Incidence and degree of Salmonella Heidelberg colonization of day old broiler chicks using several methods of inoculation

Authors: OLADEINDE, ADELUMOLA - Orise Fellow; Cook, Kimberly - Kim; Cox Jr, Nelson; RITZ, CASEY - University Of Georgia; Cosby, Douglas; Plumblee Lawrence, Jodie; House, Sandra; Zock, Gregory; JACKSON, JEREMY - University Of Georgia

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2018
Publication Date: 2/1/2018
Citation: Oladeinde, A., Cook, K.L., Cox Jr, N.A., Ritz, C., Cosby, D.E., Plumblee Lawrence, J.R., House, S.L., Zock, G.S., Jackson, J. 2018. Incidence and degree of Salmonella Heidelberg colonization of day old broiler chicks using several methods of inoculation . Meeting Abstract. 97(E-Suppl 1):65.

Interpretive Summary: Before beginning a study that involves a large number of birds, it may be helpful to know what method of inoculation would be best for the experiment in question. The objective of this study was to compare several methods of Salmonella challenge (oral gavage, intracloacal inoculation and the seeder bird approach). Day-old broiler chicks (n=100) were obtained from a commercial hatchery and inoculated either orally, intracloacally or using seeder birds with 106 cells of a nalidixic acid resistant strain of Salmonella Heidelberg (SH). Chicks (n=25) inoculated by each route were placed in floor pens at a stocking density of 650.3 cm2/chick on fresh pine shavings litter. For the seeder batch, 5 colonized chicks were placed with 20 pen mates. All birds were given water and feed ad libitum. Two weeks after inoculation, 10 birds from each pen were euthanized, the abdominal cavity was sprayed with 70% alcohol and the ceca were aseptically removed, placed in a stomacher bag, put on ice and brought to the laboratory for analysis. Next the ceca were weighed and buffered peptone water was added 3X volume to weight and mashed with a rubber mallet. Serial dilutions were made and plated onto BG Sulfa plates containing 200 ppm nalidixic acid. The plates were incubated along with the smashed ceca and broth for 24 h at 37 ° C. If no colonies appeared on the plates then an additional plate was streaked from the enriched broth bag and it was incubated for an additional 24 h at 37 ° C. Number of SH positive birds out of 10 sampled in each group was 5, 8, 5 for oral gavage, intracloacal and seeder, respectively. Following 24 h enrichment it was 8, 10, 7. The level of SH per gram of ceca was log (standard error) 2.45 (0.42), 1.66 (0.22), 2.87 (0.28) for oral, intracloacal and seeder, respectively. Also, the level of the SH per gram of litter for the different groups was log 6 for oral and intracloacal and log 4.6 for the seeder bird group. In conclusion, this study suggests that intracloacal is the method to use if you want to make sure all of the challenged birds are colonized. However, if you prefer to have a smaller percentage of the birds colonized with higher levels, then oral or seeder bird challenge may be better.

Technical Abstract: Before beginning a study that involves a large number of birds, it may be helpful to know what method of inoculation would be best for the experiment in question. The objective of this study was to compare several methods of Salmonella challenge (oral gavage, intracloacal inoculation and the seeder bird approach). Day-old broiler chicks (n=100) were obtained from a commercial hatchery and inoculated either orally, intracloacally or using seeder birds with 106 cells of a nalidixic acid resistant strain of Salmonella Heidelberg (SH). Chicks (n=25) inoculated by each route were placed in floor pens at a stocking density of 650.3 cm2/chick on fresh pine shavings litter. For the seeder batch, 5 colonized chicks were placed with 20 pen mates. All birds were given water and feed ad libitum. Two weeks after inoculation, 10 birds from each pen were euthanized, the abdominal cavity was sprayed with 70% alcohol and the ceca were aseptically removed, placed in a stomacher bag, put on ice and brought to the laboratory for analysis. Next the ceca were weighed and buffered peptone water was added 3X volume to weight and mashed with a rubber mallet. Serial dilutions were made and plated onto BG Sulfa plates containing 200 ppm nalidixic acid. The plates were incubated along with the smashed ceca and broth for 24 h at 37 ° C. If no colonies appeared on the plates then an additional plate was streaked from the enriched broth bag and it was incubated for an additional 24 h at 37 ° C. Number of SH positive birds out of 10 sampled in each group was 5, 8, 5 for oral gavage, intracloacal and seeder, respectively. Following 24 h enrichment it was 8, 10, 7. The level of SH per gram of ceca was log (standard error) 2.45 (0.42), 1.66 (0.22), 2.87 (0.28) for oral, intracloacal and seeder, respectively. Also, the level of the SH per gram of litter for the different groups was log 6 for oral and intracloacal and log 4.6 for the seeder bird group. In conclusion, this study suggests that intracloacal is the method to use if you want to make sure all of the challenged birds are colonized. However, if you prefer to have a smaller percentage of the birds colonized with higher levels, then oral or seeder bird challenge may be better.