Submitted to: World Congress on Anaerobic Bacteria and Infections
Publication Type: Abstract Only
Publication Acceptance Date: 8/4/1998
Publication Date: N/A
Technical Abstract: Competitive exclusion (CE) is an attractive strategy to enhance colonization resistance of animals to infections by enteric pathogens. Recent approval of the avian CE culture PREEMPT**TM as a drug by the US FDA attests to the efficacy of this strategy and we are now developing similar technology for other species of food producing animals. Pigs treated at birth with a CE culture also show enhanced colonization resistance to Salmonella typhimurium and S. choleraesuis (SC), but such treatment is less effective against the invasiveness of these pathogens. Since horizontal transmission plays a vital role in the spread of disease, it is reasonable to propose that reduced shedding should reduce the spread of infections. To test this hypothesis, we challenged pigs at 15 days of age (one day post weaning) with approximately 10**7 colony forming units of SC and then commingled these (seeders) 1 to 2 days later with an equal number of pigs having no known exposure to the pathogen (contacts). Some of the seeders and contacts were treated at birth with a porcine derived CE culture. In this study, all seeder pigs (whether CE treated or not) were found to be infected by SC at 23 to 26 days of age, as determined by culture of ileocolic lymph nodes and cecal contents collected by necropsy. Shedding of the SC, however, as determined by daily culture of rectal swabs, was less for the CE treated seeder groups (30%) compared to that by the untreated seeder groups (47%). Horizontal transmission occurred readily between untreated seeders commingled with untreated contacts, with 3 of the 4 contacts becoming infected. In contrast, only 1 of 5 CE treated contacts became infected when commingled with CE treated seeders thus demonstrating a benefit of CE treatment in stemming the spread of SC.