Abstract
Physicochemical and biological properties of josamycin propionate (JM-P) were studied, and the following results were obtained.
1. Josamycin propionate is a new derivative of josamycin (JM) having no bitter taste, physicochemical properties of which were described.
2. Like josamycin, josamycin propionate showed strong antibacterial activity against gram-positive bacteria, but very weak activity against enteric gram-negative bacteria. Its MIC's were 0.78-1.56 mcg/ml against Staphylococcus aureus, 7.8mcg/ml against Streptococcus hemolyticus and 0.09 mcg/ml against Diplococcus pneumoniae, which were equal to or a little weaker than those of josamycin. It showed cross resistance to macrolides but not to other antibiotics.
3. Antibacterial activity of josamycin propionate increased at the alkaline side of medium pH, but was not so affected by inoculum sizes.
4. Josamycin propionate showed bactericidal activity against Staphylococcus aureus SC-17 at 6.25 mcg/ml which was 8 times MIC.
5. Josamycin propionate showed strong propective effect against gram-positive infections in mice. ED50'S of oral josamycin propionate were as follows:
JM-P JM
Staphylococcus aureus Smith 143 217mg/kg
Streptococcus hemolyticus S-23 95 116
Diplococcus pneunsoniae Type I 540 620
Escherichia coli NIHJ >1000 >1000
6. In protection of subcutaneous staphylococcal infections in mice, josamycin propionate was as active as josamycin.
