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Previous studies have reported that intestinal populations of Clostridium perfringens, the causative agent of necrotic enteritis (NE), are correlated with diets high in glycine. To establish a direct causative link, 3 trials were conducted to examine the effect of dietary glycine levels on gut populations of C. perfringens, alpha-toxin production, and NE lesion scores in broiler chickens. In trials 1 and 2, 12 groups of 4 birds were fed 4 different ideal protein-balanced diets formulated to contain 0.75, 1.58, 3.04, or 4.21% glycine from d 14 to 28 of age. In trial 3, 24 groups of 4 birds were given 6 different ideal protein-balanced diets formulated to contain 0.50, 0.75, 1.00, 1.50, 2.00, or 4.00% glycine. All birds were orally challenged with a broth culture of C. perfringens type A on d 1 and between d 14 and 21 of age and killed on d 28. The majority of birds showed clinical signs of NE with 4.16 to 8.33% mortality in the 3 trials. The highest mortality and intestinal lesion scores were observed in chickens receiving 3.04% glycine in trials 1 and 2, and 4.00% glycine in trial 3. Clostridium perfringens populations in the cecum varied quadratically with increasing dietary glycine, with the maximal response seen at 3.30,3.89, and 3.51% dietary glycine in trials 1, 2, and 3, respectively. Numbers of lactobacilli in cecum declined significantly (P < 0.05) with increasing levels of glycine. The results suggest that dietary glycine level has a significant effect on C. perfringens and lactobacilli populations and may be a predisposing factor for NE in broiler chickens.

[185][186][187][188][189][190][191][192][193]. An experiment was performed to examine the effect of protein source and dietary amino acid profile on intestinal levels of C. perfringens in broiler chickens. Broiler chickens (age = 14 d; n = 192) were fed diets containing 400 g kg -1 crude protein with fish meal, meat/bone meal, feather meal, corn gluten meal, soy protein concentrate, pea protein concentrate, or potato protein concentrate as the primary protein source along with a control diet containing 230 g kg -1 crude protein. The birds were orally inoculated daily, with 1 mL (~1.0 × 10 8 CFU mL -1 ) of an overnight culture of C. perfringens between 14 and 21 d of age, killed at 28 d of age and C. perfringens numbers in ileum and cecum were enumerated. Birds fed fish meal, meat/bone meal, feather meal and potato protein concentrate had significantly higher intestinal C. perfringens counts than the birds fed corn gluten meal, soy or pea protein concentrates or the control diet (P < 0.05). The glycine content of the diets and ileal contents was significantly, positively correlated with C. perfringens numbers in ileum and cecum. Dietary glycine may be an important factor in the intestinal overgrowth of C. perfringens in broiler chickens.

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Germ theory and pure culture methods have provided invaluable information concerning the role of bacteria in diseases resulting from a single organism which bypasses a host's defenses. However, they do not provide sufficient information concerning the synergisms which allow the members of biofilm communities to proliferate more effectively as communities rather than as individuals. The mechanisms of these synergies are potential targets for antimicrobial agents as well as potential mechanisms of resistance to antimicrobial agents. Understanding community-level phenomena in oral biology requires the culture, identification, and classification of functional plaque communities as well as new methods of identifying and quantifying communal relationships. Cultured biofilm communities also provide ideal models of bacterial self-organization in which information related to adaptive strategies arises not only through the recombination of genes within genomes, but also through the recombination of organisms within communities.