Most Common Foodborne Pathogens and Mycotoxins on Fresh Produce: A Review of Recent Outbreaks

Every year millions of people are affected and thousands of them die due to infections and intoxication as a result of foodborne outbreaks, which also cause billions of dollars' worth of damage, public health problems, and agricultural product loss. A considerable portion of these outbreaks is related to fresh produce and caused by foodborne pathogens on fresh produce and mycotoxins. Escherichia coli O104:H4 outbreak, occurred in Germany in 2011, has attracted a great attention on foodborne outbreaks caused by contaminated fresh produce, and especially the vulnerability and gaps in the early warning and notification networks in the surveillance systems in all around the world. In the frame of this paper, we reviewed the most common foodborne pathogens on fresh produce, traceback investigations of the outbreaks caused by these pathogens, and lastly international early warning and notification systems, including PulseNet International and Rapid Alert System for Food and Feed, aiming to detect foodborne outbreaks.     

Foodborne outbreaks of microbial infection from fresh produce in Europe and North America: a systematic review of data from this millennium

This study focuses on foodborne outbreaks of microbial infection associated with fresh produce in Europe and North America from this millennium. A total of 277 outbreaks with 44 524 individual cases were identified. Foodborne pathogens associated with the most outbreak frequency include Cryptosporidium (20.5%) in Europe and Salmonella (52.2%) in North America although Norovirus (54.3%) and Salmonella (61.3%) were associated with the number of cases in Europe and North America, respectively. Vegetables were the most implicated fresh produce category with outbreak frequencies of 34.1% in Europe and 47.4% in North America. Increased consumption of fresh produce in Europe and North America, as measures to improve diets, correlates with the increased fresh produce-related outbreaks of microbial infection. This systematic review suggests the need for more rapid methodologies for traceback investigations in order to determine trends and epicentres of foodborne infections related to fresh produce.     

Microbial Risks Associated with Cabbage,Carrots, Celery,Onions, and Deli Salads Made with These Produce Items

Abstract: The microbiological safety of cabbage, carrots, celery, and onions/scallions as well as deli (mayonnaise‐based) salads that contain these items is the subject of this review. Between 2000 and 2007, the number of outbreaks in the United States associated with these raw produce items ranged from 6 (celery) to 18 (carrots). For cases with confirmed etiologies involving these 4 types of produce as well as coleslaw, chicken, seafood, and other vegetable‐based salads, more than 50% of the outbreaks were attributed to viral agents. In contrast, Salmonella spp. served as the major etiological agent in outbreaks associated with potato salad. Surveys conducted on these produce items within the United States and other developed countries found either an absence or infrequent contamination with foodborne pathogens. Despite this low prevalence, experimental studies have demonstrated the potential for preharvest contamination, and this event is more likely to occur when exposure is close to harvest. Postharvest contamination of these produce items has been documented in several cases with water, equipment, and incoming product serving as the principal cross‐contamination agent. Survival of contaminated product during subsequent storage is dependent on the storage temperature, produce type, and presence of mayonnaise. Chemical interventions may be relied on to reduce cross‐contamination during produce washing operations but are limited in their ability to inactivate pathogens on the produce surface. In contrast, irradiation at dosages (1.0 kGy) approved for use in the United States is an effective treatment for killing pathogenic bacteria in fresh‐cut cabbage, carrots, and celery.     

Microbiological safety of ready-to-eat minimally processed vegetables in Brazil: an overview

The market of ready-to-eat minimally processed vegetables (RTE-MPV) is increasing in Brazil and many other countries. During processing, these vegetables go through several steps that modify their natural structure while maintaining the same nutritional and sensory attributes as the fresh produce. One of the most important steps is washing-disinfection, which aims to reduce the microbial load, prevent cross-contamination and inactivate pathogenic microorganisms that may be present. Nonetheless, the presence of pathogens and occurrence of foodborne illnesses associated with consumption of RTE-MPV concern consumers, governments and the food industry. This review brings an overview on the microbiological safety of RTE-MPV, focusing on Brazilian findings. Most of the published data are on detection of Salmonella spp. and Listeria monocytogenes, indicating that their prevalence may range from 0.4% to 12.5% and from 0.6% to 3.1%, respectively. The presence of these pathogens in fresh produce is unacceptable and risky, mainly in RTE-MPV, because consumers expect them to be clean and sanitized and consequently safe for consumption without any additional care. Therefore, proper control during the production of RTE-MPV is mandatory to guarantee products with quality and safety to consumers. © 2020 Society of Chemical Industry     

Prevalence,Distribution, and Diversity of Salmonella spp. in Meat Samples Collected from Italian Slaughterhouses

Recently worldwide food safety authorities indicated the rise of foodborne outbreaks linked to Salmonella: this highlighted the need to intensify monitoring and apply more targeted controls to help manage the spread of the disease. The aim of this study was to assess the prevalence and distribution of Salmonella serotypes in 7 slaughterhouses, located in different areas of Naples province (Regione Campania, Italy). Meat samples collected from the slaughterhouses were submitted for standardized microbiological analysis in 2015. Results of routine testing for Salmonella spp. were analyzed and then compared to biochemical and molecular evaluations. Salmonella spp. were detected in 12% of 320 samples examined (39/320) and the isolation rates ranged from 87% (32 samples) for raw poultry meat to 13% (7 samples) for pork meat. Biochemical serotyping showed that approximately 50% of the isolates belonged to Salmonella enterica serotype Choleraesuis. Rapid detection methods, such as molecular analysis (polymerase chain reaction and gel electrophoresis), able to confirm food matrices contamination, represent a valid support to the fast identification of Salmonella species. A further aspect of the study consisted, indeed, on analyzing isolated strains through molecular evaluations. By amplifying bacterial DNA—using invA primers, selective for Salmonella—it was possible, in less than 3 h, to classify the isolates as Salmonella spp., confirming the results of microbiological outcomes. Results of distribution analysis, supported by rapid molecular approaches, showed the difficulty of reducing Salmonella risk on food chain. This emphasized the importance of periodic surveillance to prevent outbreaks.     

PHILIPPINE FOODBORNE-DISEASE OUTBREAKS (1995–2004)

The study presented details about 60 reported Philippines foodborne outbreaks for the period of 1995–2004. It was established that meat‐containing dishes were the more common causes of the outbreaks evaluated, with spaghetti as the leading food vehicle. Common risk settings for the outbreaks were the food services of schools and workplaces. Salmonella and Vibrio spp. were cited as the primary causes of infections, while human intoxications involved staphylococcal enterotoxins, paralytic shellfish poisoning (PSP) toxins and histamine.     

Food Safety Interventions to Control Listeria monocytogenes in the Fresh Apple Packing Industry: A Review

Listeria monocytogenes, in fresh and ready‐to‐eat produce such as whole fresh apples, is of concern as there is no “kill step” in their packing process that would eliminate the pathogenic bacteria. Recent listeriosis outbreaks revealed that insufficient cleaning and sanitation practices in fresh apple packing houses may lead to contamination of fruit with L. monocytogenes. This article discusses three fundamental aspects for ensuring microbiological safety of fresh apples: protection of fresh apples from microbial contamination during the packing process, decontamination intervention techniques, and the challenges in removal of L. monocytogenes from fresh apples. Currently used and novel methods of fresh produce decontamination are discussed and evaluated on their usefulness for the apple packing process. Additionally, present regulatory requirements, possible routes of produce contamination, and bacteria attachment and survival mechanisms are described. Optimum methods for microbial decontamination of whole fresh apples are still to be determined. Critical aspects that should be considered in developing the interventions include apple morphology, conditions and scale of the packing process, and influence of the interventions on apple quality. Evaluation of the currently used and emerging decontamination methods indicated that the hurdle technology and rotating use of sanitizers to avoid development of bacterial biofilm resistance may give the best results, although not conclusively.     

Foodborne outbreaks in Canada linked to produce.

Examples of foodborne outbreaks traced to fresh fruits and vegetables can be found worldwide. The quantity of produce eaten per capita has been increasing steadily over the past two decades, creating a heightened potential for produce-related foodborne disease. A number of outbreaks identified during this time period were reviewed, with particular emphasis placed on incidents that have occurred in Canada. The collective information highlights the diversity of infectious agents and produce items involved, with a view to the prevention of fresh produce-related foodborne disease in the future.     

Microbial Contamination of Fresh Produce: What,Where, and How?

Promotion of healthier lifestyles has led to an increase in consumption of fresh produce. Such foodstuffs may expose consumers to increased risk of foodborne disease, as often they are not subjected to processing steps to ensure effective removal or inactivation of pathogenic microorganisms before consumption. Consequently, reports of ready‐to‐eat fruit and vegetable related disease outbreak occurrences have increased substantially in recent years, and information regarding these events is often not readily available. Identifying the nature and source of microbial contamination of these foodstuffs is critical for developing appropriate mitigation measures to be implemented by food producers. This review aimed to identify the foodstuffs most susceptible to microbial contamination and the microorganisms responsible for disease outbreaks from information available in peer‐reviewed scientific publications. A total of 571 outbreaks were identified from 1980 to 2016, accounting for 72,855 infections and 173 deaths. Contaminated leafy green vegetables were responsible for 51.7% of reported outbreaks. Contaminated soft fruits caused 27.8% of infections. Pathogenic strains of Escherichia coli and Salmonella, norovirus, and hepatitis A accounted for the majority of cases. Large outbreaks resulted in particular biases such as the observation that contaminated sprouted plants caused 31.8% of deaths. Where known, contamination mainly occurred via contaminated seeds, water, and contaminated food handlers. There is a critical need for standardized datasets regarding all aspects of disease outbreaks, including how foodstuffs are contaminated with pathogenic microorganisms. Providing food business operators with this knowledge will allow them to implement better strategies to improve safety and quality of fresh produce.     

Microencapsulated antimicrobial compounds as a means to enhance electron beam irradiation treatment for inactivation of pathogens on fresh spinach leaves

Abstract: Recent outbreaks associated to the consumption of raw or minimally processed vegetable products that have resulted in several illnesses and a few deaths call for urgent actions aimed at improving the safety of those products. Electron beam irradiation can extend shelf‐life and assure safety of fresh produce. However, undesirable effects on the organoleptic quality at doses required to achieve pathogen inactivation limit irradiation. Ways to increase pathogen radiation sensitivity could reduce the dose required for a certain level of microbial kill. The objective of this study was to evaluate the effectiveness of using natural antimicrobials when irradiating fresh produce. The minimum inhibitory concentration of 5 natural compounds and extracts (trans‐cinnamaldehyde, eugenol, garlic extract, propolis extract, and lysozyme with ethylenediaminetetraacetate acid (disodium salt dihydrate) was determined against Salmonella spp. and Listeria spp. In order to mask odor and off‐flavor inherent of several compounds, and to increase their solubility, complexes of these compounds and extracts with β‐cyclodextrin were prepared by the freeze‐drying method. All compounds showed bacteriostatic effect at different levels for both bacteria. The effectiveness of the microencapsulated compounds was tested by spraying them on the surface of baby spinach inoculated with Salmonella spp. The dose (D₁₀ value) required to reduce the bacterial population by 1 log was 0.190 kGy without antimicrobial addition. The increase in radiation sensitivity (up to 40%) varied with the antimicrobial compound. These results confirm that the combination of spraying microencapsulated antimicrobials with electron beam irradiation was effective in increasing the killing effect of irradiation. Practical Application: Foodborne illness outbreaks attributed to fresh produce consumption have increased and present new challenges to food safety. Current technologies (water washing or treating with 200 ppm chlorine) cannot eliminate internalized pathogens. Ionizing radiation is a viable alternative for eliminating pathogens; however, the dose required to inactivate these pathogens is often too high to be tolerated by the fresh produce without undesirable quality changes. This study uses natural antimicrobial ingredients as radiosensitizers. These ingredients were encapsulated and applied to fresh produce that was subsequently irradiated. The process results in high level of microorganism inactivation using lower doses than the conventional irradiation treatments.     

Fresh produce: a growing cause of outbreaks of foodborne illness in the United States, 1973 through 1997

Fresh produce is an important part of a healthy diet. During the last three decades, the number of outbreaks caused by foodborne pathogens associated with fresh produce consumption reported to the Centers for Disease Control and Prevention has increased. To identify trends, we analyzed data for 1973 through 1997 from the Foodborne Outbreak Surveillance System. We defined a produce-associated outbreak as the occurrence of two or more cases of the same illness in which epidemiologic investigation implicated the same uncooked fruit, vegetable, salad, or juice. A total of 190 produce-associated outbreaks were reported, associated with 16,058 illnesses, 598 hospitalizations, and eight deaths. Produce-associated outbreaks accounted for an increasing proportion of all reported foodborne outbreaks with a known food item, rising from 0.7% in the 1970s to 6% in the 1990s. Among produce-associated outbreaks, the food items most frequently implicated included salad, lettuce, juice, melon, sprouts, and berries. Among 103 (54%) produce-associated outbreaks with a known pathogen, 62 (60%) were caused by bacterial pathogens, of which 30 (48%) were caused by Salmonella. During the study period, Cyclospora and Escherichia coli O157:H7 were newly recognized as causes of foodborne illness. Foodborne outbreaks associated with fresh produce in the United States have increased in absolute numbers and as a proportion of all reported foodborne outbreaks. Fruit and vegetables are major components of a healthy diet, but eating fresh uncooked produce is not risk free. Further efforts are needed to better understand the complex interactions between microbes and produce and the mechanisms by which contamination occurs from farm to table.     

Control of Salmonella Contamination of Shell Eggs—Preharvest and Postharvest Methods: A Review

Salmonella Enteritidis is one of the most prevalent foodborne pathogen, its main reservoir being considered the shell egg. As the concerns related to the increasing human salmonellosis cases grow, the need for an application of preventive methods either at the farm level or during the processing steps is crucial for a better control of the foodborne outbreaks due to the consumption of this specific food product. This review focuses on the application of preventive methods at the farm level, on preharvest step, in order to reduce the risk of shell eggs contamination with Salmonella, especially S. Enteritidis, through a better control of the laying hens’ infection with this pathogen. As postharvest methods, a 1st approach is the egg storage conditions and the prevention of Salmonella spp. growth and multiplication. In addition, shell eggs may be subjected to eggshell decontamination, to reduce the risk of foodborne outbreaks. Several of these latter mentioned methods are already authorized to be put in place in different countries, as it is the case in the United States of America and Canada. Their efficacy has been proven and their use is regarded by some as mandatory for ensuring shell eggs safety for the consumers.     

Application of electron beam to inactivate Salmonella in food: Recent developments

Food is a transmission vehicle for Salmonella that causes about 96% of all salmonellosis cases. The high frequency and incidence of foodborne outbreaks makes Salmonella a significant public health concern and economic burden worldwide. Although thermal pasteurization is commonly applied to food products to inactivate Salmonella, heat simply cannot be used for fresh food products such as produce, eggs, and many ready-to-eat (RTE) foods. It has also been demonstrated that Salmonella can survive thermal pasteurization in peanut butter. Besides an on-going concern with Salmonella in eggs, the recent outbreaks in fresh produce and peanut butter clearly indicate a need for non-thermal technologies to adequately inactivate this pathogen.Electron beam (e-beam) uses linear accelerator to accelerate electrons from electricity to near-speed-of-light. As with other types of ionizing radiation, e-beam inactivates microorganisms directly by DNA damage resulting in reproductive death and indirectly by free radicals generated during water radiolysis that disintegrate cell membrane. Since e-beam inactivates microorganisms non-thermally, it may be used to inactivate Salmonella in fresh food products such as produce, eggs, RTEs, and peanut butter. A new development is secondary emission electron gun (SEEG) e-beam. This compact SEEG e-beam has a potential to be incorporated into a microwave oven. This incorporation would allow non-thermal inactivation of foodborne pathogens including Salmonella at the point-of-consumption (i.e., household level and food service).This article reviews the application of e-beam to inactivate Salmonella in various food matrices with an emphasis on most recent Salmonella outbreaks. The article also succinctly reviews the latest understanding of the mechanism of microbial inactivation by e-beam and radio-resistance as well as microbial inactivation kinetics.     

A field study of the microbiological quality of fresh produce of domestic and Mexican origin

Produce is responsible for an increasingly larger proportion of foodborne disease outbreaks. In particular, the globalization of the food supply may introduce new food safety risks and allow widespread distribution of contaminated food, particularly produce. The objectives of this study were to: (i) compare the overall quality of domestic and Mexican produce throughout the packing process; (ii) examine changes in microbiological quality of both domestic and Mexican produce at each stage of production and processing; and (iii) evaluate the prevalence of select pathogens on fresh produce, including leafy green, herbs, melons, and vegetables. Furthermore, we also sought to characterize the antibiotic resistance profiles of Enterococcus faecium and Enterococcus faecalis strains isolated from fresh produce. A total of 466 produce and matching environmental swab samples was collected from various locations in packing sheds in the southern US from November 2002 through December 2003. These samples were assayed by enumerative tests for total aerobic bacteria (APC), total coliforms, total Enterococcus, and E. coli. Produce samples were also analyzed for the presence of Salmonella, Listeria monocytogenes, Shigella, and E. coli O157:H7. A total of 112 E. faecium and E. faecalis isolates were further screened for antibiotic resistance using a panel of seventeen antibiotics. Overall, the microbiological quality of fresh produce ranged from 4.0 to 7.9 log(10) CFU/g (APC); less than 1.0 log(10) to 4.5 log(10) CFU/g (coliforms); less than 1.0 log(10) to 4.0 log(10) CFU/g (E. coli); and less than 1.0 log(10) to 5.4 log(10) CFU/g (Enterococcus). No Salmonella, Shigella, or E. coli O157:H7 were detected from the 466 25-g produce samples tested. However, three domestic cabbage samples were found to be positive for L. monocytogenes. Of the Enterococcus isolates, E. faecium had a higher degree of resistance to antibiotics in general, while Enterococcus spp. isolated from Mexican produce had a higher degree of antibiotic resistance when compared to strains isolated from produce samples of domestic origin. Despite increased attention to the role of imported produce in foodborne disease, this study does not support the assumption that domestic produce is of higher microbial quality than Mexican produce.     

Combined effect of calcium oxide and sonication to reduce foodborne pathogens on fresh produce

This study was conducted to investigate the antibacterial activity of calcium oxide (CaO), sonication, and their combination against foodborne pathogens on several fresh produce. The results showed that combined treatment inhibited Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium on fresh produce. However, the effectiveness of treatments for reducing populations of foodborne pathogens varied depending on the types and condition of the fresh produce. This study demonstrated that the antibacterial potency of CaO and its application with sonication could be one of alternatives for controlling foodborne pathogens on fresh produce.     

Fate of Escherichia coli in apple and reduction of its growth using the postharvest biocontrol agent Candida sake CPA‐1

BACKGROUND: Generally, acidic fruits and fruit juices are considered ‘safe’ from a microbiological point of view. However, some outbreaks of foodborne illnesses have been linked to the consumption of unpasteurised cider. The aim of this work was to study the survival of Escherichia coli in apple juice, wounds and flesh and on apple surfaces at different temperatures and to determine the effect of the fungal biocontrol agent Candida sake CPA‐1 against the colonisation of apple by E. coli. RESULTS: Trials were conducted with a mixture of five strains of E. coli isolated from apples. E. coli was unable to grow in apple juice at 5, 15 and 25 °C but survived. At 10 °C and above, E. coli thrived in fresh‐cut apple and wounds. At 5 °C it survived in apple wounds after 27 days of storage and after 21 days in fresh‐cut apples. When E. coli was inoculated in apple wounds together with the yeast antagonist C. sake, its growth was reduced by approximately 1 log cfu wound^?1 at 25 °C. At 5 °C no effect of the biocontrol agent was observed. CONCLUSION: Despite the low pH of apple, a rapid increase in the bacterial population is possible if the temperature is not kept low enough. The biocontrol agent C. sake, developed to prevent fruit decay during storage, could also reduce E. coli growth in wounded apples at abusive temperatures. This would represent an additional benefit of using this biocontrol agent when applied to control postharvest diseases. Copyright © 2009 Society of Chemical Industry     

Microbiological Quality and Safety of Fresh Fruits and Vegetables at Retail Levels in Korea

The aim of this study was to evaluate the microbiological quality and safety of fresh produce at retail level in Korea in order to periodically update information and establish available risks associated with consumption of fresh fruits and vegetables. The samples from different markets located in 3 provinces of South Korea were collected. The protocol in the Korean Food Standards Codex was applied and generic Escherichia coli, coliforms, aerobic mesophilic bacteria (AMB), and yeast and mold (YM) in 360 packaged and unpackaged fresh fruits and vegetables were analyzed. Presence of pathogens was examined using real‐time polymerase chain reaction (q‐PCR) after enrichment of samples. For all, the microbial counts ranged from 1.7 to 10.6 log cfu/g for AMB, 2.2 to 7.9 log cfu/g for coliforms, and 5.5 to 7.9 log cfu/g for YM. Three lettuce samples were contaminated by E. coli with a bacterial load ranging from 2 to 4 log cfu/g. Salmonella spp. were not detected in any fresh produce. Listeria monocytogenes, E. coli O157:H7, and Staphylococcus aureus were found in 1 (0.6%), 3 (0.8%), and 5 (1.4%) fresh produce samples, respectively. Bacillus cereus (50.3%) and Clostridium perfringens (13.3%) had the highest prevalence. These results indicate the need for employing strict control measures and developing preventive strategies to improve the quality and safety of fresh produce in Korea.     

Overview of Recent Events in the Microbiological Safety of Sprouts and New Intervention Technologies

There has been an increasing trend in consumption of sprouts worldwide due to their widespread availability and high nutrient content. However, microbial contamination of sprouts readily occurs due to the presence of pathogenic bacteria in seeds; and the germination and sprouting process provide optimal conditions for bacterial growth. In recent years, there has been a rise in the number of outbreaks associated with sprouts. These outbreaks occurred mainly in the US, Canada, UK, as well as Europe. More recently in 2011, there were 4 sprout‐related outbreaks, with the Escherichia coli O104:H4 outbreak in Germany causing around 50 deaths and 4000 illnesses reported. On top of pathogenic E. coli, Salmonella spp. are often associated with sprout‐related foodborne disease outbreaks. The contamination of sprouts has become a worldwide food safety concern. Hence, this review paper covers the outbreaks associated with sprouts, prevalence and characteristics of pathogens contaminating sprouts, their survival and growth, and the source of these pathogens. Physical, biological, and chemical interventions utilized to minimize microbial risks in sprouts are also discussed.     

Microbial contamination associated with the processing of grilled pork,a ready-to-eat street food in Benin

This study aimed to assess the microbial contamination associated with the traditional processing of fresh pork into grilled pork in Benin. Sixty samples of meat, including fresh pork and processed pork were randomly collected from different processing/selling sites, and the main foodborne microorganisms were sought using standard methods. The Aerobic Mesophilic Bacteria load in all samples ranged between 2.7 and 7.4 Log₁₀ CFU g⁻¹, with 16.7% of samples exceeding the acceptable limit of <7.0 Log₁₀ CFU g⁻¹ recommended by the Health Protection Agency for this criterion. Likewise, Enterobacteriaceae, Escherichia coli, and Clostridium perfringens loads exceeded the acceptable limit in 20.8, 20.8, and 12.5% of the samples, respectively. None of the samples contained Salmonella spp., Staphylococcus aureus or Listeria monocytogenes. Sources of contamination of grilled pork were identified and grouped into five types of causes related to processors, processing methods, equipment used, raw materials, and processing/selling environment. Similarly, a microbiological hazard analysis of grilled pork processing practices identified the sensitive steps where additional hygiene measures needed to be implemented.