During the harvesting process, meat products can become contaminated with
enteric pathogens, such as Escherichia coli O157:H7 and Salmonella Typhimurium.
Surrogates for these pathogens would be beneficial for validating carcass
decontamination treatments. Surrogate organisms are organisms that behave similarly to
specific pathogens but are non-pathogenic and can be used to determine efficacy of
decontamination regimes for pathogens. The surrogates proposed are non-pathogenic,
ampicillin-resistant E. coli biotype I strains that were previously isolated from beef cattle
hides. Each E. coli strain was transformed to express a fluorescent protein (red: EcRFP;
green: EcGFP; yellow: EcYFP) that is detectable under an ultraviolet light source.
Surface areas on hot boned beef carcasses (clod, brisket, outside round) were inoculated
with a fecal slurry containing EcRFP, EcGFP, EcYFP and rifampicin-resistant E. coli
O157:H7 and S. Typhimurium. Surface regions were then treated in a model spray
cabinet using an initial water wash (28ºC) followed by treatments using 2% L-lactic acid
(55ºC), hot water (95ºC at source) or a combination of the two. Treatments were
compared for their effectiveness at reducing populations of inoculated (4.7 to 6.7 log CFU/cm2) E. coli, S. Typhimurium, EcRFP, EcGFP and EcYFP. Log reductions for
inoculated organisms were calculated individually and then total and average surrogate
cocktail values were calculated.
All decontamination treatments reduced the inoculated numbers of pathogens and
surrogates to near or below the detection limit of 0.5 log CFU/cm2. The combined
treatment resulted in the greatest log reductions. The three individual surrogate
organisms varied in log reductions according to the different decontamination treatments
applied; however, log reductions for the total surrogate cocktail did not differ
significantly from that of E. coli O157:H7. With the exception of EcYFP, the individual
surrogates and average surrogate cocktail were significantly more resistant to microbial
interventions including lactic acid than S. Typhimurium. Because abattoirs utilize
different carcass decontamination treatments, it is difficult for one single fluorescent
protein-producing isolate to accurately represent the behavior of E. coli O157:H7 or S.
Typhimurium. Instead, surrogates should be used as a total cocktail to accurately
represent the effectiveness of different treatments for reduction of enteric pathogens.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1311 |
| Date | 15 May 2009 |
| Creators | Moseley, Tiffany Marie |
| Contributors | Acuff, Gary R. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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