%0 Journal Article %A Coste, M. %A Gouet, Ph. %A Escoula, L. %T Ampicillin Inactivation in the Caecum of Axenic, Gnotoxenic and Conventional Lambs: Interaction with Resistant or Sensitive Escherichia coli %D 1984 %J Microbiology, %V 130 %N 6 %P 1325-1330 %@ 1465-2080 %R https://doi.org/10.1099/00221287-130-6-1325 %I Microbiology Society, %X The fate of orally administered ampicillin was studied in axenic lambs, in gnotoxenic lambs given a complex microflora and a mixture of ampicillin resistant and/or sensitive strains of Escherichia coli, and in conventional lambs. In axenic lambs or animals with a sensitive micro-flora, antibiotic concentrations of 500-1600 g ml−1 were detected in the intestine, and most of the ampicillin passed through the small intestine and entered the large intestine, within 12-15 h of administration. These antibiotic concentrations were sufficient to decrease the numbers of ampicillin-sensitive E. coli from 108 109 bacteria ml−1 to about 105-106bacteria ml−1 by 8 h after ampicillin administration. Second and third doses of antibiotic had no further effect on the bacterial count. Administration of ampicillin to animals hosting ampicillin-resistant E. coli resulted in a significant inactivation of the antibiotic in the intestine. As might be expected there was little reduction in the numbers of these organisms. These results are similar to those observed in conventional lambs hosting resistant E. coli as the dominant colibacillary flora. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-130-6-1325