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

Abstract

SUMMARYOral administration to newly hatched chickens or to chicks up to 5 days of age with an avirulent, rough, spectinomycin-resistant mutant of Salmonella typhimurium strain F98 inhibited the colonization of a nalidixic acid-resistant mutant of the same strain administered by the same route 1 day later. The second strain passed rapidly through the alimentary tract and persisted in the caeca of only a few chickens. Resistance to colonization did not develop until 24 h after inoculation of the first strain but was still evident if the second strain was inoculated up to 7 days later. Resistance occurred in 5 different breeds of chicken and in chickens reared on 5 different diets. Protection was evident against a very high challenge dose and could be produced by the introduction of small numbers of the first strain. Pre-colonization of chicks with the first strain of F98 reduced faecal excretion of the second strain over many weeks, whether chickens were challenged directly or by contact with other infected chickens. The rough strain F98 produced protection against only a few S. typhimurium strains and not against other serotypes. However, strains of S. infantis and S. heidelberg, chosen because they colonized the chicken alimentary tract better than did F98, produced inhibition of a wider range of serotypes.

Emergence of Salmonella epidemics: The problems related to Salmonella enterica serotyp Enteritidis and multiple antibiotic resistance in other major serotypes

“…It has recently been proposed that the eradication of S. Gallinarum opened an ecological niche, which allowed the introduction of S. Enteritidis into poultry flocks [12]. Because the immunodominant epitope of the lipopolysaccharide of S. Gallinarum and S. Enteritidis is the O9-antigen, mathematical models predict that the coexistence of these two serotypes would prompt competition where the more transmissible bacterium will eliminate the other from the host population [62], either as a result of adaptive immunity, or as a result of microbial competition, which is also partially clonal at the level of the serotype [14]. S. Gallinarum may have generated immunity at the flock level against the O9-serotype, thereby excluding S. Enteritidis from poultry flocks [126].…”

Influence of genes encoding proton-translocating enzymes on suppression of Salmonella typhimurium growth and colonization

“…This phenomenon has been termed "competitive exclusion," and its discovery has led to a search for individual strains of bacteria which can inhibit colonization by pathogens to the same extent as the normal flora. Oral administration of an avirulent Salmonella typhimurium strain to day-old chicks can confer protection against oral infection by a virulent strain (known as colonization inhibition) (8,10). Colonization inhibition is normally genus specific, is not caused by bacteriophage or bacteriocin activity, and is not a consequence of immunity induced by the first strain (8).…”

“…For studying the behavior of the avian strain S. typhimurium F98 (3,4,10) in mixed cultures and in vivo, nalidixic acid-or spectinomycinresistant mutants (30) were used for ease of enumeration. These resistance determinants do not affect growth suppression or colonization inhibition (8,10,11).…”

A colonisation-inhibition culture consisting of Salmonella Enteritidis and Typhimurium ΔhilAssrAfliG strains protects against infection by strains of both serotypes in broilers

“…As the ability of Salmonella strains to colonise represents an important prerequisite for effective colonisation inhibition of wildtype strains, persistence of a CI strain and protection offered by a CI strain are probably related to each other. Furthermore, it has been suggested that a CI strain is more protective against challenge when it is highly colonising [16,25]. It is therefore not improbable that the observed strong protective effect of the Salmonella Typhimurium hilAssrAfliG strain is due to its high colonising capacity.…”