Studies on the ex vivo survival of Lawsonia intracellularis

Methods: Two co-cultured strains of L. intracellularis were suspended in vitro for 30 minutes at 20°C in various disinfectants according to label recommendations for usage, then washed in saline. Disinfectanttreated and Control bacteria were then added to fresh cells for co-culture for a standard 5-day incubation. Further cell-free suspensions were exposed to air at 5°C, 20°C, or 37°C for up to 8 days, then added to fresh cells for co-culture for a standard 5-day incubation. Lawsonia intracellularis within co-cultures were determined to be viable by visualization after indirect immunoperoxidase staining that incorporated specific monoclonal antibody. Groups of weaned pigs were inoculated orally with L. intracellularis-infected feces, either on the day the feces were collected, or after storage for 1, 2, or 5 weeks at temperatures between 5°C and 15°C.