Lactobacilli are autochthonous residents in the chicken gastrointestinal tract, where they may potentially be used as probiotics, competitive exclusion agents, or delivery vehicles. The aim of this study was to use an in vivo model to investigate the effect of diet and competing lactic acid bacteria on the colonization of inoculated Lactobacillus strains, with the goal of identifying strains which can consistently colonize or persist for an extended period of several weeks. Chicken-derived Lactobacillus strains were genetically marked with rifampin resistance and administered on day 0 to chickens fed either a normal commercial diet or a specially formulated high-protein diet. Chickens fed the high-protein diet were also coinoculated with two different mixes of additional lactic acid bacteria. Enterobacterial repetitive intergenic consensus sequence-based PCR (ERIC-PCR) was used to identify rifampin-resistant isolates recovered from chickens. Three strains, belonging to the species Lactobacillus agilis, Lactobacillus crispatus, and Lactobacillus vaginalis, were commonly reisolated from the chickens on both diets at days 21 and 42. The ability of these strains to persist was confirmed in a second chicken trial. All three strains persisted throughout the production period in the chickens fed a commercial diet, while only the L. agilis and L. vaginalis strains persisted in the chickens fed the high-protein diet. In both in vivo trials, competing lactic acid bacteria modified representation of the strains recovered, with all three stains capable of competing in the presence of one or both mixes of coinoculated strains. The in vivo model successfully identified three persistent strains that will be characterized further.The ecology of the chicken gastrointestinal tract (GIT) has been studied in depth using both culture-dependent (5,7,21,40) and -independent methods (2,3,7,33,54). These studies have revealed that lactobacilli are autochthonous residents in chickens, where they predominate in the proximal GIT and are present but less abundant within the distal GIT (52). The most commonly identified Lactobacillus species are Lactobacillus crispatus, Lactobacillus reuteri, and Lactobacillus salivarius (1,7,15,26,28). A detailed understanding of the relationship between these bacteria and their host under different dietary and environmental conditions will facilitate the development of lactobacilli for various applications directed toward increasing broiler production efficiency and improving chicken health.Since the withdrawal of antimicrobial growth promoters from chicken feed in Europe, the incidence of necrotic enteritis (NE) has increased (9, 51). Consequently, there is a need to develop alternative methods for controlling the causative agent of NE, Clostridium perfringens, in the chicken GIT. Lactobacilli are excellent candidates for alternative control methods due to their autochthonous nature and dominance of the upper GIT microbiota, particularly within the small intestine where NE occurs. Their potential utility ...
