Mitigation of avian reproductive tract function by Salmonella enteritidis producing high-molecular-mass lipopolysaccharide

Summary Hens were infected with a wild‐type Salmonella enteritidis and its wzz mutant, which lacked the ability to make high‐molecular‐mass lipopolysaccharide (LPS), in six experiments paired by dosage and route of exposure. Involution of the reproductive tract occurred in 86% of hens that were injected subcutaneously with 108 cfu of the wild‐type strain, but none did so when injected with the wzz mutant. In spite of the lack of a specific effect on the reproductive tract, infection of hens with the mutant produced more contaminated eggs and heterophilic granulomas in developing ova (yolks) than wild type; thus, overall, the mutant appeared to be more virulent except after intravenous injection. The mutant also decreased shell quality more often than wild type, regardless of dosage or route of infection. These results suggest that egg‐contaminating Salmonella enteritidis that produces high‐molecular‐mass LPS mitigates signs of illness in poultry by altering the response of the avian reproductive tract to infection, but without altering the incidence of egg contamination following bacteraemia. Further research is warranted to determine whether analyses of shell quality might aid in identification of flocks at risk of producing contaminated eggs.