Storage of intestinal bacteria in samples frozen with glycerol

For clinical studies, it would be useful to store faecal samples before bacteriological analyses. However, information is needed on the effect of freezing on the survival of micro-organisms. In this study, faecal samples were stored in glycerol at -80°C for four months. Although the concentrations of predominant anaerobic bacterial populations (>8 log(cfu g -1 ), total anaerobes and bifidobacteria, decreased significantly (p<0.05) after freezing, this decrease did not exceed interindividual variation. The facultative anaerobes, enterobacteria, enterococci and lactobacilli, were not significantly affected by freezing. Furthermore, the magnitude of individual variability was similar before and after freezing. These results confirm the relevance of our freezing technique for studying the intestinal microflora which involves numerous samples that cannot be analysed simultaneously for practical reasons.