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Bacteriophage Involvement in the Dissemination of Multi-Drug Resistance by Salmonella


The stated objectives for this work were:
<ol><li>We will collect 120 fecal samples from each of the above locations (480 total samples). Each sample will be assayed for populations of Salmonella spp., multi drug-resistant (MDR) Salmonella, phage, and phage active against Salmonella spp.</li>
<li>Feces will be stressed with UV light to cause excision of lysogenic phage present in the population</li>
<li>Salmonella isolates will be separately stressed through application of UV light to determine how many of these isolates contain latent phages capable of excising and carrying genes to new hosts.</li>
<li>We will combine phage-susceptible Salmonella strains with MDR Salmonella from our cattle samples (that represent different sero-groups) in continuous flow culture (to simulate the intestinal tract). Phages active against both the MDR strain and the susceptible strain will be added to the mixed culture. We will collect samples from the
continuous flow culture over a period of 7 d and plate a 10-fold dilution series on 3 types of BGA plates each supplemented with an antibiotic that the MDR Salmonella is resistant to, but not the susceptible Salmonella. Isolates from each dilution will be identified by sero-group to determine if the susceptible Salmonella strains acquired resistance from the MDR Salmonella.</li></ol>

Callaway, Todd
USDA - Agricultural Research Service
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