Competitive exclusion of salmonellas from the chick caecum using a defined mixture of bacterial isolates from the caecal microflora of an adult bird

Abstract

SummaryColonization of the caeca of newly hatched chicks by Salmonella typhimurium was prevented by oral administration of a mixture of cultures comprising 48 different bacterial strains originating from an adult bird known to be free from salmonellas. The treatment conferred protection to the same degree as that obtained previously with a suspension of adult caecal contents or an undefined anaerobic culture from the same source and was demonstrated in four separate laboratory trials.Examination of the caecal microflora of chicks one day after being given the protective treatment showed that the presence of high levels of lactobacilli and Bacteroides spp. which are not found usually at two days of age in chicks produced under commercial conditions was indicative of the successful establishment of an adult-type microflora.Although the usual method of administering the protective organisms was to dose the chicks directly into the crop, it was also found possible to incorporate the organisms in the drinking water given to the birds at dilutions up to one in five, the maximum tested.When chicks were given the bacterial mixture via the crop and fed on a diet containing 10 mg kg−1 nitrovin and 100 mg kg−1 monensin, the bacteroides failed to establish in the caeca and the birds were not protected against salmonella colonization. However, when the bacterial cultures were incorporated in the drinking water and the chicks given the same feed, normal protection was obtained; possible reasons for these observations are discussed.

Inhibition of colonization of the chicken caecum withSalmonella typhimuriumby pre-treatment with strains ofEscherichia coli

“…Although, by using the methods we described, we were unable to isolate a strain of Gram-negative facultative anaerobe which was inhibitory for salmonellas when inoculated on its own we found that a mixture of three strains of bacteria, identified as E. coli, produced a profound reduction in the caecal count of S. typhimurium F98, a strain used by ourselves in previous studies (Smith & Tucker, 1975;Smith & Tucker, 1980) and also by other workers (Impey, Mead & George, 1982). Good protection against colonization of the caeca by this strain was also obtained in chickens reared on different diets and in different breeds of chickens, including a commercial broiler breed.…”

“…This absence of complete protection has also been observed using the system involving pre-treatment with faeces or caecal contents obtained from adult chickens Rantala, 1974;Impey, Mead & George, 1982). It was considered that, since strains of E. coli were being used for pre-treatment, interference of the colonization of these organisms by E. coli strains already in the alimentary tract may have occurred leading to poor establishment of the protective strains.…”

“…One of the ways in which this problem can be overcome is to administer a mixture of pure cultures of micro-organisms obtained from the same source. Barnes, Impey & Cooper (1980) and Impey, Mead & George (1982) were able to induce protection against salmonella infection in young chicks using a pool of cultures of both obligate and facultative anaerobes obtained from chickens. Although these workers have found that simultaneous administration of a relatively large number of bacterial strains was necessary to produce protection, others have found that individual strains were effective.…”

Poultry-borne salmonellosis in Scotland

“…The ideals behind the two Orders are sound, but they require to be more strictly enforced. In addition the development of techniques for competitive exclusion in young birds (Impey, Mead & George, 1982) could be more actively pursued under commercial conditions. This measure may reduce the degree of salmonella carriage in broiler flocks at the time of slaughter.…”

Further studies on the inhibition of colonization of the chicken alimentary tract withSalmonella typhimuriumby pre–colonization with an avirulent mutant

“…Very soon after treatment with such material the chicks acquire the same degree of resistance to colonization by salmonella shown by the adult bird (for review see Mead and Impey [8]). To avoid the possibility of inadvertent introduction of avian pathogens with such material, mixtures of pure cultures of the appropriate microorganisms can be used [9].…”