摘要：One function of the microbial ecosystem formed by the bacterial flora of the gastrointestinal tract is to create a barrier to colonization by ingested bacteria, including opportunistic pathogens. There are no validated tests that predict the amount of antibiotic residue in food that can be ingested by humans without causing an effect on this barrier. Semi-continuous cultures (S-CC) of fecal bacteria are frequently used as models of the colon flora, since bacteria in these cultures form relatively stable microbial ecosystems. These models may provide a basis for developing a test system to determine no effect concentrations of antibiotic residues, and thereby derive (for drug registration purposes) a human acceptable daily intake of antibiotic residues in foods from treated animals. Clindamycin is one of many antibiotics that can disrupt the colonization barrier of the colonic microflora in vivo in humans. This may be evidenced clinically as pseudomembranous colitis, if toxigenic Clostridium difficile are present and proliferate in the intestinal tract. Therefore, we tested clindamycin as a reference compound and used proliferation of Clostridium difficile as a functional indicator of disruption of the otherwise stable populations of human fecal bacteria in an S-CC test system. The objective of the studies was to examine test conditions and responses that could be used in an S-CC in vitro test to detect colonization barrier disruption in this model of the human gut flora. The hypothesis was that a clindamycin dose response would be detectable by monitoring the C. difficile concentration within the S-CCs.
