Inhibitory Effect of Select Nitrocompounds and Chlorate against Yersinia ruckeri and Yersinia aleksiciae In Vitro.

Yersinia ruckeri is an important fish pathogen causing enteric redmouth disease. Antibiotics have traditionally been used to control this pathogen, but concerns of antibiotic resistance have created a need for alternative interventions. Presently, chlorate and certain nitrocompounds were tested against Y. ruckeri as well as a related species within the genus, Y. aleksiciae, to assess the effects of these inhibitors. The results reveal that 9 mM chlorate had no inhibitory effect against Y. ruckeri, but inhibited growth rates and maximum optical densities of Y. aleksciciae by 20-25% from those of untreated controls (0.46 h-1 and 0.29 maximum optical density, respectively). The results further reveal that 2-nitropropanol and 2-nitroethanol (9 mM) eliminated the growth of both Y. ruckeri and Y. aleksiciae during anaerobic or aerobic culture. Nitroethane, ethyl nitroacetate and ethyl-2-nitropropionate (9 mM) were less inhibitory when tested similarly. Results from a mixed culture of Y. ruckeri with fish tank microbes and of Y. aleksiciae with porcine fecal microbes reveal that the anti-Yersinia activity of the tested nitrocompounds was bactericidal, with 2-nitropropanol and 2-nitroethanol being more potent than the other tested nitrocompounds. The anti-Yersinia activity observed with these tested compounds warrants further study to elucidate the mechanisms of action and strategies for their practical application.

A quantitative risk metric to support individual sanitary measure reviews in international trade.

In order for the United States Department of Agriculture's (USDA) Food Safety and Inspection Service (FSIS) to make an equivalence determination for a foreign meat, poultry or egg products inspection procedure that differs from FSIS inspection procedures (an Individual Sanitary Measure or ISM), a country must demonstrate objectively that its food safety inspection system provides the same level of public health protection as the FSIS inspection system. To evaluate microbiological testing data that such countries may submit to this end, we present a possible risk metric to inform FSIS's assessment of whether products produced under an alternative inspection system in another country pose no greater consumer risk of foodborne illness than products produced under FSIS inspection. This metric requires evaluation of prevalence estimates of pathogen occurrence in products for the foreign country and the U.S. and determining what constitutes an unacceptable deviance of another country's prevalence from the U.S. prevalence, i.e., the margin of equivalence. We define the margin of equivalence as a multiple of the standard error of the U.S. prevalence estimate. Minimizing the margin of equivalence ensures the maximum public health protection for U.S. consumers, but an optimum choice must also avoid undue burden for quantitative data from alternative inspection systems in the foreign country. Across a wide range of U.S. prevalence levels and sample sizes, we determine margin of equivalence values that provide high confidence in conclusions as to whether or not the country's product poses no greater risk of foodborne illness from microbiological pathogens. These margins of equivalence can be used to inform FSIS's equivalence determination for an ISM request from a foreign country. Illustrative examples are used to support this definition of margin of equivalence. This approach is consistent with the World Trade Organization's concept of risk equivalence and is transparent and practical to apply in situations when FSIS makes an equivalence determination for an ISM requested by a foreign country.

Whole-Genome Sequence of Aeromonas hydrophila CVM861 Isolated from Diarrhetic Neonatal Swine.

Aeromonas hydrophila are ubiquitous in the environment and are highly distributed in aquatic habitats. They have long been known as fish pathogens but are opportunistic human pathogens. Aeromonas spp. have persisted through food-processing safeguards and have been isolated from fresh grocery vegetables, dairy, beef, pork, poultry products and packaged ready-to-eat meats, thus providing an avenue to foodborne illness. A beta-hemolytic, putative Escherichia coli strain collected from diarrheic neonatal pigs in Oklahoma was subsequently identified as A. hydrophila, and designated CVM861. Here we report the whole-genome sequence of A. hydrophila CVM861, SRA accession number, SRR12574563; BioSample number, SAMN1590692; Genbank accession number SRX9061579. The sequence data for CVM861 revealed four Aeromonas-specific virulence genes: lipase (lip), hemolysin (hlyA), cytonic enterotoxin (ast) and phospholipid-cholesterolacyltransferase (GCAT). There were no alignments to any virulence genes in VirulenceFinder. CVM861 contained an E. coli resistance plasmid identified as IncQ1_1__M28829. There were five aminoglycoside, three beta-lactam, and one each of macrolide, phenicol, sulfonamide, tetracycline and trimethoprim resistance genes, all with over 95% identity to genes in the ResFinder database. Additionally, there were 36 alignments to mobile genetic elements using MobileElementFinder. This shows that an aquatic pathogen, rarely considered in human disease, contributes to the resistome reservoir and may be capable of transferring resistance and virulence genes to other more prevalent foodborne strains such as E. coli or Salmonella in swine or other food production systems.

Assessment of the Risk of Salmonellosis Linked to the Consumption of Liquid Egg Products Made from Internally Contaminated Shell Eggs Initially Stored at 65°F (18°C) Compared with Eggs Stored at 45°F (7°C).

ABSTRACT: According to the U.S. Food and Drug Administration's (FDA's) rule on "Prevention of Salmonella Enteritidis in Shell Eggs during Production, Storage, and Transportation," shell eggs intended for human consumption are required to be held or transported at or below 45°F (7.2°C) ambient temperature beginning 36 h after time of lay. Meanwhile, eggs in hatcheries are typically stored at a temperature of 65°F (18.3°C). Although most of those eggs are directed to incubators for hatching, excess eggs have the potential to be diverted for human consumption as egg products through the "breaker" market if these eggs are refrigerated in accordance with FDA's requirement. Combining risk assessment models developed by the U.S. Department of Agriculture's Food Safety and Inspection Service for shell eggs and for egg products, we quantified and compared Salmonella Enteritidis levels in eggs held at 65°F versus 45°F, Salmonella Enteritidis levels in the resulting egg products, and the risk of human salmonellosis from consumption of those egg products. For eggs stored 5 days at 65°F (following 36 h at 75°F [23.9°C] in the layer house), the mean level of Salmonella Enteritidis contamination is 30-fold higher than for eggs stored at 45°F. These increased levels of contamination lead to a 47-fold increase in the risk of salmonellosis from consumption of egg products made from these eggs, with some variation in the public health risk on the basis of the egg product type (e.g., whole egg versus whole egg with added sugar). Assuming that 7% of the liquid egg product supply originates from eggs stored at 65°F versus 45°F, this study estimates an additional burden of 3,562 cases of salmonellosis per year in the United States. A nominal range uncertainty analysis suggests that the relative increase in the risk linked to the storage of eggs at higher temperature estimated in this study is robust to the uncertainty surrounding the model parameters. The diversion of eggs from broiler production to human consumption under the current storage practices of 65°F (versus 45°F) would present a substantive overall increase in the risk of salmonellosis.

Parametric distributions of underdiagnosis parameters used to estimate annual burden of illness for five foodborne pathogens.

Estimates of the burden of bacterial foodborne illness are used in applications ranging from determining economic losses due to a particular pathogenic organism to improving our understanding of the effects of antimicrobial resistance or changes in pathogen serotype. Estimates of the total number of illnesses can be derived by multiplying the number of observed illnesses, as reported by a specific active surveillance system, by an underdiagnosis factor that describes the relationship between observed and unobserved cases. The underdiagnosis factor can be a fixed value, but recent research efforts have focused on characterizing the inherent uncertainty in the surveillance system with a computer simulation. Although the inclusion of uncertainty is beneficial, re-creating the simulation results for every application can be burdensome. An alternative approach is to describe the underdiagnosis factor and its uncertainty with a parametric distribution. The use of such a distribution simplifies analyses by providing a closed-form definition of the underdiagnosis factor and allows this factor to be easily incorporated into Bayesian models. In this article, we propose and estimate parametric distributions for the underdiagnosis multipliers developed for the FoodNet surveillance systems in the United States. Distributions are provided for the five foodborne pathogens deemed most relevant to meat and poultry.

Fate of Shiga toxin-producing O157:H7 and non-O157:H7 Escherichia coli cells within blade-tenderized beef steaks after cooking on a commercial open-flame gas grill.

We compared the fate of cells of both Shiga toxin-producing Escherichia coli O157:H7 (ECOH) and Shiga toxin-producing non-O157:H7 E. coli (STEC) in blade-tenderized steaks after tenderization and cooking on a gas grill. In phase I, beef subprimal cuts were inoculated on the lean side with about 5.5 log CFU/g of a five-strain mixture of ECOH or STEC and then passed once through a mechanical blade tenderizer with the lean side facing up. In each of two trials, 10 core samples were removed from each of two tenderized subprimals and cut into six consecutive segments starting from the inoculated side. Ten total cores also were obtained from two nontenderized (control) subprimals, but only segment 1 (the topmost segment) was sampled. The levels of ECOH and STEC recovered from segment 1 were about 6.0 and 5.3 log CFU/g, respectively, for the control subprimals and about 5.7 and 5.0 log CFU/g, respectively, for the tenderized subprimals. However, both ECOH and STEC behaved similarly in terms of translocation, and cells of both pathogen cocktails were recovered from all six segments of the cores obtained from tenderized subprimals, albeit at lower levels in segments 2 to 6 than those found in segment 1. In phase II, steaks (2.54 and 3.81 cm thick) cut from tenderized subprimals were subsequently cooked (three steaks per treatment) on a commercial open-flame gas grill to internal temperatures of 48.9, 54.4, 60.0, 65.6, and 71.1°C. Regardless of temperature or thickness, we observed 2.0- to 4.1-log and 1.5- to 4.5-log reductions in ECOH and STEC levels, respectively. Both ECOH and STEC behaved similarly in response to heat, in that cooking eliminated significant numbers of both pathogen types; however, some survivors were recovered due, presumably, to uneven heating of the blade-tenderized steaks.

Inactivation of Shiga toxin-producing O157:H7 and non-O157:H7 Shiga toxin-producing Escherichia coli in brine-injected, gas-grilled steaks.

We quantified translocation of Escherichia coli O157:H7 (ECOH) and non-O157:H7 verocytotoxigenic E. coli (STEC) into beef subprimals after brine injection and subsequently monitored their viability after cooking steaks cut therefrom. Beef subprimals were inoculated on the lean side with ca. 6.0 log CFU/g of a five-strain cocktail of rifampin-resistant ECOH or kanamycin-resistant STEC, and then passed once through an automatic brine-injector tenderizer, with the lean side facing upward. Brine solutions (9.9% ± 0.3% over fresh weight) consisted of 3.3% (wt/vol) of sodium tripolyphosphate and 3.3% (wt/vol) of sodium chloride, prepared both with (Lac(+), pH = 6.76) and without (Lac(-), pH = 8.02) a 25% (vol/vol) solution of a 60% potassium lactate-sodium diacetate syrup. For all samples injected with Lac(-) or Lac(+) brine, levels of ECOH or STEC recovered from the topmost 1 cm (i.e., segment 1) of a core sample obtained from tenderized subprimals ranged from ca. 4.7 to 6.3 log CFU/g; however, it was possible to recover ECOH or STEC from all six segments of all cores tested. Next, brine-injected steaks from tenderized subprimals were cooked on a commercial open-flame gas grill to internal endpoint temperatures of either 37.8 °C (100 °F), 48.8 °C (120 °F), 60 °C (140 °F), or 71.1 °C (160 °F). Regardless of brine formulation or temperature, cooking achieved reductions (expressed as log CFU per gram) of 0.3 to 4.1 of ECOH and 0.5 to 3.6 of STEC. However, fortuitous survivors were recovered even at 71.1 °C (160 °F) for ECOH and for STEC. Thus, ECOH and STEC behaved similarly, relative to translocation and thermal destruction: Tenderization via brine injection transferred both pathogens throughout subprimals and cooking highly contaminated, brine-injected steaks on a commercial gas grill at 71.1 °C (160 °F) did not kill all cells due, primarily, to nonuniform heating (i.e., cold spots) within the meat.

Determining relationships between the seasonal occurrence of Escherichia coli O157:H7 in live cattle, ground beef, and humans.

The prevalence and concentration of many foodborne pathogens exhibit seasonal patterns at different stages of the farm-to-table continuum. Escherichia coli O157:H7 is one such pathogen. While numerous studies have described the seasonal trend of E. coli O157:H7 in live cattle, ground beef, and human cases, it is difficult to relate the results from these different studies and determine the interrelationships that drive the seasonal pattern of beef-related human illnesses. This study uses a common modeling approach, which facilitates the comparisons across data sets, to relate prevalence in live cattle to raw ground beef and human illness. The results support an intuitive model where a seasonal rise of E. coli O157:H7 in cattle drives increased ground beef prevalence and a corresponding rise in the human case rate. We also demonstrate the use of these models to assess the public health impact of consumer behaviors. We present an example that suggests that the probability of illness, associated with summertime cooking and handling practices, is not substantially higher than the baseline probability associated with more conventional cooking and handling practices during the remainder of the year.

Streamlined analysis for evaluating the use of preharvest interventions intended to prevent Escherichia coli O157:H7 illness in humans.

The U.S. Department of Agriculture Food Safety Inspection Service is responsible for ensuring the safety of meat, poultry, and egg products consumed in the United States. Here we describe a risk assessment method that provides quantitative criteria for decision makers tasked with developing food safety policies. To demonstrate the utility of this method, we apply it to a hypothetical case study on the use of an Escherichia coli O157:H7 cattle vaccine to prevent human illness caused by consuming beef. A combination of quantitative risk assessment methods and marginal economic analysis are used to describe the maximum cost per unit that would still allow the vaccine to be a cost-effective intervention as well as the minimum effectiveness it could have at a fixed cost. We create two economic production functions where the input is number of vaccinated cattle and the output is human illnesses prevented. The production functions are then used for marginal economic analysis to assess the cost/benefit ratio of using the vaccine to prevent foodborne illness. In our case study, it was determined that vaccinating the entire U.S. herd at a cost of between $2.29 and $9.14 per unit (depending on overall effectiveness of the vaccine) would be a cost-effective intervention for preventing E. coli O157:H7 illness in humans. In addition, we determined that vaccinating only a given fraction of the herd would be cost effective for vaccines that are less effective or more costly. For example, a vaccine costing $9.00 per unit that had a 100% efficacy but required 100% herd coverage for immunity would be cost effective for use in about 500,000 cattle each year-equating to an estimated 750 human illnesses prevented per annum. We believe this approach could be useful for public health policy development in a wide range of applications.

Risk assessment to estimate the probability of a chicken flock infected with H5N1 highly pathogenic avian influenza virus reaching slaughter undetected.

Highly pathogenic avian influenza (HPAI) H5N1 is an infectious disease of fowl that can cause rapid and pervasive mortality resulting in complete flock loss. It has also been shown to cause death in humans. Although H5N1 HPAI virus (HPAIV) has not been identified in the United States, there are concerns about whether an infected flock could remain undetected long enough to pose a risk to consumers. This paper considers exposure from an Asian lineage H5N1 HPAIV-infected chicken flock given that no other flocks have been identified as H5N1 HPAIV positive (the index flock). A state-transition model is used to evaluate the probability of an infected flock remaining undetected until slaughter. This model describes three possible states within the flock: susceptible, infected, and dead, and the transition probabilities that predict movements between the possible states. Assuming a 20,000-bird house with 1 bird initially infected, the probability that an H5N1 HPAIV-infected flock would be detected before slaughter is approximately 94%. This is because H5N1 HPAIV spreads rapidly through a flock, and bird mortality quickly reaches high levels. It is assumed that approximately 2% or greater bird mortality due to H5N1 HPAIV would result in on-farm identification of the flock as infected. The only infected flock likely to reach slaughter undetected is one that was infected within approximately 3.5 days of shipment. In this situation, there is not enough time for high mortality to present. These results suggest that the probability of an infected undetected flock going to slaughter is low, yet such an event could occur if a flock is infected at the most opportune time.

Review of induced molting by feed removal and contamination of eggs with Salmonella enterica serovar Enteritidis.

As laying hens age, egg production and quality decreases. Egg producers can impose an induced molt on older hens that results in increased egg productivity and decreased hen mortality compared with non-molted hens of the same age. This review discusses the effect of induced molting by feed removal on immune parameters, Salmonella enterica serovar Enteritidis (SE) invasion and subsequent production of SE-contaminated eggs. Experimental oral infections with SE show molted hens are more susceptible to SE infection and produce more SE-contaminated eggs in the first few weeks post-molt compared with pre-molt egg production. In addition, it appears that molted hens are more likely to disseminate SE into their environment. Molted hens are more susceptible to SE infection by contact exposure to experimentally infected hens; thus, transmission of SE among molted hens could be more rapid than non-molted birds. Histological examination of the gastrointestinal tracts of molted SE-infected hens revealed more frequent and severe intestinal mucosal lesions compared with non-molted SE-infected hens. These data suggest that induced molting by feed deprivation alters the normal asymptomatic host-pathogen relationship. Published data suggest the highest proportion of SE-positive eggs is produced within 1-5 weeks post-molt and decreases sharply by 6-10 weeks and dissipates to the background level for non-molted hens by 11-20 weeks. Appropriate treatment measures of eggs produced in the fist 5 weeks post-molting may decrease the risk of foodborne infections to humans.

Evaluating the effectiveness of pasteurization for reducing human illnesses from Salmonella spp. in egg products: results of a quantitative risk assessment.

As part of the process for developing risk-based performance standards for egg product processing, the United States Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) undertook a quantitative microbial risk assessment for Salmonella spp. in pasteurized egg products. The assessment was designed to assist risk managers in evaluating egg handling and pasteurization performance standards for reducing the likelihood of Salmonella in pasteurized egg products and the subsequent risk to human health. The following seven pasteurized liquid egg product formulations were included in the risk assessment model, with the value in parentheses indicating the estimated annual number of human illnesses from Salmonella from each: egg white (2636), whole egg (1763), egg yolk (708), whole egg with 10% salt (407), whole egg with 10% sugar (0), egg yolk with 10% salt (11), and egg yolk with 10% sugar (0). Increased levels of pasteurization were predicted to be highly effective mitigations for reducing the number of illnesses. For example, if all egg white products were pasteurized for a 6-log(10) reduction of Salmonella, the estimated annual number of illnesses from these products would be reduced from 2636 to 270. The risk assessment identified several data gaps and research needs, including a quantitative study of cross-contamination during egg product processing and characterization of egg storage times and temperatures (i) on farms and in homes, (ii) for eggs produced off-line, and (iii) for egg products at retail. Pasteurized egg products are a relatively safe food; however, findings from this study suggest increased pasteurization can make them safer.

Overview and summary of the Food Safety and Inspection Service risk assessment for Salmonella enteritidis in shell eggs, October 2005.

In 1998, the United States Department of Agriculture's Food Safety and Inspection Service (FSIS) and the Food and Drug Administration completed a risk assessment that indicated multiple interventions along the farm-to-table chain were needed to reduce the risk of human illness from Salmonella Enteritidis in shell eggs. Based on newly available data and improved modeling techniques, FSIS completed an updated risk assessment to examine the effect of pasteurization and refrigeration on reducing human illnesses from S. Enteritidis in shell eggs. The risk assessment model was written in Visual Basic for Applications (Microsoft, Redmond, WA) and run using Monte Carlo methods. The model estimated that if all shell eggs produced in the United States were pasteurized for a 3-log10 reduction of S. Enteritidis, the annual number of illnesses from S. Enteritidis in eggs would decrease from approximately 130,000 to 40,000. Pasteurization for a 5-log10 reduction of S. Enteritidis was estimated to reduce the annual number of illnesses to 19,000. The model also estimated that if all eggs produced in the United States were stored and held at 7.2 degrees C within 12 hours of lay, the annual number of illnesses from S. Enteritidis in eggs would decrease from 130,000 to 28,000. As a result, rapid cooling and pasteurization of shell eggs were predicted to be highly effective mitigations for reducing illnesses from consumption of S. Enteritidis in shell eggs.

Salmonella enteritidis in broiler chickens, United States, 2000-2005.

US Department of Agriculture Food Safety and Inspection Service (FSIS) data on Salmonella enterica serotype Enteritidis in broiler chicken carcass rinses collected from 2000 through 2005 showed the annual number of isolates increased >4-fold and the proportion of establishments with Salmonella Enteritidis-positive rinses increased nearly 3-fold (test for trend, p<0.0001). The number of states with Salmonella Enteritidis in broiler rinses increased from 14 to 24. The predominant phage types (PT) were PT 13 and PT 8, 2 strains that a recent Foodborne Diseases Active Surveillance Network (FoodNet) case-control study associated with eating chicken. FSIS is directing more sampling resources toward plants with marginal Salmonella control to reduce prevalence in products including broilers. The policy targets establishments with common Salmonella serotypes of human illness, including Salmonella Enteritidis. Voluntary interventions should be implemented by industry.

Estimate of illnesses from Salmonella enteritidis in eggs, United States, 2000.

Results from our model suggest that eating Salmonella enterica serovar Enteritidis-contaminated shell eggs caused 182,060 illnesses in the United States during 2000. Uncertainty about the estimate ranged from 81,535 (5th percentile) to 276,500 illnesses (95th percentile). Our model provides but 1 approach for estimating foodborne illness and quantifying estimate uncertainty.

Considering the complexity of microbial community dynamics in food safety risk assessment.

The potential for competitive inhibition to limit the growth of microbial pathogens in food raises questions about the external validity of typical predictive microbiology studies and suggests the need to consider microbial community dynamics in food safety risk assessment. Ecological theory indicates, however, that community dynamics are highly complex and may be very sensitive to initial conditions and random variation. Seemingly incongruous empirical results for Escherichia coli O157:H7 in ground beef are shown to be consistent with a simple theoretical model of interspecific competition. A potential means of incorporating community-level microbial dynamics into the food safety risk assessment process is explored.

Hazard analysis and critical control point (HACCP) history and conceptual overview.

The concept of Hazard Analysis and Critical Control Point (HACCP) is a system that enables the production of safe meat and poultry products through the thorough analysis of production processes, identification of all hazards that are likely to occur in the production establishment, the identification of critical points in the process at which these hazards may be introduced into product and therefore should be controlled, the establishment of critical limits for control at those points, the verification of these prescribed steps, and the methods by which the processing establishment and the regulatory authority can monitor how well process control through the HACCP plan is working. The history of the development of HACCP is reviewed, and examples of practical applications of HACCP are described.

Surveys of Salmonella enteritidis in Unpasteurized Liquid Egg and Spent Hens at Slaughter.

In a 1995 national survey of 937 unpasteurized liquid egg samples collected in breaker plants, 179 of 937 samples (19%) were Salmonella enterica serotype Enteritidis ( S. Enteritidis ) positive. The proportion of unpasteurized liquid egg samples positive for S. Enteritidis was highest in the Northern Region where 106 of 267 samples collected (40%) were S. Enteritidis -positive. These Northern Region results were over three times the S. Enteritidis prevalence detected from the other three regions, whose results ranged between 10% and 12% S. Enteritidis -positive samples. In a 1995 national survey of spent hens at slaughter, 136 of 305 flocks (45%) had at least one S. Enteritidis -positive pooled sample detected. Flock prevalence was highest in the Northern and Central Regions (64% and 40%, respectively); Southeastern and Western Regional flock prevalence levels were much lower (17% and 23%, respectively). A comparison of the 1991 and 1995 unpasteurized liquid egg and spent hen results suggest there has been no decline in S. Enteritidis occurrence in the commercial egg industry between 1991 and 1995. Salmonella Enteritidis phage type 4 was detected in the 1995 surveys of both spent hens and unpasteurized liquid egg but was not found in either survey in 1991. With the exception of one liquid egg sample from the Southeastern Region, S. Enteritidis phage type 4 was found only in the Western Region of the U.S. S. Enteritidis phage type 4 has emerged in the egg industry in the Western U.S. concurrently with an increase in the number of sporadic human phage type 4 isolates in California and Utah.

Environmental Survey by Manure Drag Sampling for Salmonella enteritidis in Chicken Layer Houses.

The Salmonella enteritidis Pilot Project (SEPP) was started in April 1992 as a cooperative effort between federal and state agencies, university laboratories, and the poultry industry in Pennsylvania to identify on-farm management practices which would reduce the S. enteritidis threat to public health. The SEPP evolved into the Pennsylvania Egg Quality Assurance Program (PEQAP) in 1994. This program uses many production practices and testing protocols outlined in the SEPP. A survey was conducted in 1995 to help evaluate the effectiveness of the program in reducing the prevalence of S. enteritidis in layer flocks. Forty-seven egg laying houses that had been in the SEPP since 1992 were evaluated in 1995 for the presence of S. enteritidis in the environment. Six of 47 houses (13%) were found positive for S. enteritidis on the basis of data collected by manure drag sampling, whereas in 1992 18 of the 47 houses (38%) had been positive for S. enteritidis . The percentage of S. enteritidis -positive samples declined from 21% in 1992 to 3.2% in 1995. This survey provides some evidence that the on-farm risk-reduction management practices identified in the SEPP and subsequently incorporated into the PEQAP have reduced S. enteritidis infections in Pennsylvania flocks.