Culture-based knowledge on biodiversity, development and stability of human gastrointestinal microflora. Micro Ecol Health Dis 2000;12:53–63

The human large intestine harbours an abundant and extremely diverse microora with more than 400–500 microbial species estimated. The dominant microora in faecal samples is obligately anaerobic: Especially Bacteroides spp., Eubacterium spp., Bidobacterium spp., lactobacilli, anaerobic cocci and Clostridium spp. are detected in high numbers by bacterial culture. In addition, facultatively anaerobic organisms such as Escherichia coli, enterococci and streptococci are commonly encountered. Although several thorough studies on the diversity of the faecal ora has been performed during 1970’s, investigation of intestinal ora by culture-based methods has several limitations: The lack of culture media supporting the growth of some components of dominant ora, difculties in identication of bacteria by traditional phenotypic methods and continuous changes in taxonomy complicate studies on the intestinal ora by bacterial culture. Since invasive sampling techniques are required to obtain intestinal samples, most studies on human intestinal ora have been restricted mainly to the analysis of the faecal ora. A faecal sample seems to represent the microora in the large intestine, whereas the microora in the upper parts of the intestinal tract is sparse and less diverse. During the development of the intestinal ora in newborns, facultatively anaerobic species, especially E. coli, staphylococci and streptococci are colonising rst and subsequently obligate anaerobes including Bacteroides spp., Bidobacterium spp. and Clostridium spp. appear in faeces within few days. By the end of the second year of life the faecal ora resembles that of adults. Although a great variation in the ora composition exists between individuals, the faeca