Significant effort has been targeted at reducing the risk of pathogens in U.S. beef products since the mid-1990s. These efforts were focused on Escherichia coli O157:H7 after it was declared an ...adulterant in ground beef or its components. Post-harvest interventions applied to hides and carcasses by beef processors resulted in significant progress. Effective pre-harvest approaches proved hard to identify and implement. Six additional pathogenic E. coli serogroups were made adulterants in some beef products in 2012 and discussion regarding Salmonella is ongoing. Success to date has resulted from the combination of regulatory, research, and industry efforts to reduce the presence of pathogens in beef.
•Review of post-harvest interventions for beef•Review of pre-harvest interventions for beef•Status of U.S. beef safety•Industry activities to improve beef safety
The objective of this study is to investigate individual animal variation of bovine fecal microbiota including as affected by diets. Fecal samples were collected from 426 cattle fed 1 of 3 diets ...typically fed to feedlot cattle: 1) 143 steers fed finishing diet (83% dryrolled corn, 13% corn silage, and 4% supplement), 2) 147 steers fed late growing diet (66% dry-rolled corn, 26% corn silage, and 8% supplement), and 3) 136 heifers fed early growing diet (70% corn silage and 30% alfalfa haylage). Bacterial 16S rRNA gene amplicons were determined from individual fecal samples using next-generation pyrosequencing technology. A total of 2,149,008 16S rRNA gene sequences from 333 cattle with at least 2,000 sequences were analyzed. Firmicutes and Bacteroidetes were dominant phyla in all fecal samples. At the genus level, Oscillibacter, Turicibacter, Roseburia, Fecalibacterium, Coprococcus, Clostridium, Prevotella, and Succinivibrio were represented by more than 1% of total sequences. However, numerous sequences could not be assigned to a known genus. Dominant unclassified groups were unclassified Ruminococcaceae and unclassified Lachnospiraceae that could be classified to a family but not to a genus. These dominant genera and unclassified groups differed (P < 0.001) with diets. A total of 176,692 operational taxonomic units (OTU) were identified in combination across all the 333 cattle. Only 2,359 OTU were shared across 3 diet groups. UniFrac analysis showed that bacterial communities in cattle feces were greatly affected by dietary differences. This study indicates that the community structure of fecal microbiota in cattle is greatly affected by diet, particularly between forage- and concentrate-based diets.
Aims
The objective of the study was to determine levels of Escherichia coli O157:H7 colonization in the gastrointestinal tract (GIT) of naturally shedding cattle shedding the pathogen at low‐ or ...super‐shedder levels.
Methods and Results
Over 2 years, feedlot cattle were sampled multiple times for faecal shedding of E. coli O157:H7. Just prior to harvest (1–2 days), animals that were super‐shedders (≥104 CFU per gram of faeces) were specifically identified, and based on the longer term screening data, pen cohorts that were low‐shedders (years 1 and 2) or chronic‐shedders (year 1) were also identified. At harvest, samples were collected from throughout the GIT, including the rectoanal junction (RAJ) for enumeration and enrichment of E. coli O157:H7. The mouth samples exhibited the greatest prevalence for the pathogen, and the abomasum and rumen exhibited the lowest prevalence (P < 0·05). Super‐shedders had significantly greater prevalence for all GIT locations except the mouth and abomasum compared to low‐shedders, but the super‐shedders were the only animals with positive abomasum samples. Samples from the super‐shedders were enumerable for most GIT locations, and the rectum and RAJ locations were the only locations that were significantly greater than other locations (P < 0·05).
Conclusions
Across all animals naturally exposed to E. coli O157:H7, the risk of ingestion is high, but rumen and abomasum are potential barriers to passage. In super‐shedders, the passage through the GIT was greater, allowing colonization in the rectum and at the RAJ.
Significance and Impact of the Study
Escherichia coli O157:H7 low‐shedding cattle had lower pathogen levels throughout the GIT, indicating intrinsic GIT factors to these cattle may reduce pathogen passage through the GIT, including the abomasum, and minimize risk of RAJ colonization.
The objective of this study is to determine the interactions between high hydrostatic pressure, pressurization temperature, time and pH during pressurization on death and injury of pressure-resistant ...and pressure-sensitive strains of four foodborne pathogens:
Staphylococcus aureus 485 and 765,
Listeria monocytogenes CA and OH
2,
Escherichia coli O157:H7 933 and 931,
Salmonella enteritidis FDA and
Salmonella typhimurium E21274. Among these strains
S. aureus 485,
L. monocytogenes CA,
E. coli O157:H7 933 and
S. enteritidis FDA were reported to be more pressure-resistant than the respective strain of the same species (
Alpas et al., 1999). In general, viability loss of all pathogens was enhanced significantly as the level of pressure and temperature were increased (
P<0.05). All the strains except
S. aureus 485 demonstrated more than 8 log cycle reduction when pressurized at 345 MPa at 50°C for 5 min. This strain seemed to be the most pressure-resistant strain within the conditions of the study. Pressurization in the presence of either citric or lactic acid increased the viability loss by an additional 1.2–3.9 log cycles at pH 4.5 for both acids at 345 MPa. This study has indicated that high hydrostatic pressure applied in conjunction with mild heat and acidity can be an effective method for inactivating pressure-resistant and pressure-sensitive strains of four foodborne pathogens in organic acid solutions. This combination treatment indicates possible pressure pasteurization applications to liquid foods that have low pH.
Two experiments were conducted to study the effects of monensin dose on growth performance and O157:H7 shedding in finishing beef cattle. In Exp. 1, 198 heifers (298 ± 1.1 kg BW) were allocated to 1 ...of 2 treatments consisting of 1) 200 mg/heifer daily of monensin and 2) 400 mg/heifer daily of monensin and fed for 151 d. In Exp. 2, 199 steers (430 ± 1.9 kg BW) were stratified by BW and allocated to 1 of 2 treatments consisting of 1) 0 mg/steer daily of monensin and 2) 400 mg/steer daily of monensin and fed for 128 d. For both experiments, there were 4 pen replicates per treatment. For Exp. 1 and Exp. 2, the model included the fixed effect of treatment for growth performance measures and the fixed effects of treatment, time, and treatment × time interaction, respectively, for O157:H7 shedding. In Exp. 1, final BW was 1.9% greater for heifers fed 400 mg/d monensin than for heifers fed 200 mg/d monensin ( = 0.05). Furthermore, ADG was 4.9% greater ( = 0.05) and G:F was 3.1% greater ( = 0.04) when the heifers were fed 400 mg/d monensin vs. 200 mg/d monensin. Pen prevalence for O157:H7 ( = 0.96) and the percentage of animals in the pen shedding O157:H7 at enumerable levels ( = 0.82) did not differ between heifers fed 200 mg/d monensin and heifers fed 400 mg/d monensin over the 4 sampling periods. For Exp. 2, steers fed the supplement containing monensin had a 1.9% greater final BW ( = 0.04) and a 5.2% greater ADG ( = 0.02) than steers fed a control supplement without monensin. No differences in DMI or G:F were noted across the treatments ( ≥ 0.14). O157:H7 percentage of enumerable cattle within the pen was greater for the steers fed monensin than the control steers not fed monensin than the control steers not fed monensin ( = 0.02) over the 4 sampling periods. However, the percentage of animals in the pen shedding O157:H7 (prevalence positive) did not differ between treatments ( = 0.18), nor did the average fecal counts ( = 0.45). In conclusion, feeding a higher dose (400 mg/d) of monensin improved final BW and ADG compared with a low dose of monensin or a no-monensin control in steers and heifers across multiple years. The percentage of animals shedding O157:H7 at enumerable levels was greater for steers fed the monensin supplement than for steers fed the control supplement, yet the presence of monensin, irrespective of the dose, did not affect the percentage of animals in the pen shedding O157:H7.
The present study was conducted to determine the repeatability of color stability measurements and to evaluate relationships among color stability data collected under differing sampling and aging ...protocols. Beef (Bos taurus) carcasses (n = 100) were selected at grading in a commercial facility, after which a LM steak was removed from the 13th rib of each carcass and immediately placed in simulated retail display. Steaks were removed from the remainder of each loin after 14 (duplicate) and 35 d of aging and placed in display. Color attributes L*, a*, b*, hue angle, chroma, K/S(572)/K/S(525), and overall color change (ΔE) were determined on d 0, 1, 4, 7, and 11 of display. Duplicate 14-d aged steaks differed (P < 0.05) initially with regard to L*, b*, hue angle, chroma, K/ S(572)/K/S(525), and ΔE. However, changes in these attributes during display were equivalent in the duplicate steaks. Furthermore, repeatability estimates were high for all attributes, particularly when measured late in the display period (R = 0.55 to 0.97 on d 4, 7, and 11 of display). Differences in the trends associated with color change of steaks removed from the carcass after grading and those aged for 14 d were generally insignificant. Changes in color attributes of steaks aged for 35 d before simulated retail display generally were much more rapid than those obtained after grading or those aged for 14 d. Despite differences in the rate of discoloration during simulated retail display, color attributes were moderately to highly correlated (P < 0.05) between aging treatments, though the degree of correlation between attributes varied across days of display. In steaks collected after grading and those aged for 14 d, the greatest correlation was observed in the latter part of the display period with coefficients ranging from 0.61 to 0.94 on d 4, 7, and 11 of display. The greatest correlation between steaks aged for 14 d and those aged for 35 d were detected in the middle portion of the display period, presumably because many steaks aged for 35 d had reached an ultimate level of discoloration by d 11 of display with correlation coefficients ranging from 0.51 to 0.95 on d 4 and 7 of display. Thus, these results indicate that color stability data is highly repeatable and that, although aging impacts color-life, animal variation is consistent across aging times. Furthermore, steaks obtained from carcasses after grading can provide color stability evaluations applicable to steaks from aged subprimals.
AIMS: The objective of this study was to determine the effect of lysozyme and antibiotics on zoonotic pathogen shedding in faeces from nursery pigs housed without and with an indirect disease ...challenge. METHODS AND RESULTS: Two replicates of approximately 650 pigs each were weaned and randomly assigned to one of 24 pens in either a nursery room that had been fully disinfected or a nursery room left unclean. Pigs were randomly assigned to control diet (Control), control diet + antibiotics (Antibiotic; chlortetracycline and tiamulin), or control diet + lysozyme (Lysozyme; 100 mg kg⁻¹diet). Rectal swab samples were collected on day 0 and 28 of treatment, and enriched and cultured for Campylobacter spp. and shiga‐toxigenic Escherichia coli (STEC). Enrichments from rectal swab samples also were analysed for presence of enterohaemorrhagic E. coli (EHEC) virulence genes (hlyA, eae, stx1 and stx2). Room hygiene had little effect on day 28 results. Percentage of samples culture positive for Campylobacter spp. was lowest for lysozyme diets (P < 0·01), but similar for control and antibiotic diets (43·2, 83·7, and 84·8 respectively). Diet had little effect on the EHEC virulence genes hlyA or eae (P > 0·1), but there was a tendency for fewer samples positive for stx1/stx2 in antibiotic or lysozyme diet groups (P < 0·07) compared to control diet (1·2, 2·1 and 5·8% respectively). Salmonella spp. and specific STEC types tested were rarely detected in the study. CONCLUSIONS: In nursery swine, room hygiene had little effect on pathogen shedding. Dietary chlortetracycline and tiamulin did not reduce pathogen shedding but dietary lysozyme reduced faecal shedding of Campylobacter. SIGNIFICANCE AND IMPACT OF THE STUDY: Lysozyme can effectively replace antibiotics in the diet of nursery swine and can be effective for pathogen control.
To develop and validate high throughput methods for the direct enumeration of viable and culturable Salmonella and Escherichia coli O157:H7 in ground beef, carcass, hide and faecal (GCHF) samples ...from cattle. The hydrophobic grid membrane filtration (HGMF) method and the spiral plate count method (SPCM) were evaluated as rapid tools for the estimation of pathogen load using GCHF samples spiked with known levels of Salmonella serotype Typhimurium. Validation studies showed that for a single determination of each sample type the low end of the detection limits were approx. 2·0 x 10⁰ CFU g⁻¹ for ground beef, 5·0 x 10⁻¹ CFU (100 cm²)⁻¹ for Salmonella and 8·0 x 10⁻¹ CFU (100 cm²)⁻¹ for E. coli O157:H7 on carcasses, 4·0 x 10¹ CFU (100 cm²)⁻¹ for hide and 2·0 x 10² CFU g⁻¹ for faecal samples. In addition, ground beef (n = 609), carcass (n = 1520) and hide (n = 3038) samples were collected from beef-processing plants and faecal samples (n = 3190) were collected from feed-lot cattle, and these samples were tested for the presence of Salmonella and E. coli O157:H7 by enrichment and enumeration methods. The direct enumeration methods described here are amenable to high throughput sample processing and were found to be cost-effective alternatives to other enumeration methods for the estimation of Salmonella and E. coli O157:H7, in samples collected during cattle production and beef processing. Use of the methods described here would allow for more routine testing and quantification data collection, providing useful information about the effectiveness of beef processing intervention strategies.
Among food-borne pathogens, some strains could be resistant to hydrostatic pressure treatment. This information is necessary to establish processing parameters to ensure safety of ...pressure-pasteurized foods (N. Kalchayanand, A. Sikes, C. P. Dunne, and B. Ray, J. Food Prot. 61:425-431, 1998). We studied variation in pressure resistance among strains of Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella species at two temperatures of pressurization. Early-stationary-phase cells in 1% peptone solution were pressurized at 345 MPa either for 5 min at 25 degrees C or for 5, 10, or 15 min at 50 degrees C. The viability loss (in log cycles) following pressurization at 25 degrees C ranged from 0.9 to 3.5 among nine L. monocytogenes strains, 0.7 to 7.8 among seven S. aureus strains, 2.8 to 5.6 among six E. coli O157:H7 strains, and 5.5 to 8.3 among six Salmonella strains. The results show that at 25 degrees C some strains of each species are more resistant to pressure than the others. However, when one resistant and one sensitive strain from each species were pressurized at 345 MPa and 50 degrees C, the population of all except the resistant S. aureus strain was reduced by more than 8 log cycles within 5 min. Viability loss of the resistant S. aureus strain was 6.3 log cycles even after 15 min of pressurization. This shows that strains of food-borne pathogens differ in resistance to hydrostatic pressure (345 MPa) at 25 degrees C, but this difference is greatly reduced at 50 degrees C. Pressurization at 50 degrees C, in place of 25 degrees C, will ensure greater safety of foods.
The objective of this study was to determine if wet distillers grains with solubles (WDGS) from corn in diets affected Escherichia coli O157:H7 in growing and finishing cattle; steers (n = 603) were ...randomly assigned to diets with or without WDGS. Hide and fecal samples were collected monthly (October through June) from each animal for enumeration and enrichment of E. coli O157:H7. In the growing phase (0 or 13.9% WDGS diets), fecal prevalence for E. coli O157:H7 in steers fed a diet with WDGS was twice that of the prevalence in control steers (P < 0.001). In the finishing phase (0 or 40% WDGS diets), the average prevalence in feces (P < 0.001) and on hides (P < 0.001) was higher for cattle fed WDGS. The average percentage of fecal E. coli O157:H7 enumerable samples during the finishing phase for cattle fed WDGS was 2.7% compared with 0.1% for control steers (P < 0.001). The average percentage of E. coli O157:H7 enumerable hide samples was not different between diets, but the cattle fed WDGS had higher levels (P < 0.05) of the pathogen. Animals fed WDGS had higher levels of E. coli (P < 0.001), higher pH values (P < 0.001), and lower concentrations of L-lactate (P < 0.001) in feces than those values of the control steers. These results indicate that feeding 40% WDGS could increase the level and prevalence of E. coli O157:H7 in and on feedlot cattle when E. coli O157:H7 is seasonally low.
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