Lactobacilli and the normal human anaerobic microflora.

The normal human microflora is a complex and usually stable ecosystem. The intestinal microflora is important to the host with regard to many metabolic functions and in resistance to bacterial infections. Administration of antimicrobial agents may disrupt the normal microflora, leading to a decrease in colonization resistance and alterations in metabolic activities of the intestinal bacteria. Antimicrobial therapy may also be accompanied by gastrointestinal disturbances and a reduction or elimination of lactobacilli in the intestinal microflora. Lactobacilli are part of the normal gram-positive anaerobic microflora. Through the production of lactic and acetic acids, hydrogen peroxide, and antimicrobial substances, these microorganisms possibly contribute to the maintenance of colonization resistance. Several studies have indicated a protective effect of lactobacilli against potential pathogens in the gastrointestinal tract. In view of these beneficial properties, it is considered important to maintain or increase the levels of lactobacilli in the intestinal microflora.