Low dose oral tobramycin treatment for selective decontamination of the digestive tract: a study in human volunteers.

Tobramycin has been given orally to eight human volunteers for four successive days, to investigate its effect on the Gram-negative enterobacilli as well as on the endogenous anaerobic microflora. The effect was investigated in three treatment legs; i.e. in daily doses of 300 mg, in daily doses of 500 mg and thirdly in daily doses of 200 mg in combination with 1000 mg of neomycin. With 300 mg tobramycin daily, seven of eight volunteers had no Gram-negative bacilli in their faecal cultures by about four days after the onset of treatment. Their anaerobic micro-flora was slightly affected during treatment as evidenced by the appearance of low concentrations of beta-aspartylglycine in their stools. The other dose regimens were not significantly more effective in eliminating Gram-negative bacilli from the intestines; the anaerobic flora however, was more severely affected. Because evidence of induction of resistance was noticed it is recommended that if tobramycin is used for selective decontamination of the intestinal tract it should be given in combination with another antimicrobial drug such as polymyxin.