Quantitative studies of the distribution pattern for Salmonella Enteritidis in the internal organs of chicken after oral challenge by a real-time PCR

Abstract

This research was undertaken to identify and understand the regular distribution pattern for Salmonella Enteritidis (S. enteritidis) in the internal organs of chicken after oral challenge over a 3wk period. We used a real-time, fluorescence-based quantitative polymerase chain reaction (FQ-PCR) to detect genomic DNA of S. enteritidis in the blood and the internal organs, including heart, liver, spleen, kidney, pancreas, and gallbladder, from chicken after oral challenge at different time points. The results showed that the spleen was positive at 12h post inoculation (PI), and the blood was at 14h PI. The organism was detected in the liver and heart at 16h PI, pancrea was positive at 20h PI, and the final organ to show a positive results were the kidney and gallbladder at 22h PI. The copy number of S. enteritidis DNA in each tissue reached a peak at 24h-36h PI, with the liver and spleen containing high concentrations of S. enteritidis, whereas the blood, heart, kidney, pancreas, and gallbladder had low concentrations. S. enteritidis populations began to decrease and were not detectable at 3d PI, but were still present up to 12d PI in the gallbladder, 2wk for the liver, and 3wk for the spleen without causing apparent symptoms. The results showed that the liver and spleen may be the primary sites for S. enteritidis setting itself up as a commensa over a long time after oral challenge. Interestingly, it may be the first time reported that the gallbladder is a site of carriage for S. enteritidis over a 12d period. This study will help to understand the mechanisms of action of S. enteritidis infection in vivo.