Abstract
For the transduction of drug resistance, strains TK 5553 and TIC 5568 were selected from gentamicin (GM)-resistant Staphylococcus aureus as donor. Strain MS 353 which has already been shown to lack plasmid deoxyribonucleic acid (DNA), was used as a recipient. Transduction experiments were performed by the phage lysate induced from donor strain with mitomycin C. Analysis of plasmid DNA was attempted to the resulting GM-resistant transductants.
The results were as follows:
1. In the transduction experiments by use of the phage lysate induced from strain TK 5553, resistance to penicillin G (PCG), erythromycin (EM), kanamycin (KM) and GM was always transduced to recipient strain simultaneously, and the transduction frequency was 1.4-2.3×10-8. It was also found that the quadruple drug resistance was jointly eliminated by the treatment with ethidium bromide. Moreover, a single class of plasmid DNA was isolated from a transductant and found to be 32.1×106 daltons in molecular weight. From the above findings, it was strongly suggested that PCGEM-KM-GM resistance was located on a single plasmid (named pTU 053).
2. In the transduction experiments by use of the phage lysate induced from strain TK 5568, transductants obtained from selective plates containing KM or GM could be classified into two resistant types: PCG-EM-KM resistance, KM-GM resistance. The transduction frequency of KM-GM resistance was about 4.9×10-7, and the plasmid DNA was 36.2×106 daltons (named pTU 068).
3. In heteroduplex experiments of two DNA's pTU 512 (PCG-EM-KM resistance) and pTU 053 (PCG-EM-KM-GM resistance), 92.9% of pTU 053 DNA was found to be homologous with pTU 512 DNA.
