Interventions Targeting Deep Tissue Lymph Nodes May Not Effectively Reduce the Risk of Salmonellosis from Ground Pork Consumption: A Quantitative Microbial Risk Assessment.

The inclusion of deep tissue lymph nodes (DTLNs) or nonvisceral lymph nodes contaminated with Salmonella in wholesale fresh ground pork (WFGP) production may pose risks to public health. To assess the relative contribution of DTLNs to human salmonellosis occurrence associated with ground pork consumption and to investigate potential critical control points in the slaughter-to-table continuum for the control of human salmonellosis in the United States, a quantitative microbial risk assessment (QMRA) model was established. The model predicted an average of 45 cases of salmonellosis (95% CI = [19, 71]) per 100,000 Americans annually due to WFGP consumption. Sensitivity analysis of all stochastic input variables showed that cooking temperature was the most influential parameter for reducing salmonellosis cases associated with WFGP meals, followed by storage temperature and Salmonella concentration on contaminated carcass surface before fabrication. The input variables were grouped to represent three main factors along the slaughter-to-table chain influencing Salmonella doses ingested via WFGP meals: DTLN-related factors, factors at processing other than DTLNs, and consumer-related factors. The evaluation of the impact of each group of factors by second-order Monte Carlo simulation showed that DTLN-related factors had the lowest impact on the risk estimate among the three groups of factors. These findings indicate that interventions to reduce Salmonella contamination in DTLNs or to remove DTLNs from WFGP products may be less critical for reducing human infections attributable to ground pork than improving consumers' cooking habits or interventions of carcass decontamination at processing.

Antimicrobial Efficacy of Cinnamaldehyde Against Escherichia coli O157:H7 and Salmonella enterica in Carrot Juice and Mixed Berry Juice Held at 4°C and 12°C.

The effectiveness of cinnamaldehyde for inactivating Salmonella enterica and Escherichia coli O157:H7 in carrot juice (CRJ) and mixed berry juice (MBJ) was investigated. Brain heart infusion broth (BHI), CRJ, and MBJ, with concentrations of added cinnamaldehyde ranging from 0.15 to 1.5 µL/mL, 0.25 to 2.0 µL/mL, and 0.25 to 1.5 µL/mL, respectively, were each inoculated with a 5-strain mixture of Salmonella enterica or Escherichia coli O157:H7 to give an initial viable count of 5.07 log10 colony-forming units/mL. Inoculated BHI or juices without cinnamaldehyde served as controls. Growth of the pathogens in BHI (35°C) was monitored by taking absorbance readings (optical density [OD] 600 nm) for 24 h. The inoculated juices were held at 4°C or 12°C for 24 h, and numbers of viable pathogens were determined at 0, 2, 4, 8, and 24 h by plating samples on selective agar followed by incubation (35°C) and counting bacterial colonies at 48 h. The minimum inhibitory concentration of cinnamaldehyde for both pathogens in BHI was 0.25 µL/mL. The pathogens were more sensitive to cinnamaldehyde in MBJ compared with CRJ, irrespective of storage temperature (p < 0.05). At 4°C, cinnamaldehyde (1.5 µL/mL) completely inactivated S. enterica and E. coli in MBJ (negative by enrichment) within 2 h and 8 h, respectively; whereas both pathogens were detected in CRJ (4°C; with 2.0 µL/mL cinnamaldehyde) at 8 and 24 h. At 12°C, S. enterica and E. coli were undetected in MBJ (1.5 µL/mL cinnamaldehyde) within 2 and 4 h, respectively; however, in CRJ (12°C; 2.0 µL/mL cinnamaldehyde), complete inactivation of S. enterica and E. coli occurred within 4 and 24 h, respectively. Cinnamaldehyde is an effective antimicrobial from natural sources that can be used for inactivating bacterial pathogens in fruit and vegetable juices to enhance microbial safety of these nutritious food products.

Generalized linear mixed model analysis of risk factors for contamination of moisture-enhanced pork with Campylobacter jejuni and Salmonella enterica Typhimurium.

Translocation of foodborne pathogens into the interior tissues of pork through moisture enhancement may be of concern if the meat is undercooked. In the present study, a five-strain mixture of Campylobacter jejuni or Salmonella enterica Typhimurium was evenly spread on the surface of fresh pork loins. Pork loins were injected, sliced, vacuum packaged, and stored. After storage, sliced pork was cooked by traditional grilling. Survival of Salmonella Typhimurium and C. jejuni in the interior tissues of the samples were analyzed by enumeration. The populations of these pathogens dropped below the detection limit (10 colony-forming units/g) in most samples that were cooked to 71.1°C or above. The general linear mixed model procedure was used to model the association between risk factors and the presence/absence of these pathogens after cooking. Estimated regression coefficients associated with the fixed effects indicated that the recovery probability of Salmonella Typhimurium was negatively associated with increasing level of enhancement. The effects of moisture enhancement and cooking on the recovery probability of C. jejuni were moderated by storage temperature. Our findings will assist food processors and regulatory agencies with science-based evaluation of the current processing, storage condition, and cooking guideline for moisture-enhanced pork.

Survival of methicillin-resistant Staphylococcus aureus during thermal processing of frankfurters, summer sausage, and ham.

Infections from antibiotic-resistant bacteria are a major concern for human health professionals around the world. Methicillin-resistant Staphylococcus aureus (MRSA) is just one of the resistant organisms of concern. MRSA prevalence has also been recently reported in retail meat products at rates higher than originally thought. Although the risk of contracting an infection from handling contaminated meat products is thought to be low, very little is known about this organism from a food safety perspective. The objective of this study was to determine the survival of MRSA during thermal processing of frankfurters, summer sausage, and boneless ham. Frankfurters, summer sausage, and boneless ham were manufactured using formulations and processing procedures developed at the Iowa State University meat laboratory. Thermal processing resulted in a significant log reduction (p<0.05) for boneless ham, summer sausage, and frankfurters when compared to uncooked, positive controls for each of the three processed meat products. All products were thermally processed to an internal temperature of 70°C and promptly cooled to 7.2°C. Boneless ham showed the highest log reduction (7.28 logs) from cooking, followed by summer sausage (6.75 logs) and frankfurters (5.53 logs). The results of this study indicate that thermal processing of ham, summer sausage, and frankfurters to 70°C is sufficient to reduce the risk of MRSA as a potential food safety hazard.

Investigating the control of Listeria monocytogenes on a ready-to-eat ham product using natural antimicrobial ingredients and postlethality interventions.

Ready-to-eat (RTE) meat and poultry products manufactured with natural or organic methods are at greater risk for Listeria monocytogenes growth, if contaminated, than their conventional counterparts due to the required absence of preservatives and antimicrobials. Thus, the objective of this study was to investigate the use of commercially available natural antimicrobials and postlethality interventions in the control of L. monocytogenes growth and recovery on a RTE ham product. Antimicrobials evaluated were cranberry powder (90MX), vinegar (DV), and vinegar/lemon juice concentrate (LV1X). Postlethality interventions studied were high hydrostatic pressure at 400 (HHP400) or 600 (HHP600) MPa, lauric arginate (LAE), octanoic acid (OA), and postpackaging thermal treatment (PPTT). Parameters evaluated through 98 days of storage at 4±1°C were residual nitrite concentrations, pH, a(w), and viable L. monocytogenes on modified Oxford (MOX) media. On day 1, OA, 90MX, DV, and LV1X yielded lower residual nitrite concentrations than the control, whereas HHP400, HHP600, and LAE did not. LAE, HHP400, and OA reduced L. monocytogenes population compared to the control after 1 day of storage by 2.38, 2.21, and 1.73 log10 colony-forming units per gram, respectively. PPTT did not achieve a significant reduction in L. monocytogenes populations. L. monocytogenes recovered and grew in all postlethality intervention treatments except HHP600. 90MX did not inhibit the growth of L. monocytogenes, while DV and LV1X did. Results of this study demonstrate the bactericidal properties of HHP, OA, and LAE and the bacteriostatic potential of natural antimicrobial ingredients such as DV and LV1X against L. monocytogenes.

Practice and Progress: Updates on Outbreaks, Advances in Research, and Processing Technologies for Low-moisture Food Safety.

Large, renowned outbreaks associated with low-moisture foods (LMFs) bring to light some of the potential, inherent risks that accompany foods with long shelf lives if pathogen contamination occurs. Subsequently, in 2013, Beuchat et al. (2013) noted the increased concern regarding these foods, specifically noting examples of persistence and resistance of pathogens in low-water activity foods (LWAFs), prevalence of pathogens in LWAF processing environments, and sources of and preventive measures for contamination of LWAFs. For the last decade, the body of knowledge related to LMF safety has exponentially expanded. This growing field and interest in LMF safety have led researchers to delve into survival and persistence studies, revealing that some foodborne pathogens can survive in LWAFs for months to years. Research has also uncovered many complications of working with foodborne pathogens in desiccated states, such as inoculation methods and molecular mechanisms that can impact pathogen survival and persistence. Moreover, outbreaks, recalls, and developments in LMF safety research have created a cascading feedback loop of pushing the field forward, which has also led to increased attention on how industry can improve LMF safety and raise safety standards. Scientists across academia, government agencies, and industry have partnered to develop and evaluate innovate thermal and nonthermal technologies to use on LMFs, which are described in the presented review. The objective of this review was to describe aspects of the extensive progress made by researchers and industry members in LMF safety, including lessons-learned about outbreaks and recalls, expansion of knowledge base about pathogens that contaminate LMFs, and mitigation strategies currently employed or in development to reduce food safety risks associated with LMFs.

Impact of nitrite-embedded packaging film on quality and sensory attributes of alternatively-cured and nitrite-free bologna.

The objectives were to determine the effects of post-thermal processing nitrite-embedded film (NEF) packaging on the quality attributes of alternatively-cured (nitrite from celery juice powder (AC)) and nitrite-free bologna. Attributes evaluated included lipid oxidation, instrumental color, pigment concentration, and sensory properties such as cured meat flavor, aroma, and color. Three bologna formulations, each packaged with two packaging films were produced. A conventionally-cured control formulation (with nitrite from sodium nitrite; CON), a nitrite-free formulation (UCC), and an alternatively cured formulation (nitrite from cultured celery juice powder; AC) were packaged in conventional (CF) or nitrite-embedded (NEF) film. Instrumental a* values (measured during both light and dark storage at intervals of 7 or 14 days over 126 days of storage) and cured pigment concentration (measured at 14-day intervals over 84 days of storage) were significantly greater (P < 0.05) for the UCC-NEF treatment compared to its conventional film counterpart, UCC-CF. No significant differences (P > 0.05) for lipid oxidation (TBARS values) were observed with NEF. Trained sensory panelists, who evaluated samples at 14-day intervals over 70 days of storage, found significantly greater (P < 0.05) cured aroma, cured flavor, pink color and less off-flavor for uncured bologna packaged in NEF compared to conventional film. For the uncured bologna formulation, NEF packaging provided cured meat attributes comparable to the control formulation that included nitrite. This is the first time that cured aroma and flavor have been observed when nitrite from packaging film is added to a cooked meat product under anaerobic conditions.

A longitudinal study of the establishment and proliferation of Enterococcus on a dairy farm.

Enterococci are Gram-positive, facultative anaerobic cocci. They are found in many environments (including milk and dairy products, vegetables, plants, cereals, and meats). Enterococci are considered commensal organisms, but can also be opportunistic pathogens associated with morbidity and mortality of humans and animals. A longitudinal study of antibiotic resistance of Enterococcus to ampicillin, erythromycin, and tetracycline was conducted on an academic teaching farm. Environmental samples were collected by drag swabs at select locations prior to and after the introduction of livestock. All samples were initially processed and screened with specialized media, and then replica plated on tryptic soy agar containing a predetermined amount of antibiotic. There was some variation in the quantity of bacterial and antibiotic-resistant colonies; however, resistance to tetracycline was extremely high. The increases of too numerous to count populations were not time-dependent and appeared consistently after the placement of cows. There is little information on the prevalence and epidemiology of antibiotic resistance of Enterococci outside of the hospital setting, including on dairy farms. Longitudinal studies are important in providing insight into the dynamics of establishment and proliferation of bacteria and of antibiotic resistance.

Survival of Clostridium perfringens, Staphylococcus aureus and Salmonella enterica in alternatively cured bacon during cooking and process deviations.

Pork bellies were injected with four different alternative curing brines. The bellies were inoculated on the surface and at a depth of 1 cm with multiple strains of Clostridium perfringens, Staphylococcus aureus and Salmonella enterica. The bellies were processed using either a standard process cycle or an interrupted process cycle to simulate a process deviation. Additionally, laboratory simulation of the same cycles was conducted where surface inoculated pork belly samples (22 ± 1 g) were processed in a circulating water bath. Microbiological populations were determined at the beginning, mid-point and end of the cycles, and the change in population was calculated for each bacterium at each time point, by comparing the population to the initial inoculated population. Irrespective of the brine or process cycle, the populations of all of the inoculated bacteria on both the surface and interior samples had decreased by the end of the process. There was no difference in the reductions in bacterial populations for all of the inoculated bacteria by brine type or by sample location (P > 0.30). There were differences in the microbial population reductions for C. perfringens attributable to the processing cycle (P < 0.001), with less population reductions associated with the standard cycle when compared to the interrupted cycle. However, no differences (P > 0.10) were observed in the population reductions between the two processing cycles for either S. aureus or S. enterica.

The establishment of Enterobacteriaceae and Salmonella London in a new dairy farm environment.

Salmonella spp. are important zoonotic pathogens in humans and animals. A longitudinal study was conducted at the Iowa State University's campus (at the Dairy/Animal Science Education and Discovery Facility) to observe change in Enterobacteriaceae (specifically Salmonella) before and after the placement of dairy livestock. To our knowledge, this is the first study that evaluated environmental changes of Gram-negative organisms in a new dairy farm environment. Environmental samples were taken using drag swabs and immediately processed in the laboratory using phenotypic methods (replica plating, the BBL Crystal Identification System for enteric/nonfermenter organisms™, and plating on specialized media/broths). Genotypic methods were also used (BAX PCR™ and pulsed-field gel electrophoresis). Organisms identified as Salmonella were sent to the National Veterinary Services Laboratory (Ames, IA) for confirmatory serotyping. Resistance to antibiotics (ampicillin, nalidixic acid, and tetracycline) was determined by replica plating of Enterobacteriaceae and Salmonella isolates using the guidelines of the National Antimicrobial Resistance Monitoring System and Clinical and Laboratory Standards Institute. The microflora of Enterobacteriaceae changed as cattle were introduced and as time progressed. Additionally, multidrug-resistant isolates began to appear immediately after cattle were introduced (multidrug-resistant isolates were rare prior to introduction of livestock). Variables such as temperature and humidity did not affect the proliferation of bacterial organisms. Seventeen Salmonella isolates were identified as Salmonella London and three isolates as Salmonella Montevideo. Based on pulsed-field gel electrophoresis-generated dendrograms, it is likely that 17 Salmonella London isolates and 3 Salmonella Montevideo isolates are clonal.

Comparison of Antimicrobial Resistance Profiles in Salmonella spp. from Swine Upon Arrival and Postslaughter at the Abattoir.

Antimicrobial resistance (AMR) developed by Salmonella within animals used for food products is a major global issue. Monitoring AMR in animals destined for slaughter is, therefore, critical. Abattoirs may serve as potential candidate checkpoints for monitoring resistance patterns on farms. A complicating factor, however, is the impact of lairage on Salmonella detected in pigs at slaughter. This study sought to compare AMR patterns in Salmonella spp. in swine collected upon arrival (fecal samples) at the abattoir with those at postslaughter (cecal samples) and evaluate the feasibility of using slaughterhouse samples for surveillance of prevailing AMR Salmonella on farms. Eighty-four Salmonella isolates were recovered from a large, midwestern U.S. abattoir between September and November 2013. Isolates were tested for phenotypic AMR to 12 antimicrobials using the broth microdilution assay. Whole-genome sequencing identified the AMR genes harbored by the strains. Significant differences were observed in the isolate phenotypes and genotypes; however, no significant difference was observed in genotypic resistance patterns. Hence, the AMR profiles of Salmonella spp. postslaughter cannot be predicted from preslaughter samples. Further research considering the genetic diversity of isolates and statistical power of the genotypic analysis is warranted to improve the performance of WGS-inferred antimicrobial susceptibility.

Efficacy of ultraviolet light exposure against survival of Listeria monocytogenes on conveyor belts.

Listeria monocytogenes has been repeatedly isolated from foods and food-processing facilities including food contact surfaces such as conveyor belts (CB). CBs are often difficult to clean and require rigorous sanitation programs for decontamination. Ultraviolet (UV) light has exhibited microbicidal properties on food contact surfaces and this study was conducted to determine the efficacy of UV against L. monocytogenes on CB made of different materials. A four-strain cocktail of L. monocytogenes (serotypes 3A, 4A, 4B, and 4C) was made to give a suspension of approximately 10(7) CFU/mL. CBs made from four different types of materials, (1) Ropanyl DM 8/2 A2 + 04 (belt 1), (2) Volta FRMW-3.0 (belt 2), (3) Volta FRMB-3.0 (belt 3), and (4) Ropanyl DM (belt 4), were inoculated with 1 mL of the four-strain cocktail (approximately 10(7) CFU/mL) of the bacterial suspension. CBs were treated with UV light (254 nm) for 1 and 3 sec at 5.53 and 5.95 mW/cm(2). Three replications of the experiments were conducted. Two-way analysis of variance of survival populations of L. monocytogenes showed that bacterial counts were significantly reduced (p < 0.05) on all belt types irrespective of UV light intensities and times of exposure. L. monocytogenes populations were reduced (p < 0.05) to below detection limits on belts 1, 2, and 3 after exposure to 5.95 mW/cm(2) UV light intensity for 3 sec. L. monocytogenes-inoculated CBs that were exposed to 5.53 mW/cm(2) showed higher (p < 0.05) survival populations of L. monocytogenes compared with 5.95 mW/cm(2) on all the four CBs. Belt 4 showed survival populations of L. monocytogenes ranging from 1.42 to 1.73 log(10) CFU/cm(2) after UV light treatment for 1 and 3 sec. UV light can be effectively used to reduce L. monocytogenes contamination on CBs.

Evaluation of Escherichia coli biotype 1 as a surrogate for Escherichia coli O157:H7 for cooking, fermentation, freezing, and refrigerated storage in meat processes.

Five Escherichia coli biotype I isolates were compared with E. coli O157:H7 under four common meat processing conditions. The processes that were evaluated were freezing, refrigerating, fermentation, and thermal inactivation. For each study, at least one surrogate organism was not statistically different when compared with E. coli O157:H7. However, the four studies did not consistently show the same isolate as having this agreement. The three studies that involved temperature as a method of controlling or reducing the E. coli population all had at least one possible surrogate in common. In the fermentation study, only one isolate (BAA-1429) showed no statistical difference when compared with E. coli O157:H7. However, the population reductions that were observed indicated the isolates BAA-1427 and BAA-1431 would overestimate the surviving E. coli O157:H7 population in a fermented summer sausage. When all of the data from all of the surrogates were examined, it was found that isolates BAA-1427, BAA-1429, and BAA-1430 would be good surrogates for all four of the processes that were examined in this study. There was no statistical difference noted between these three isolates and E. coli O157:H7 in the refrigeration study. These isolates resulted in smaller population reductions than did E. coli O157:H7 in the frozen, fermentation, and thermal inactivation studies. This would indicate that these isolates would overpredict the E. coli O157:H7 population in these three instances. This overprediction results in an additional margin of safety when using E. coli biotype 1 as a surrogate.

Fluorescent protein-marked Escherichia coli biotype I strains as surrogates for enteric pathogens in validation of beef carcass interventions.

The efficacy of antimicrobial interventions implemented in slaughter establishments to reduce enteric pathogens on beef carcasses should optimally be validated under commercial operation conditions. This study was conducted to identify surrogate organisms for enteric pathogens that could be used to validate beef carcass interventions. The growth, resistance, and attachment properties of nonpathogenic fluorescent protein-marked Escherichia coli strains were compared with those of E. coli O157:H7 and Salmonella strains. Growth curves were obtained based on growth in tryptic soy broth at 37 degrees C. In general, growth parameters were not different among potential surrogates and target pathogens (P > 0.05). Thermal resistance was compared in phosphate-buffered saline (pH 7.4) at 55, 60, and 65 degrees C, and D-values of potential surrogates were not different (P > 0.05) or were higher (P < 0.05) than those of the target pathogens. Acid resistance was tested in phosphate-buffered saline acidified with L-lactic acid at pH 2.5, 3.0, and 3.5, and log reductions (CFU per milliliter) were not different (P > 0.05) among potential surrogates and E. coli O157:H7 strains; however, some Salmonella serotypes were less acid resistant than were surrogates (P < 0.05). The cell surface hydrophobicity was different (P < 0.05) among surrogates and some E. coli O157:H7 strains, but the strength of attachment to beef carcasses was not different (P > 0.05) among all microorganisms. Log reductions (CFU per square centimeter) after application of hot water washes and 2% L-lactic acid sprays on beef carcasses were not different (P > 0.05) among surrogates and pathogens. The nonpathogenic E. coli strains evaluated in this study could be used as surrogates for E. coli O157:H7 and Salmonella to validate hot water and lactic acid interventions on beef carcasses.

Antimicrobial-resistant bacterial infections from foods of animal origin: understanding and effectively communicating to consumers.

Consumers are increasingly interested in the attributes of the food they consume. This includes what is in the food and how it was raised; and at least some consumers are willing to pay a premium for products with specific attributes. However, the current plethora of labels on the market does not adequately address this issue; rather than providing actionable information, most labels add to the consumer confusion. In addition, there is a tendency toward "absence labels" that can contribute to a negative consumer perception of conventional products that may or may not include the attribute in question. Communication with consumers about the complex and highly technical issue of antimicrobial resistance (AMR) is challenging, and experiences from communication efforts about food safety-related issues demonstrate exactly how challenging this is to communicate clearly. General lessons learned from the science of risk communication can help guide efforts to communicate about the challenging issue of AMR. There are efforts underway to chart out a new approach. A new labeled animal production certification program is under development to provide choice for consumers, while reducing consumer confusion, which mandates antibiotic stewardship practices.

Application of colicin E1 as a prefabrication intervention strategy.

Colicin E1 (ColE1) is a bacteriocin produced by and effective against Escherichia coli and related species. The current study examined ColE1 as a potential intervention strategy for controlling E. coli O157:H7 contamination on beef carcasses. Untrimmed beef round roasts were cut into sample sizes of 5.08 by 2.52 by 5.08 cm, with an adipose layer covering an entire surface of lean beef. Samples were placed on sterile metal hooks and inoculated with E. coli O157:H7 at a level of 5 log CFU/ml in sterile tryptic soy broth. After inoculum attachment, ColE1 in doses of 0, 100 microg, 500 microg, and 1 mg/ml of 10 mM Tris, pH 7.6, was sprayed on the samples for a period of 10 min. Samples were evaluated at 0 and 30 min, 1, 2, 3, 4, and 5 days post-spraying at 10 degrees C for E. coli O157:H7 inhibition. Treating samples with 500 microg and 1 mg of ColE1 effectively inhibited E. coli O157:H7 growth. When these doses were applied to samples inoculated with E. coli WS 3331, E. coli contamination was reduced by 4 and 7 log CFU/cm2, respectively, compared with the untreated control samples. In strain WS 3331, treatment with 1 mg ColE1 significantly inhibited growth of E. coli O157:H7 compared with the untreated control during the entire study. ColE1 provided powerful reduction of E. coli O157:H7 as a beef carcass spray intervention.

Use of Nonpathogenic Escherichia coli Surrogates as Predictors of the Survival of Nontyphoidal Salmonella, non-O157 Shiga Toxin-Producing Escherichia coli, and Escherichia coli O157 Populations after High Hydrostatic Pressure Processing.

Validated surrogates are a useful tool for studying the response of pathogens to food safety interventions, but better surrogates are needed for studies using high pressure processing. Ground beef (85% lean, 15% fat) was inoculated separately with mixed cultures of Escherichia coli O157, non-O157 Shiga toxin-producing E. coli, nontyphoidal Salmonella, and nonpathogenic E. coli surrogate bacteria. The inoculated ground beef was subjected to high hydrostatic pressures of 200, 400, and 600 MPa for 4, 6, and 8 min at each pressure. High pressure processing at 200 MPa reduced the inoculated populations of the pathogenic bacteria by 0.9 to 1.8 log CFU/g, 400 MPa reduced the inoculated populations by 2.5 to 3.6 log CFU/g, and 600 MPa reduced the inoculated populations by 4.5 to 5.6 log CFU/g. The nonpathogenic E. coli surrogates were more resistant to the effects of high pressure processing than were the inoculated pathogen populations. This finding suggests that the nonpathogenic E. coli surrogates could be used as process control indicators for high pressure processing of ground beef to predict a specific level of pathogen reduction. The surviving populations of the potential surrogate bacteria were proportional to the surviving populations of the pathogenic bacteria. The models allow for an estimation of the potential surviving populations of the pathogenic bacteria based on quantitative results of the populations of the surrogate bacteria.

Inhibitory activity of colicin E1 against Listeria monocytogenes.

Colicins are gram-negative bacteriocins produced by and effective against Escherichia coli and related species. Colicin E1 (ColE1) is composed of three functional domains, which collectively have a pore-forming effect on targeted bacteria. ColE1 binding and translocation domains are highly specific in contrast to the pore-forming domain, implying that ColE1 could be broadly effective. In this study, the activity of ColE1 against Listeria monocytogenes was evaluated in broth and on surfaces of ready-to-eat products. Individual strains of L. monocytogenes were examined in broth containing ColE1 at 0, 0.1, 1, or 10 microg/ml. Although strain differences in sensitivity to ColE1 existed, growth was significantly reduced in all strains at doses as low as 0.1 microg/ml. Sterilized ham slices were submerged in a five-strain L. monocytogenes cocktail (either 7 or 4 log CFU/ ml) and placed in vacuum packages containing 0, 1, 5, 10, 25, or 50 microg of ColE1. Ham slices were then stored at 4 or 10 degrees C, and samples were removed and examined for L. monocytogenes after 1, 3, 7, and 14 days. Reduction of L. monocytogenes by ColE1 was dependent on initial inoculum concentration and storage temperature. For slices stored at 4 degrees C, treatment with 25 microg reduced Listeria growth below detection limits for the slices inoculated with 4 log CFU/ml for the entire 14 days, whereas for the 7-log CFU/ml slices, growth was detected at 7 days postinoculation. For slices stored at 10 degrees C, 10 microg/ml ColE1 significantly inhibited growth of L. monocytogenes for up to 3 days for both inoculation groups. These data indicate that ColE1 is highly effective against Listeria.

Modeling the relationship between food animal health and human foodborne illness.

To achieve further reductions in foodborne illness levels in humans, effective pre-harvest interventions are needed. The health status of food animals that are destined to enter the human food supply chain may be an important, although often overlooked, factor in predicting the risk of human foodborne infections. The health status of food animals can potentially influence foodborne pathogen levels in three ways. First, diseased animals may shed higher levels of foodborne pathogens. Second, animals that require further handling in the processing plant to remove affected parts may lead to increased microbial contamination and cross-contamination. Finally, certain animal illnesses may lead to a higher probability of mistakes in the processing plant, such as gastrointestinal ruptures, which would lead to increased microbial contamination and cross-contamination. Consequently, interventions that reduce the incidence of food animal illnesses might also help reduce bacterial contamination on meat, thereby reducing human illness. Some of these interventions, however, might also present a risk to human health. For example, the use of antibiotics in food animals can reduce rates of animal illness but can also select for antibiotic-resistant bacteria which can threaten human treatment options. In this study, we present a mathematical model to evaluate human health risks from foodborne pathogens associated with changes in animal illness. The model is designed so that potential human health risks and benefits from interventions such as the continued use of antibiotics in animal agriculture can be evaluated simultaneously. We applied the model to a hypothetical example of Campylobacter from chicken. In general, the model suggests that very minor perturbations in microbial loads on meat products could have relatively large impacts on human health, and consequently, small improvements in food animal health might result in significant reductions in human illness.

Processes to Preserve Spice and Herb Quality and Sensory Integrity During Pathogen Inactivation.

Selected processing methods, demonstrated to be effective at reducing Salmonella, were assessed to determine if spice and herb quality was affected. Black peppercorn, cumin seed, oregano, and onion powder were irradiated to a target dose of 8 kGy. Two additional processes were examined for whole black peppercorns and cumin seeds: ethylene oxide (EtO) fumigation and vacuum assisted-steam (82.22 °C, 7.5 psia). Treated and untreated spices/herbs were compared (visual, odor) using sensory similarity testing protocols (α = 0.20; ß = 0.05; proportion of discriminators: 20%) to determine if processing altered sensory quality. Analytical assessment of quality (color, water activity, and volatile chemistry) was completed. Irradiation did not alter visual or odor sensory quality of black peppercorn, cumin seed, or oregano but created differences in onion powder, which was lighter (higher L* ) and more red (higher a* ) in color, and resulted in nearly complete loss of measured volatile compounds. EtO processing did not create detectable odor or appearance differences in black peppercorn; however visual and odor sensory quality differences, supported by changes in color (higher b* ; lower L* ) and increased concentrations of most volatiles, were detected for cumin seeds. Steam processing of black peppercorn resulted in perceptible odor differences, supported by increased concentration of monoterpene volatiles and loss of all sesquiterpenes; only visual differences were noted for cumin seed. An important step in process validation is the verification that no effect is detectable from a sensory perspective.