Recontamination after gastrointestinal decontamination with non-absorbable antibiotics.

In an attempt to restore the colonization resistance we administered anaerobic microflora to prevent an abnormal colonization of the intestine after antibiotic treatment had been discontinued. After the antibiotics had been discontinued and before the donor flora had been administered and had colonized the intestine, microorganisms present were "unopposed" and expanded to a high density. A mouse model was used to investigate which antibiotics negatively influenced the donor flora and reduced the colonization resistance when administered intraperitoneally. Erythromycin, clindamycin and carbenicillin suppressed the donor flora permanently, as could be seen by the reduced colonization resistance. Benzylpenicillin, ampicillin, doxycycline and the combination gentamicin-cephalothin affected the colonization resistance as long as these agents were present. Gentamicin alone and cephalothin and oxytetracycline had no effect on the colonization resistance.