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Department of Animal Sciences

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https://hdl.handle.net/10217/100318

These digital collections include faculty publications and theses and dissertations from the Department of Animal Sciences, and proceedings of the "Beef Cow Efficiency Forum" (1984). Due to departmental name changes, materials from the following historical departments are also included here: Animal Husbandry; Animal Nutrition.

See also the archival collection of Dr. Temple Grandin, a Colorado State University professor of animal sciences and world-renowned autism spokesperson.

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Browsing Department of Animal Sciences by Subject "aerobic mesophilic flora"

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    Evaluation of GENE-UP and TEMPO AC for determination of Shiga-Toxin producing Escherichia coli and total aerobic microbial populations from MicroTally sheets used to sample beef carcasses and hides
    (Colorado State University. Libraries, 2020) Liu, Tianqing, author; Belk, Keith E., advisor; Yang, Hua, advisor; Weir, Tiffany L., committee member; Zagmutt, Francisco J., committee member
    Two studies were conducted to evaluate GENE-UP and TEMPO AC (bioMerieux, Marcy-l'Étoile, France) for determination of Shiga-Toxin producing Escherichia coli and total aerobic microbial populations from MicroTally Sheets (Fremonta Corporation, Fremont, CA) used to sample beef carcasses and hides. The first study was conducted to evaluate the automated TEMPO® AC Test in comparison with traditional direct agar plating method for enumeration of aerobic mesophilic flora in MicroTally sheets used to sample beef carcasses and hides. A total of 160 MicroTally (MT) sheet samples were collected from commercial beef processing plants by swab-sampling on the surface of naturally contaminated pre-evisceration carcasses, hides and post-chill final carcasses, and analyzed within 24 h after sample collection. Of these, all 160 samples were within detection limit and analyzed by both automated TEMPO AC test and a traditional direct agar plating method. For these results, the aerobic count correlation coefficient was high (0.93) for pre-evisceration carcasses, which had mean (± standard deviation) counts of 3.3 ± 0.9 and 3.1 ± 0.8 log CFU/mL for those two methods, respectively. The aerobic count correlation coefficients were higher (0.95 and 0.96) for MT samples from hides and post-chill final carcasses, which had mean (± standard deviation) counts of 5.3 ± 1.2 and 5.0 ± 1.2, 3.0 ± 1.4 and 3.0 ± 1.3 log CFU/mL for those two methods, respectively. Overall, 98.8% of aerobic count results were within 1.0-log difference between the two enumeration methods. The correlation coefficient (r = 0.97) and linearity regression (log TEMPO MPN/mL = 1.06 x log PCA-CFU/mL +0.03) between the two methods was calculated for our whole sample set (n = 160). Our results demonstrated that the automated MPN method-TEMPO AC Test generated total aerobic mesophilic microflora counts that were highly correlated and consistent with the counts obtained by traditional plating methods on enumerating total aerobic mesophilic microbial populations recovered from MicroTally sheets. Use of TEMPO AC test for MicroTally sheet analysis could save time and labor for the meat industry as it conducts microbial analyses. The second study was conducted to determine the specificity of bioMérieux's GENE-UP, a PCR-based molecular diagnostic system, to detect Shiga Toxin-producing Escherichia coli (STEC) from samples collected from beef processing plants using MicroTally sheets with the manual sampling device method. A total of 194 MicroTally (MT) samples were collected from beef processing plants and analyzed for determination of the top 6 STEC and E. coli O157: H7 (top 7 STEC) using the GENE-UP system, BioRad commercial kits and BioControl GDS kits. Fifty MT samples were collected from swabbing pre-evisceration carcasses and inoculated with hide-derived inocula, while the remaining 144 MT samples were obtained from post-chill final carcasses in sales coolers and inoculated with E. coli strains. All inoculated MT samples were enriched for 8-hour and 10-hour at 42ᵒC in buffered peptone water (BPW) and re-collected after incubation. Eight-hour and 10-hour enrichment samples were analyzed using the GENE-UP system at Colorado State University and sent to U.S Meat Animal Research Center (USMARC, Clay Center, NE) for detection of top 6 STEC and E. coli O157: H7. The GENE-UP system uses EH1 assay to detect stx and eae genes, ECO assay to detect genes specific to O157:H7 serogroup, and EH2 assay to differentiate top 6 serogroups. These virulence genes including Shiga-toxin gene (stx), intimin-encoding eae gene and genes specific to top 7 serogroups are highly related to pathogenic STEC. The NM-EHEC assay targeting virulence genes espK, espV and CRISPR_O26E does not directly differentiate the top 7 STEC, but serves as additional screening test to help identify presence of any of the top 7 STEC. All potential positive samples determined by PCR screening were plated onto selective agar for culture confirmation. After the immunoconcentration step, isolates picked from selective agar were subjected to additional PCR screening. BioRad and BioControl GDS PCR screening methods were used following their standard protocols for determination of top 7 STEC at USMARC. Presumptive positive samples confirmed by the additional PCR test were designated as "true positives." Presumptive positive samples that were not confirmed by the additional PCR test were designated as "regulatory false positives." Overall, our results indicated that the GENE-UP system worked well in the detection of the top 7 STEC recovered from the MicroTally sheets. In order to reduce or eliminate false negative results, a 10-h enrichment time in BPW was required for detection of both the top 6 STEC and E. coli O157:H7. Compared to GENE-UP and GDS, BioRad generated a much higher number of potential positives that required cultural confirmation. Moreover, use of the NM-EHEC kit targeting virulence genes (espK, espV and CRISPR_O26E), as an additional PCR screening after EH1 PCR (stx and eae), has potential to reduce the number of samples that require further O-type determination. However, the GENE-UP E. coli O157:H7 detection system needs to reduce rates of false negative results caused by the shift of Tm when E. coli O157:H7 and O157: non-H7 co-exist in a sample.