Multistate outbreaks of salmonellosis linked to contact with backyard poultry-United States, 2015-2022.

AIMS: Contact with backyard poultry (i.e., privately-owned, non-commercial poultry) was first associated with a multistate outbreak of salmonellosis in 1955. In recent years, backyard poultry-associated salmonellosis outbreaks have caused more illnesses in the United States than salmonellosis outbreaks linked to any other type of animal. Here, we describe the epidemiology of outbreaks from 2015-2022 to inform prevention efforts. METHODS AND RESULTS: During 2015-2022, there were 88 multistate backyard poultry-associated salmonellosis outbreaks and 7866 outbreak-associated illnesses caused by 21 different Salmonella serotypes. Salmonella Enteritidis accounted for the most outbreaks (n = 21) and illnesses (n = 2400) of any serotype. Twenty-four percent (1840/7727) of patients with available information were <5 years of age. In total, 30% (1710/5644) of patients were hospitalized, and nine deaths were attributed to Salmonella infection. Throughout this period, patients reported behaviours that have a higher risk of Salmonella transmission, including kissing or snuggling poultry or allowing poultry inside their home. CONCLUSIONS: Despite ongoing efforts to reduce the burden of salmonellosis associated with backyard poultry, outbreak-associated illnesses have nearly tripled and hospitalizations more than quadrupled compared with those in 1990-2014. Because this public health problem is largely preventable, government officials, human and veterinary healthcare providers, hatcheries, and retailers might improve the prevention of illnesses by widely disseminating health and safety recommendations to the public and by continuing to develop and implement prevention measures to reduce zoonotic transmission of Salmonella by backyard poultry.

Investigation of a Multistate Outbreak of Listeria monocytogenes Infections Linked to Frozen Vegetables Produced at Individually Quick-Frozen Vegetable Manufacturing Facilities.

In 2016, the U.S. Food and Drug Administration (FDA), the Centers for Disease Control and Prevention (CDC), and state partners investigated nine Listeria monocytogenes infections linked to frozen vegetables. The investigation began with two environmental L. monocytogenes isolates recovered from Manufacturer A, primarily a processor of frozen onions, that were a match by whole genome sequencing (WGS) to eight clinical isolates and historical onion isolates with limited collection details. Epidemiologic information, product distribution, and laboratory evidence linked suspect food items, including products sourced from Manufacturer B, also a manufacturer of frozen vegetable/fruit products, with an additional illness. The environmental isolates were obtained during investigations at Manufacturers A and B. State and federal partners interviewed ill people, analyzed shopper card data, and collected household and retail samples. Nine ill persons between 2013 and 2016 were reported in four states. Of four ill people with information available, frozen vegetable consumption was reported by three, with shopper cards confirming purchases of Manufacturer B brands. Two identified outbreak strains of L. monocytogenes (Outbreak Strain 1 and Outbreak Strain 2) were a match to environmental isolates from Manufacturer A and/or isolates from frozen vegetables recovered from open and unopened product samples sourced from Manufacturer B; the investigation resulted in extensive voluntary recalls. The close genetic relationship between isolates helped investigators determine the source of the outbreak and take steps to protect public health. This is the first known multistate outbreak of listeriosis in the United States linked to frozen vegetables and highlights the significance of sampling and WGS analyses when there is limited epidemiologic information. Additionally, this investigation emphasizes the need for further research regarding food safety risks associated with frozen foods.

Multistate reptile- and amphibian-associated salmonellosis outbreaks in humans, United States, 2009-2018.

Non-typhoidal Salmonella cause an estimated 1.4 million human illnesses, 26,000 hospitalizations and 400 deaths annually in the United States. Approximately 11% of these infections are attributed to animal contact. Reptiles and amphibians are known sources of salmonellosis; young children (aged <5 years) are disproportionately affected by reptile- and amphibian-associated salmonellosis (RAAS) outbreaks. We describe multistate RAAS outbreaks to characterize illnesses and inform prevention efforts. RAAS outbreaks were defined as ≥2 culture-confirmed human Salmonella infections with similar pulsed-field gel electrophoresis patterns and epidemiologic, laboratory or traceback evidence linking them to a common reptile/amphibian exposure. Data sources included the Animal Contact Outbreak Surveillance System; CDC Outbreak Response and Prevention Branch's outbreak management database; PulseNet, the national molecular subtyping network for foodborne disease surveillance in the United States; and the National Antimicrobial Resistance Monitoring System. Twenty-six RAAS outbreaks were reported during 2009-2018, resulting in 1465 illnesses and 306 hospitalizations. The outbreaks were associated with turtles (19), lizards (5), snakes (1) and frogs (1). Sixteen (61.5%) outbreaks were linked to small turtles (<4 inches), resulting in 914 illnesses. Forty-nine percent of outbreak-associated patients were aged <5 years. Of 362 patients/caregivers interviewed, 111 (30.7%) were aware that reptiles/amphibians can carry Salmonella. Among 267 patient isolates with antimicrobial susceptibility information, 20 (7.5%) were non-susceptible to ≥1 antibiotic used to treat human salmonellosis. RAAS outbreaks result in considerable morbidity, particularly among young children. Illnesses linked to small turtles are preventable through education, targeted outreach to caregivers and paediatricians, and when appropriate, enforcement. Historically, individual states and jurisdictions have enforced existing or promulgated new authorities to address outbreaks. Preventing future RAAS outbreaks requires addressing challenges related to the illegal sale/distribution of small turtles; and for legal reptile sales, providing information on RAAS risk to consumers at point of sale to support informed pet ownership decisions.

A 2019 Outbreak Investigation of Hepatitis A Virus Infections in the United States Linked to Imported Fresh Blackberries.

Globally, hepatitis A virus (HAV) is one of the most common agents of acute viral hepatitis and causes approximately 1.4 million cases and 90,000 deaths annually despite the existence of an effective vaccine. In 2019, federal, state, and local partners investigated a multi-state outbreak of HAV infections linked to fresh blackberries sourced from multiple suppliers in Michoacán, Mexico. A total of 20 individuals with outbreak-related HAV infection were reported in seven states, including 11 hospitalizations, and no deaths. The Food and Drug Administration (FDA), the Centers for Disease Control and Prevention (CDC), and Nebraska State and Douglas County Health Departments conducted a traceback investigation for fresh blackberries reportedly purchased by 16 ill persons. These individuals reported purchasing fresh blackberries from 11 points of service from September 16 through 29, 2019 and their clinical isolates assessed through next-generation sequencing and phylogenetic analysis were genetically similar. The traceback investigation did not reveal convergence on a common grower or packing house within Mexico, but all of the blackberries were harvested from growers in Michoacán, Mexico. FDA did not detect the pathogen after analyzing fresh blackberry samples from four distributors, one consumer, and from nine importers at the port of entry as a result of increased screening. Challenges included gaps in traceability practices and the inability to recover the pathogen from sample testing, which prohibited investigators from determining the source of the implicated blackberries. This multi-state outbreak illustrated the importance of food safety practices for fresh produce that may contribute to foodborne illness outbreaks.

Multistate outbreak of Salmonella Typhimurium linked to pet hedgehogs, United States, 2018-2019.

In December 2018, PulseNet, the national laboratory network for enteric disease surveillance, identified an increase in Salmonella Typhimurium isolates with an uncommon pulsed-field gel electrophoresis pattern which was previously isolated from hedgehogs. CDC, state, and local health partners interviewed patients with a questionnaire that focused on hedgehog exposures, conducted traceback of patients' hedgehog purchases, and collected hedgehog faecal pellets and environmental samples. Isolates in this outbreak were analysed using core-genome multi-locus sequence typing (cgMLST) and compared to sequence data from historic clinical isolates from a 2011-2013 outbreak of Salmonella Typhimurium illnesses linked to pet hedgehogs. Fifty-four illnesses in 23 states were identified between October 2018 and September 2019. Patients ranged from <1 to 95 years, and 65% were female. Eight patients were hospitalized. Eighty-one per cent (29/36) of patients interviewed reported contact with a hedgehog before becoming ill; of these, 21 (72%) reported owning a hedgehog. Analysis of 53 clinical, 11 hedgehog, and two hedgehog bedding isolates from this outbreak, seven hedgehog isolates obtained prior to this outbreak, and two clinical isolates from the 2011-2013 outbreak fell into three distinct groupings (37 isolates in Clade 1 [0-10 alleles], 28 isolates in Clade 2 [0-7 alleles], and eight isolates in Clade 3 [0-12 alleles]) and were collectively related within 0-31 alleles by cgMLST. Purchase information available from 20 patients showed hedgehogs were purchased from multiple breeders across nine states, a pet store, and through an online social media website; a single source of hedgehogs was not identified. This outbreak highlights the ability of genetic sequencing analysis to link historic and ongoing Salmonella illness outbreaks and demonstrates the strain of Salmonella linked to hedgehogs might continue to be a health risk to hedgehog owners unless measures are taken to prevent transmission.

Salmonella illness outbreaks linked to backyard poultry purchasing during the COVID-19 pandemic: United States, 2020.

Poultry contact is a risk factor for zoonotic transmission of non-typhoidal Salmonella spp. Salmonella illness outbreaks in the United States are identified by PulseNet, the national laboratory network for enteric disease surveillance. During 2020, PulseNet observed a 25% decline in the number of Salmonella clinical isolates uploaded by state and local health departments. However, 1722 outbreak-associated Salmonella illnesses resulting from 12 Salmonella serotypes were linked to contact with privately owned poultry, an increase from all previous years. This report highlights the need for continued efforts to prevent backyard poultry-associated outbreaks of Salmonella as ownership increases in the United States.

Ongoing Outbreak of Extensively Drug-Resistant Campylobacter jejuni Infections Associated With US Pet Store Puppies, 2016-2020.

Importance: Extensively drug-resistant Campylobacter jejuni infections cannot be treated with any commonly recommended antibiotics and pose an increasing public health threat. Objectives: To investigate cases of extensively drug-resistant C jejuni associated with pet store puppies and describe the epidemiologic and laboratory characteristics of these infections. Design, Setting, and Participants: In August 2017, health officials identified, via survey, patients with C jejuni infections who reported contact with puppies sold by pet stores. In conjunction with state and federal partners, the Centers for Disease Control and Prevention investigated cases of culture-confirmed C jejuni infections in US patients with an epidemiologic or molecular association with pet store puppies between January 1, 2016, and February 29, 2020. Available records from cases occurring before 2016 with genetically related isolates were also obtained. Main Outcomes and Measures: Patients were interviewed about demographic characteristics, health outcomes, and dog exposure during the 7 days before illness onset. Core genome multilocus sequence typing was used to assess isolate relatedness, and genomes were screened for resistance determinants to predict antibiotic resistance. Isolates resistant to fluoroquinolones, macrolides, and 3 or more additional antibiotic classes were considered to be extensively drug resistant. Cases before 2016 were identified by screening all sequenced isolates submitted for surveillance using core genome multilocus sequence typing. Results: A total of 168 patients (median [interquartile range] age, 37 [19.5-51.0] years; 105 of 163 female [64%]) with an epidemiologic or molecular association with pet store puppies were studied. A total of 137 cases occurred from January 1, 2016, to February 29, 2020, with 31 additional cases dating back to 2011. Overall, 117 of 121 patients (97%) reported contact with a dog in the week before symptom onset, of whom 69 of 78 (88%) with additional information reported contact with a pet store puppy; 168 isolates (88%) were extensively drug resistant. Traceback investigation did not implicate any particular breeder, transporter, distributer, store, or chain. Conclusions and Relevance: Strains of extensively drug-resistant C jejuni have been circulating since at least 2011 and are associated with illness among pet store customers, employees, and others who come into contact with pet store puppies. The results of this study suggest that practitioners should ask about puppy exposure when treating patients with Campylobacter infection, especially when they do not improve with routine antibiotics, and that the commercial dog industry should take action to help prevent the spread of extensively drug-resistant C jejuni from pet store puppies to people.

A Series of Papaya-Associated Salmonella Illness Outbreak Investigations in 2017 and 2019: A Focus on Traceback, Laboratory, and Collaborative Efforts.

ABSTRACT: In 2017 and 2019, five outbreaks of infections from multiple strains of Salmonella linked to the consumption of whole, fresh Maradol papayas were reported in the United States, resulting in 325 ill persons. Traceback, laboratory, and epidemiologic evidence indicated papayas as the likely vehicle for each of these outbreaks and identified the source of papayas. State and U.S. Food and Drug Administration (FDA) laboratories recovered Salmonella from papaya samples from various points of distribution, including at import entry, and conducted serotyping, pulsed-field gel electrophoresis, and phylogenetic analyses of whole genome sequencing data. Federal and state partners led traceback investigations to determine the source of papayas. Four different suppliers of papayas were linked by traceback and laboratory results to five separate outbreaks of Salmonella infections associated with papayas. In 2017, multiple states tested papaya samples collected at retail, and Maryland and Virginia investigators recovered strains of Salmonella associated with one outbreak. FDA collected 183 papaya samples in 2017, and 11 samples yielded 62 isolates of Salmonella. Eleven serotypes of Salmonella were recovered from FDA papaya samples, and nine serotypes were closely related genetically by pulsed-field gel electrophoresis and whole genome sequencing to clinical isolates of four outbreaks, including the outbreak associated with positive state sample results. Four farms in Mexico were identified, and their names were released to the general public, retailers, and foreign authorities. In 2019, FDA collected 119 papaya samples, three of which yielded Salmonella; none yielded the 2019 outbreak strain. Investigators determined that papayas of interest had been sourced from a single farm in Campeche, Mexico, through traceback. This information was used to protect public health through public guidance, recalls, and import alerts and helped FDA collaborate with Mexican regulatory partners to enhance the food safety requirements for papayas imported from Mexico.

COVID-19 Outbreak Among Employees at a Meat Processing Facility - South Dakota, March-April 2020.

On March 24, 2020, the South Dakota Department of Health (SDDOH) was notified of a case of coronavirus disease 2019 (COVID-19) in an employee at a meat processing facility (facility A) and initiated an investigation to isolate the employee and identify and quarantine contacts. On April 2, when 19 cases had been confirmed among facility A employees, enhanced testing for SARS-CoV-2, the virus that causes COVID-19, was implemented, so that any employee with a COVID-19-compatible sign or symptom (e.g., fever, cough, or shortness of breath) could receive a test from a local health care facility. By April 11, 369 COVID-19 cases had been confirmed among facility A employees; on April 12, facility A began a phased closure* and did not reopen during the period of investigation (March 16-April 25, 2020). At the request of SDDOH, a CDC team arrived on April 15 to assist with the investigation. During March 16-April 25, a total of 929 (25.6%) laboratory-confirmed COVID-19 cases were diagnosed among 3,635 facility A employees. At the outbreak's peak, an average of 67 cases per day occurred. An additional 210 (8.7%) cases were identified among 2,403 contacts of employees with diagnosed COVID-19. Overall, 48 COVID-19 patients were hospitalized, including 39 employees and nine contacts. Two employees died; no contacts died. Attack rates were highest among department-groups where employees tended to work in proximity (i.e., <6 feet [2 meters]) to one another on the production line. Cases among employees and their contacts declined to approximately 10 per day within 7 days of facility closure. SARS-CoV-2 can spread rapidly in meat processing facilities because of the close proximity of workstations and prolonged contact between employees (1,2). Facilities can reduce this risk by implementing a robust mitigation program, including engineering and administrative controls, consistent with published guidelines (1).

Comparison of Molecular Subtyping and Antimicrobial Resistance Detection Methods Used in a Large Multistate Outbreak of Extensively Drug-Resistant Campylobacter jejuni Infections Linked to Pet Store Puppies.

Campylobacter jejuni is a leading cause of enteric bacterial illness in the United States. Traditional molecular subtyping methods, such as pulsed-field gel electrophoresis (PFGE) and 7-gene multilocus sequence typing (MLST), provided limited resolution to adequately identify C. jejuni outbreaks and separate out sporadic isolates during outbreak investigations. Whole-genome sequencing (WGS) has emerged as a powerful tool for C. jejuni outbreak detection. In this investigation, 45 human and 11 puppy isolates obtained during a 2016-2018 outbreak linked to pet store puppies were sequenced. Core genome multilocus sequence typing (cgMLST) and high-quality single nucleotide polymorphism (hqSNP) analysis of the sequence data separated the isolates into the same two clades containing minor within-clade differences; however, cgMLST analysis does not require selection of an appropriate reference genome, making the method preferable to hqSNP analysis for Campylobacter surveillance and cluster detection. The isolates were classified as sequence type 2109 (ST2109)-a rarely seen MLST sequence type. PFGE was performed on 38 human and 10 puppy isolates; PFGE patterns did not reliably predict clustering by cgMLST analysis. Genetic detection of antimicrobial resistance determinants predicted that all outbreak-associated isolates would be resistant to six drug classes. Traditional antimicrobial susceptibility testing (AST) confirmed a high correlation between genotypic and phenotypic antimicrobial resistance determinations. WGS analysis linked C. jejuni isolates in humans and pet store puppies even when canine exposure information was unknown, aiding the epidemiological investigation during the outbreak. WGS data were also used to quickly identify the highly drug-resistant profile of these outbreak-associated C. jejuni isolates.

COVID-19 Among Workers in Meat and Poultry Processing Facilities - 19 States, April 2020.

Congregate work and residential locations are at increased risk for infectious disease transmission including respiratory illness outbreaks. SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is primarily spread person to person through respiratory droplets. Nationwide, the meat and poultry processing industry, an essential component of the U.S. food infrastructure, employs approximately 500,000 persons, many of whom work in proximity to other workers (1). Because of reports of initial cases of COVID-19, in some meat processing facilities, states were asked to provide aggregated data concerning the number of meat and poultry processing facilities affected by COVID-19 and the number of workers with COVID-19 in these facilities, including COVID-19-related deaths. Qualitative data gathered by CDC during on-site and remote assessments were analyzed and summarized. During April 9-27, aggregate data on COVID-19 cases among 115 meat or poultry processing facilities in 19 states were reported to CDC. Among these facilities, COVID-19 was diagnosed in 4,913 (approximately 3%) workers, and 20 COVID-19-related deaths were reported. Facility barriers to effective prevention and control of COVID-19 included difficulty distancing workers at least 6 feet (2 meters) from one another (2) and in implementing COVID-19-specific disinfection guidelines.* Among workers, socioeconomic challenges might contribute to working while feeling ill, particularly if there are management practices such as bonuses that incentivize attendance. Methods to decrease transmission within the facility include worker symptom screening programs, policies to discourage working while experiencing symptoms compatible with COVID-19, and social distancing by workers. Source control measures (e.g., the use of cloth face covers) as well as increased disinfection of high-touch surfaces are also important means of preventing SARS-CoV-2 exposure. Mitigation efforts to reduce transmission in the community should also be considered. Many of these measures might also reduce asymptomatic and presymptomatic transmission (3). Implementation of these public health strategies will help protect workers from COVID-19 in this industry and assist in preserving the critical meat and poultry production infrastructure (4).

Outbreak of human infections with uncommon Salmonella serotypes linked to pet bearded dragons, 2012-2014.

Reptiles are one of the fastest growing sectors in the United States pet industry. Reptile-associated salmonellosis (RAS) continues to be an important public health problem, especially among children. We investigated an outbreak of human Salmonella infections resulting from serotypes Cotham and Kisarawe, predominately occurring among children. An outbreak of illnesses was identified in persons with exposure to pet bearded dragon lizards. Human and animal health officials, in cooperation with the pet industry, conducted epidemiologic, traceback and laboratory investigations. Onsite sampling was conducted at two US breeding facilities, one foreign breeding facility, and a large pet retail chain. A total of 166 patients in 36 states were identified with illness onset dates from 02/2012-06/2014. The median patient age was 3 years (range, <1-79 years), 57% were aged ≤5 years, and 37% were aged ≤1 year. Forty-four patients (37%) were hospitalized, predominantly children. Sampling at breeding facilities and a national pet store chain resulted in isolation of outbreak serotypes at each facility; isolation proportions ranged from 2%-24% of samples collected at each facility.Epidemiologic, microbiologic and traceback evidence linked an outbreak of uncommon Salmonella serotypes to contact with pet bearded dragons. The high proportion of infants involved in this outbreak highlights the need to educate owners about the risk of RAS in children and the potential for household contamination by pet reptiles or their habitats. Strategies should be developed to improve breeding practices, biosecurity and monitoring protocols to reduce Salmonella in the pet reptile trade.

Shiga Toxin-Producing Escherichia coli Infections Associated With Romaine Lettuce-United States, 2018.

BACKGROUND: Produce-associated outbreaks of Shiga toxin-producing Escherichia coli (STEC) were first identified in 1991. In April 2018, New Jersey and Pennsylvania officials reported a cluster of STEC O157 infections associated with multiple locations of a restaurant chain. The Centers for Disease Control and Prevention (CDC) queried PulseNet, the national laboratory network for foodborne disease surveillance, for additional cases and began a national investigation. METHODS: A case was defined as an infection between 13 March and 22 August 2018 with 1 of the 22 identified outbreak-associated E. coli O157:H7 or E. coli O61 pulsed-field gel electrophoresis pattern combinations, or with a strain STEC O157 that was closely related to the main outbreak strain by whole-genome sequencing. We conducted epidemiologic and traceback investigations to identify illness subclusters and common sources. A US Food and Drug Administration-led environmental assessment, which tested water, soil, manure, compost, and scat samples, was conducted to evaluate potential sources of STEC contamination. RESULTS: We identified 240 case-patients from 37 states; 104 were hospitalized, 28 developed hemolytic uremic syndrome, and 5 died. Of 179 people who were interviewed, 152 (85%) reported consuming romaine lettuce in the week before illness onset. Twenty subclusters were identified. Product traceback from subcluster restaurants identified numerous romaine lettuce distributors and growers; all lettuce originated from the Yuma growing region. Water samples collected from an irrigation canal in the region yielded the outbreak strain of STEC O157. CONCLUSIONS: We report on the largest multistate leafy greens-linked STEC O157 outbreak in several decades. The investigation highlights the complexities associated with investigating outbreaks involving widespread environmental contamination.

Onsite investigation at a mail-order hatchery following a multistate Salmonella illness outbreak linked to live poultry-United States, 2018.

Centers for Disease Control and Prevention (CDC), health departments, and other state and federal partners have linked contact with live poultry to 70 human Salmonella outbreaks in the United States from 2000 to 2017, which resulted in a total of 4,794 illnesses, 894 hospitalizations, and 7 deaths. During human salmonellosis outbreaks environmental sampling is rarely conducted as part of the outbreak investigation. CDC was contacted by state health officials on June 12, 2018, to provide support during an investigation of risk factors for Salmonella infections linked to live poultry originating at a mail-order hatchery. From January 1, 2018, to June 15, 2018, 13 human Salmonella infections in multiple states were attributed to exposure to live poultry from a single hatchery. Two serotypes of Salmonella were associated with these infections, Salmonella Enteritidis and Salmonella Litchfield. Molecular subtyping of the S. Enteritidis clinical isolates revealed they were closely related genetically (within 0 to 9 alleles) by core genome multi-locus sequence typing (cgMLST) to isolates obtained from environmental samples taken from hatchery shipping containers received at retail outlets. Environmental sampling and onsite investigation of practices was conducted at the mail-order hatchery during an investigation on June 19, 2018. A total of 45 environmental samples were collected, and 4 (9%) grew Salmonella. A chick box liner from a box in the pre-shipping area yielded an isolate closely related to the S. Enteritidis outbreak strain (within 1 to 9 alleles by cgMLST). The onsite investigation revealed lapses in biosecurity, sanitation, quality assurance, and education of consumers. Review of Salmonella serotype testing performed by the hatchery revealed that the number of samples and type of samples collected monthly varied. Also, S. Enteritidis was identified at the hatchery every year since testing began in 2016. Recommendations to the hatchery for biosecurity, testing, and sanitation measures were made to help reduce burden of Salmonella in the hatchery and breeding flocks, thereby reducing the occurrence of human illness.

Multistate Outbreak of Listeriosis Associated with Packaged Leafy Green Salads, United States and Canada, 2015-2016.

We investigated an outbreak of listeriosis detected by whole-genome multilocus sequence typing and associated with packaged leafy green salads. Nineteen cases were identified in the United States during July 5, 2015-January 31, 2016; isolates from case-patients were closely related (median difference 3 alleles, range 0-16 alleles). Of 16 case-patients interviewed, all reported salad consumption. Of 9 case-patients who recalled brand information, all reported brands processed at a common US facility. The Public Health Agency of Canada simultaneously investigated 14 cases of listeriosis associated with this outbreak. Isolates from the processing facility, packaged leafy green salads, and 9 case-patients from Canada were closely related to US clinical isolates (median difference 3 alleles, range 0-16 alleles). This investigation led to a recall of packaged leafy green salads made at the processing facility. Additional research is needed to identify best practices and effective policies to reduce the likelihood of Listeria monocytogenes contamination of fresh produce.