Further Studies in Competitive Exclusion and Salmonella in Chickens

Abstract

This study was an attempt to isolate and test individual bacteria from adult chicken caecal material for use in the control of salmonella in chickens. The initial experiments confirmed the theory of competitive exclusion of salmonella i.e. that the treatment of day-old chickens with intestinal or caecal contents from a healthy adult bird, or cultures from these makes them far more resistant to a subsequent challenge with salmonella. Succeeding experiments were predominantly involved with problem solving. These problems were (in order of appearance): 1. contamination of experimental chicks with 'Citrobacter freundii', another member of the family 'Enterobacteriacea' 2. lack of consistency in infection level of control chicks in different isolation pens 3. breakdown in the resistance to nalidixic acid of a nalidixic acid resistant strain of 'S. typhimurium' 4. sensitivity of the 'S. typhimurium' challenge strain used to the addition of sulphapyridine in the isolation media 5. lack of infection caused by keeping the control birds in close proximity to treated birds 6. overall lack of consistency in results between and within experiments.