Antimicrobial interventions implemented in slaughter establishments for the
reduction of enteric pathogens on beef carcasses must be validated to demonstrate
efficacy under commercial operation conditions. Validation studies can be conducted
using surrogates which are nonpathogenic organisms that respond to a particular
treatment in a manner equivalent to a target pathogen. The purpose of this study was to
identify surrogates for enteric pathogens to validate antimicrobial interventions on beef
carcasses. The growth, attachment, resistance properties as well as the response to
interventions on beef carcasses of nonpathogenic fluorescent protein-marked E. coli
strains were evaluated and compared to E. coli O157:H7 and Salmonella strains.
Growth curves were performed in tryptic soy broth at 37°C and it was
demonstrated that in general, growth parameters were not different among surrogates
and target pathogens. Thermal resistance was compared in phosphate buffered saline
(PBS) at 55, 60 and 65°C; D-values of surrogates were not different or were higher than those of target pathogens. The acid resistance of surrogates was not different to that of E.
coli O157:H7 in PBS acidified with lactic acid at pH 2.5, 3.0 and 3.5. Some Salmonella
serotypes were found to be less acid resistant than the surrogates. Survival of surrogates
after storage at low temperatures (4°C and -18°C) was not different or was longer than
survival of E. coli O157:H7 and Salmonella. Additionally, the cell surface
hydrophobicity and attachment to beef carcasses surfaces was not different among
surrogates and pathogens. Antimicrobial interventions were applied on carcass surfaces
under laboratory controlled conditions. After application of hot water washes, D-values
were not different among surrogates and pathogens, while no differences were observed
in log reductions (CFU/cm2) among surrogates and pathogens when 2% L-lactic acid
sprays at 25 and 55°C were applied, regardless of the temperature and volume of the
acid solution. The response of surrogates to water washes and lactic acid sprays on beef
carcasses was also evaluated in commercial slaughter facilities. Reductions of surrogates
were not different to those of aerobic plate count, coliforms and E. coli. However, the
surrogates showed less variation and provided more consistent results than traditional
indicators.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2513 |
| Date | 15 May 2009 |
| Creators | Cabrera-Diaz, Elisa |
| Contributors | Acuff, Gary R. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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