Potential egg contamination by Salmonella enterica serovar Typhimurium definitive type 104 following experimental infection of pullets at the onset of lay

The present study investigated the potential of Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) definitive type 104 (DT104) to contaminate eggs in vivo. Of 10 strains of Salmonella Typhimurium DT104, none caused egg contamination when hens were inoculated orally. Three passages of the strains through recovery from the reproductive organs of intravenously infected laying hens resulted in no egg contamination after oral infection of the hens. Feed and water withdrawal for 24 h at 5 and 10 d after oral infection with Salmonella Typhimurium DT104 slightly decreased egg production but did not lead to egg contamination. Finally, oral infection of pullets at the onset of lay (approximately 50% of egg production) resulted in egg contamination (1.7%) in 2 wk. In conclusion, the Salmonella Typhimurium DT104 strains used in the present study have a low possibility of causing egg contamination; however, because infection at the onset of lay can cause egg contamination, the introduction of Salmonella Typhimurium DT104 into the layer houses should be prevented, especially when hens start laying eggs.