Distribution of Salmonella Enteritidis in internal organs and variation of cecum microbiota in chicken after oral challenge.

The aim study was to explore the distribution of Salmonella Enteritidis (S. enteritidis) in internal organs and variation of cecum microbiota in newly hatched chicken after oral challenge during a 21-day period. The quantities of S. enteritidis DNA in different internal organs (heart, liver, spleen, stomach, pancreas, small intestine, blood and cecum contents) were determined by real-time fluorescent quantitative polymerase chain reaction (FQ-PCR). The result showed that all of the above-mentioned samples were positive at 12 h post inoculation (PI) after oral challenge. The highest copy numbers of S. enteritidis in all tissue were heart and liver, with about 2 × 102 to 6 × 106 copies of DNA target sequences/0.5 g. The copy number of S. enteritidis in the stomach was only lower than the heart and liver. The blood at 8 d PI, the pancreas at 10 d PI, the heart at 14 d PI and the stomach at 17 d PI didn't have a positive result. However, the liver, spleen, cecum contents and small intestine were all positive during the 21-day period. The cecum contents at 0 d PI, 4 d PI and 10 d PI from the control group and experiment group were collected for bacterial 16 S rRNA sequencing targeting the V3-V4 hypervariable region. The result showed that at the 0 d PI, the main cecum microbiota ingredient of the two-day old chicken was Enterobacteriaceae (Proteobacteria) and the other microbiology species were fewer. At the 10 d PI, the microbiota ingredient of cecum became abundant and stable mainly including the families Ruminococcaceae (Firmicutes), Enterobacteriaceae (Proteobacteria), Lachnospiraceae (Firmicutes) and clostridiacaea (Firmicutes) both of the two group, suggesting Salmonella infection with 2-day old chicken might not significantly change cecum microbiota community. The study indicated the major organs, which carried numerous S. enteritidis, providing a significantly guideline for salmonella detection in poultry and revealed the main microbiota ingredient of chicken cecum.