STUDIES ON THE MECHANISM OF APPEARANCE OF DRUG-RESISTANT BACTERIA AND THE R FACTOR INT THE GERM FREE PIGS I

Abstract

The results derived from experiments using germ free pigs were summarized as follows.1) Drug-sensitive bacteria, 8 E. coli strains and 1 Klebsiella strain, were orally administrated to the germ free pigs. From their faeces, 5 E. coli strains and Klebsiella strain were recovered by cultivation. The E. coli strain, p-38 was most frequently isolated.2) The animals administrated with bacteria were treated with TC and then with CM. TC-resistant E. coli strains were found in their faeces a few days after the TC treatment and the TC. CM-resistant ones appeared and increased after the CM treatment, However, TC. CM-resistant Klebsiella strains were detected after the single treatment. with TC.3) TC. CM-resistance in 2 out of 5 strains and TC-resistance in most of the strains of E. coli were shown to be transferable. Transferable TC-resistance and TC CM-resistance were also found from TC. CM-resistant Klebsiella strains isolated after CM treatment.4) From those pigs treated with only CLM or without any antibiotics, no drug-resistant bacteria was isolated.These results supported a prediction that the bacteria become resistant to drugs by mutation selection events after the treatment with antibiotics and that the R factor is formed in these bacteria by acquisition of transferability in vitro by some mechanisms under investigation.