Probiotics competitive exclusion

Microorganisms approved for feed use under the EU regulations comprise Enterococcus faecium (in various forms) and Saccharomyces ceremsiae. Their use as probiotics (as an alternative to antibiotics) is based on the principle of promoting the growth of lactobacilli and reducing the numbers of enteropathogenic bacteria in the gut. Sometimes this principle is referred to as competitive exclusion. This aspect will be addressed in more detail in Chapter 7 (this volume). 

FIGURE 1.1 Probiotics may protect against infection by pathogens through (1) Direct antagonism via bacteriocin production. (2) Immunomodulation via immune cell (T-cell, Dendritic cell) activation. (3) Improvement of epithelial barrier function and competitive exclusion via induction of mucus and blocking of epithelial binding receptors. 

Mulder, R.W.A.W., Havenaar, R., and Huis in t Veld, J.H.J., Intervention strategies the use of probiotics and competitive exclusion microflora against contamination with pathogens in pigs and poultry, in Probiotics 2 Applications and Practical Aspects, Fuller, R., Ed., Chapman Hall, London, 1997, pp. 187-207. 

Remark Biopesticides are used elsewhere, as well. Certain bacteria can be sprayed on strawberries and other fruit crops to protect them against late frosts. Other bacteria, fungi, and yeasts are used to control diseases of stored fruits. Beneficial bacteria, called probiotics, can be fed to humans and animals to relieve the symptoms of diseases and maladies. Probiotics can produce useful biochemicals (such as vitamin K in the human gut), attack harmful viruses and bacteria through natural antibiotics, and crowd out harmful microbes. Competitive exclusion is a powerful weapon that has only begun to be used to advantage. 

The inoculation of chickens with non-pathogenic cultures of bacteria has been reported to reduce Salmonella populations in chickens (Nurmi and Rantala, 1973 Wierup et al, 1988 Rehe, 1991). Probiotic administration is quite similar in approach to competitive exclusion in that a specific bacterial culture, often lactic acid bacteria, is administered to live birds. The two procedures may also accomplish the same goals with respect to pathogen reduction. However, a tenet of probiotic administration has been that it improves animal growth (Jernigan et al., 1985). 

After establishment of the basic concept of competitive exclusion, considerable research has been done to identify the mechanisms by which bacteria are competitively excluded from host sites (Nurmi et al. 1992 Zhao et al. 1995). Responsible factors include competition for receptor sites on the intestinal epithelium, production of volatile fatty acids and/or other antibacterial substances, and competition among different bacteria for limited nutrients. The use of LAB as a probiotic for live poultry and livestock has been extensively studied and has... 

Nurmi E, Nuotio L, Schneitz C (1992) The competitive exclusion concept development and future. Int J Food Microbiol 15 237-240 Okereke A, Montville TJ (1991) Bacteriocin-mediated inhibition of Clostridium botulinum spores by lactic acid bacteria at refrigeration and abuse temperatures. Appl Environ Microbiol 57 3423-3428 Ouwehand AC, Sondberg Svendsen L, Leyer G (2011) Probiotics from strain to product. In Kniebel W, Salminen S (eds) Probiotics and health claims. Wiley, W. Sussex, pp 37-47... 

---