Small filter membrane bags for the study of antibiotic action in the digestive tract: bioavailability and in situ activity of oxytetracycline, chloramphenicol, neomycin and gentamicin in the pig caecum.

Observations were made for two consecutive days on the disposition of oxytetracycline, chloramphenicol, neomycin and gentamicin through the digestive tract of pigs given an oral drench. The effect of these antibiotics upon the colibacilli flora and upon an Escherichia coli 127 strain in small filter membrane bags placed into the caecum was also investigated. For chloramphenicol, inactivation by antibiotic resistant colibacilli and, for neomycin, losses of activity by digestive content may explain the lower concentrations obtained in the gut and the correlative lack of curative or preventive action against E coli 127 in small bags. Tetracycline and gentamicin prevented growth of E coli 127 from the second day.