Correlation of enterohemorrhagic Escherichia coli O157 prevalence in feces, hides, and carcasses of beef cattle during processing

A survey was performed to estimate the frequency of enterohemorrhagic Escherichia coli O157:H7 or O157:nonmotile (EHEC O157) in feces and on hides within groups of fed cattle from single sources (lots) presented for slaughter at meat processing plants in the Midwestern United States, as well as frequency of carcass contamination during processing from cattle within the same lots. Of 29 lots sampled, 72% had at least one EHEC O157-positive fecal sample and 38% had positive hide samples. Overall, EHEC O157 prevalence in feces and on hides was 28% (91 of 327) and 11% (38 of 355), respectively. Carcass samples were taken at three points during processing: preevisceration, postevisceration before antimicrobial intervention, and postprocessing after carcasses entered the cooler. Of 30 lots sampled, 87% had at least one EHEC O157-positive preevisceration sample, 57% of lots were positive postevisceration, and 17% had positive postprocessing samples. Prevalence of EHEC O157 in the three postprocessing samples was 43% (148 of 341), 18% (59 of 332) and 2% (6 of 330), respectively. Reduction in carcass prevalence from preevisceration to postprocessing suggests that sanitary procedures were effective within the processing plants. Fecal and hide prevalence were significantly correlated with carcass contamination (P = 0.001), indicating a role for control of EHEC O157 in live cattle.

Effects of direct-fed microbials on growth performance, gut morphometry, and immune characteristics in broiler chickens

This study was conducted to compare growth performance, gut morphometry, and parameters of local and systemic immunity in broiler chickens fed for 22 consecutive days with a diet supplemented with Bacillus spp. as direct-fed microbials (DFM), a commercial product incorporating 3 DFM, or a nonsupplemented diet. Direct-fed microbials did not significantly modify BW gain and most failed to affect serum antibody levels in response to immunization with a recombinant Eimeria protein. However, altered intestinal morphometric measurements were readily apparent in DFM-fed chickens as revealed by increased villus height and crypt depth compared with non-DFM-fed controls. In addition, serum levels of alpha-1-acid glycoprotein as an inflammatory marker were reduced in DFM-fed birds, whereas splenic lymphocyte proliferation, intestine intraepithelial lymphocyte subpopulations, and cytokine mRNA levels in intraepithelial lymphocytes were increased, decreased, or unchanged compared with controls depending on the DFM used. These results provide a rational scientific basis for future studies to investigate DFM as immunomodulating agents to enhance host protective immunity against enteric pathogens in broiler chickens.

Efficacy of Organic Acids Against Escherichia coli O157:H7 Attached to Beef Carcass Tissue Using a Pilot Scale Model Carcass Washer1

The efficacy of organic acids for controlling Escherichia coli O157:H7 attached to beef carcass tissue was determined using a pilot scale model carcass washer. Lean or adipose surface tissues from beef carcasses were inoculated with three strains of Escherichia coli O157:H7 or Pseudomonas fluorescens . After spraying either water, 1, 3, or 5% acetic, lactic, or citric acids at 24°C, tissues were incubated for 24 h at 4°C and bacterial populations enumerated. Statistical analyses of the data indicated that acid type was not a significant treatment factor (p ≥ = 0.05); however, concentration, tissue type, and bacterial strain were significant (p ≤ = 0.0001) factors that influenced the reduction of bacterial populations on lean or adipose tissue. Of the concentrations tested on lean tissue, spray treatments with 5% were the most effective for reducing populations of E. coli O157:H7 or P. fluorescens . Differences in the resistances of the E. coli O157:H7 strains to acid washing also were observed. The magnitude of bacterial population reductions was consistently greater on adipose versus lean tissue for all bacterial strains. Surface pH data indicated that reductions of bacterial populations may have been due to the effects of acidic pH. This study demonstrates that, while organic acids did reduce populations of E. coli O157:H7 on red meat, treatments did not completely inactivate the pathogen.

Microbial Decontamination of Beef and Sheep Carcasses by Steam, Hot Water Spray Washes, and a Steam-Vacuum Sanitizer

Three separate studies were conducted to determine the effectiveness of various temperature water spray washes (W_t), wash and steam combinations (W_tS), and vacuum and wash combinations (VW_t) for reducing fecal bacteria on sheep and beef carcasses. W_t of 15.6, 54.4, and 82.2°C were administered to sheep carcasses contaminated with feces, using a hand-held spray nozzle. Initial carcass bacterial populations of approximately 2.5, 4, and 6 log CFU/cm² were subjected to all wash combinations. W_82.2 and W_82.2S reduced 6 log CFU/cm² bacterial populations as much as 4.0 log cycles. When carcasses were subjected to W_tS and W_82.2, the initial contamination levels (4 and 6 log CFU/cm²) had little effect on final bacterial levels (2.7 to 3.3 log CFU/cm²). However, uninoculated carcasses with initial bacterial populations of 2.5 log CFU/cm² experienced a 1.5-log-cycle reduction when subjected to W_tS and W_82.2. It is possible that hydration of a carcass before and during interventions affords some protection to bacteria. The next study used a commercial carcass washer to apply a hot water (72°C), low pressure (20 psi) wash in combination with a high pressure (125 psi), warm water (30°C) wash (W_72/30). Reductions on beef of 2.7, 3.3, and 3.4 log cycles for aerobic plate count (APC), coliforms, and E. coli populations, respectively, were observed. When a commercial steam-vacuum was used in conjunction with W_72/30, reductions of 3.1, 4.2, and 4.3 log cycles for APC, coliforms, and E. coli populations, respectively, were achieved. Implementation of these interventions could reduce the amount of trimming needed on carcass-processing lines and would increase the microbial safety of beef carcasses.

Improved antimicrobial activity of nisin-incorporated polymer films by formulation change and addition of food grade chelator

AIMS

The following polymers were developed: polyethylene (PE), a PE and polyethylene oxide (70% PE and 30% PEO; PE + PEO) blend, PE and nisin (PE + nisin), PE, nisin, and EDTA (PE + nisin + EDTA), and PE + PEO with nisin (PE + PEO + nisin).

METHODS AND RESULTS

Of the polymers tested, PE and PE + PEO did not exhibit any antimicrobial activity against Brochothrix thermosphacta (BT); however, PE + nisin, PE + nisin + EDTA, and PE + PEO + nisin did. Beef surfaces were experimentally inoculated with 3.50 log10 cfu/cm2 of BT, vacuum packaged with each of the five polymers, and held at 4 degrees C for 21 d. After 3 d at 4 degrees C, BT was reduced > 1.70 log(10) by PE + nisin and > 3.50 log(10) with PE + nisin + EDTA or PE + PEO + nisin. By 21 d at 4 degrees C, BT was reduced to 0.30 log(10) cfu/cm(2) when treated with PE + PEO + nisin.

CONCLUSION

It appears that PE + PEO + nisin or PE + nisin + EDTA were more effective for reducing BT, as compared to polymers composed of PE + nisin.

SIGNIFICANCE AND IMPACT OF THE STUDY

Nisin-incorporated polymers may control the growth of undesirable bacteria, thereby extending the shelf life and possibly enhancing the microbial safety of meats.

Effects of Acetic Acid, Lactic Acid and Trisodium Phosphate on the Microflora of Refrigerated Beef Carcass Surface Tissue Inoculated with Escherichia coli O157:H7, Listeria innocua , and Clostridium sporogenes †

The microbial profiles of inoculated beef carcass tissue (BCT) were monitored during prolonged refrigerated vacuum-packaged storage following antimicrobial treatment. An industrial spray wash cabinet was used to deliver water (W), 1.5 and 3.0% lactic (LA) or acetic (AA) acid, or 12% trisodium phosphate (TSP) washes. Fresh unaltered bovine feces spiked with antibiotic-resistant strains of Escherichia coli O157:H7, Listeria innocua , and Clostridium sporogenes were used to inoculate BCT prior to all treatments. The effect of treatments on bacterial populations was tracked by monitoring levels of specific-antibiotic-resistant(marked) bacteria along with mesophilic aerobic bacteria (APC), lactic acid bacteria (LAB), and pseudomonads for up to 21 days of storage at 5°C. Initial APC levels of approximately 5.6 log CFU/cm² were reduced by 1.3to 2.0 log CFU/cm² by LA, AA, and TSP treatments. Marked bacteria were reduced to <1.3 log CFU/cm², remaining that way throughout the 21-day storage. TSP treatments were not different in effectiveness from acids for controlling growth of E. coli O157:H7 and C. sporogenes , but were less effective for APC, L. innocua , or LAB. The aerobic bacteria, L. innocua , and LAB had counts ≥7 log CFU/cm² by 7 days in all but one case and by 14 days all had counts >7 log CFU/cm² on the untreated controls and water-washed samples. Treatments generally added a degree of safety regarding the foodborne pathogens and pathogen models used for the present study when beef tissue was stored up to 21 days and in no case did the treatments appear to offer any competitive advantage to select microorganisms on BCT.

Genotypic analyses of Escherichia coli O157:H7 and O157 nonmotile isolates recovered from beef cattle and carcasses at processing plants in the Midwestern states of the United States

Escherichia coli O157:H7 and O157 nonmotile isolates (E. coli O157) previously were recovered from feces, hides, and carcasses at four large Midwestern beef processing plants (R. O. Elder, J. E. Keen, G. R. Siragusa, G. A. Barkocy-Gallagher, M. Koohmaraie, and W. W. Laegreid, Proc. Natl. Acad. Sci. USA 97:2999-3003, 2000). The study implied relationships between cattle infection and carcass contamination within single-source lots as well as between preevisceration and postprocessing carcass contamination, based on prevalence. These relationships now have been verified based on identification of isolates by genomic fingerprinting. E. coli O157 isolates from all positive samples were analyzed by pulsed-field gel electrophoresis of genomic DNA after digestion with XbaI. Seventy-seven individual subtypes (fingerprint patterns) grouping into 47 types were discerned among 343 isolates. Comparison of the fingerprint patterns revealed three clusters of isolates, two of which were closely related to each other. Remarkably, isolates carrying both Shiga toxin genes and nonmotile isolates largely fell into specific clusters. Within lots analyzed, 68.2% of the postharvest (carcass) isolates matched preharvest (animal) isolates. For individual carcasses, 65.3 and 66.7% of the isolates recovered postevisceration and in the cooler, respectively, matched those recovered preevisceration. Multiple isolates were analyzed from some carcass samples and were found to include strains with different genotypes. This study suggests that most E. coli O157 carcass contamination originates from animals within the same lot and not from cross-contamination between lots. In addition, the data demonstrate that most carcass contamination occurs very early during processing.

The poultry-associated microbiome: network analysis and farm-to-fork characterizations

Microbial communities associated with agricultural animals are important for animal health, food safety, and public health. Here we combine high-throughput sequencing (HTS), quantitative-PCR assays, and network analysis to profile the poultry-associated microbiome and important pathogens at various stages of commercial poultry production from the farm to the consumer. Analysis of longitudinal data following two flocks from the farm through processing showed a core microbiome containing multiple sequence types most closely related to genera known to be pathogenic for animals and/or humans, including Campylobacter, Clostridium, and Shigella. After the final stage of commercial poultry processing, taxonomic richness was ca. 2-4 times lower than the richness of fecal samples from the same flocks and Campylobacter abundance was significantly reduced. Interestingly, however, carcasses sampled at 48 hr after processing harboured the greatest proportion of unique taxa (those not encountered in other samples), significantly more than expected by chance. Among these were anaerobes such as Prevotella, Veillonella, Leptrotrichia, and multiple Campylobacter sequence types. Retail products were dominated by Pseudomonas, but also contained 27 other genera, most of which were potentially metabolically active and encountered in on-farm samples. Network analysis was focused on the foodborne pathogen Campylobacter and revealed a majority of sequence types with no significant interactions with other taxa, perhaps explaining the limited efficacy of previous attempts at competitive exclusion of Campylobacter. These data represent the first use of HTS to characterize the poultry microbiome across a series of farm-to-fork samples and demonstrate the utility of HTS in monitoring the food supply chain and identifying sources of potential zoonoses and interactions among taxa in complex communities.

Quantitative analysis of the intestinal bacterial community in one- to three-week-old commercially reared broiler chickens fed conventional or antibiotic-free vegetable-based diets

AIMS

To explore the effect of drug-free poultry production on the intestinal microflora of broiler chickens, the bacterial community of this environment was quantitatively profiled in both conventionally reared birds and birds reared without antibiotic growth promotants (AGPs) on a vegetable-based diet.

METHODS AND RESULTS

Quantitative, real-time PCR with group-specific 16S rDNA primer sets was used to enumerate the abundance of the following chicken gastrointestinal (GI) tract phylogenetic groups: the Clostridium leptum-Faecalibacterium prausnitzii subgroup (Clostridium genus cluster IV), the Clostridium coccoides - Eubacterium rectale subgroup (Clostridium cluster XIVa and XIVb), the Bacteroides group (including Prevotella and Porphyromonas), Bifidobacterium spp., the Enterobacteriaceae, the Lactobacillus group (including the genera Leuconostoc, Pediococcus, Aerococcus and Weissella), the Clostridium perfringens subgroup (Clostridium cluster I), Enterococcus spp., Veillonella spp., Atopobium spp., Campylobacter spp. and the domain Bacteria. A species-specific 5'-nuclease (Taqman) assay was also employed to specifically assess Cl. perfringens abundance. Ten birds were sampled from each of two commercial chicken houses, one in which feed was supplemented with AGPs and exogenous animal protein, and the other vegetable-based and drug-free, at 7, 14 and 21 days of age. The ileal community was dominated by two large populations, the lactobacilli and the Enterobacteriaceae, with those taxa much more numerous in drug-free vegetable-based diet fed birds than those conventionally reared at the 7- and 14-day time periods. The progressive changes in microflora in both the conventional and drug-free caeca were similar to each other, with the Enterobacteriaceae sequences dominating at day 7, but being replaced by obligate anaerobe signature sequences by day 14. Of note was the finding that all the day 14 and day 21 replicate caecal samples from the drug-free house were positive for Campylobacter spp. averaging >10(8) 16S rDNA gene copies per gram wet weight.

CONCLUSIONS

Quantitative, real-time PCR indicates that the effects of drug-free rearing on the chicken GI tract microbial community are most pronounced in the ileal region, but AGPs may be important in controlling Campylobacter colonization of the caecum.

SIGNIFICANCE AND IMPACT OF THE STUDY

A quantitative taxonomic understanding of the shifting microbial ecology of the broiler chicken gut microbiota is important in the light of AGP withdrawal. AGP withdrawal has occurred in response to concerns over the transfer of antimicrobial-resistant bacteria to humans via the food production chain.

Quantitative detection of Clostridium perfringens in the broiler fowl gastrointestinal tract by real-time PCR

Strains of Clostridium perfringens are a frequent cause of food-borne disease and gas gangrene and are also associated with necrotic enteritis in chickens. To detect and quantify the levels of C. perfringens in the chicken gastrointestinal tract, a quantitative real-time PCR assay utilizing a fluorogenic, hydrolysis-type probe was developed and utilized to assay material retrieved from the broiler chicken cecum and ileum. Primers and probe were selected following an alignment of 16S rDNA sequences from members of cluster I of the genus Clostridium, and proved to be specific for C. perfringens. The assay could detect approximately 50 fg of C. perfringens genomic DNA and approximately 20 cells in pure culture. Measurements of the analytical sensitivity determined with spiked intestinal contents indicated that the consistent limit of detection with ileal samples was approximately 10(2) CFU/g of ileal material, but only about 10(4) CFU/g of cecal samples. The decreased sensitivity with the cecal samples was due to the presence of an unidentified chemical PCR inhibitor(s) in the cecal DNA purifications. The assay was utilized to rapidly detect and quantify C. perfringens levels in the gut tract of broiler chickens reared without supplementary growth-promoting antibiotics that manifested symptoms of necrotic enteritis. The results illustrated that quantitative real-time PCR correlates well with quantification via standard plate counts in samples taken from the ileal region of the gastrointestinal tract.

Antimicrobial Effects of Trisodium Phosphate Against Bacteria Attached to Beef Tissue

Sliced beef tissue was artificially contaminated with Salmonella typhimurium , Listeria monocytogenes and Escherichia coli O157:H7. The contaminated tissue was immersed in 8, 10 and 12% solutions of trisodium phosphate at 25, 40 and 55°C with contact times of up to 3 min. The concentration of the trisodium phosphate solution was not a significant factor in reducing the populations of the bacteria on either lean or adipose tissue. Reductions in bacterial populations of 1 to 1.5 log₁₀ cycles were obtained on lean tissue contaminated with the gram-negative pathogens, although less reduction in population was seen with L. monocytogenes . Greater reductions in bacterial populations were observed on adipose tissue, with maximum reductions of 2 to 2.5 log₁₀ cycles and 1 to 1.5 log₁₀ cycles for the gram-negative and the gram-positive pathogens, respectively. Typically greater reductions in bacterial populations were seen as the temperature of the trisodium phosphate solution increased. Surface beef carcass tissue was inoculated with E. coli ATCC 25922 and sanitized with 8% trisodium phosphate using a model carcass washing system. Population reductions with the carcass washer and lean tissue were comparable to those observed in the laboratory with E. coli O157:H7. However, greater reductions were observed on adipose tissue from the model system, suggesting that the physical washing procedure may have contributed to the reduction in the bacterial population.

Population Reductions of Gram-Negative Pathogens Following Treatments with Nisin and Chelators under Various Conditions

When used in combination with chelating agents (EDTA, EGTA, citrate, phosphate), the bacteriocin nisin is effective for reducing populations of gram-negative bacteria in vitro. This study examined parameters (buffers, temperature presence of divalent cations) that affect nisin inhibition of Escherichia coli O157:H7 and Salmonella typhimurium . Approximately 7 log₁₀ colony-forming units (CFU) per ml of E. coli and S. typhimurium were treated in PBS or MOPS buffers containing 50 μg/ml of purified nisin, alone or in combination with 500 mM lactate, 100 mM citrate, 50 mM EDTA, and 1% (wt/vol) sodium hexametaphosphate (pH 7.0) at 37°C for 60 min or 5°C for 30 min. Surviving bacterial populations were compared to untreated controls (buffers without nisin). Data indicated that treatments with nisin in buffers resulted in reductions of 4.30 and 2.30 log₁₀ CFU/ml of E. coli and S. typhimurium , respectively, as compared to untreated controls. Population reductions ranging from 2.29 to 5.49 log₁₀ CFU/ml were observed when cells were treated with nisin and chelator combinations at either 37°C for 60 min or 5°C for 30 min. The addition of magnesium and calcium to buffers with nisin decreased inhibition. Data obtained from spectrophotometric experiments indicated that treatments were causing the release of cellular constituents. However, transmission electron microscopy (TEM) analyses were inconclusive, since cellular membranes did not appear to be disrupted.

Diverse antimicrobial killing by Enterococcus faecium E 50-52 bacteriocin

An effective bacteriocin was identified and characterized. Lactic acid bacteria were screened against Campylobacter jejuni. One bacteriocin producer, Enterococcus faecium (NRRL B-30746), was studied. The isolate was grown, and the bacteriocin was purified to single-band homogeneity. Biochemical traits indicated that the peptide was a Class IIa bacteriocin, and it was named E 50-52. The bacteriocin had a molecular weight of 3339.7 and an isoelectric point of 8.0. The minimal inhibitory concentrations of E 50-52 against C. jejuni, Yersinia spp., Salmonella spp., Escherichia coli O157:H7, Shigella dysenteriae, Morganella morganii, Staphylococcus spp., and Listeria spp. ranged from 0.025 to 32 microg/mL. In therapeutic broiler trials, oral treatment with E 50-52 reduced both C. jejuni and Salmonella enteritidis by more than 100,000-fold in the ceca, and systemic S. enteritidis was reduced in the liver and spleen. The wide range of antibacterial activity of bacteriocin E 50-52 against pathogens provides a promising alternative to antibiotics.

Formation of biofilm at different nutrient levels by various genotypes of Listeria monocytogenes

Strains of Listeria monocytogenes differ in their ability to form biofilms. The objectives of this study were to determine whether genetically related strains have similar biofilm-forming capacities and what effect nutrient concentration has on the ability of different strains to produce biofilms. Biofilms of 30 strains of L. monocytogenes, obtained from a variety of sources were grown on stainless steel in tryptic soy broth (TSB) or in a 1:10 dilution of TSB (DTSB) for 24 h at 32 degrees C. The amount of biofilm formed was determined with image analysis after cells were stained with bisBenzimide H 33258 (Hoechst 33258). The strains were genetically subtyped by repetitive element sequence-based PCR (rep-PCR) with the primer set rep-PRODt and rep-PROG5. Data were analyzed with an analysis of variance and Duncan's multiple range test. Eleven strains produced the same amount of biofilm in both media. Fourteen strains produced more biofilm in TSB than in DTSB. Five strains produced more biofilm in DTSB than in TSB. Serotype 4b strains produced more biofilm in TSB than did serotype 1/2a strains, whereas serotype 1/2a strains produced more biofilm in DTSB than did serotype 4b strains. Growth in DTSB resulted in decreased biofilm accumulation for serotype 4b strains. There was no correlation between genetic subtype and the amount of biofilm accumulation. These results indicate that strains of serotype 1/2a and serotype 4b differ in the regulation of their biofilm phenotype. The poor biofilm accumulation of serotype 4b isolates when grown in DTSB could be a factor in the predominance of serogroup 1/2 strains in food processing plants, where nutrients may be limited.

Real-time monitoring of Escherichia coli O157:H7 adherence to beef carcass surface tissues with a bioluminescent reporter

A method for studying bacteria that are attached to carcass surfaces would eliminate the need for exogenous sampling and would facilitate understanding the interaction of potential human food-borne pathogens with food animal tissue surfaces. We describe such a method in which we used a bioluminescent reporter strain of Escherichia coli O157:H7 that was constructed by transformation with plasmid pCGLS1, an expression vector that contains a complete bacterial luciferase (lux) operon. Beef carcass surface tissues were inoculated with the bioluminescent strain, and adherent bacteria were visualized in real time by using a sensitive photon-counting camera to obtain in situ images. The reporter strain was found to luminesce from the tissue surfaces whether it was inoculated as a suspension in buffer or as a suspension in a bovine fecal slurry. With this method, areas of tissues inoculated with the reporter strain could be studied without obtaining, excising, homogenizing, and culturing multiple samples from the tissue surface. Use of the complete lux operon as the bioluminescent reporter eliminated the need to add exogenous substrate. This allowed detection and quantitation of bacterial inocula and rapid evaluation of adherence of a potential human pathogen to tissue surfaces. Following simple water rinses of inoculated carcass tissues, the attachment duration varied with different carcass surface types. On average, the percent retention of bioluminescent signal from the reporter strain was higher on lean fascia-covered tissue (54%) than on adipose fascia-covered tissue (18%) following water washing of the tissues. Bioluminescence and culture-derived viable bacterial counts were highly correlated (r2 = 0.98). Real-time assessment of microbial attachment to this complex menstruum should facilitate evaluation of carcass decontamination procedures and mechanistic studies of microbial contamination of beef carcass tissues.

Agar underlay method for recovery of sublethally heat-injured bacteria

A method of recovering sublethally heat-injured bacteria was developed. The procedure (termed the agar underlay method) uses a nonselective agar underlaid with a selective medium. In a two-chambered petri dish, the Lutri plate (LP), a nonselective agar is inoculated with a population of sublethally heat-injured bacteria. After a 2-h repair incubation period, selective agar is added to the bottom chamber of the LP and incubated. By diffusing through the nonselective top agar, selective agents from the underlay medium impart selectivity to the system. By the agar underlay method, recovery rates of the heat-injured food-borne pathogens Escherichia coli O157:H7 and Salmonella typhimurium were not different (P > 0. 05) from recovery rates determined with nonselective media. Sublethally heat-injured cells (60 degrees C for 1.5 min in buffer or 80 degrees C for 30 s on meat surfaces) grew and produced a typical colony morphology and color reaction when the agar underlay procedure was used with the appropriate respective selective agars. Unlike agar overlay methods for injury repair, the agar underlay procedure allows the typical selective-medium colony morphology to develop and allows colonies to be more easily picked for further characterization. Higher recovery rates of heat-injured fecal enterococci from bovine fecal samples and total coliforms from animal waste lagoons were obtained by the agar underlay method with selective agars than by direct plating on the respective selective media.

Effect of Bacillus-based direct-fed microbials on Eimeria maxima infection in broiler chickens

The effect of dietary Bacillus-based direct-fed microbials (DFMs; eight single strains designated as Bs2084, LSSAO1, 3AP4, Bs18, 15AP4, 22CP1, Bs27, and Bs278, and one multiple-strain DFM product [AVICORR]) on growth performance, intestinal lesions, and innate and acquired immunities were evaluated in broiler chickens following Eimeria maxima (EM) infection. EM-induced reduction of body weight gain and intestinal lesions were significantly decreased by addition of 15AP4 or Bs27 into broiler diets compared with EM-infected control birds. Serum nitric oxide levels were increased in infected chickens fed with Bs27, but lowered in those given Bs2084, LSSAO1, 3AP4 or 15AP4 compared with the infected controls. Recombinant coccidial antigen (3-1E)-stimulated spleen cell proliferation was increased in chickens given Bs27, 15AP4, LSSAO1, 3AP4, or Bs18, compared with the infected controls. Finally, all experimental diets increased concanavalin A-induced splenocyte mitogenesis in infected broilers compared with the nonsupplemented and infected controls. In summary, dietary Bacillus subtilis-based DFMs reduced the clinical signs of experimental avian coccidiosis and increased various parameters of immunity in broiler chickens in a strain-dependent manner.

Treatments with Nisin and Chelators to Reduce Salmonella and Escherichia coli on Beef †

Salmonella typhimurium ATCC 14028 or Escherichia coli O157:H7 attached to lean beef tissue were treated with citrate, lactate, sodium hexametaphosphate, or EDTA, alone or in combination with nisin in simple buffers, and incubated at 4°C for up to 3 days. Lactate with nisin reduced S. typhimurium attached to beef by 040 log₁₀ CFU/cm², while EDTA and nisin reduced E. coli O157:H7 by 0.42 log₁₀ CFU/cm². Unlike earlier in vitro studies in which treatments with nisin and chelating agents resulted in reductions of > 4 log₁₀ CFU/cm², such reductions were not observed in situ.

Use of a Rapid Microbial ATP Bioluminescence Assay to Detect Contamination on Beef and Pork Carcasses †

A new microbial ATP bioluminescence assay was shown to be an accurate and rapid method to determine the levels of generic bacterial contamination on beef (n = 400 and pork (n = 320) carcasses sampled in commercial processing plants. Based on in vitro fecal dilution studies, the rapid microbial ATP (R-mATP) assay is as accurate as the standard plate count method for estimating bacteria in bovine or porcine fecal samples. The correlations (r) between the R-mATP assay and the standard aerobic plate count for beef and pork carcasses sampled in commercial processing were 0.91 and 0.93, respectively. A segmented-model statistical approach to determine the lower limits of assay sensitivity was developed. By using this model to analyze the in-plant data, the R-mATP test responded in a linear fashion to levels of microbial contamination of > log₁₀ 2.0 aerobic CFU/cm² on beef carcasses and of > log₁₀ 3.2 aerobic CFU/cm² for pork carcasses. The R-mATP assay requires approximately 5 min to complete, including sampling. Given the rapidity and accuracy of the assay, processors interested in monitoring critical control points in the slaughter process could potentially use the R-mATP assay to monitor microbiological prevention and intervention procedures for minimizing carcass contamination.

Isomaltooligosaccharide increases cecal Bifidobacterium population in young broiler chickens

A newly developed compound derived by fermentation, isomaltooligosaccharide (IMO), was hypothesized to enrich cecal bifidobacterial populations and reduce colonization levels of Salmonella in the ceca of broiler chickens. Broiler starter diets were prepared with final IMO concentrations of 1% (wt/wt), 2% (wt/wt), and 4% (wt/wt) and a control diet without IMO supplementation. Chickens were divided into 4 groups and challenged with 10(8) cell of Salmonlella enterica ser. Typhimurium with 200 microg/mL nalidixic acid resistant (S. Typhimurium Nalr) after 7 d of placement. The experiment was done in 3 replications. IMO-supplemented diets resulted in significantly higher cecal bifidobacteria compared with the control diet (P < 0.05). However, there was no significant difference in bifidobacteria counts among the treatment groups. Chickens fed diets with 1% IMO had a significant 2-log reduction in the level of inoculated S. Typhimurium Nalr (P < 0.05) present in, the ceca compared with the control group, but no differences were found between the control group and the groups fed 2 or 4% IMO for S. Typhimurium Nalr. No differences in feed consumption, feed conversion, or feed efficiency compared with the control group were observed; however, the result showed a significant reduction in weight for birds fed 1% IMO diet compared with those fed the control diet.

Reduction of Brochothrix thermosphacta on beef surfaces following immobilization of nisin in calcium alginate gels

Lean and adipose beef carcass tissues inoculated with Brochothrix thermosphacta (BT) (approx. 4.50 log10 cfu cm-2) were left untreated (U) or treated with 100 micrograms ml-1 nisin (N), calcium alginate (A) or 100 micrograms ml-1 nisin immobilized in a calcium alginate gel (AN). Tissue samples were refrigerated after treatments and bacterial populations and nisin activity were determined at 0, 1, 2 and 7 d. U, A and N treatments of lean and adipose tissues did not suppress bacterial growth ( > 6 log10 cfu cm-2 by day 7) while treatments of lean and adipose tissues with AN suppressed bacteria ( > 2.42 log10 cfu cm-2 by day 7). Bacteriocin titres from both tissues were higher in AN vs N samples after the 7 d incubation. This study demonstrates that immobilization of nisin in a gel may be a more effective delivery system of a bacteriocin to the carcass surface than direct application.

Evaluation of six sampling methods for recovery of bacteria from beef carcass surfaces

Six bacterial sampling methods that might be used for rapid sampling of beef carcasses were evaluated in two separate studies. In Study 1, bacterial recovery from uninoculated beef rounds was 2.6, 2.3, 2.1 and 1.3 log10 cfu cm-2, respectively for excision (EX), and swabbing with cheesecloth (CC), sponge (SP) and cotton-tipped wooden swabs (CS). For Study 2, beef tissue was inoculated with bovine faeces at different levels and the mean recovery was 3.7, 3.0, 3.1 and 3.1 log10 cfu cm-2, respectively for EX, and swabbing with SP, griddle screen (GS) and 3M mesh (M). For both studies EX was determined to be the most consistently effective method while the initial study determined swabbing with CS was the least effective of the methods used. In both studies the most abrasive materials approached the effectiveness of EX even at low inoculation levels. As the inoculation levels increased, the additional effect of abrasiveness was lessened. When the carcasses were contaminated with bovine faeces, the bacterial populations that were rapidly recoverable from beef tissue using SP, GS or M were not significantly lower than those recovered using EX. Consequently SP, GS or M are an adequate method of beef carcass sampling for rapid, in-plant process monitoring to detect faecal contamination.

Incorporation of nisin into a meat binding system to inhibit bacteria on beef surfaces

In two separate experiments, the bacteriocin, nisin, was incorporated into a commercially available meat binding system (Fibrimex) and applied to meat surfaces as a way of inhibiting the meat spoilage organism, Brochothrix thermosphacta during extended refrigerated storage. In experiment 1, pre-rigor lean beef carcass tissue (BCT) was inoculated with B. thermosphacta, left untreated (U), treated with 10 micrograms ml-1 nisin (N), Fibrimex (F) or Fibrimex containing 10 micrograms ml-1 nisin (FN), held aerobically at 4 degrees C for up to 7 d, and populations of B. thermosphacta and nisin activity determined. Experiment 2 determined the effects of the same treatments but on post-rigor, frozen and thawed lean BCT that was inoculated, vacuum-packaged, and stored at 4 degrees C for up to 14 d. In both experiments, N- and FN-treated tissues exhibited significantly lower populations of B. thermosphacta compared to U- and F-treated tissues, for the duration of refrigerated storage. Nisin activity was detected up to 7 d in N- and FN-treated samples from experiment 1. However, activity was detected only to days 0 and 2 in FN- and N-treated samples, respectively, from experiment 2. These studies indicate that the addition of a bacteriocin to a meat binding system and application to meat surfaces may be useful in reducing undesirable bacteria in restructured meat products.

Effectiveness of a steam-vacuum sanitizer for reducing Escherichia coli O157:H7 inoculated to beef carcass surface tissue

A steam-vacuum sanitizer reduced aerobic plate counts associated with bovine faecal contamination from 5.5 log10 cfu cm-2 to 3.0 +/- 0.21 log10 cfu cm-2 on beef carcass short plates. The same beef carcass short plates inoculated with 7.6 +/- 0.09 log10 cfu cm-2 Escherichia coli O157:H7 in faeces, yielded an average residual level of E. coli O157:H7 of 2.1 +/- 0.21 log10 cfu cm-2, after steam-vacuum treatments. This study demonstrates the effectiveness of a steam-vacuum sanitizer for removing E. coli O157:H7 from beef carcasses.

Effects of postmortem injection time, injection level, and concentration of calcium chloride on beef quality traits

Two experiments were conducted to determine the optimum protocol for maximizing meat quality with CaCl2 injection. Experiment 1 compared the effects of 30 min or 24 h postmortem injection of 175 mM CaCl2 or water at 10% (wt/wt) to controls on various measures of meat quality. An injection of CaCl2 reduced (P < .05) shear force values in all three beef muscles evaluated (longissimus, semimembranosus, and triceps brachii). Retail lean color was not affected (P > .05) by a CaCl2 injection at 24 h postmortem, but was slightly darker (P < .05) for an injection at 30 min postmortem. Psychrophilic and total aerobic microbial counts were higher (P < .05) in 30-min than in 24-h treatments and were higher (P < .05) in CaCl2- or water-injected semimembranosus muscle than in the control, but the treatment differences were minimal in 24-h injected meat. Experiment 2 compared the effects of 24-h postmortem injection of 200 mM or 250 mM CaCl2 at either 5 or 10% (wt/wt) to controls on meat quality traits. Both 200 and 250 mM CaCl2 reduced (P < .05) shear force values compared with the control. In addition, variation in shear force was decreased (P < .05) with CaCl2 injection. Beef flavor intensity was slightly lower (P < .05) and off-flavor ratings were slightly higher (P < .05) in CaCl2-injected meat, but the small differences were of no practical significance. Retail lean color was not affected (P > .05) by injection of the CaCl2 at 24 h. Injecting 200 mM CaCl2 at 5% (wt/wt) into 24 h postmortem meat can produce consistently tender meat without compromising other palatability or lean quality traits.