Lactobacillus, normal flora

To understand the role of antibiotics, it is important to understand their effects on the fecal flora. The normal flora consists of a complex bacterial population with 400-500 distinct species of bacteria (table 2a). More than 99% of the total organisms are accounted for by non-sporeforming anaerobic rods [28] the four major species are Bacteroides, bifidobacteria, eubacteria and peptostrepto-cocci [29], Other common species are Escherichia coli, Streptococcus viridans, Streptococcus salivarius and lacto-bacilli. Mette et al. [30] clarified the prevalence of species in fecal flora by listing the four most common anaerobes Bacteroides spp., Eubacterium spp., Bifidobacterium spp. and anaerobic cocci) and three common aerobes E. coli spp., Enterococcus spp. and Lactobacillus spp.) (table 2b). 

Lactobacillus preparation is intended to replace colonic microflora. This supposedly restores intestinal functions and suppresses the growth of pathogenic microorganisms. However, a dairy product diet containing 200 to 400 g of lactose or dextrin is equally effective in recolonization of normal flora. 

A number of reviews have now appeared on the subject. It has been known since 1900 that differences exist between the intestinal flora of breast-fed babies and those fed on cows milk, the flora of the former being composed almost exclusively of L. bifidus. In 1926, it was shown that a growth factor for L. bifidus occurs, associated with the lactose fraction in whey, in human milk, but it was not found in cream, in the proteins, or in the inorganic material. Later the nutritional requirements of L. bifidus were reinvestigated and, in the course of this work, there was isolated, from the feces of infants, a variant of L. bifidus which gave only a scanty growth on the normal media, but which responded to the addition of human milk. This variant was named Lactobacillus bifidus var. pennsyl-... 

The normal balance of intestinal flora may be maintained or restored to normal from an unbalanced state by a well-balanced diet or by oral bacteriotherapy. Oral bacteriotherapy, using intestinal strains of lactic acid bacteria (LAB), such as Lactobacillus and Bifidobacterium, can restore normal intestinal balance and produce beneficial effects. 

As suggested by its name, this genus of bacteria ferments glucose Into lactic acid and is widely used in the food industry. Lactobacillus is also a component of the normal human bacterial flora of the urogenital tract where, because of its ability to generate an acidic environment, it prevents the growth of harmful bacteria. [Dr. Dennis Kunkel/PhotoTake.]... 

An emerging concept is that a balance in the GI tract normally exists among the mucosal epithelium, the normal gut flora, and the immune response. Some data suggest that colonic bacteria may either initiate or perpetuate the inflammation of IBD, and specific bacterial antigens in the pathogenesis of Crohn s disease. Thus, certain bacterial strains may be either pro- (e.g., Bacteroides) or antiinflammatory (e.g., Lactobacillus), prompting attempts to manipulate the colonic flora in patients with IBD. Traditionally, antibiotics have been used to this end, most prominently in Crohn s disease. More recently, probiotics have been used to treat specific chnical situations in IBD. 

Ahrne, S., Nobaek, S., Jeppsson, B., Adlerberth, L, Wold, E. E., MoUn, G. (1998). The normal Lactobacillus flora of healthy human rectal and oral mucosa. Journal of Applied Microbiology, 85, 88-94. 

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