J. Chance Brooks

Cross-sectional Study Examining Salmonella enterica Carriage in Subiliac Lymph Nodes of Cull and Feedlot Cattle at Harvest

Bovine peripheral lymph nodes (LNs), including subiliac LNs, have been identified as a potential source of human exposure to Salmonella enterica, when adipose trim containing these nodes is incorporated into ground beef. In order to gain a better understanding of the burden of S. enterica in peripheral LNs of feedlot and cull cattle, a cross-sectional study was undertaken in which 3327 subiliac LNs were collected from cattle at harvest in seven plants, located in three geographically distinct regions of the United States. Samples were collected in three seasons: Fall 2010, Winter/Spring 2011, and Summer/Fall 2011. A convenience sample of 76 LNs per day, 2 days per season (approximately 1 month apart), was collected per plant, from carcasses held in the cooler for no less than 24 h. Every 10(th) carcass half on a rail was sampled, in an attempt to avoid oversampling any single cohort of cattle. Median point estimates of S. enterica contamination were generally low (1.3%); however, median Salmonella prevalence was found to be greater in subiliac LNs of feedlot cattle (11.8%) compared to those of cull cattle (0.65%). Enumeration analysis of a subset of 618 feedlot cattle LNs showed that 67% of those harboring S. enterica (97 of 144) did so at concentrations ranging from <0.1 to 1.8 log10 CFU/g, while 33% carried a higher burden of S. enterica, with levels ranging from 1.9 to >3.8 log10 CFU/g. Serotyping of S. enterica isolated identified 24 serotypes, with the majority being Montevideo (44.0%) and Anatum (24.8%). Antimicrobial susceptibility phenotypes were determined for all isolates, and the majority (86.1%) were pansusceptible; however, multidrug-resistant isolates (8.3%) were also occasionally observed. As Salmonella contained within LNs are protected from carcass interventions, research is needed to define opportunities for mitigating the risk of Salmonella contamination in LNs of apparently healthy cattle.

Inhibition of Escherichia coli O157:H7 and Clostridium sporogenes in spinach packaged in modified atmospheres after treatment combined with chlorine and lactic acid bacteria.

UNLABELLED Implementation of modified atmospheric packaging (MAP) into retail produce is a less commonly practiced method due to differences among commodities and the potential growth of anaerobes. Pathogens including Escherichia coli O157:H7 have been responsible for spinach outbreaks across the United States. In this study, hurdles, including those currently used with produce safety, such as MAP and chlorine, were combined with lactic acid bacteria (LAB) to inhibit pathogens. Spinach was coinoculated with E. coli O157:H7 and Clostridium sporogenes, a surrogate for C. botulinum, and treated with water or a hurdle that included water, chlorine, and LAB. Spinach from treatments were packaged in air (traditional), oxygen (80% O₂, 20% CO₂), or nitrogen (80% N₂, 20% CO₂) and stored in a retail display case for 9 d at 4 to 7 °C. The hurdle inhibited E. coli O157:H7 and C. sporogenes compared to controls with reductions of 1.43 and 1.10 log (P < 0.05), respectively. The nitrogen atmosphere was outperformed by air and oxygen in the reduction of E. coli O157:H7 (P < 0.05) with a decrease of 0.26 and 0.15 logs. There were no significant differences among the 3 atmospheres on C. sporogenes survival. Relative to these hurdles, we also chose to evaluate the potential benefits of LAB in pathogen control. The survival of LAB in interventions demonstrates implementation of LAB into produce could control pathogens, without damaging produce or altering organoleptic properties. PRACTICAL APPLICATION The goal of our work was to identify methods that could reduce food-borne pathogens in packaged spinach products. Using current industry techniques in combination with unique methods, such as the use of beneficial bacteria, our research identified whether harmful microorganisms could be eliminated. Our data demonstrate that specific packaging conditions with beneficial bacteria can help eliminate or reduce the survival of E. coli O157:H7 and C. sporogenes (a model for C. botulinum) in produce.

Salmonella and Campylobacter baseline in retail ground beef and whole-muscle cuts purchased during 2010 in the United States.

Salmonella enterica and Campylobacter spp. cause a considerable number of human illnesses each year, and the vast majority of cases are foodborne. The purpose of this study was to establish the baseline of Salmonella and Campylobacter in beef products purchased from U.S. retail markets. Sampling was carried out in 38 American cities. Retail raw ground and whole-muscle beef (n = 2,885) samples were purchased and examined for the presence of Salmonella. Samples testing positive for Salmonella were identified with the commercial BAX System, which is a real-time PCR-based system. Of the original samples purchased, 1,185 were selected and tested for the presence of Campylobacter. Positive samples were isolated via direct plating and confirmed via agglutination and biochemical testing. Salmonella was detected in 0.66% of the total samples purchased. The prevalence of Salmonella in ground beef packages was 0.42% for modified atmosphere packaging, 0.63% for chub packaging, and 0.59% for overwrapped packages. Salmonella was detected in 1.02% of whole-muscle cuts. There was no relationship (P = 0.18) between product type (ground or whole muscle) and the percentage of positive samples. Campylobacter was recovered from 9.3% of samples. A greater percentage (17.24%, P < 0.01) of whole-muscle cuts tested positive for Campylobacter compared with ground beef samples (7.35%). Estimating pathogen baselines in U.S. retail beef is essential for allotting resources and directing interventions for pathogen control. These data can be utilized for a more complete understanding of these pathogens and their impact on public health from the consumption of beef products.

Implementation of targeted interventions to control Escherichia coli O157:H7 in a commercial abattoir

The objective of this study was to define locations on the carcass with highest contamination of E. coli O157 throughout the harvest process and implement targeted interventions to reduce or eliminate contamination. To establish a pathogen baseline, samples were collected at the foreshank, hindshank, inside round, neck and midline area and evaluated for E. coli O157:H7 presence. Environmental samples were also collected in the harvest area and the fabrication area of the facility. E. coli O157:H7 prevalence was highest on the foreshank, hindshank and inside rounds in the baseline study and steam vacuums/cones were implemented as an intervention in these specific areas on the harvest floor. At pre-evisceration, foreshank prevalence of E. coli O157:H7 was significantly (P<0.05) reduced from 21.7% to 3.1% after the application of steam interventions. At the final rail, foreshank prevalence in the baseline study was 4.2% while no E. coli O157:H7 was detected post-intervention implementation. E. coli O157:H7 on hindshanks and inside rounds was significantly reduced after intervention implementation from 24.2 to 11.5% and 37.5 to 16.7%, respectively at the final rail. Pathogen contamination of environmental samples collected in fabrication declined from 6.7% to 0.7% after slaughter interventions were implemented. Data indicate the identifying areas of contamination on the carcass and implementing interventions can significantly reduce E. coli O157 on the carcasses and in the fabrication environment.

Antimicrobial interventions for O157:H7 and non-O157 Shiga toxin-producing Escherichia coli on beef subprimal and mechanically tenderized steaks.

Non-O157 Shiga toxin-producing Escherichia coli (STEC) is an emerging risk for food safety. Although numerous postharvest antimicrobial interventions have been effectively used to control E. coli O157:H7 during beef harvesting, research regarding their effectiveness against non-O157 STEC is scarce. The objectives of this study were (i) to evaluate effects of the spray treatments-ambient water, 5% lactic acid (LA), 200 ppm of hypobromous acid (HA), and 200 ppm of peroxyacetic acid (PA)-on the reduction of O157:H7 or non-O157 STEC (O26, O103, O111, and O145) with high (10(6) log CFU/50 cm(2)) or low (10(2) log CFU/50 cm(2)) levels on beef subprimals after vacuum storage for 14 days and (ii) to evaluate the association of the antimicrobial treatments and cooking (50 or 70°C) on the reduction of the pathogens in blade-tenderized steaks. The treatment effects were only observed (P = 0.012) on samples taken immediately after spray intervention treatment following inoculation with a high level of O157:H7. The LA and PA treatments significantly reduced low-inoculated non-O157 STEC after spray intervention; further, the LA and HA treatments resulted in significant reductions of non-O157 STEC on the low-inoculated samples after storage. Although cooking effectively reduced the detection of pathogens in internal steak samples, internalized E. coli O157:H7 and non-O157 STEC were able to survive in steaks cooked to a medium degree of doneness (70°C). This study indicated that the reduction on surface populations was not sufficient enough to eliminate the pathogens detection following vacuum storage, mechanical tenderization, and cooking. Nevertheless, the findings of this study emphasize the necessity for a multihurdle approach and further investigations of factors that may influence thermal tolerance of internalized pathogenic STEC.