Robert Buchanan

University of Maryland, College Park | UMD, UMCP, University of Maryland College Park · Center for Food Safety and Security Systems

Increased thermal resistance of Salmonella at low water activity (aw) is a significant food safety concern in low-moisture foods (LMFs). We evaluated whether trans-cinnamaldehyde (CA, 1000 ppm) and eugenol (EG, 1000 ppm), which can accelerate thermal inactivation of Salmonella Typhimurium in water, can show similar effect in bacteria adapted to low...

Our previous study found that water activity (aw)- and matrix-dependent bacterial resistance wasdeveloped in Salmonella Typhimurium during antimicrobial-assisted heat treatment in low moisture foods (LMFs) matrices. To better understand the molecular mechanism behind the observed bacterial resistance, gene expression analysis was conducted on S. Ty...

After studies with powdered infant formula indicated that the enhancement of thermal inactivation of Cronobacter sakazakii by butyl para-hydroxybenzoate (BPB) was blocked by high protein concentrations, we hypothesized that BPB would retain its synergistic activity in foods with limited protein and lipid concentrations. This hypothesis was tested b...

In previous studies, parabens in model systems enhanced the thermal inactivation of foodborne pathogens, including Cronobacter sakazakii, Salmonella enterica serotype Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes. However, few studies have been conducted to evaluate this phenomenon in actual food systems. In the present study, t...

Subtyping of bacterial isolates of the same genus and species is an important tool in epidemiological investigations. A number of phenotypic and genotypic subtyping methods are available; however, most of these methods are labor-intensive and time-consuming and require considerable operator skill and a wealth of reagents. Matrix-Assisted Laser Deso...

Heat‐resistant foodborne pathogens have been a concern in low‐moisture foods and ingredients (LMFs). Due to low thermal conductivity of low moisture materials, thermal treatment is not efficient and may cause nutritional loss. This study investigated the enhancement of thermal treatment of meat and bone meal (MBM) at low water activity (aw) by incl...

As risk-based approaches are increasingly recognized and used to manage food safety hazards, their implementation requires a recognition and appreciation of residual risk. We define residual risk as the one that remains even after a fully compliant food safety system has been implemented. As true “zero risk” is essentially unattainable, understandi...

Although high-temperature heat treatments can efficiently reduce pathogen levels, they also affect the quality and nutritional profile of foods and increase the cost of processing. The food additive butyl para-hydroxybenzoate (BPB) was investigated for its potential to synergistically enhance thermal microbial inactivation at mild heating temperatu...

Pre-harvest testing is increasingly used to enhance the microbial safety of fresh produce. Traditional sampling assumes that sample collectors have no information on potential contamination sources. Knowledge of such factors could potentially increase the effectiveness of pre-harvest sampling programs. Simulation modeling and field validation trial...

Domestic and wild animal intrusions are identified as a food safety risk during fresh produce production. The purpose of this study was to evaluate the survival of Shiga toxin-producing Escherichia coli (STEC) in cattle, feral pig, waterfowl, deer, and raccoon feces from sources in California, Delaware, Florida, and Ohio. Fecal samples were inocula...

Heightened concerns about wildlife on produce farms and possible introduction of pathogens to the food supply have resulted in required actions following intrusion events. The purpose of this study was to evaluate the survival of Salmonella in feces from cattle and various wild animals (feral pigs, waterfowl, deer, and raccoons) in California, Dela...

Microgreens have gained increasing popularity as food ingredients in recent years because of their high nutritional value and diverse sensorial characteristics. Microgreens are edible seedlings including vegetables and herbs, which have been used, primarily in the restaurant industry, to embellish cuisine since 1996. The rapidly growing microgreen...

This randomized controlled trial characterized the transfer of E. coli from animal feces and/or furrow water onto adjacent heads of lettuce during foliar irrigation, and the subsequent survival of bacteria on the adaxial surface of lettuce leaves. Two experiments were conducted in Salinas Valley, California: (1) to quantify the transfer of indicato...

Ability of bacteria to develop cross-protection to various stresses is well-known. However, exploration into cross-protection between conventional physiological stresses and emerging antimicrobial treatments is limited. Previously, we developed two new antimicrobial treatments based on a combined UV-A light and gallic acid (UVA+GA) treatment and en...

Listeriosis is an atypical foodborne illness of major public health concern because of the severity of the disease (meningitis, septicemia, and spontaneous abortion), the high case fatality rate (approximately 20 to 30%), the long incubation time (up to 70 days), and a predilection for individuals who have an underlying condition that leads to impa...

Antibiotic resistance is attributed to the misuse or overuse of antibiotics in agriculture, and antibiotic resistance genes can also be transferred to bacteria under environmental stress. In this study, we report a unidirectional alteration in antibiotic resistance from susceptibility to increased resistance. Highly sensitive Salmonella enterica se...

Regulatory Issues Associated with Preharvest Food Safety: United States Perspective, Page 1 of 2 Abstract The microbial safety of agricultural products starts at the preharvest/preslaughter level of primary production, and this stage may be considered as one of the most crucial steps in enhancing safety along the entire farm-to-table continuum. I...

Leafy green vegetables, including lettuce, are recognized as potential vehicles for foodborne pathogens such as Escherichia coli O157:H7. Fresh-cut lettuce is potentially at high risk of causing foodborne illnesses, as it is generally consumed without cooking. Quantitative microbial risk assessments (QMRAs) are gaining more attention as an effectiv...

The majority of foodborne outbreaks in the United States associated with the consumption of leafy greens contaminated with Escherichia coli O157:H7 have been reported during the period of July to November. A dynamic system model consisting of subsystems and inputs to the system (soil, irrigation, cattle, wild pig, and rainfall) simulating a hypothe...

Leafy greens contaminated with _Salmonella enterica_ have been linked to large number of illnesses in many countries in recent years. _Listeria monocytogenes_ is also a pathogen of concern for leafy greens because of its prevalence in the growing and processing environment and its ability to grow at refrigeration temperatures. Experimental data for...

A recent study by the Centers for Disease Control and Prevention reported that between 1998 and 2008, leafy greens outbreaks accounted for 22.3% of foodborne outbreaks in the United States. Several studies on the growth of bacteria at different temperatures have been conducted; however, there is a need for the prediction of bacterial growth when le...

Pathogens in soil are readily mobilized by infiltrating water to travel downward through the soil. However, limited data are available on the horizontal movement of pathogens across a field. This study used a model system to evaluate the influence of soil type, initial soil moisture content, and field slope on the movement of Salmonella enterica se...

A continuing goal in predictive microbiology is models directly based on physiological behavior. Buchanan et al.1 hypothesized that (1) the curvilinear lag/exponential transition represents the variability of cells in the adjustment (ta) and metabolic (tm) periods, and (2) the exponential/stationary transition is determined by limiting nutrient dif...

The goal of this study is to develop mathematical models that describe the enhanced thermal inactivation of Cronobacter sakazakii by the inclusion of “parabens”. The key parameters include heating temperature, parabens concentration, and the length of parabens’ alkyl side chains. The heating trials were conducted in a submerged coil apparatus using...

Improved control measures starting in the 1990s have greatly reduced the prevalence of L. monocytogenes in many food categories, particularly in meats and meat products. However, the rate of listeriosis has remained constant during the last decade and the more severe, systemic (invasive) form of listeriosis is now recognized as occurring more frequ...

BackgroundA substantial percentage of dog owners add water to dry dog food to increase its palatability. The recent association of Salmonella contamination of dry pet foods with salmonellosis cases in both dogs and their owners has generated a need to determine the ability of Salmonella to grow in eight commercial brands of rehydrated dry dog food....

Toxoplasma gondii is one of the leading foodborne pathogens in the United States. The Centers for Disease Control and Prevention (CDC) reported that T. gondii accounts for 24% of deaths due to foodborne illness in the United States. Consumption of undercooked pork products in which T. gondii has encysted has been identified as an important route of...

Prevention of microbial cross-contamination during postharvest handling is an important step to minimize microbial food safety hazards. Dump tanks and flume systems are widely used in states like Florida to transfer/wash tomatoes, and are one of the most critical points where cross-contamination may occur. Some processors in states such as New Jers...

Unlabelled: Toxoplasma gondii is a prevalent protozoan parasite worldwide. Human toxoplasmosis is responsible for considerable morbidity and mortality in the United States, and meat products have been identified as an important source of T. gondii infections in humans. The goal of this study was to develop a farm-to-table quantitative microbial ri...

Leafy green vegetables are highly susceptible to microbial contamination because they are minimally processed. Pathogenic bacteria of concern include _Escherichia coli_ O157:H7, _Salmonella_ spp., and _Listeria monocytogenes_. Leafy greens are a highly perishable commodity, and in some cases have a postharvest shelf-life limited to one week. This s...

Importance: To our knowledge, this study is the first to track the movement ofEscherichia colifrom floodwater across a horizontal plane of soil, and the potential for the contamination of distant leafy green produce. The purpose of this study was to address the validity of the California Leafy Green Products Handler Marketing Agreement recommendat...

Major concern in the Mixed Crop-Livestock (MCL) farms, in which livestock and vegetables grown closely in the same facility, is cross-contamination of zoonotic bacterial pathogens especially Salmonella. To investigate the distribution of Salmonella serovars in MCL and their products, a total of 1,287 pre-harvest samples from various farms and 1,377...

Toxoplasma gondii is a widely distributed protozoan parasite. The Centers for Disease Control and Prevention reported that T. gondii is one of three pathogens (along with Salmonella and Listeria), that together account for >70% of all deaths due to foodborne illness in the United States. Food animals are reservoirs for T. gondii and act as one of t...

Toxoplasma gondii is a global protozoan parasite capable of infecting most warm-blooded animals. Although healthy adult humans generally have no symptoms, severe illness does occur in certain groups, including congenitally infected fetuses and newborns, immunocompromised individuals including transplant patients. Epidemiological studies have demons...

Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of deaths attributed to foodborne pathogens in the United States. It is thought that a substantial portion of human T. gondii infections is acquired through the consumption of meats. The dose-response relationship for human exposures to T. gondii-infected meat is un...

Concerns about the microbiological safety of fresh produce have attracted attention in the past three decades due to multiple foodborne outbreaks. Animal manure contaminated with enteric pathogens has been identified as an important preharvest pathogen source. This study investigated the survival of Salmonella enterica in dust particles of dehydrat...

Consumption of locally, organically grown produce is increasing in popularity. Organic farms typically produce on a small scale, have limited resources, and adopt low technology harvest and postharvest handling practices. Data on the food safety risk associated with hand harvesting, field packing, and packing-house handling with minimal treatment,...

In 2013, we were approached by the PEW Charitable Trusts (PEW] to develop a scientific "white paper" describing the principles, concepts, and potential applications of microbiological testing to verify preventive controls implemented as part of food safety system that combined both HACCP and Good Hygienic Practices. This was undertaken with the kno...

Recent Salmonella outbreaks associated with dry pet food and treats raised the level of concern for these products as vehicle of pathogen exposure for both pets and their owners. The need to characterize the microbiological and risk profiles of this class of products is currently not supported by sufficient specific data. This systematic review sum...

Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of all estimated deaths attributed to foodborne pathogens in the United States. Human infection results from accidental ingestion of oocysts from the environment, in water, or on insufficiently washed produce or from consumption of raw or undercooked meat products t...

Small- and medium-sized farms in the mid-Atlantic region of the U.S. use varied agricultural practices to produce leafy greens during spring and fall, but the impact of pre-harvest practices on food safety risk remains unclear. To assess farm level risk factors, bacterial indicators, Salmonella enterica, and Shiga toxin-producing Escherichia coli (...

Low-moisture foods have been responsible for a number of salmonellosis outbreaks worldwide over the last few decades, with cross contamination from contaminated equipment being the most predominant source. To date, actions have been focused on stringent hygienic practices prior to production, namely periodical sanitization of the processing equipme...

Consumption of poultry and poultry products is growing rapidly in both developing and developed countries as a result of increasing demand for foods rich in proteins and increased concern about the role of red meat in health and nutrition. This chapter discusses important poultry pests, the role of these pests in transmitting microbial pathogens to...

The Food Safety Objective is one of a series of microbial risk management metrics (MRM) that uses an assessment-based approach to design and control processes to achieve a regulatory agency's articulation of the Acceptable Level of Protection. The assessment evaluates reductions in microbial pathogens during processing and food-preparation steps an...

Peanuts and peanut-containing products have been linked to at least seven salmonellosis outbreaks worldwide in the past two decades. In response, the Technical Committee on Food Microbiology of the North American Branch of the International Life Sciences Institute collaborated with the American Peanut Council to convene a workshop to develop a fram...

Peanuts and peanut-containing products have been linked to at least seven salmonellosis outbreaks worldwide in the past two decades. In response, the Technical Committee on Food Microbiology of the North American Branch of the International Life Sciences Institute collaborated with the American Peanut Council to convene a workshop to develop a fram...

Microbiological testing for various indicator microorganisms is used extensively as a means of verifying the effectiveness of efforts to ensure the microbiological quality and safety of a wide variety of foods. However, for each use of an indicator organism the underlying scientific assumptions related to the behavior of the target microorganism, t...

As existing technologies are refined and novel microbial inactivation technologies are developed, there is a growing need for a metric that can be used to judge equivalent levels of hazard control stringency to ensure food safety of commercially sterile foods. A food safety objective (FSO) is an output-oriented metric that designates the maximum le...

The safety of the food supply is a subject of intense interest to consumers, particularly as a result of large-scale outbreaks that involve hundreds and sometimes thousands of consumers. During the last decade, this concern about food safety has expanded to include the diets of companion animals as a result of several incidences of chemical toxicit...

This chapter describes past outbreaks, potential routes of contamination for specific pathogens, potential interventions, and operational procedures associated with tropical and subtropical fruits. Various preharvest sources can result in contamination of fruits. Survival and growth of pathogens on whole and fresh-cut fruits are variable depending...

Contains wealth of information on food microbiology and food safety Provides guidance on the appropriate testing of food processing environments Presents ways to improve the microbiological safety of food Continuing the ICMSF series, Microorganisms in Foods 8 provides practical guidance on appropriate testing of food processing environments, proces...

Foods are one of the major vehicles for the transmission of a broad range of infectious diseases. The ability to prevent these diseases is becoming more complex as the world increasingly relies on global marketplaces. National governments have agreed that the best way to prevent food-related infectious diseases is through international trade that s...

The past decade has seen rapid developments in risk assessment techniques and tools related to food safety and food defense. These advances are beginning to have a significant impact on the decision making processes used by risk managers in both government and industry. Furthermore, the highly complex issues currently facing the management of food...

Microbiological criteria, food safety objectives and performance objectives, and the relationship between them are discussed and described in the context of risk-based food safety management. A modified method to quantify the sensitivity of attributes sampling plans is presented to show how sampling plans can be designed to assess a microbiological...

The Key Events Dose-Response Framework (KEDRF) is an analytical approach that facilitates the use of currently available data to gain insight regarding dose-response relationships. The use of the KEDRF also helps identify critical knowledge gaps that once filled, will reduce reliance on assumptions. The present study considers how the KEDRF might b...

An independent collaborative approach was developed for stimulating research on high-priority food safety issues. The Fresh Express Produce Safety Research Initiative was launched in 2007 with $2 million in unrestricted funds from industry and independent direction and oversight from a scientific advisory panel consisting of nationally recognized f...

Microbial risk assessment (MRA) is used to evaluate foodborne hazards, the likelihood of exposure to those hazards, and the resulting public-health impact. It is generally recognized to consist of four parts: hazard identification, hazard characterization, exposure assessment, and risk characterization. Model predictions generated by MRAs are most...

Microbial risk assessment (MRA) is a systematic tool to evaluate the likelihood of exposure to food-borne pathogens and the resulting impact of exposure on consumer health. In addition, MRA can be used to evaluate the public health impact of intervention or control measures designed to prevent or reduce pathogens at any or all of the steps in our c...

IntroductionFactors Contributing to Emergence or ReemergenceEscherichza Coli 0157:H7 as a Model for the Emergence of a Foodborne PathogenAnticipating the Next Emerging PathogenForecast for Pathogen EmergenceTwo-Tiered Approach to Addressing Research NeedsWars Avoided; Battles WonConclusions References

Recently, multivariant models based on the use of the Gompertz function in combination with response surface analysis have been developed to predict the behavior of foodborne pathogens in response to food formulation and storage parameters, including temperature, pH, sodium chloride content, sodium nitrite concentration, and atmosphere. These model...

Recent surveys of retail fresh foods (fish and seafood, poultry, red meat, raw milk and vegetables) have indicated the presence of organisms of the Aeromonas hydrophila group in virtually every sample examined. As part of these surveys, A. hydrophila was observed to increase in number during storage of the food at 5°C. Thus, other measures to contr...

Modified Vogel Johnson agar (MVJ) has high selectivity for Listeria monocytogenes; however, it does not permit the repair and subsequent colony formation of injured cells. By the addition of 0.4% Tween 80, 25 mL/L bovine fetal serum, or 50 mL/L egg yolk tellurite enrichment (50%), the ability of MVJ to detect heat injured L. monocytogenes (Scott A...

Epidemiological and toxicological evidence implicating Aeromonas hydrophila and Aermononas sobria as agents of human gastroenteritis is reviewed. These psychrotrophic species are common contaminants of refrigerated animal products, and the possibility that they may cause food poisoning is discussed.

The effects of pyruvate, succinate, citrate, alpha-keto glutarate, fumarate, malate, lactate, and glycerol supplementation (0.5, 1.0, and 2.0 g/100 ml) on aflatoxin production by A. parasiticus NRRL 2999 were examined in synthetic and semi-synthetic media. Glycerol, lactate, and the 0.5 g/100 ml level of pyruvate stimulated production in the synthe...

The inhibitory effect of sodium nitrite upon glucose catabolism by Staphylococcus aureus was investigated using [U–1 4C] glucose, liquid chromatography, and gas-liquid chromatography. Acetate and acetoin are the end-products of glucose metabolism by S. aureus at 37°C and pH 6.3. In the presence of inhibitory levels of sodium nitrite, acetate and la...

Theobromine (0, 2, 4, and 8 mg/ml) had little effect on growth and aflatoxin production by Aspergillus parasiticus NRRL 2999 in a glucose-mineral salts-yeast extract medium, indicating that the anti-aflatoxigenic activity of cocoa beans is not due to the presence of this methylxanthine.

Earlier work characterizing the effects of glucose analogs on growth and aflatoxin production by Aspergillus parasiticus was expanded by assessing the effects of β-methylglucose (βMG), 3-0-methylglucose (3MG) and thioglucose (TG). As sole carbon source of conidia-initiated cultures, βMG and 3MG, but not TG, supported growth, but none supported toxi...

The potential for controlling the growth of Listeria monocytogenes in refrigerated foods using Carnobacterium piscicola LK5, a bacteriocin-producing strain originally isolated from raw ground beef, was studied using co-culture techniques. Eight foods, including UHT milk, canned “all-beef”dog food (cooked meat), raw ground beef, irradiation-steriliz...

Control of foodborne emerging or reemerging microbial pathogens has proven to be difficult. Even the Hazard Analysis Critical Control Point (HACCP) approach is intended to manage known hazards. We propose that each change occurring in the food chain – encompassing human, technological, and environmental factors – creates a new selection pressure th...

The effects and interactions of temperature (12–45C), initial pH (4.5–9.0), NaCl (0.5–16.5%), and sodium nitrite (1–200 μg/ml) on the aerobic and anaerobic growth of Staphylococcus aureus 196E were studied using 50 ml portions of Brain Heart Infusion Broth in 250ml unsealed and sealed trypsinizing flasks, respectively. The flasks were inoculated to...

This chapter deals with advances in both microbiological modeling and risk assessment. The abundance of data acquired has led to major advances in the ability to study food safety microbiology in a quantitative manner. The importance of environmental contamination, recontamination of heat-processed foods, and the numerous potential pathways for cro...

The Microbiological Criteria (MC) is a set of parameters used to determine whether a specific lot of food is acceptable or not. These parameters are the microbial test protocol and its sensitivity, the confidence level that an unacceptable lot will be detected, the number of samples to be taken and the number of positive samples that are allowed be...

ABSTRACTA caffeine-resistant mutant of Aspergillus parasiticus NRRL 2999 was isolated and subsequently designated strain BCR1. The mutant strain grew in the presence of > 8 mg/mL caffeine, while growth of the parent strain was delayed by 1 mg/mL and inhibited by 2 mg/mL. Strain BCR1 produced abundant amounts of aflatoxin only when cultured in media...

The ability of various compounds to induce aflatoxin biosynthesis by Aspergillus parasiticus was investigated by initially culturing the organism in a peptone basal medium that does not support aflatoxin production, and then transferring the organism to a replacement medium containing the test compound. Ribose, xylose, glucose, fructose, sorbose, m...

The effects of CAMP, cGMP, AMP, and GMP on aflatoxin accumulation were studied using flask and test tube cultures of Aspergillus parasiticus. The response to cGMP supplementation was variable, depending on the type of culture system employed. Cyclic AMP produced a dose-related increase in aflatoxin production, with 5.0 mM supplementation resulting...

Growth of clinical isolates of Aeromonas hydrophila at various temperatures, pH values, and salt levels was studied in BHI broth. A majority of the isolates grew at 4-5°C and 42°C, and all grew equally well over the range 20-35°C. At 28°C, most isolates could tolerate 4% NaCl, while at 4°C only a limited number grew in 3% NaCl. Similarly, isolates...

The production of aflatoxin B1 and G1 in regular and decaffeinated coffee beans (green and roasted) inoculated with Aspergillus parasiticus was examined to determine the effect of decaffeination on aflatoxigenic potential. Aflatoxins were not detected in either the inoculated green or roasted regular beans. Small amounts of aflatoxin (0.30 μ/g) wer...

Studies were performed to characterize further Aspergillus parasiticus BCR1, a caffeine-resistant mutant of A. parasiticus NRRL 2999, particularly in regard to its caffeine-dependent production of aflatoxins. The enhanced synthesis of aflatoxins by caffeine was highly specific since neither dimethylxanthines nor purines could substitute for the tri...