Beef Carcass Surfaces Research Articles

Isolation of Shiga Toxin-Producing Escherichia coli from the Surfaces of Beef Carcasses in Slaughterhouses in Japan

Shiga toxin-producing E. coli (STEC) is an important foodborne pathogen worldwide. It is necessary to control and prevent STEC contamination on beef carcasses in slaughterhouses because STEC infection is associated with beef consumption. However, the frequencies of STEC contamination of beef carcasses in various slaughterhouses in Japan are not well known. Herein, we investigated the contamination of beef carcasses with STEC in slaughterhouses to assess the potential risks of STEC. In total, 524 gauze samples were collected from the surfaces of beef carcasses at 12 domestic slaughterhouses from November 2020 to February 2023. The samples were measured for aerobic plate counts and tested for pathogenic genes (stx and eae) and major O-serogroups (O26, O45, O103, O111, O121, O145, and O157) by real-time PCR screening. Subsequently, immunomagnetic separation (IMS) was performed on samples positive for stx, eae, and at least one of the seven O-serogroups of STEC. Isolation process without IMS was performed on samples positive for stx, including those subjected to IMS. STEC O157:H7 and stx-positive E. coli other than serotype O157:H7 were isolated from 0.6% and 4.6% of beef carcass surfaces, respectively. Although the STEC O157:H7 isolation rate was low and stx-positive E. coli other than serotype O157:H7 belonged to minor O-serogroups, the results mean a risk of foodborne illness. Furthermore, a moderate correlation was observed between aerobic plate counts and detection rates of stx-positive samples by real-time PCR screening. The STEC O157:H7 isolated facilities showed higher values on aerobic plate counts and detection rates of stx-positive samples than the mean values of total samples. Therefore, these results suggest that it is important to evaluate hygiene treatments against beef carcasses for the reduction of STEC contamination risk, particularly in facilities with high aerobic plate counts.

Efficiency of using lactic acid and beefxide to reduce indicator microorganisms on beef in Mosul slaughterhouse.

Meat contamination occurs in various ways, the most important of which are live animals before slaughter and the slaughter process (de-hiding and evisceration). For this, many substances were used that have an antimicrobial effect and can disinfect the surfaces of the carcass and extend its shelf life. This research aimed to study the efficiency of using some organic acids (lactic acid and beefxide) to reduce the microbial load (indicator microorganisms) on the surfaces of beef carcasses and some edible organs in the Mosul slaughterhouse. Two hundred sixty-four swabs (192 carcasses + 72 edible organ samples) were collected over the course of three months from the Mosul slaughterhouse in Nineveh Governorate between September 2023, and December 2023 (132 treated with organic acids and 132 not treated). The petrifilm method was used to detect indicator microorganisms in the samples. Our results showed that the contamination rate in beef carcasses with generic Escherichia coli, coliforms, total coliform counts, and Enterobacteriaceae before treatment was 0.81, 1.22, 1.48, and 1.38 mean log colony forming unit (CFU/cm2), respectively. While the contamination rate in samples treated with organic acids for generic E. coli, coliforms, total coliform counts, and Enterobacteriaceae was -0.1, 0.31, 0.45, and 0.41 mean log CFU/cm2, respectively. Moreover, the level of contamination with indicator microorganisms in edible organs treated with organic acids was lower compared to untreated samples. Even though there was contamination with indicator microorganisms in the liver, heart, and kidney, there was no "significant" difference between them. Whereas there was no significant difference (p > 0.05) between lactic acid and beefxide solution in terms of reducing the rate of contamination of the indicator microorganisms in carcasses and the edible organs samples. Regarding the type of swabs used in the study, the results showed the effectiveness of sponge swabs, as the rate of microbial recovery (indicator microorganisms) was higher (p < 0.01) compared to cotton swabs. The study demonstrated the efficiency of using organic acids (lactic acid and beefxide solution) in reducing the microbial load to a level that does not cause diseases.

Coliform and Escherichia coli Contamination on External and Internal Surfaces of Beef Carcasses with and without Tissue Adhesion Excision

Following removal of hides and viscera during beef processing, carcasses are inspected for tissue adhesions that can affect meat quality or harbor bacteria. Carcasses with pleural or abdominal adhesions may be diverted from the production line for manual excision and then returned to the line. No published data indicate whether adhesion excision is associated with bacterial contamination. Therefore, our objective was to determine the presence and concentration of generic Escherichia coli and non-E. coli coliforms from the internal and external surfaces of carcasses that were, or were not, diverted for adhesion excision. During 9 processing days over a 4-month period in a large commercial beef processing facility, 1,738 carcass sponge samples from 2,730 cm2 areas on both the internal and the external surfaces of carcasses with and without tissue adhesions were collected. Coliforms and E. coli were cultured and enumerated using Petrifilm procedures, and data were analyzed with mixed models. Coliforms were present at higher concentrations than E. coli, and prevalence and mean log concentrations of both coliforms and E. coli were significantly higher for samples from the external than from the internal surfaces of carcasses. However, differences in prevalence and concentration of coliforms between external and internal surfaces varied significantly based on whether carcasses had adhesions excised. The difference was greatest for coliforms present on the external (2.06 log CFU/100 cm2) versus the internal (0.93 log CFU/100 cm2) carcass surfaces without adhesions, whereas the difference in concentrations from the external (1.80 log CFU/100 cm2) and the internal (1.31 log CFU/100 cm2) surfaces of carcasses with adhesions was not as large. These results indicate that surveillance of carcass bacteria may be affected by whether the external versus the internal surfaces are sampled and whether carcasses are diverted for excision of adhesions.

Evaluation of Bacterial Contamination of Beef Carcasses in Namwala and Lusaka Districts of Zambia

Abattoirs have been purported to be ideal areas were possible microbial contamination of meat products is likely to occur. Food of animal origin, mainly beef, has been identified as a source of dietary protein for humans albeit it being a source of food-borne diseases including zoonoses. This study was carried out to evaluate bacterial contamination and the risk factors associated with contamination of beef carcasses during processing. A total of four abattoirs were sampled within three months with one in Namwala and three in Lusaka districts. A total of 314 beef carcass surface swabs were obtained from the neck region by swabbing the carcasses, immediately after evisceration and after washing. Results The results of mean total viable counts (TVC) of carcass contamination were enumerated as the mean log from 4.7 Log10 cfu/cm2 in an abattoir where Hazard Analysis and Critical Control Points (HACCP) was practiced to 5.8 Log10 cfu/cm2 without HACCP. Bivariate analysis showed a significant difference in carcass contamination when town abattoirs (Lusaka) were compared with rural ones (Namwala); χ2 = 43.87, P &lt; 0.0001. Multiple logistic regression analysis identified poor hygiene practices, the absence of antemortem inspection, and lack of Hazard Analysis and Critical Control Points (HACCP) implementation as significant factors associated with carcass contamination. Conclusion A high microbial load as determined by the Total Viable Count is an indicator that beef is being produced under poor abattoir hygiene conditions. Therefore, beef carcasses with high bacterial loads are potential sources of foodborne pathogens leading to foodborne disease and hence there is need for advocating for good hygiene practices in the abattoirs.

Microbial Decontamination of Beef Carcass Surfaces by Lactic Acid, Acetic Acid, and Trisodium Phosphate Sprays.

The present study was undertaken to investigate the effect of lactic acid (LA), acetic acid, (AA) and trisodium phosphate (TSP) spray on the microbiological population of beef carcass surfaces slaughtered in a traditional abattoir in Zagazig, Egypt. Higher microbial populations were determined on the shoulder than on the thigh surfaces, and meat sampling by tissue excision technique yielded significantly higher (P < 0.01) microbial count than swabbing method. The application of LA (2%), AA (2%), and TSP (12%) sprays for 30 seconds significantly (P < 0.01) reduced the microbial population counts on the beef surfaces by 0.9 to 2.2 logs. A complete inhibition of enterococci growth was achieved by LA and AA sprays. In general, LA and AA sprays were more efficient as antimicrobial agents than the TSP spray. Among the studied organisms, enterococci were the most reducible bacteria by LA and AA, followed by Enterobacteriaceae and coliforms, while Staphylococcus aureus being the least. This study also indicated that microbial populations determined on the shoulder were higher than on the thigh surfaces, and meat sampling by tissue excision technique yielded significantly higher (P < 0.01) microbial count than swabbing method.

Antimicrobial Efficacy of Acidified Peroxyacetic Acid Treatments Against Surrogates for Enteric Pathogens on Prerigor Beef

Two studies were conducted to evaluate the antimicrobial effects of pH-adjusted solutions of peroxyacetic acid (PAA) against nonpathogenic Escherichia coli surrogates for Shiga toxin–producing E. coli and Salmonella, inoculated on beef. In both studies, prerigor beef carcass surface tissue (10 × 10 cm pieces) was inoculated (6–7 log colony-forming units [CFU]/cm2) on the adipose side with a 5-strain mixture of E. coli biotype I. In the first study, samples were left untreated (control) or were immersed (10 s) in solutions of PAA (300 parts per million [ppm]) acidified with a sulfuric acid and sodium sulfate blend (SSS) (pH 1.2) or PAA (400 ppm) acidified with acetic acid (2%), citric acid (1%), lactic acid (3.5%), or SSS (pH 1.2 or pH 1.8). In the second study, samples were left untreated or were spray treated (10 s) using a spray cabinet, with water, PAA (350 ppm or 400 ppm), PAA (350 ppm or 400 ppm) acidified with SSS (pH 1.2), or PAA (400 ppm) acidified with acetic acid (2%). All immersion treatments effectively (P &amp;lt; 0.05) reduced inoculated E. coli populations (6.2 log CFU/cm2) by 2.3 to 2.8 log CFU/cm2. When the test solutions were applied by spraying, the water and all PAA-containing treatments lowered inoculated populations (6.4 log CFU/cm2) by 0.4 (P ≥ 0.05) and 1.7–1.9 (P &amp;lt; 0.05) log CFU/cm2, respectively. No (P ≥ 0.05) differences in decontamination efficacy were observed between the 5 PAA-containing spray treatments. Overall, the results showed that PAA and the pH-adjusted PAA treatments were effective in reducing levels of the surrogates for Shiga toxin–producing E. coli and Salmonella. Although no differences in antimicrobial efficacy were noted between the nonacidified and acidified PAA treatments immediately after treatment application, further studies are needed to evaluate how the acidified PAA treatments perform as part of a sequential multi-hurdle decontamination strategy to reduce pathogen contamination on beef carcasses.

Prevalence of Arcobacter and Campylobacter in beef meat samples and characterization of the recovered isolates

The present study aimed to isolate Arcobacter spp. and Campylobacter spp. from beef meat samples including cattle carcasses, cube meat and minced meat, and to determine the antibacterial susceptibility and genetic diversity of the recovered isolates. One hundred beef carcass surface samples from slaughterhouses and 100 beef meat samples (50 samples of cube meat and 50 minced meat) taken from different retail units were analysed. Of the examined samples, 17 (8.5%) and 43 (21.5%) were positive for Arcobacter spp. and Campylobacter spp. respectively. Twenty Arcobacter and 53 Campylobacter isolates were obtained from positive samples. Both Arcobacter and Campylobacter were concurrently isolated from 7 (3.5%) of the 17 positive samples. Arcobacter butzleri (18 isolates) and Campylobacter jejuni (37 isolates) were the most commonly isolated species. The results of Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction revealed extensive genetic heterogeneity among both Arcobacter and Campylobacter isolates. Seventeen and 30 different genotypes were identified in 18 A. butzleri and 37 C. jejuni isolates, respectively. Each of A. cryaerophilus, C. fetus and C. hyointestinalis isolates had two genotypes. Three and seven genotypes were identified in five C. lari and in seven C. coli isolates, respectively. While 5% of 20 Arcobacter isolates were resistant to amoxicillin-clavulanic acid, 5% of the isolates were resistant to neomycin. Of the 53 Campylobacter isolates, 9.43%, 22.64%, 7.54% and 3.77% were resistant to enrofloxacin, neomycin, tetracycline and streptomycin, respectively. Contaminated beef carcasses, cube meat and minced meat with various species and subspecies of arcobacters and campylobacters may pose a risk factor for human infections. Our study reveals the necessity of improving the hygiene quality in slaughterhouses and other meat processing units as there are different sources of contamination.

Modified time-temperature combinations reduce beef carcass contamination but will this benefit be seen thoughout the food chain?

The overall value of Irelands beef exports is worth approximately €2.5bn which is an annual increase of 5 % in 2017. However, the beef industry faces many challenges to export products to distant markets including a short shelf life and other economic losses that are mainly caused by microbial contamination. One of the simplest approaches to limit this contamination on the surfaces of beef carcasses is to use alternative carcass chill regimes. Carcasses underwent an industry standard chill process (10 °C for 10 h followed by 0 °C for 38 h) and were compared with carcasses that underwent a more rapidly chilled process (0 °C for 5 h and −2 °C for 3 h). Bacterial concentrations (mesophilic and psychrophilic total viable counts, total Enterobacteriaceae counts, Lactic Acid Bacteria, Pseudomonas spp., Brochothrix thermosphacta, Clostridium spp.), physiochemical (pH, temperature, water activity (aw)) and organoleptic (colour, odour, texture) changes were monitored throughout the entire beef food chain (carcass → primal → retail steak) until end of shelf life. Rapidly chilled carcasses had significantly (P&lt;0.05) less bacterial surface contamination compared to conventionally chilled carcasses. There was also significantly (P&lt;0.05) less evaporative loss on carcasses and primals which will have a positive economic impact on the beef industry. This longitudinal study is one of the largest trials ever performed on beef shelf life extension.

The identification of dark cutting beef carcasses in Australia, using Nix Pro Color Sensor™ colour measures, and their relationship to bolar blade, striploin and topside quality traits

Within 24 h post-mortem, loin surfaces of Australian beef carcasses (n = 436) were evaluated using the Nix Pro Color Sensor™ (NIX). The potential for colorimetrics (L*, a*, b*, hue and chroma) to discriminate between dark cutting (DC) and non-dark cutting (nDC) carcasses was compared. For this purpose, a chroma threshold of 30.5 delivered maximum total sensitivity and specificity. The bolar blade, striploin and topside from a selection of DC and nDC carcasses were also removed, aged for 14 d and tested for shear force, drip loss, cooking loss, ultimate pH, colour change over 3 d display (ΔE), and sarcomere length. Association between chroma values and these quality traits were investigated by linear models. The hypothesis of zero slope was rejected (P < 0.05) for pH on striploin and topside, but the models had poor predictive ability (R2 = 0.23). The NIX was found to be a viable grading tool, with limited capacity to provide additional insights into beef quality.

Antimicrobial Effects of Peroxyacetic Acid Acidified with Various Acids when Applied to Inoculated Prerigor Beef Carcass Surface Tissue

Antimicrobial Effects of Peroxyacetic Acid Acidified with Various Acids when Applied to Inoculated Prerigor Beef Carcass Surface Tissue

Comparison of the Efficacy of a Sulfuric Acid–Sodium Sulfate Blend and Lactic Acid for the Reduction of Salmonella on Prerigor Beef Carcass Surface Tissue

A study was conducted to compare the efficacy of a commercially available sulfuric acid-sodium sulfate blend (SSS) and lactic acid (LA) in reducing inoculated Salmonella populations on beef. Sixty pieces of prerigor beef carcass surface brisket tissue, collected directly from the processing line of a commercial beef processing plant, were cut into two sections (10 by 10 cm each) and spot inoculated (6 to 7 log CFU/cm2) on the adipose side with a six-strain mixture of Salmonella. One section per piece of brisket tissue was left untreated (control), while the second section was spray treated (5 s, 15 lb/in2, and 33 mL/s flow rate) with unheated (21°C) or heated (52°C) solutions of SSS (pH 1.1) or LA (4%). Unheated and heated SSS lowered (P < 0.05) total bacterial counts from 6.3 to 4.6 and 4.3 log CFU/cm2, respectively. Likewise, unheated and heated LA reduced (P < 0.05) total bacterial counts from 6.3 to 4.7 and 4.4 log CFU/cm2, respectively. Initial counts of inoculated Salmonella populations (6.1 to 6.2 log CFU/cm2) were reduced (P < 0.05) to 4.2 and 3.9 log CFU/cm2 following treatment with unheated and heated SSS, respectively, and to 3.7 and 3.8 log CFU/cm2 after treatment with unheated and heated LA, respectively. Overall, the temperature of the chemical solutions had a small (0.3 log CFU/cm2), but significant (P < 0.05), effect on total bacterial counts but not (P > 0.05) on Salmonella counts. Regardless of solution temperature, Salmonella counts for LA-treated samples were 0.3 log CFU/cm2 lower (P < 0.05) than those of samples treated with SSS. These results indicate that both unheated and heated solutions of SSS and LA are effective interventions for reducing Salmonella contamination on prerigor beef carcass surface tissue.

Prevalence and antimicrobial susceptibility of Escherichia coli O157 in beef at butcher shops and restaurants in central Ethiopia

BackgroundEthiopia bears the largest burden of foodborne diseases in Africa, and diarrheal diseases are the second leading causes of premature deaths. Enterohemorrhagic Escherichia coli O157 causes an asymptomatic infection to severe diarrhea and/or hemolytic-uremic syndrome in humans.MethodsA total of 440 beef carcass and in-contact surface swabs from 55 butcher shops and 85 minced beef samples from 40 restaurants in central Ethiopia were collected and examined for the presence of E. coli O157. Standard microbiological methods were used to isolate and identify E. coli O157 and to characterize the antimicrobial resistance of the isolates.ResultsE. coli O157 was detected in 4.5% carcass swabs (n = 5) and 3.6% cutting board swabs (n = 4) samples from butcher shops. E. coli O157 was not detected in any of the minced beef samples obtained from restaurants. All isolates (n = 9) were 100% susceptible to five drugs, but five isolates were resistant to amoxicillin, two isolates to streptomycin and three isolates to chloramphenicol. One isolate was resistant to two drugs and another to three drugs.ConclusionsThe present study shows a low prevalence of E. coli O157 in beef sold at butcher shops. Nevertheless, given the low infective dose of this pathogen and the deep-rooted tradition of consuming raw or undercooked beef, the current prevalence should not be considered lightly from a public health perspective.

Antimicrobial Efficacy of a Lactic Acid and Citric Acid Blend against Shiga Toxin-Producing Escherichia coli, Salmonella, and Nonpathogenic Escherichia coli Biotype I on Inoculated Prerigor Beef Carcass Surface Tissue

Studies were conducted to (i) determine whether inoculants of nonpathogenic Escherichia coli biotype I effectively served as surrogates for E. coli O157:H7, non-O157 Shiga toxin-producing E. coli, and Salmonella when prerigor beef carcass tissue was treated with a commercially available blend of lactic acid and citric acid (LCA) at a range of industry conditions of concentration, temperature, and pressure; (ii) determine the antimicrobial efficacy of LCA; and (iii) investigate the use of surrogates to validate a hot water and LCA sequential treatment as a carcass spray intervention in a commercial beef harvest plant. In an initial laboratory study, beef brisket tissue samples were left uninoculated or were inoculated (∼6 log CFU/cm(2)) on the adipose side with E. coli O157:H7 (5-strain mixture), non-O157 Shiga toxin-producing E. coli (12-strain mixture), Salmonella (6-strain mixture), or nonpathogenic E. coli (5-strain mixture). Samples were left untreated (control) or were treated with LCA, in a spray cabinet, at one of eight combinations of solution concentration (1.9 and 2.5%), solution temperature (43 and 60°C), and application pressure (15 and 30 lb/in(2)). In a second study, the E. coli surrogates were inoculated (∼6 log CFU/cm(2)) on beef carcasses in a commercial facility to validate the use of a hot water treatment (92.2 to 92.8°C, 13 to 15 lb/in(2)) followed by an LCA treatment (1.9%, 50 to 51.7°C, 13 to 15 lb/in(2), 10 s). In the in vitro study, surrogate and pathogen bacteria did not differ in their response to the tested LCA treatments. Treatment with LCA reduced (P < 0.05) inoculated populations by 0.9 to 1.5 log CFU/cm(2), irrespective of inoculum type. The hot water and LCA sequential treatments evaluated in the commercial facility reduced (P < 0.05) the inoculated nonpathogenic E. coli surrogates on carcasses by 3.7 log CFU/cm(2). This study therefore provides the meat industry with data for this sequential multiple hurdle system for the operation parameters described.

Investigation into Formation of Lipid Hydroperoxides from Membrane Lipids in Escherichia coli O157:H7 following Exposure to Hot Water

Although studies have shown antimicrobial treatments consisting of hot water sprays alone or paired with lactic acid rinses are effective for reducing Escherichia coli O157:H7 loads on beef carcass surfaces, the mechanisms by which these interventions inactivate bacterial pathogens are still poorly understood. It was hypothesized that E. coli O157:H7 exposure to hot water in vitro at rising temperatures for longer time periods would result in increasing deterioration of bacterial outer membrane lipids, sensitizing the pathogen to subsequent lactic acid application. Cocktails of E. coli O157:H7 strains were subjected to hot water at 25 (control) 65, 75, or 85uC incrementally up to 60 s, after which surviving cells were enumerated by plating. Formation of lipid hydroperoxides from bacterial membranes and cytoplasmic accumulation of L-lactic acid was quantified spectrophotometrically. Inactivation of E. coli O157:H7 proceeded in a hot water exposure duration- and temperature-dependent manner, with populations being reduced to nondetectable numbers following heating of cells in 85°C water for 30 and 60 s (P < 0.05). Lipid hydroperoxide formation was not observed to be dependent upon increasing water temperature or exposure period. The data suggest that hot water application prior to organic acid application may function to increase the sensitivity of E. coli O157:H7 cells by degrading membrane lipids.

Ветеринарно-санітарний контроль мікробіологічних показників яловичих туш та санітарних умов їх виробництва

It is determined that the number of Enterobacteriaceae family bacteria and total bacterial count (TBC) on the surfaces of beef carcasses depends on the level of sanitation in slaughterhouses, season and the sampling place. It is established that given an adequate level of sanitation the number of Enterobacteriaceae family bacteria on the surface of the carcass averaged: after skinning 3,22±0,7 Log CFU / cm 2 , and after evisceration - 3,37±0,7 Log CFU / cm 2

Salmonella spp. in lymph nodes of fed and cull cattle: Relative assessment of risk to ground beef

Ground beef products have been implicated as the vehicle for the transmission of Salmonella in a number of outbreaks. Although carcass surface interventions have proven effective, Salmonella contamination in ground beef still occurs. Recent studies indicate that deep tissue lymph nodes (DTLNs) may be an important source of Salmonella contamination in ground beef products. We developed a stochastic simulation model covering the pre-to post-harvest stages to assess the relative contribution of DTLN as compared with carcass surface, to Salmonella in ground beef, and the impact of various pre- and post-harvest interventions. The model addressed fed and cull cattle, and in high and low prevalence seasons. Contamination from carcass surfaces and DTLNs was simulated separately. Linear relationships were used to describe the changes of Salmonella surface concentration and prevalence at different processing stages. The baseline results indicate that on average over 90% of the Salmonella CFU load in a 2000 lb (907 kg) production lot originates from DTLN contamination as compared with carcass surface contamination. The relative contribution of DTLN contamination was fairly robust to changes in model parameters for ground beef from fed cattle, while it was comparatively more sensitive to changes in model parameters for cull cattle. The predicted mean Salmonella CFU load from DTLN contamination was considerably greater in ground beef production lots from fed cattle compared with cull cattle. Correspondingly, our scenario analysis suggested that generic pre-harvest interventions which can reduce Salmonella contamination in DTLNs would cause a greater total CFU load reduction in ground beef production lots from fed cattle compared with cull cattle. The study provides some valuable information for prioritizing control measures targeted at Salmonella contamination from the beef carcass surface or DTLNs based on the current knowledge.

Impact of Sampling Area and Location on Measurement of Indicator Organisms during Beef Carcass Interventions

The effect of the sponge sample collection site on the recovery of multiple indicator organisms from beef carcass surfaces was evaluated to simplify and validate our previous sampling method for ease of implementation as a general protocol. Sponge samples were collected at three beef processing plants using hot water or acidic antimicrobials as interventions. Two 4,000-cm(2) samples were collected from preevisceration carcasses (n = 248), one from the inside and outside round area (top site) and one from the navel-plate-brisket-foreshank area (bottom site). One-half of the samples (n = 124) were collected before a wash cabinet intervention and the other half after the intervention. The numbers of total aerobic bacteria, Enterobacteriaceae, coliforms, and Escherichia coli were determined for one-half of each individual sponge sample. The other halves of the sponges were combined to represent a top plus bottom 8,000-cm(2) SAMPLE: For the preintervention carcasses, 4,000-cm(2) samples collected from the top or bottom sites of the carcasses were not significantly different (P > 0.05) from each other or from the 8,000-cm(2) combined sample in recovery of the indicator organisms. Significant reductions of indicator organisms were observed in all three types of sponge samples after intervention; however, samples collected from the bottom site recovered less organisms (P < 0.05) compared with samples of the other types. These results suggested that samples collected from either the top or the bottom site of the carcasses with this method are suitable for monitoring indicator organisms as long as the same sampling site is consistently used.

Evaluation of Lactic Acid as an Initial and Secondary Subprimal Intervention for Escherichia coli O157:H7, Non-O157 Shiga Toxin–Producing E. coli, and a Nonpathogenic E. coli Surrogate for E. coli O157:H7

Lactic acid can reduce microbial contamination on beef carcass surfaces when used as a food safety intervention, but effectiveness when applied to the surface of chilled beef subprimal sections is not well documented. Studies characterizing bacterial reduction on subprimals after lactic acid treatment would be useful for validations of hazard analysis critical control point (HACCP) systems. The objective of this study was to validate initial use of lactic acid as a subprimal intervention during beef fabrication followed by a secondary application to vacuum-packaged product that was applied at industry operating parameters. Chilled beef subprimal sections (100 cm(2)) were either left uninoculated or were inoculated with 6 log CFU/cm(2) of a 5-strain mixture of Escherichia coli O157:H7, a 12-strain mixture of non-O157 Shiga toxin-producing E. coli (STEC), or a 5-strain mixture of nonpathogenic (biotype I) E. coli that are considered surrogates for E. coli O157:H7. Uninoculated and inoculated subprimal sections received only an initial or an initial and a second "rework" application of lactic acid in a custombuilt spray cabinet at 1 of 16 application parameters. After the initial spray, total inoculum counts were reduced from 6.0 log CFU/cm(2) to 3.6, 4.4, and 4.4 log CFU/cm(2) for the E. coli surrogates, E. coli O157:H7, and non-O157 STEC inoculation groups, respectively. After the second (rework) application, total inoculum counts were 2.6, 3.2, and 3.6 log CFU/cm(2) for the E. coli surrogates, E. coli O157:H7, and non-O157 STEC inoculation groups, respectively. Both the initial and secondary lactic acid treatments effectively reduced counts of pathogenic and nonpathogenic strains of E. coli and natural microflora on beef subprimals. These data will be useful to the meat industry as part of the HACCP validation process.

Survival of Pseudomonas fluorescens on beef carcass surfaces in a commercial abattoir

The influence of a commercial chilling process (18 h at 10 degrees C followed by up to 78 h at 2 degrees C) on Pseudomonas fluorescens inoculated on beef carcass surfaces at four sites, neck (NE), outside round (OR), brisket (BR) and foreshank/brisket (FB) before chilling ("hot inoculated") or after chilling for 24h ("cold inoculated") was investigated. Pseudomonas counts increased significantly at all sites on "hot inoculated" carcasses during storage, but on "cold inoculated" carcasses, counts declined or remained unchanged. On hot and cold inoculated carcasses, differences in Pseudomonas growth or survival were demonstrated between sites. No clear relationships were observed between Pseudomonas growth or survival and chiller relative humidity (RH) or surface water activity (a(w)) at the different sites. These results were unexpected, and are discussed in relation to environmental factors that affect the growth/survival of P. fluorescens on carcass surfaces during chilling i.e. temperature, RH, and the relationship of these parameters to surface water activity (a(w)).

Survival of Escherichia coli O157:H7 and non-pathogenic E. coli on irradiated and non-irradiated beef surfaces

This study examined changes in numbers of pathogenic (PEC) and non-pathogenic (NPEC) Escherichia coli during storage at 10 °C on the surfaces of irradiated (IR) and non-irradiated (NIR) meat pieces excised from the neck, brisket and rump of beef carcasses and in Brain Heart Infusion Broth (BHI) and Maximum Recovery Diluent (MRD). On irradiated meat pieces, there were significant differences between mean PEC and NPEC counts at all sites. Differences in counts were also observed between IR and NIR surfaces and among the three meat sites for both E. coli types. These differences occurred only on IR samples, suggesting that the irradiation associated reductions in normal beef surface flora influenced survival of both E. coli types. PEC and NPEC counts increased during storage in BHI, but only NPEC counts increased in MRD. The results of this study highlight the impact of meat surface type and the presence/absence of the normal beef carcass surface flora on E. coli survival and/or growth during meat storage. Such previously unreported effects, and their precise mechanisms, have direct implications in the development and application of accurate models for the prediction of the safety and shelf life of stored meat.