Inoculation Route and Serotype Alter Salmonella Recovery in the Broiler's Digestive Tract

Salmonella enterica serotypes Enteritidis (SE) and Heidelberg (SH) are consistently linked to poultry-related foodborne outbreaks and can be isolated from broiler parts in processing facilities. In order to control this pathogen's establishment in the broiler, entryways at the farm that lead to colonization must be considered. The objective of these trials was to determine if the inoculation route of either SE or SH altered its recovery in a market-age broiler's digestive tract if chicks were dosed on day of hatch. Chicks were given a 104 colony-forming units inoculation of SE or SH on day 0 via one of five inoculation routes (oral, intratracheal, subcutaneous, ocular, or cloacal) and then placed in pens (60-100 chicks/treatment). Broilers were reared for 32-36 days, then euthanatized, and samples of trachea, crop, liver and spleen (pooled), cecum, and a cloacal swab were collected. Samples were enriched and then analyzed on yes/no criteria based on Salmonella growth. Data were analyzed in JMP Pro 14.1 using the GLM procedure with the Student t-test to separate serotype means and a Tukey honestly significant difference test to separate inoculation means (P ≤ 0.05). All samples collected and all inoculation routes resulted in recovery of either serotype. The intratracheal inoculation, mimicking inhaled fomites, resulted in significantly higher recovery of Salmonella serotypes than did the other inoculation routes (P < 0.0001), indicating the importance of controlling respiratory contamination. When comparing serotypes, there was a significantly greater recovery of SH compared to SE based on samples collected (P = 0.001). SH also had significantly greater recovery from the cecum (P < 0.001) and the cloacal swab (P = 0.02). These trials indicate the need for further investigation of the intratracheal route, as well as reinforcing that the potential of systemic infection through grow out with either serotype is highly probable preharvest.