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<OL> <LI> Determine the prevalence and genotypic and phenotypic characteristics of L.
monocytogenes strains present in Pacific Northwest dairy farms. <LI>Use microarray
technology to rapidly and accurately subtype L. monocytogenes isolates for use in
both epidemiological studies and gene discovery.<LI> Use microarray and PFGE subtyping
to examine on-farm ecology of L. monocytogenes and to compare on-farm subtypes to
those obtained from human listeriosis cases.
Preliminary microarray subtyping data indicate that a relatively simple mixed genome
DNA microarray is capable of reconstructing previously described phylogenetic
relationships between major serogroups and PFGE classifications.
<p>
Importantly, probes unique to each microarray and serotypic cluster were also
identified. An expanded microarray has been used to increase subtyping resolution and
identify a greater number of informative probes. A condensed micorarray consisting
entirely of unique, informative probes will be constructed and used to study on-farm
ecology and epidemiology of L. monocytogenes. The phenotypic importance of
potentially virulence-associated probes will be accessed via gene knock out and
infection of an in vitro or in vivo model. Formerly 5348-32000-017-00D (12/02). BSL-
1; 9/4/01.