Influence of Antimicrobial Drugs on Segmented Filamentous Bacteria in the Ileum of Mice

The effects of various types of 3 d antibiotic treatment of mice on the presence of segmented filamentous bacteria (SFBs) in the ileum were measured in order to further characterise these microorganisms. To assess any specific effects of the antimicrobial drugs on SFBs, relative caecal weight, relative number of fusiform-shaped bacteria in the caecum and the number of faecal Enterobacteriaceae were also determined. All drugs tested, i.e. amoxycillin, doxycyclin, gentamicin, vancomycin, ciprofloxacin, trimethoprim, metronidazole, clindamycin, streptomycin and cefotaxim, reduced the presence of SFBs in the ileum, although to different degrees. None of the drugs affected body weight of the mice. There was no correlation of the drug effects on SFBs and those on either relative caecal weight, percentage of caecal fusiforms or faecal Enterobacteriaceae. Thus, the effects of the antimicrobial drugs on SFBs can be considered rather specific. The sensitivity pattern of SFBs suggests that they are facultatively anaerobic bacteria with relatively high sensitivity to antimicrobial drugs.