Modeling the growth of Salmonella in raw ground pork under dynamic conditions of temperature abuse.

Salmonella contamination of pork products is a significant public health concern. Temperature abuse scenarios, such as inadequate refrigeration or prolonged exposure to room temperature, can enhance Salmonella proliferation. This study aimed to develop and validate models for Salmonella growth considering competition with background microbiota in raw ground pork, under isothermal and dynamic conditions of temperature abuse between 10 and 40 °C. The maximum specific growth rate (µmax) and maximum population density (MPD) were estimated to quantitatively describe the growth behavior of Salmonella. To reflect more realistic microbial interactions in Salmonella-contaminated product, our model considered competition with the background microbiota, measured as mesophilic aerobic plate counts (APC). Notably, the µmax of Salmonella in low-fat samples (∼5 %) was significantly higher (p < 0.05) than that in high-fat samples (∼25 %) at 10, 20, and 30 °C. The average doubling time of Salmonella was 26, 4, 2, 1.5, 0.8, and 1.1 h at 10, 15, 20, 25, 30, and 40 °C, respectively. The initial concentration of Salmonella minimally impacted its growth in ground pork at any temperature. The MPD of APC consistently exceeded that of Salmonella, indicating the growth of APC without competition from Salmonella. The competition model exhibited excellent fit with the experimental data, as 95 % (627/660) of residual errors fell within the desired acceptable prediction zone (pAPZ >0.70). The theoretical minimum and optimum growth temperatures for Salmonella ranged from 5 to 6 °C and 35 to 36 °C, respectively. The dynamic model displayed strong predictive performance, with 90 % (57/63) of residual errors falling within the APZ. Dynamic models could be valuable tools for validating and refining simpler static or isothermal models, ultimately improving their predictive capabilities to enhance food safety.

Antimicrobial efficacy of a citric acid/hydrochloric acid blend, peroxyacetic acid, and sulfuric acid against Salmonella and background microbiota on chicken hearts and livers.

This study aimed at evaluating the efficacy of a blend of citric acid and hydrochloric acid (CP), peroxyacetic acid (PAA), and sulfuric acid (SA) against Salmonella and mesophilic aerobic plate counts (APC) on chicken hearts and livers. Samples were inoculated with a five-serovar cocktail of Salmonella at ca. 4.8 log CFU/g and treated by immersion with a water control (90 s), CP (5% v/v, 30 s), PAA (0.05% v/v or 500 ppm, 90 s), or SA (2% v/v, 30 s), all at 4°C and with mechanical agitation. Samples were vacuum packed and stored for up to 3 days at 4°C. Three independent replications were performed for each product, treatment, and time combination. The average Salmonella reductions in chicken hearts after 3 days were 1.33 ± 0.25, 1.40 ± 0.04, and 1.32 ± 0.12 log CFU/g for PAA, SA, and CP, respectively. For chicken livers, the values were 1.10 ± 0.12, 1.09 ± 0.19, and 0.96 ± 0.27 for PAA, SA, and CP, respectively. All antimicrobials reduced Salmonella counts in both chicken hearts and livers by more than one log, in contrast to the water control. All treatments effectively minimized the growth of APC for up to 3 days of refrigerated storage, and no differences in objective color values (L, a, or b) were observed. The poultry industry may use these antimicrobials as components of a multifaceted approach to mitigate Salmonella in nonconventional chicken parts.

Spoilage Pseudomonas survive common thermal processing schedules and grow in emulsified meat during extended vacuum storage.

Some Pseudomonas species are common meat spoilage bacteria that are often associated with the spoilage of fresh meat. The recently reported ability of these bacteria to also spoil cooked and vacuum packaged meat products has created the need to investigate all potential routes of spoilage they may be able to utilize. The objective of this experiment was to determine if spoilage Pseudomonas spp. survive thermal processing and grow during refrigerated storage under vacuum. Pseudomonas spp. isolates collected from spoiled turkey products were inoculated into a salted and seasoned meat emulsion that was vacuum sealed and thermally treated to final temperatures of 54.4 and 71.1°C to mimic thermal processes commonly used in the meat industry. Samples were stored for a total of 294 days at 4 and 10°C and plated using Pseudomonas spp. specific agar plates. Pseudomonas spp. concentrations were below the detection limit (0.18 log10 CFU/g) immediately after thermal processing and were first recovered from thermally processed samples after 14 days of storage. The final concentration was greater than 2 log10 CFU/g (p < 0.05 compared to post-thermal processing) in thermally processed treatment groups at the end of storage, indicating that these Pseudomonas spp. isolates were able to survive thermal processing and grow during extended vacuum storage. This raises concerns about the ability of spoilage bacteria to survive the thermal processing schedules commonly used in the meat industry and confirms that some Pseudomonas spp. are capable of thriving in products other than aerobically stored fresh meat. Practical Application: Spoilage Pseudomonas spp. can survive traditional thermal processing schedules. Heat resistance should be evaluated for commensal and spoilage bacteria to better understand possible ways spoilage of food products may occur.

Inactivation of Salmonella in nonintact beef during low-temperature sous vide cooking.

Sous vide cooking is a method of food preparation in which food is vacuum sealed and cooked in a water bath that is set to a precise temperature and circulated by a sous vide device. Due to ease of use and affordability, this cooking method has grown increasingly popular in food service kitchens and domestic settings. However, low-temperature, long holding time sous vide cooking recommendations from manufacturers and chefs in popular press raise food safety concerns - specifically those for the preparation of nonintact beef products. The objective of this experiment was to address these concerns by validating a 5 log reduction of Salmonella spp. in sous vide cooked, nonintact beef steaks. Beef semitendinosus sliced into 2.54 cm steaks were internally inoculated to 7 log with Salmonella Typhimurium, Enteritidis, and Heidelberg via a needle inoculation pin pad. Steaks were individually vacuum sealed, and sous vide cooked at 46.1, 51.6, and 54.4°C. The minimum time measured for a 5 log reduction at 51.6 and 54.4°C was 150 and 64.5 min, respectively (P < 0.01). Additionally, a 7.28 log final reduction was achieved at 51.6°C after 322.5 min (P < 0.01). However, 46.1°C was only able to achieve a final reduction of 2.01 log (P < 0.01) after a holding time of 420 min. The results of this experiment validate in sous vide cooked products the time and temperature combinations provided in the USDA-FSIS Appendix A guidance for a 5 log reduction of Salmonella spp. in meat products. Moreover, more research is needed with other relevant foodborne pathogens to determine if sous vide cooking below Appendix A recommendations could lead to unsafe products.

Growth behavior of Shiga toxin-producing Escherichia coli, Salmonella, and generic E. coli in raw pork considering background microbiota at 10, 25, and 40 °C.

Recent epidemiological evidence suggests that pork products may be vehicles for the transmission of Shiga toxin-producing Escherichia coli (STEC) to humans. The severe morbidity associated with STEC infections highlights the need for research to understand the growth behavior of these bacteria in pork products. Classical predictive models can estimate pathogen growth in sterile meat. However, competition models considering background microbiota reflect a more realistic scenario for raw meat products. The objective of this study was to estimate the growth kinetics of clinically significant STEC (O157, non-O157, and O91), Salmonella, and generic E. coli in raw ground pork using competition primary growth models at temperature abuse (10 and 25 °C) and sublethal temperature (40 °C). A competition model incorporating the No lag Buchanan model was validated using the acceptable prediction zone (APZ) method where >92 % (1498/1620) of the residual errors fell within the APZ (pAPZ > 0.70). The background microbiota (mesophilic aerobic plate counts, APC) inhibited the growth of STEC and Salmonella indicating a simple one-directional competitive interaction between pathogens and the mesophilic microbiota of ground pork. The maximum specific growth rate (µmax) of all the bacterial groups was not significantly different (p > 0.05) based on fat content (5 vs 25 %) except for generic E. coli at 10 °C. E. coli O157 and non-O157 behaved similarly in terms of µmax and maximum population density (MPD). Salmonella showed a similar (p > 0.05) µmax to E. coli O157 and non-O157 at 10 and 40 °C but a significantly higher rate (p < 0.05) at 25 °C. STEC were more prone to be inhibited by APC than Salmonella at 10 and 25 °C. The µmax of O91 was lower (p < 0.05) than other STEC and Salmonella at 10 and 25 °C but similar (p > 0.05) at 40 °C. Generic E. coli showed a two- to five-times higher (p < 0.05) µmax (0.028 ± 0.011 log10 CFU/h) than other bacterial groups (0.006 ± 0.004 to 0.012 ± 0.003 log10 CFU/h) at 10 °C making it a potential indicator bacteria for process control. Industry and regulators can use competitive models to develop appropriate risk assessment and mitigation strategies to improve the microbiological safety of raw pork products.

Method validation for the recovery of the porcine respiratory and reproductive syndrome virus, a potential SARS-CoV-2 surrogate, from stainless steel.

Virus survival on fomites may represent a vehicle for transmission to humans. This study was conducted to optimize and validate a recovery method for the porcine respiratory and reproductive syndrome virus (PRRSV), a potential SARS-CoV-2 surrogate, from stainless steel. Coupons (1.5 × 1.5 cm) inoculated with ca. 7 logs TCID50 of PRRSV were dried for 15 min at room temperature, followed by incubation at 4°C and 35% relative humidity. After 1 h and 24 h, the coupons were processed by four different methods: vortex in DMEM media, vortex in DMEM media with beads, vortex in elution buffer, and shake in elution buffer. The rinsates were processed for titration using the TCID50 method in the MARC-145 cell line. All four methods were equally effective to recover the virus from the soiled SS surfaces (> 79% recovery). The amount of infectious virus recovered after 24 h was similar (P > 0.05) to that recovered after 1 h, indicating that the virus was stable at 4°C for up to 24 h. Using an elution buffer followed by shaking was the least labor-intensive and most economical method. Therefore, this method will be used for future experiments on PRRSV survival and transfer from food-contact surfaces.

Peroxyacetic Acid Effectiveness against Salmonella on Raw Poultry Parts Is Not Affected by Organic Matter.

ABSTRACT: Organic matter (OM) accumulation is common in chill tanks used to decontaminate raw poultry parts during processing. OM negatively affects the antimicrobial activity of chlorine-based compounds, but its effect on the antimicrobial effectiveness of peroxyacetic acid (PAA) on poultry meat has not been described. Therefore, this study evaluated the effect of OM on the efficacy of PAA solutions in simulated postchill tanks to reduce Salmonella artificially inoculated onto chicken parts. Chicken thighs were inoculated with a five-strain cocktail of poultry-borne Salmonella enterica serovars at ca. 6 log CFU/mL. Then, the thighs were immersed for 30 or 45 s in PAA solutions (500 or 1,000 ppm) with chicken slurry to simulate OM accumulation (0, 15, or 30 g/L). The thighs were rinsed with neutralizing buffered peptone water (100 mL), and rinsates were plated onto xylose lysine desoxycholate agar. Experiments were performed in triplicate (three thighs per treatment per replicate). Chemical oxygen demand, total nitrogen, and pH were measured as the water quality parameters of the PAA solutions before and after use. Chemical oxygen demand ranged from 2,905 mg/L in unused 500-ppm solutions without added OM to 6,290 mg/L in used 1,000-ppm solutions with 30 g/L OM. Initial total nitrogen was 42.5 ± 2.0 and 60.9 ± 8.3 mg/L for 15 and 30 g/L OM, which increased by 27 ± 17 mg/L after use. The pH of solutions ranged from 3.16 ± 0.14 to 3.42 ± 0.09 for the 1,000-ppm solutions and from 3.59 ± 0.06 to 3.96 ± 0.06 for the 500-ppm solutions. Mean Salmonella reductions were 0.9 ± 0.1 log CFU/mL of rinsate for the 500-ppm PAA treatment and 1.1 ± 0.1 log CFU/mL of rinsate for 1,000-ppm PAA treatment. Exposure time did not have a significant effect on the logarithmic reductions. There was no significant effect of OM concentration (P > 0.05) on the reductions, indicating that the antimicrobial efficacy was not affected and that PAA solutions may continue to be reused as long as the PAA concentration is actively monitored.

A review of Shiga-toxin producing Escherichia coli (STEC) contamination in the raw pork production chain.

Epidemiological evidence of Shiga toxin-producing Escherichia coli (STEC) infections associated with the consumption of contaminated pork highlight the need for increased awareness of STEC as an emerging pathogen in the pork supply chain. The objective of this review is to contribute to our understanding of raw pork products as potential carriers of STEC into the food supply. We summarize and critically analyze primary literature reporting the prevalence of STEC in the raw pork production chain. The reported prevalence rate of stx-positive E. coli isolates in live swine, slaughtered swine, and retail pork samples around the world ranged from 4.4 % (22/500) to 68.3 % (82/120), 22 % (309/1395) to 86.3 % (69/80), and 0.10 % (1/1167) to 80 % (32/40), respectively, depending upon the sample categories, detection methods, and the hygiene condition of the slaughterhouses and retail markets. In retail pork, serogroup O26 was prevalent in the U.S., Europe, and Africa. Serogroup O121 was only reported in the U.S. Furthermore, serogroup O91 was reported in the U.S., Asia, and South American retail pork samples. The most common virulence gene combination in retail pork around the globe were as follows: the U.S.: serogroup O157 + stx, non-O157 + stx, unknown serogroups+stx + eae; Europe: unknown serogroups+(stx + eae, stx2 + eae, or stx1 + stx2 + eae); Asia: O157 + stx1 + stx2 + ehxA, Unknown+stx1 + eaeA + ehxA, or only eae; Africa: O157 + stx2 + eae + ehxA. STEC strains derived from retail pork in the U.S. fall under low to moderate risk categories capable of causing human disease, thus indicating the need for adequate cooking and prevention of cross contamination to minimize infection risk in humans.

Thermal inactivation of Salmonella on chicken wings cooked in domestic convection and air fryer ovens.

Chicken wings are among the most popular poultry products for home and foodservice consumption. Poultry products must be handled and cooked safely to decrease the risk of foodborne salmonellosis for consumers. This study aims to validate the use of domestic appliances (convection and air fryer ovens) for the thermal inactivation of Salmonella on chicken wings. Wings (n = 3, 46.5 ± 4.3 g) were inoculated with a five-strain cocktail of Salmonella (ca. 8 log10 CFU/wing) and cooked in a convection oven (179.4°C) or an air fryer (176, 190, or 204°C) for 2, 5, 10, 15, 20, 22, or 25 min. Thermocouples recorded temperature profiles of wings and appliances. Salmonella counts were determined on XLD agar for rinsates (100 ml/sample), and rinsates were enriched to recover bacteria below the limit of quantification. The recommended internal cooking temperature (73.8°C) was achieved after a range of 7.5 to 8.5 min in both appliances. Salmonella counts were reduced by 6.5 log10 CFU/wing when this temperature was achieved. Cumulative lethality (F-value) calculations predicted a 9-log reduction after 7.0 to 8.1 min of cooking. However, sample enrichments tested positive for Salmonella for all cooking times below 22 min. Ultimately, cooking at the temperature-time combinations recommended by manufacturers and online recipes helped achieve complete microbial elimination in both appliances. This study contributes to the validation of home cooking methods to ensure consumer safety.

Application of Peroxyacetic Acid for Decontamination of Raw Poultry Products and Comparison to Other Commonly Used Chemical Antimicrobial Interventions: A Review.

ABSTRACT: Poultry remains one of the top food commodities responsible for foodborne illness in the United States, despite poultry industry efforts since the inception of hazard analysis and critical control point to reduce the burden of foodborne illness implicating poultry products. The appropriate use of antimicrobial compounds during processing of raw poultry can help minimize this risk. Currently, peroxyacetic acid (PAA) is the most popular antimicrobial in the poultry industry, displacing chlorine compounds and others. The aim of this review was to compare the effectiveness of PAA to that of other antimicrobials for the decontamination of raw poultry carcasses and parts. Twenty-six articles were found that compared PAA with over 20 different antimicrobials, applied as spray or immersion treatments for different exposure times and at different concentrations. The most common comparisons were to chlorine compounds (17 articles), to lactic acid compounds (five articles), and to cetylpyridinium chloride (six articles). Studies measured effectiveness by reductions in native flora or inoculated bacteria, usually Salmonella or Campylobacter. PAA was found to be more effective than chlorine under most conditions studied. Effectiveness of PAA was higher than or comparable to that of lactic acid compounds and cetylpyridinium chloride depending on product and treatment conditions. Overall, the results of primary literature studies support the popularity of PAA as an effective intervention against pathogenic bacteria during poultry processing.

Thermal Inactivation Kinetics of Salmonella and Enterococcus faecium NRRL-B2354 on Whole Chia Seeds (Salvia hispanica L.).

ABSTRACT: Intervention technologies for inactivating Salmonella on whole chia seeds are currently limited. Determination of the thermal inactivation kinetics of Salmonella on chia seeds and selection of an appropriate nonpathogenic surrogate will provide a foundation for selecting and optimizing thermal pasteurization processes for chia seeds. In this study, chia seed samples from three separate production lots were inoculated with a five-strain Salmonella cocktail or Enterococcus faecium NRRL-B2354 and equilibrated to a water activity of 0.53 at room temperature (25°C). After equilibration for at least 3 days, the inoculated seeds were subjected to isothermal treatments at 80, 85, or 90°C. Samples were removed at six time points, and surviving bacteria were enumerated. Whole chia seeds were diluted in a filter bag at 1:30 because bacterial recovery with this method was similar to that obtained from ground seeds. Survivor data were fitted to consolidated models: one primary model (log linear or Weibull) and one secondary model (Bigelow). E. faecium had higher thermal resistance than did Salmonella, suggesting that E. faecium may be a suitable conservative nonpathogenic surrogate for Salmonella. The Weibull model was a better fit for the survivor data than was the log-linear model for both bacteria based on the lower root mean square error and corrected Akaike's information criterion values. Lipid oxidation measurements and fatty acid concentrations were significantly different from those of the control samples, but the overall magnitude of the differences was relatively small. The thermal inactivation kinetics of Salmonella and E. faecium on chia seeds may be used as a basis for developing thermal pasteurization processes for chia seeds.

Thermal inactivation kinetics of Salmonella and Enterococcus faecium NRRL B-2354 on dried basil leaves.

The enhanced heat resistance of Salmonella developed at low water activity makes it a serious challenge to eliminate them during thermal processing. The objectives of this research are to (i) investigate the effect of water activity on thermal inactivation of Salmonella cocktail (Agona, Tennessee, Mbandaka, Montevideo, and Reading) in dried basil leaves, and (ii) evaluate Enterococcus faecium NRRL B-2354 as an appropriate surrogate for Salmonella in dried basil leaves. Dried basil leaves, inoculated with a Salmonella cocktail and E. faecium separately, were equilibrated to different water activities (aw: 0.40, 0.55, and 0.70) in a humidity-controlled chamber. The basil samples were packed (1.6 ± 0.1 g) in aluminum pouches and thermally treated at 70, 75, and 80 °C using a dry heating method for 0-180 min to obtain the thermal death curve. The microbial survival data was fit using two primary models (Log-linear and Weibull model). Results from AICc showed that the log-linear model fits well for thermal inactivation of both microorganisms. As the aw decreases from 0.70 to 0.40 at 75 °C, the D-value increases from 3.30 to 9.14 min for Salmonella and 6.53 to 14.07 min for E. faecium. Based on the AICc values, the modified Bigelow model fits the D-values better than the response surface model for both the microorganisms. The kill ratio of surrogate to pathogen ranged from 1.4 to 2.8, indicating that it is a conservative surrogate for Salmonella for performing validation of the thermal pasteurization process. The identification of suitable surrogate and development of modified Bigelow model will help the spice industry in developing the thermal processes for improving the safety of basil leaves.

Inactivation of Salmonella enterica and Enterococcus faecium NRRL B2354 on cumin seeds using gaseous ethylene oxide.

The objectives of this study were to investigate the effects of processing parameters (relative humidity (RH), temperature, and exposure time) on the ethylene oxide (EtO) microbial inactivation of Salmonella spp. and to evaluate Enterococcus faecium NRRL B2354 as a suitable surrogate for Salmonella inactivation on cumin seeds. Five grams of cumin seeds inoculated with either Salmonella or E. faecium were treated with EtO at different temperatures (46, 53, and 60 °C) and RH (30, 40, and 50%) levels for different exposure time to investigate the effects of process parameters on the microbial inactivation. The Weibull model fit the survival data of both bacteria with a shape parameter p < 1, which showed a tailing effect with concave shape indicating that the sensitive cells were inactivated first, and the sturdy ones survived at low RH treatment conditions. In general, the log reductions of both bacteria on cumin seeds increased with the increasing RH and temperature for EtO treatment. RH is a critical factor for successful EtO inactivation treatment. RH must be higher than 40% to implement a successful and efficient EtO decontamination of cumin seeds. E. faecium consistently showed lower log reductions than those of Salmonella under all EtO treatment conditions investigated in this study, demonstrating that E. faecium is a suitable surrogate for Salmonella. Twenty minutes of EtO treatment at 50% RH achieved ~5 log reductions of both bacteria at all three temperatures. A response surface model was developed to predict the log reductions of both bacteria under different treatment conditions and the contour plots representing log reductions were created. Inactivation is positively correlated to temperature and RH. Therefore, a higher temperature is required to achieve the desired log reduction at lower RH and vice versa. The developed response surface model is a valuable tool for the spice industry in identifying the possible combinations of EtO process parameters (temperature, RH, and exposure time) required to achieve a desired microbial reduction of Salmonella for ensuring microbial food safety of spices.

Effect of water activity on the thermal inactivation kinetics of Salmonella in milk powders.

Persistence of Salmonella in milk powders has caused several foodborne outbreaks. The determination of proper pasteurization processing conditions requires an understanding of the thermal inactivation kinetics of Salmonella in milk powders. However, there is a lack of knowledge related to the effects of water activity (aw) and fat content on Salmonella inactivation in milk powder during thermal processing. Two types of milk powders, nonfat dry milk and whole milk powder, with different fat contents (0.62 and 29.46% wt/wt, respectively) were inoculated with a 5-strain cocktail of Salmonella and equilibrated to 3 aw levels (0.10, 0.20, and 0.30) for isothermal treatments at 75, 80, and 85°C to obtain D-values (the time required to achieve a 10-fold reduction of the bacteria at the isothermal treatment temperature) and z-values (the increase in temperature required to achieve a 90% reduction of the decimal reduction time D). Stability tests showed that the inoculation method used in this study provided a high and stable population of Salmonella for thermal inactivation studies. A moisture sorption isotherm was measured to understand the relationship between aw and moisture content of milk powders. The thermal resistance of Salmonella was found to significantly increase as aw decreased, which suggested that a higher temperature or longer processing time would be required at low aw to achieve the desired inactivation of Salmonella. The microbial inactivation kinetics were not significantly different for the 2 milk powders; therefore, data were combined to develop a universal model. A response surface model was compared with a modified Bigelow model. The modified Bigelow model performed well to predict D-values [root mean square error (RMSE) = 1.47 min] and log reductions (RMSE = 0.48 log cfu/g). The modified Bigelow model developed here could be used to estimate D-value as a function of water activity and temperature to design a thermal pasteurization system for milk powders.

Ozone-Based Interventions To Improve the Microbiological Safety and Quality of Poultry Carcasses and Parts: A Review.

HIGHLIGHTS: Ozone treatment achieved microbial population reductions. Gaseous ozone was most commonly used on poultry parts. Carcasses were treated exclusively with aqueous ozone or ozonated water. Ozone treatment can extend poultry product shelf life without significant quality effects.

The diversity of beef safety: A global reason to strengthen our current systems.

The purpose of this paper is to propose a more integrated and more aggressive system approach to food safety rather than focusing on one segment of the industry, or on one approach as described by or constrained by one set of regulations. We focus on the prevalence and control measures for Salmonella and pathogenic Escherichia coli, particularly, Shiga toxin-producing E. coli (STEC) in live cattle on the farm and in the final raw beef product at retail. We describe the antimicrobial and process control strategies most commonly used during slaughter and processing to prevent and reduce the frequency and concentration of these pathogens in the final product, and we propose points along the food chain where more interventions can be applied to ultimately reduce the prevalence of foodborne pathogens associated with beef and beef products, and to protect public health as well the global food supply.

Revisiting the STEC Testing Approach: Using espK and espV to Make Enterohemorrhagic Escherichia coli (EHEC) Detection More Reliable in Beef.

Current methods for screening Enterohemorrhagic Escherichia coli (EHEC) O157 and non-O157 in beef enrichments typically rely on the molecular detection of stx, eae, and serogroup-specific wzx or wzy gene fragments. As these genetic markers can also be found in some non-EHEC strains, a number of "false positive" results are obtained. Here, we explore the suitability of five novel molecular markers, espK, espV, ureD, Z2098, and CRISPRO26:H11 as candidates for a more accurate screening of EHEC strains of greater clinical significance in industrialized countries. Of the 1739 beef enrichments tested, 180 were positive for both stx and eae genes. Ninety (50%) of these tested negative for espK, espV, ureD, and Z2098, but 12 out of these negative samples were positive for the CRISPRO26:H11 gene marker specific for a newly emerging virulent EHEC O26:H11 French clone. We show that screening for stx, eae, espK, and espV, in association with the CRISPRO26:H11 marker is a better approach to narrow down the EHEC screening step in beef enrichments. The number of potentially positive samples was reduced by 48.88% by means of this alternative strategy compared to the European and American reference methods, thus substantially improving the discriminatory power of EHEC screening systems. This approach is in line with the EFSA (European Food Safety Authority) opinion on pathogenic STEC published in 2013.

Seasonal prevalence of potentially positive non-O157 Shiga toxin-producing Escherichia coli (STEC) bovine hides and carcasses in Costa Rica.

The prevalence of potentially positive Shiga toxin-producing Escherichia coli (STEC) bovine hides and carcasses in three abattoirs in Costa Rica was estimated. Two export facilities (A and B) and one non-export establishment (C) were visited during the dry and rainy seasons of 2013. Swabs of hides pre-eviscerated and treated (180-220 peroxyacetic acid spray) carcasses were tested for the potential presence of STEC serogroups O26, O45, O103, O111, O121, and O145. The prevalence on hides during the rainy season was 86.7, 96.7 and 96.7% for facilities A, B, and C, respectively. During the dry season, the prevalence on hides was significantly lower in plants A and B (40% and 26.7%, respectively), but was marginally associated with the season in plant C (76.7%, P=0.0523). The prevalence of non-O157 STEC markers on treated carcasses was low (0 to 3.3%), suggesting that all plants were effective in minimizing the target non-O157 STEC in beef destined for export and for domestic consumption.