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Title: Spread of a marker Salmonella in the presence of background Salmonella as detected from broiler litter

item Buhr, Richard - Jeff
item Richardson, Larry
item Cox Jr, Nelson

Submitted to: Poultry Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/22/2007
Publication Date: 7/8/2007
Citation: Buhr, R.J., Richardson, L.J., Cox Jr, N.A., Fairchild, B.D. 2007. Spread of a marker Salmonella in the presence of background Salmonella as detected from broiler litter. Poultry Science 86:(Supp. 1)333, P.227.

Interpretive Summary:

Technical Abstract: In small scale poultry Salmonella colonization research, experiments are typically conducted using multiple adjacent floor pens within a single room or building. The spread of Salmonella among the pens and the presence of preexisting Salmonella may complicate the experimental design and influence the outcome of the experiments. The impact of preexisting Salmonella in day old chicks on the colonization ability of subsequent marker Salmonella strains is not known as both may compete for the same intestinal niches. Chick-box pads were sampled to detect the presence of background Salmonella at placement and the flock was determined to be positive (serogroup C3). Day old chicks were placed 40/pen into 6 adjacent pens. In the two end pens (pens 1 and 6, the challenge pens) one chick was orally inoculated with 0.1 mL of a 10X3 cfu/mL suspension of a naladixic acid resistant Salmonella cocktail (s. heidelberg, s. montevideo, and s. typhimurium). The challenged seeder chicks were removed at 2 wk. At 1 through 7 wk, the pens were sampled using both conventional drag swabs (CDS) and intermittently stepped on drag swabs (ISODS), two of each per wk. From the swabs the marker Salmonella were isolated using enrichment and when the presence of the marker was negative, then standard laboratory procedures were utilized for recovery of background Salmonella. At 1 and 2 wk both the challenge and adjacent pens were positive for the marker Salmonella from all drag swab samples (16/16). At 2 wk the middle pens were still negative for the marker strain and 1 positive sample for the background Salmonella was detected with an ISODS. At 3 wk the number of Salmonella-positive samples peaked and extended into the middle pens with 4/4 ISODS and 2/4 CDS positive samples (overall 22/24). Then at 4 and 5 wk, the number of marker Salmonella-positive samples gradually decreased, mainly from the middle pens from 17/24 to 16/24 total samples positive. The marker Salmonella continued to decline at 6 and 7 wk from 12/24 and 3/24. Overall, ISODS samples had significantly more positive samples (57/84) than CDS (45/84) and all but 10/84 positive samples coming from the challenged or adjacent pens. By challenging only one chick per pen, the marker Salmonella spread easily from the challenged to adjacent pens and into the center pens. The Salmonella prevalence in the litter was the highest at 3 wk and then decreased by 7 wk. At 6 wk the ceca from broilers in the two challenge pens was determined to be 23% positive (8/35) and significantly less than the 92% positive litter (11/12) samples. The presence of a background Salmonella at placement does not appear to inhibit colonization by the marker Salmonella or the spread into adjacent pens. However, at 6 wk Salmonella recovery from litter had progressively declined from the challenge pens (7/8), to the adjacent pens (4/8), to the middle pens (1/8).