Abstract
The jejunal, ileal and colonic microfloras were determined in 14 control rats and in six rats after a 5d course of metronidazole in high dose. Faecal short-chain fatty acids (SCFAs) were determined in 49 controls and in 14 treated rats. Metronidazole caused different changes in the microflora of different sites. In the jejunal lumen and on the mucosa the drug suppressed the numbers of lactobacilli and anaerobic cocci. In the ileal contents the levels of streptococci and lactobacilli increased and those of anaerobic cocci decreased, whereas no changes took place on the ileal mucosa. The microflora of colonic contents also remained unaffected but on the colonic mucosa the numbers of bacteroides decreased significantly. Metronidazole also caused significant changes in faecal SCFAs. The concentration of all acids decreased but the relative proportion of acetic acid increased (81 per cent versus 60 per cent in controls), obviously reflecting the suppression of anaerobic bacteria. It is concluded that metronidazole, given orally in high doses, has a significant effect upon the normal intestinal microflora that may not be reflected in faecal cultures. For evaluating an individual it seems to be useful to account for not only the absolute amounts of microbes but also their relative distribution and predominant/subordinate pattern in a particular site of the gastrointestinal tract.