抗生物質の動物の発育に及ぼす影響並びにその作用機転に関する研究 : 特に腸内菌叢との関係に就いて

概要

論文の詳細を見る
For the purpose of carrying out investigations on the influence the antibiotic might exert on animals, the author performed experiments on raising chicks on a diet containing aureomycin(1/10000) and made observations on their growth and the change in the numbers of Lactobacillus acidophilus, Enterococcus and Escherichia coli that are assumed to be the normal intestinal bacterial organisms of the domestic fowl, in comparison with control chicks. The experiments were conducted twice, and 70 rooster chicks of white leghorn were fed on a specially prepared diet, since immediately after being hatched, for the period of sixty days in each experiment. The number of each intestinal organism was counted in the selective medium by the M.F.N. method. The results of the experiments are summarized as follows. 1) The chicks raised on the diet containing aureomycin grew heavier than control chicks by the end of the first week; and at the end of the eighth week, the former was heavier than the latter by 10 % in the first experiment and 13 % in the second one. 2) The numbers of species of organisms in 1 g of the feces of control chicks were as follows: a) When the chicks were less than one month and a half old, the numbers of E. coli and Enterococcus were 10^<6〜7>, with both numbers varying from time to time, sometimes the former becoming larger than the latter, and vice versa. The number of L. acidophilus was 10^8. b) When the chicks were more than one month and a half old, the numbers were : 10^6 for E. coli, 10^7 for Enterococcus and 10^8 for L. acidophilus. 3) The numbers of 3 species of organisms in 1 g of the feces of the chicks raised on the diet containing aureomycin were as follows: a) The number of E. coli was reduced from 6〜7 to 10^<4〜5> in the course of experiments and remained on that level till the end of the experiment. b) There was no change in the number of Enterococcus. c) The number of L. acidophilus diminished temporarily, then began to increase at around the fourth or the fifth week until finally it exceeded that of Enterococcus and rose to 10^8. 4) Comparative studies of the two groups of chicks have revealed the following relation .between body weight and the numbers of 3 different species of organisms: a) The chicks raised on the diet containing aureomycin began to grow heavier than control chicks as soon as the number of E. coli in the former began to decrease as a result of the administration of aureomycin. b) Keeping pace with an increase in the number of L. acidophilus in the former, the difference in the body weight grew larger. c) In the seventh week (when the numbers of organisms found in control chicks were: 10^6 for E. coli, 10^7 for Enterococcus and 10^8 for L. acidophilus), the difference became slightly smaller. 5) Marked correlation was observed between the rate of increase in body weight and the ratio E. coli/Enterococcus in individual chick. a) When the ratio was less than 0.01, the rate of increase was remarkably well. b) When the ratio was more than 1, the increase of body weight was markedly deterred. 6) A few control chicks manifested an increase of body weight of the same degree and the same pattern of change in the numbers of 3 species of organisms as did the chicks raised on the diet containing aureomycin. 7) Discontinuance of the administration of aureomycin resulted in the falling off in the increase of body weight and in the increase in the number of E. coli. 8) Resistance to aureomycin was examined in 20 strains each of 3 species of organisms. a) Before the administration of aureomycin, the marginal concentrations of aureomycin that restricted the growth of each organism were: 1γ for L. acidophilus, 5γ for Enterococcus and 0.1γ for E. coli. The marginal concentrations of aureomycin that inhibited the growth of each organism were: 1γ for L. acidophilus, 10γ for Enterococcus and 5γ for E. coli. b) On the sixtieth day after the administration of aureomycin had begun, the marginal concentrations of aureomycin that restricted the growth of each organism were: 100γ for L. acidophilus, 10γ for Enterococcus and 1γ for E. coli. The marginal concentrations of aureomycin that inhibited the growth of each organism were: 100γ for L. acidophilus, 50γ for Enterococcus and 100γ for E. coli. 9) Candida albicans was not found in the present experiments. 10) The results of the experiments described above have led the author to presume that acceleration of the growth of chicks associated with the administration of a minute volume of aureomycin might be due to: The action of aureomycin to inhibit the growth of E. coli, while the number of Enterococcus remains the same during the period when E. coif tends to be more predominant than Enterococcus until the chick becomes one month and a half old; and the fact that L. acidophilus becomes the most numerous of all the 3 different species of organisms when the chick becomes more than one month and a half old. 11) That the 3 different species of organisms show the pattern of change in their numbers as mentioned above as a result of the administration of a minute volume of aureomycin would be due to the fact that: a) Enterococcus is innately the most resistant to aureomycin, followed by L. acidophilus and E. coli in that order; b) L. acidophilus acquires the highest degree of resistance to aureomycin administered in a minute volume, followed by Enterococcus and E. coli in that order, and c) L. acidophilus has antagonistic effect on Enterococcus, which, in turn, has antagonistic effect on E. coli. It is the conclusion arrived at by the author that the mechanism of accelearation of the growth of chicks brought about as a result of the administration of a minute volume of aureomycin would be attributed to the specific pattern of change in the numbers of 3 different species of organisms in the intestines.
千葉大学の論文
1956-05-28

著者

吉江俊夫
千葉大学医学部衛生学教室

抗生物質の動物の発育に及ぼす影響並びにその作用機転に関する研究 : 特に腸内菌叢との関係に就いて

スポンサーリンク

概要

著者

関連論文

スポンサーリンク