An official website of the United States government.

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Microbiology and Control of Pathogen Contamination on Fresh-Cut Produce


<OL> <LI> Determine how pathogens are introduced into the environment where fresh and fresh-cut
lettuce is grown, harvested, and undergoes postharvest handling. Determine the
persistence and survival of pathogens in the environment during growing, harvesting,
postharvest handling, and/or processing of fresh and fresh-cut lettuce. <LI>Determine the
mechanism(s) of transference of pathogens to fresh and fresh-cut lettuce edible plant
surfaces during growing, harvest, postharvest handling and processing operations.
<LI>Determine the persistence and survival of pathogens in lettuce during growing,
harvest, postharvest handling and/or processing.

More information

Extrinsic factors will be evaluated to determine their effect on survival of EHEC
foodborne pathogens. Conditions will be designed so that they resemble actual pre-
harvest, farming, and post-harvest practices. Various feces types (poultry, cattle,
swine) will be inoculated with either low or high levels of pathogens and then used
in manure to be applied to crops or plants. Soil can then be tested for populations
of various pathogens. Various portions of crops (leaves, stems, edible portions) can
be analyzed for the presence of pathogens to determine if foodborne pathogens can act
as either endophytes or epiphytic organisms or be taken up systematically through
plants. <p>This may help determine the behavior of pathogens in organic farming
environments through a harvesting season. Both organic (manure that comes from
animals not receiving antibiotic and growth hormone treatments) and non-organic
animals (manure from conventionally raised animals) will be evaluated. Microbial
communities in soil will be profiled to determine if a "bloom" effect takes place
after the application of either a) chemical fertilizers containing nitrogen,
phosphorus and potassium or b) organic compost. Molecular techniques (16S rRNA) will
be employed to identify strains, and the populations of EHEC pathogens within those
communities. These efforts would help determine if crops raised organically have
different microbial communities than conventionally raised crops. Biofilms of single
and multi-species will be established on food contact surfaces to determine if
pathogens can be transferred from produce or fresh-cut produce from these surfaces.
<p>Differences in transferred populations from inoculated non-contact surfaces to fresh
or fresh-cut surfaces will be examined. Commonly employed microbial interventions
and/or sanitation measures in addition to novel interventions will then be used to
determine if biofilms from food contact surfaces and those cells transferred to
produce can be killed. Real time PCR assays will be developed for the detection of
bacterial pathogens on produce and on food contact surfaces. The assays will be
optimized to increase the sensitivity and the specificity of PCR reactions. This will
determine if there are inhibitors to PCR reactions (low pH, excess metal ion
concentration, and degrading enzymes) that could interfere with detection in produce
samples. PCR assays may provide more sensitive detection of specific pathogens in a
multi-species biofilm where the use of traditional culture methods may not be
suitable for detection.

Lindsay, James
USDA - Agricultural Research Service
Start date
End date