**8. Conclusions**

The interest in digestive physiology and the role of microorganisms has generated data whereby human and animal well-being can be enhanced and the risk of disease reduced. New molecular techniques that allow an accurate assessment of the flora composition, resulting in improved strategies for elucidating mechanisms. Given the recent international legislation and domestic consumer pressures to withdraw growth-promoting antibiotics and limit antibiotics available for treatment of bacterial infections, probiotics can offer alternative options. New advances in the application of probiotics, are directed to produce significant changes in gut physiology and provide even higher levels of health as well as increase performance parameters in poultry.

Metchnikoff founded the research field of probiotics, aimed at modulating the intestinal microflora (Dobrogosz, Peacock, & Hassan, 2010; Schmalstieg & Goldman, 2010; Weissmann, 2010). However, other parts of the body containing endogenous microflora or problems relating to the immune system may also be candidates for probiotic therapy. Research has shown that probiotics have potential for human health issues such as: vaginal candidiasis (Ehrstrom et al., 2010; Ya, Reifer, & Miller, 2010); dental caries (Chen & Wang, 2010; Stamatova & Meurman, 2009); allergies (Gourbeyre, Denery, & Bodinier, 2011; Schiavi, Barletta, Butteroni,

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Corinti, Boirivant, & Di Felice, 2010b); autoimmune diseases (Lavasani et al., 2010; Tlaskalova-Hogenova et al., 2011); urogenital infections (Pascual, Ruiz, Giordano, & Barberis, 2010; Ruiz et al., 2009); atopic diseases (Hoang, Shaw, Pham, & Levine, 2010; Nermes et al., 2011); rheumatoid arthritis (Lee et al., 2010; Mandel, Eichas, & Holmes, 2010); and respiratory infections (Harikrishnan, Balasundaram, & Heo, 2010; Silvestri et al., 2010). Current research is still heavily biased toward gastrointestinal applications for probiotics, such as: chronic constipation (Bu, Chang, Ni, Chen, & Cheng, 2007; Coccorullo et al., 2010); chronic diarrhea (Preidis et al., 2011; Swidsinski, Loening-Baucke, Verstraelen, Osowska, & Doerffel, 2008); inflammatory bowel disease (Ng, Chan, & Sung, 2011; Vanderpool, Yan, & Polk, 2008); irritable bowel syndrome (Camilleri & Tack, 2010; Enck, Klosterhalfen, & Martens, 2011); and food allergy (Gourbeyre et al., 2011; Schiavi, Barletta, Butteroni, Corinti, Boirivant, & Di Felice, 2010a), but the possibilities for impacting many areas of health are numerous. Much research has been completed in efforts to understand and apply the natural benefits of non-pathogenic bacteria, but there is much still to do.

New approaches to vaccination-based prophylaxis for *Salmonella* infection in poultry offer tremendous hope that highly effective vaccines may be on the horizion for commercial poultry. However, currently available and autogenous vaccines for *Salmonella* offer a modicum of protection that is generally only useful for breeders and laying hens at this time.

Although there are occasional successes with treatment of enteric *Salmonella* infections in live birds with bacteriophage cocktails, as described above, resistance to bacteriophage lysis generally develops very quickly, leading most scientist to conclude that these offer little promise for treating *Salmonella* infections in live poultry. However, when broadly-effective bacteriophage cocktails have been applied to poultry carcasses at processing, these cocktails have been highly efficacious and potentially cost-effective for inducing marked reductions in *Salmonella* contamination (Higgins et al., 2005). This latter approach has the probability of avoiding the resistance issues associated with treatment of live animals in that *Salmonella* contaminants would only be exposed to the bacteriophage cocktail at a single point in the vertical production scheme, thereby avoiding re-introduction of resistant *Salmonella* isolates into the integrated poultry production operation.

The scientific progress outlined in this chapter show highly encouraging progress toward intervention methods for *Salmonella* infections of poultry, and opportunities that are just becoming available to potentially impact poultry as a source of *Salmonella*-related food borne illness. *Salmonella* infections of poultry continue to be hugely problematic in both developed and developing countries. To date, no single "silver bullet" has been identified which can be applied commercially to eliminate this risk for this important and healthy human food source. Nevertheless, several tools, as described above, have been shown to be highly effective in reducing *Salmonella* levels in poultry production operations worldwide, particularly when used in combination. New probiotic/DFM products, with isolate selection based on better understanding of the mechanisms of efficacy, along with eventual regulatory approval and commercialization of exciting new vaccine technologies may make a tremendous impact in the very near future.
