The results of the studies on Vistamycin were summarized as follows :
1. A total of 683 strains of recently isolated from clinical materials and 21 standard strains were tested for their in vitro susceptibility to Vistamycin (VSM), kanamycin (KM) and aminodeoxykanamycin (AKM) by the plate dilution method.
The antibacterial spectrum of VSM was the same as that of KM or AKM. The antibacterial activity of VSM was not higher than that of KM and lower than that of AKM against most strains except α, β-Streptococci.
It was confirmed that there may be the cross-resistance among VSM, KM and AKM.
2. Minimum inhibitory concentration of VSM, KM or AKM was affected by pH of the medium for Staphylococcus aureus 209 P and Escherichia coli NIHJ. Antibacterial activities of these three drugs were more effective in alkaline medium.
3. Tissue concentration of VSM in rats after intramuscular injection (20 mg/kg) was measured by means of cup plate method using Bacillus subtilis ATCC-6633 as test organism, and it was almost equal to that of KM or AKM. The kidney showed the highest concentration, and the other organs exhibited the concentrations as follows in order of blood, lung and liver, among which the latter's concentration was especially poor.
The serum peak levels (21.9 mcg/ml) in 5 healthy humans (500 mg, I.M.) was attained on an average 1 hour after the administration, then dropped to 3.5 mcg/ml after 6 hours, indicating yet thus the higher values.
The urinary recovery rate of VSM, KM or AKM was more than 70% on an average within 6 hours.
