Predictive modeling of thermal inactivation of non-O157 Shiga toxin-producing Escherichia coli in ground beef with varying fat contents.

A mathematical model to predict the thermal inactivation of non-O157 Shiga toxin-producing Escherichia coli (STEC) in ground beef was developed, with temperature and fat content of ground beef as controlling factors. Survival curves for a cocktail of non-O157 STEC strains in ground beef at four temperatures (55, 60, 65, and 68 °C) and six fat levels (5, 10, 15, 20, 25, and 30%) were generated. Nine primary models-log-linear, log-linear with tail, biphasic, sigmoidal, four-factor sigmoidal, Baranyi, Weibull, mixed Weibull, and Gompertz-were tested for fitting the survival curves. Primary modeling analysis showed the Weibull model had the highest accuracy factor and Akaike's weight, making it the best-fitting model. The parameters of the Weibull model were estimated using a nonlinear mixed, and response surface modeling was used to develop a second-order polynomial regression to estimate the impact of fat in ground beef and cooking temperature on the heat resistance of non-O157 STEC strains. The secondary model was successfully validated by comparing predicted lethality (log10 CFU/g) with the observed values for ground beef containing 10 and 27% fat at 58 and 62 °C. Process lethality obtained from experimental data was within the prediction interval of the predictive model. The developed model will assist the food industry in estimating the appropriate time and temperature required for cooking ground beef to provide adequate protection against STEC contaminants.

Prevalence and Antimicrobial Resistance of Salmonella from Antibiotic-Free Broilers During Organic and Conventional Processing.

ABSTRACT: Salmonella is one of the top causes for bacterial foodborne infections in the United States, emphasizing the importance of controlling this pathogen for protecting public health. Poultry and poultry products are commonly associated with Salmonella, and interventions during production and processing are necessary to manage the risk of infection due to consumption of poultry products. In recent times, the demand for organic and antibiotic-free poultry has increased owing to consumer perceptions and concerns of increasing prevalence of antimicrobial-resistant (AMR) pathogens. However, the microbiological effect of these management practices is not clear. This study was conducted to determine the difference in the AMR of Salmonella isolated from poultry processed conventionally and organically. Fecal samples, carcass rinses, and environmental samples were collected over 1 year and analyzed for the prevalence of Salmonella and AMR. Results of this experiment showed that organic chickens were associated with statistically higher levels of Salmonella during early processing steps. However, no difference in Salmonella prevalence was observed between organic and conventional carcasses postchill. In addition, for most antimicrobial agents tested, prevalence of AMR Salmonella in conventional processing was lower in this study than was reported by the National Antimicrobial Resistance Monitoring System for chickens at slaughter. These observations indicate that organic methods may introduce greater risk of Salmonella contamination; however, proper interventions during processing can abate this risk. In addition, this study supports the assertion that raising chickens without the use of antibiotics may result in lower prevalence of AMR Salmonella.

Prevalence and antimicrobial resistance of Campylobacter from antibiotic-free broilers during organic and conventional processing.

Campylobacter is one of the leading cause of foodborne illness in the US and worldwide, especially linked to poultry and poultry products. In recent years, the increasing popularity of organic chicken products and chickens raised without antibiotics (RWA) has resulted in more companies adopting organic and antibiotic-free production and processing methods; however, it is not evident what effect these practices have on pathogens such as Campylobacter. The purpose of this study was to determine the effects of RWA and organic methods on the prevalence and antimicrobial resistance (AMR) of Campylobacter. Samples were collected from a processing facility that used organic and conventional methods to process RWA broilers. Samples included fecal grab samples from incoming birds, carcass rinses at important steps throughout processing, and environmental samples including equipment swabs, water samples, and air samples. Samples were analyzed for prevalence of Campylobacter by enrichment, and populations of presumptive Campylobacter were quantified. Isolates collected in this study were analyzed for AMR according to the National Antimicrobial Resistance Monitoring System (NARMS) protocol. Results showed that organic birds had a lower prevalence (P < 0.05) of Campylobacter and lower populations of presumptive Campylobacter during early processing steps, but no differences (P > 0.05) between organic and conventional birds were seen post-chill, with the exception of a lower prevalence in post-water-chill organic birds. These observations show that organic methods can be associated with lower initial Campylobacter levels than conventional methods, although appropriate processing interventions result in similar Campylobacter populations post-chill, regardless of processing method. Prevalence of AMR Campylobacter in chickens at slaughter suggest that raising birds without the use of antimicrobials may not be effective in reducing the incidence of AMR Campylobacter in chicken.

Prevalence, Persistence, and Antimicrobial Resistance of Campylobacter spp. from Eggs and Laying Hens Housed in Five Commercial Housing Systems.

Husbandry practices for laying hens in commercial egg production is a topic of interest from a social, economic, and regulatory standpoint. Animal welfare concerns regarding the use of conventional cages have arisen and consumer perceptions of hen welfare have led to a higher demand for cage-free eggs. The aim of this study was to assess the impact of housing systems on prevalence, persistence, and antimicrobial resistance (AMR) of Campylobacter from laying hens and shell eggs. A total of 425 samples were collected over a 10-month period from the North Carolina Layer Performance and Management Test and Campylobacter isolates were identified by serological, biochemical, and molecular tests. Genetic variability was evaluated using pulsed-field gel electrophoresis (PFGE) and AMR testing was performed. Prevalence of Campylobacter spp. ranged from 11.1% in the enrichable cages to 19.7% in the conventional systems. A greater prevalence of Campylobacter was found in the fecal swab samples from free-range birds compared with those of birds housed in the more intensive housing systems (p > 0.05). Overall, 72 isolates were confirmed as Campylobacter spp. by PCR. More than 90% of the isolates (n = 66) were identified as Campylobacter jejuni, followed by Campylobacter coli (n = 6). C. jejuni isolates displayed high levels of resistance to tetracycline (67%). Genetic variability of Campylobacter was high, with more than 20 PFGE patterns identified. Pattern "a" comprised 42% of isolates from all housing systems and was also the most persistent. This study suggests that housing systems of laying hens used for commercial shell egg production may impact the rate of Campylobacter shedding by layers. Isolation rates and tetracycline resistance levels of this pathogen are still of concern, emphasizing the need for well-implemented biosecurity measures on the farm.

Thermal Inactivation of Shiga Toxin-Producing Escherichia coli in Ground Beef with Varying Fat Content.

Decimal reduction time ( D-value) was calculated for six non-O157 Shiga toxin-producing Escherichia coli (STEC) in a laboratory medium and ground beef. For the laboratory medium, an overnight culture of each strain of STEC was divided into 10-mL sample bags and heated in a water bath for a specific time on the basis of the temperatures. Survival curves were generated by plotting the surviving bacterial population against time, and a linear-log primary model was used to estimate the D-values from survival curves. The z-values (the temperature raised to reduce the D-value by one-tenth) were calculated by plotting the log D-values against temperature. Similarly, for ground beef, six fat contents, 5, 10, 15, 20, 25, and 30% of ground beef were formulated for this study. Inoculated meat was divided into 5-g pouches and submerged in a water bath set at specific temperatures (55, 60, 65, 68, and 71.1°C). The average D-value for these strains in a laboratory medium was 17.96 min at 55°C, which reduced significantly ( P < 0.05) to 1.58 min at 60°C, and then further reduced ( P < 0.05) to 0.46 min at 65°C. In ground beef, a negative correlation ( P < 0.05) between fat content of ground beef and D-values was observed at 55°C. However, at temperatures greater than 60°C, there was no impact ( P > 0.05) of fat content of ground beef on the thermal resistance of non-O157 STECs. Irrespective of the fat content of ground beef, the D-values ranged from 15.93 to 11.69, 1.15 to 1.12, and 0.14 to 0.09 min and 0.05 at 55, 60, 65, and 68°C, respectively. The data generated from this study can be helpful for the meat industry to develop predictive models for thermal inactivation of non-O157 STECs in ground beef with varying fat content.

Egg Safety in the Realm of Preharvest Food Safety.

Eggs are nutritious, yet they are a highly perishable commodity like other protein sources such as meat. Even though steps are taken all along the production process of shell eggs, from farm to table, the potential for contamination of the shells and egg contents poses a high risk to consumers. The main sources of contamination can be categorized as vertical transmission, in which the layers can be carriers of pathogens and can pass them on during egg formation, and horizontal transmission, in which environmental factors such as water, feed, layer houses, and personnel are the main source of contamination. Ongoing preharvest practices might not be enough to completely eliminate pathogens from shell eggs; however, consistently following good practices along with proper handling during transportation and retail sale and by consumers can be significant in reducing the risk. This article discusses the various aspects of production practices, their potential for cross-contamination, and decontamination technologies for shell eggs.