Enteric viruses are responsible for a significant amount of foodborne disease in
the United States. Foodborne disease associated with enteric viruses has been
increasing within the last few years due to technological advances and raised
awareness. Salads and salad crops are the principal vector for transmission of
enteric viruses. The objective of this study was to determine if viruses are able to
attach non-specifically to the surface of lettuce and to determine the forces
responsible for non-specific viral adsorption to lettuce. Additionally, the impact
of the microbial flora on viral persistence was studied to determine the effect on
viruses. The four viruses studied were echovirus 11, feline calicivirus, MS2 and
ÃÂX174. The viruses were chosen based on their varying isoelectric points and
similar physicochemical attributes. The isoelectric point was not the main factor
determining virus attachment to lettuce. Viruses had varying attachment
efficiencies, with echovirus 11 having the highest affinity to lettuce and ÃÂX174 the
least. Viral adsorption to lettuce was mediated by electrostatic forces due to the
removal of virus adsorption at pH 7 and 8 with the addition of 1 M NaCl to the
buffer solutions. Microcosm studies indicated that the microbial flora did not have a negative impact on virus survival. The bacteriophages had the highest
survival rate. Virus survival in the microcosm studies was not indicative of virus
survival on the surface of the lettuce. The animal viruses exhibited survival rates
greater than or equal to the survival of bacteriophages at 4ð C, but at room
temperature viable animal viruses rapidly declined compared to the
bacteriophages. Additional studies also indicated that the microbial flora was
not able to degrade the viruses for aerobic microbial growth. Overall, these
results indicate that viruses are able to attach to the surface of lettuce, providing
a possible explanation for the high incidence of virus associated disease
involving salads and fresh produce. More importantly the use of surrogates for
virus studies involving fresh produce must be re-evaluated, because of the lack of
correlation between animal viruses and bacteriophages. Appropriate viral
surrogates, if used, have to be carefully chosen based on viral physicochemical
properties as well as the infectious route of the virus.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4158 |
| Date | 30 October 2006 |
| Creators | Vega, Everardo |
| Contributors | Pillai, Suresh D. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 3959840 bytes, electronic, application/pdf, born digital |
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