Biological evaluation was made on propionylmaridomycin which was provided by the Research Laboratories of Takeda Chemical Industries, Ltd.
1) The antibacterial activity of this macrolide antibiotic was similar to that of the known macrolide antibiotics such as leucomycin or josamycin.
2) The components and metabolites of this macrolide antibiotic showed in vitro and in vivo antibacterial activity.
3) The susceptibity distribution of this macrolide antibiotic against clinical isolates of Staphylococcus showed similar patterns as that of leucomycin or josamycin.
4) The vulnerability to the influences of the pH value, human serum concentration and inoculum size in vitro antibacterial activity of this macrolide antibiotic was also similar to the known macrolide antibiotics.
5) In vitro antibacterial effect of this macrolide was bacteriostatic at the MIC and it was bactericidal at the concentration higher than MIC.
6) By the electron microscopic observation of the antibacterial effect of this macrolide antibiotic against Staphylococcus, degeneration and lysis of the cytoplasma and the remarkable thickness of the cell wall were recognized.
7) Propionylmaridomycin acquired resistance stepwise like that of the other known macrolide antibiotics in vitro. The complete cross resistance was observed among the known macrolide antibiotics against artificial resistant strains.
There were three types of resistance in the clinical isolates, i. e.,
1) against erythromycin alone, 2) against erythromycin and oleandomycin, and 3) against erythromycin, oleandomycin, leucomycin, josamycin, propionylmaridomycin and spiramycin.
8) Propionylmaridomycin did not induce resistance.
