonella enterica serotype Manhattan (Salmonella Manhattan) were reported, 51 (74%) of them from southeastern France. At the time of the alert (November 2005), 13 cases and 33 controls were interviewed. Cases were more likely than controls to have eaten pork sausages (OR=5.9, confidence interval CI [1.3; 26.9]) and beef (OR=9.3, CI [1.3; 68.6]). At the same time, 19 strains of Salmonella Manhattan isolated from meat products in southeastern France, reported to the French food safety agency (Afssa, Agence française de sécurité sanitaire des aliments) in September and November 2005, had an indistinguishable PFGE profile to the 7 human isolates of Salmonella Manhattan from the outbreak in southeastern France. Trace-back investigations revealed that pork samples came from one wholesaler whose pork products had tested positive for S. Manhattan during routine food testing in August 2005. This wholesaler supplied retail outlets in southeastern France. Additionally, a slaughterhouse supplying the wholesaler was inspected and widespread contamination with Salmonella spp. and S. Manhattan was found. Cooperation between the national agencies in charge of human health (Institut de veille sanitaire, InVS) and food safety (Afssa) allowed us to determine the most probable source of contamination and to take appropriate control measures.

Development of computational models for the purpose of conducting individual livestock and premises traceback investigations utilizing National Animal Identification System-compliant data1

Many of the efforts surrounding the development of the National Animal Identification System have encompassed the identification of livestock production and handling premises as well as individuals or herds of animals, whereas little effort has been directed toward the ultimate goal of animal traceback within 48 h. A mock data set representative of the Colorado cattle population was created for modeling of cattle traceability. Using this data set, algorithms were developed to complete rapid and accurate traceback and traceforward of animals or premises or both. On July 19, 2005, the Colorado Department of Public Health and Environment, in conjunction with the Colorado Department of Agriculture, conducted a test exercise pertaining to homeland security. The exercise team randomly identified animal number 926,583 (of the 2 million total animals) as a potentially infected animal of interest and requested a traceback of this animal. Traceback was accomplished in 215 s, and 540 primary coresident animals were identified. However, due to animal movements, the number of coresidents (animals exposed, directly or indirectly, to the animal of interest) expanded with coresidency level (level 1 = direct contact; level 2 = direct contact with an animal that had direct contact with the animal of interest; level 3 = direct contact with an animal that had contact with an animal that had direct contact with the animal of interest, etc.) to more than 1.2 million coresidents at level 4, and more than 90% of all animals identified as a coresident at some level. In addition to the coresidency results, the premises containing the coresidents were identified and sorted by the number of coresidents. Because of animal movement, all 19,391 premises included in the data set had coresidents at some level. This exercise demonstrated the capability of the developed algorithms to complete rapid traceback and the complexity of the resulting animal traceback output.

Common Ground for the Control of Multidrug-Resistant Salmonella in Ground Beef

A strategy to combat multidrug-resistant (MDR) Salmonella in ground beef is urgently needed. A national multi-disciplinary meeting reviewed the epidemiology of MDR Salmonella infection and contamination in humans, animals, and retail meat. In spite of a recent overall decrease in human MDR Salmonella isolates, certain types, such as Salmonella enterica serotype Newport multidrug-resistant-AmpC strain and Salmonella enterica serotype Typhimurium definitive type (DT) 104, have persisted, and several recent large outbreaks of human infection have occurred. Key agencies that contribute to a safe ground beef supply were represented at the meeting and contributed to the discussion of possible control strategies from the farm to the table. Several of the control strategies suggested are unpopular to some, including restricting the use of antimicrobial agents in food animals, designation of multidrug-resistant Salmonella as an adulterant in ground beef, and improving the mechanisms for product trace-back investigations. Nevertheless, enhanced farm-based animal infection control, judicious veterinary and human antibiotic use, regulatory controls, and consumer practices will lead to important industry, veterinary, and public health outcomes.

Growth of Salmonella Enteritidis Phage Type 30 in Almond Hull and Shell Slurries and Survival in Drying Almond Hulls

Traceback investigation of a 2000 to 2001 outbreak of salmonellosis associated with consumption of raw almonds led to isolation of the outbreak strain Salmonella enterica serovar Enteritidis phage type (PT) 30 on three geographically linked almond farms. Interviews with these growers revealed that significant rain fell during the 2000 harvest when many almonds were drying on the ground. The objectives of this study were to document weather conditions during the 2000 harvest, determine the potential for growth of Salmonella Enteritidis PT 30 in hull or shell slurries, and evaluate survival of Salmonella Enteritidis PT 30 on wet almond hulls during drying. Dry almond hulls and in-shell kernels wetted for 24 h increased in weight by 250 to 300% and 100%, respectively. Both hull and shell slurries supported rapid growth of Salmonella Enteritidis PT 30 at 24°C; slurries containing hulls also supported growth at 15°C. Maximum Salmonella Enteritidis PT 30 concentrations of 6.2 and 7.8 log CFU/ml were observed at 15 and 24°C, respectively. Salmonella Enteritidis PT 30 grown in wet hulls that were incubated at 24°C survived drying at either 15 or 37°C. Reductions of 1 to 3 log CFU/g of dry hull were observed during drying; reductions generally declined as incubation time increased from 2 to 7 days. Evaluation of shipping records revealed that approximately 60% of outbreak-associated almonds had not been exposed to rain, eliminating this factor as the sole cause of the outbreak. However, the data provide evidence that wet almonds may be a greater risk for high concentrations of Salmonella, and specific guidelines should be established for harvesting and processing almonds that have been exposed to rain or other water sources.

Multistate Outbreak of Listeriosis Linked to Turkey Deli Meat and Subsequent Changes in US Regulatory Policy

Listeriosis, a life-threatening foodborne illness caused by Listeria monocytogenes, affects approximately 2500 Americans annually. Between July and October 2002, an uncommon strain of L. monocytogenes caused an outbreak of listeriosis in 9 states. We conducted case finding, a case-control study, and traceback and microbiological investigations to determine the extent and source of the outbreak and to propose control measures. Case patients were infected with the outbreak strain of L. monocytogenes between July and November 2002 in 9 states, and control patients were infected with different L. monocytogenes strains. Outcome measures included food exposure associated with outbreak strain infection and source of the implicated food. Fifty-four case patients were identified; 8 died, and 3 pregnant women had fetal deaths. The case-control study included 38 case patients and 53 control patients. Case patients consumed turkey deli meat much more frequently than did control patients (P = .008, by Wilcoxon rank-sum test). In the 4 weeks before illness, 55% of case patients had eaten deli turkey breast more than 1-2 times, compared with 28% of control patients (odds ratio, 4.5; 95% confidence interval, 1.3-17.1). Investigation of turkey deli meat eaten by case patients led to several turkey processing plants. The outbreak strain was found in the environment of 1 processing plant and in turkey products from a second. Together, the processing plants recalled > 30 million pounds of products. Following the outbreak, the US Department of Agriculture's Food Safety and Inspection Service issued new regulations outlining a L. monocytogenes control and testing program for ready-to-eat meat and poultry processing plants. Turkey deli meat was the source of a large multistate outbreak of listeriosis. Investigation of this outbreak helped guide policy changes designed to prevent future L. monocytogenes contamination of ready-to-eat meat and poultry products.

Multistate Outbreak ofListeria monocytogenesInfection Linked to Delicatessen Turkey Meat

Despite a decreasing incidence of listeriosis in the United States, molecular subtyping has increased the number of recognized outbreaks. In September 2000, the New York City Department of Health identified a cluster of infections caused by Listeria monocytogenes isolates with identical molecular subtypes by pulsed-field gel electrophoresis (PFGE) and ribotyping. To determine the magnitude of the outbreak and identify risk factors for infection, we notified state health departments and conducted a case-control study. A case was defined as a patient or mother-infant pair infected with Listeria monocytogenes whose isolate yielded the outbreak PFGE pattern. Controls were patients infected with Listeria monocytogenes whose isolate yielded a different PFGE pattern. Patients were asked about food and drink consumed during the 30 days before the onset of illness. Between May and December 2000, there were 30 clinical isolates of Listeria monocytogenes with identical PFGE patterns identified in 11 US states. Cases of infection caused by these isolates were associated with 4 deaths and 3 miscarriages. A case-control study implicated sliced processed turkey from a delicatessen (Mantel-Haenszel odds ratio, 8.0; 95% confidence interval, 1.2-43.3). A traceback investigation identified a single processing plant as the likely source of the outbreak, and the company voluntarily recalled 16 million pounds of processed meat. The same plant had been identified in a Listeria contamination event that had occurred more than a decade previously. Prevention of persistent L. monocytogenes contamination in food processing plants presents a critical challenge to food safety professionals.

An Outbreak of Salmonella München in Germany Associated with Raw Pork Meat

In summer 2001, an outbreak of Salmonella München occurred in Germany. We conducted descriptive epidemiology and hypothesis-generating interviews among case patients, two retrospective cohort studies, and a case-control study of subout-breaks. We performed pulsed-field gel electrophoresis (PFGE) from selected patient isolates and a limited trace-back investigation for analytical purposes. Four states were consecutively affected: Saxonia (SX), Brandenburg (BB), Berlin (BE), and Baden-Württemberg (BW). Although hypothesis-generating interviews failed to identify a plausible food item, descriptive data and investigations of the suboutbreaks suggested pork meat as a probable source in three states (SX, BB, and BE) but not in BW. The PFGE profiles from isolates of case patients in the first three states were indistinguishable but differed from PFGE profiles of case patients in BW. Trace-back investigation suggested that contamination of pork meat occurred early in the rearing-production chain. This outbreak demonstrates how contamination early in the production process that can yield different end products may complicate multistate outbreaks. Investigation of suboutbreaks and use of the trace-back method as investigational tools may be useful adjuncts in solving the problem of multistate outbreaks.

Outbreak of cyclosporiasis in British Columbia associated with imported Thai basil

Sporadic outbreaks of cyclosporiasis, a common cause of protracted diarrhoea in underdeveloped countries, are often undetected and undiagnosed in industrial countries. In May 2001, an outbreak of Cyclospora cayetanensis gastroenteritis was identified in British Columbia, Canada, with 17 reported cases. We conducted a case-control study involving 12 out of the 17 reported and confirmed case patients. Eleven (92%) of the patients had consumed Thai basil, an essential ingredient in Vietnamese cuisine, compared to 3 out of 16 (19%) of the control patients (P = 0.003). Trace-back investigations implicated Thai basil imported via the United States as the vehicle for this outbreak. This is the first documented sporadic outbreak of cyclosporiasis linked to Thai basil in Canada, and the first outbreak of cyclosporiasis identified in an ethnic immigrant population. This outbreak provides the opportunity to increase our understanding of this emerging pathogen and improve on our prevention and control for future outbreaks.

A Case Study of a Massive Staphylococcal Food Poisoning Incident

In the summer of 1998, approximately 8000 individuals gathered to celebrate a Catholic priest's ordination in Minas Gerais, Brazil. Within hours of food consumption, 4000 patients experienced acute gastroenteritis, and approximately 2000 (50%) overwhelmed Emergency Departments of 26 local hospitals. Of the triaged patients, 396 ( approximately 20%) required subsequent admission, and of these patients, 81 ( approximately 20%) were admitted to intensive care units. A total of 16 ( approximately 20% of those admitted to the ICU) patients progressed on to develop irreversible multi-system shock and expired while hospitalized. The trace-back investigation implicated food preparers who were culture positive for enterotoxigenic Staphylococcus aureus as the source of contamination. This study provides information on the magnitude and severity of oral exposure to Staphylococcal enterotoxin.

A multistate outbreak of Escherichia coli O157:H7 infection linked to consumption of beef tacos at a fast-food restaurant chain.

We investigated a multistate outbreak of Escherichia coli O157:H7 infections. Isolates from 13 case patients from California, Nevada, and Arizona were matched by pulsed-field gel electrophoresis subtyping. Five case patients (38%) were hospitalized, and 3 (23%) developed hemolytic uremic syndrome; none died. The median age was 12 years (range, 2-75 years), and 10 (77%) were female. Case-control studies found an association between illness and eating beef tacos at a national Mexican-style fast-food restaurant chain (88% of cases versus 38% of controls; matched OR, undefined; 95% confidence interval, 1.49 to infinity; P=.009). A trace-back investigation implicated an upstream supplier of beef, but a farm investigation was not possible. This outbreak illustrates the value of employing hospital laboratory-based surveillance to detect local clusters of infections and the effectiveness of using molecular subtyping to identify geographically dispersed outbreaks. The outbreak investigation also highlights the need for a more efficient tracking system for food products.

Alfalfa seed decontamination in a Salmonella outbreak.

Based on in vitro data, the U.S. Food and Drug Administration recommends chemical disinfection of raw sprout seeds to reduce enteric pathogens contaminating the seed coats. However, little is known about the effectiveness of decontamination at preventing human disease. In 1999, an outbreak of Salmonella enterica serotype Mbandaka occurred in Oregon, Washington, Idaho, and California. Based on epidemiologic and pulsed-field gel electrophoresis evidence from 87 confirmed cases, the outbreak was linked to contaminated alfalfa seeds grown in California’s Imperial Valley. Trace-back and trace-forward investigations identified a single lot of seeds used by five sprout growers during the outbreak period. Cases of salmonellosis were linked with two sprout growers who had not employed chemical disinfection; no cases were linked to three sprout growers who used disinfection. This natural experiment provides empiric evidence that chemical disinfection can reduce the human risk for disease posed by contaminated seed sprouts.

Alfalfa Sprouts and Salmonella Kottbus Infection: A Multistate Outbreak following Inadequate Seed Disinfection with Heat and Chlorine

Raw sprouts have been implicated in a number of foodborne disease outbreaks. Because contaminated seeds are usually responsible, many sprout producers attempt to disinfect seeds before germination and detect sprout contamination during production. In March 2001, we detected an increased number of Salmonella serotype Kottbus isolates in California. Overall, we identified 31 cases from three western states. To identify the cause, we conducted a case-control study with the first 10 identified case-patients matched to 20 controls by age, sex, and residential area. Our case-control study found illness to be statistically associated with alfalfa sprout consumption. The traceback investigation implicated a single sprouter, where environmental studies yielded Salmonella Kottbus from ungerminated seeds and floor drains within the production facility. Pulsed-field gel electrophoresis patterns of all patient, seed, and floor drain Salmonella Kottbus isolates were indistinguishable. Most implicated sprouts were from seeds that underwent heat treatment and soaking with a 2,000-ppm sodium hypochlorite solution rather than the Food and Drug Administration (FDA)-recommended 20,000-ppm calcium hypochlorite soak. Other implicated seeds had been soaked in a calcium hypochlorite solution that, when tested, measured only 11,000 ppm. The outbreak might have been averted when screening tests of sprout irrigation water detected Salmonella in January; however, confirmatory testing of these samples was negative (but testing improperly utilized refrigerated irrigation water). Producers should use the enrichment broth of positive screening samples, not refrigerated irrigation water, for confirmatory testing. Until other effective disinfection technologies are developed, producers should adhere to FDA recommendations for sprout seed disinfection.

Escherichia coli O157 and Salmonella infections associated with sprouts in California, 1996-1998.

In California, from 1996 through 1998, more than 50% of multicounty outbreaks with confirmed food vehicles were related to alfalfa or clover sprouts. To summarize investigations of sprout-associated outbreaks. Matched case-control studies. California. Outbreak-associated patients and matched population controls. Matched odds ratios and 95% CIs; traceback and environmental investigations of sprout and seed growers; and pulsed-field gel electrophoresis of isolates from patients, sprouts, and seeds. Five sprout-associated outbreaks of salmonellosis and one outbreak of infection with nonmotile Shiga toxin-producing Escherichia coli O157 occurred. Six hundred patients had culture-confirmed disease, and two died. It is estimated that these outbreaks caused 22 800 cases of gastrointestinal illness or urinary tract infection. In the case-control studies, odds ratios for the association between illness and alfalfa sprout consumption ranged from 5.0 to infinity (all were statistically significant). Three sprout growers were implicated, and each was associated with two outbreaks. Outbreak strains of Salmonella were isolated from sprouts supplied by two sprout growers and from seeds used by the third sprout grower. As currently produced, sprouts can be a hazardous food. Seeds can be contaminated before sprouting, and no method can eliminate all pathogens from seeds. Seed and sprout growers should implement measures to decrease contamination. The general public should recognize the risks of eating sprouts, and populations at high risk for complications from salmonellosis or E. coli O157 infection should avoid sprout consumption.