An antibiotic XK-41 complex consisting of five components (A1, A2, B1 B2, and C) produced by a new species named Micromonospora inositola MK-41 was isolated. The components, A1, A2, B1 and C, were found to be macrolide-type antibiotics similar to megalomicins, while one component XK-41-B2 was considered to be a new antibiotic probably belonging to megalomicin-group antibiotic. Erythronolide B was also found to be produced as a byproduct by this Micromonospora sp.
A new antibiotic XK-46 is produced optimally at 46°C by a thermophilic Streptomyces sp. MK-46. This antibiotic is a color indicator, red in acidic and blue in alkaline solutions, soluble in organic solvents and slightly soluble in water. XK-46 is active against Gram-positive bacteria and Proteus vulgaris, and strongly inhibits tyrosine hydroxylase activity.
We have found in our stock cultures of clinical origin Providencia strains that were resistant to various aminoglycoside antibiotics including lividomycin and the gentamicin C complex but sensitive to kanamycin A and a new kanamycin A derivative, BB-K8. The substrate profile of inactivation of aminoglycosides combined with structural studies of the inactivated product of 3'-deoxyparomamine, indicate that aminoglycosides were inactivated by acetylation of the amino group at the 2'-C position.
Kitasamycin was tested in vitro against 214 clinical isolates of gram-positive cocci and its activity compared to minocycline, cephalothin, erythromycin, clindamycin and dicloxacillin. All isolates of Streptococcus pyogenes were inhibited by 0.39μg/ml. At a concentration of 1.56μg/ml, kitasamycin inhibited all isolates of Diplococcus pneumoniae, 98% of isolates of Staphylococcus aureus sensitive to penicillin G and 99% of isolates of Staphylococcus aureus resistant to penicillin G. Most of the other antibiotics were as active or more active than kitasamycin against gram-positive cocci.
BL-S217 is a new cephalosporin derivative which is active in vitro against grampositivecocci and gram-negative bacilli. At a concentration of 12.5μg/ml, BL-S217inhibited 83% of isolates of Klebsiella spp., 77% of isolates of Escherichia coli and 67%of isolates of Proteus mirabilis. BL-S217 was as active in vitro as most other cephalosporinantibiotics.
Bioassays of glycosides of neamine, kanamycin A and gentamicin C1 showed that against most susceptible bacteria the potency was between 6 and 40% that of the parent compound. These alkali-labile and acid-stable glycosides appeared to be N-glycosides.
IV. ANTIMYCOPLASMA ACTIVITY OF ASPICULAMYCIN in vitro AND IN VIVOkn-subtitle=en-abstract=Aspiculamycin, a new cytosine nucleoside antibiotic produced by Streptomyces toyocaensis var. aspiculamyceticus, showed strong activity against various strains of Mycoplasma in vitro and in vivo. The minimal inhibitory concentration of the antibiotic ranged between 50 to 0.05mcg/ml by agar dilution, broth dilution or microtiter method. No influences of inoculum size and pH of the medium on the activity were observed. A number of strains of Mycoplasma gallisepticum showing resistance to macrolide antibiotics were all susceptible to the antibiotic. L-Forms derived from Staphylococcus aureus and Proteus vulgaris were insensitive to the antibiotic. After administration of 0.04% (w/w) of aspiculamycin in the basal diet for seven days, the lung and trachea of mice infected intranasally with Mycoplasma pulmonis were free of pathogen. In the experimental mice arthritis induced with M. pulmonis, the Mycoplasma could not be detected in joints of the mice after treatment with aspiculamycin at a dose of 0.05% (w/w) in the diet for ten days.
An antibiotic R4H exhibiting no delayed toxicity was isolated from the fermentation broth of Streptomyces lavendulae strain R4. It was active against Gram-positive and -negative bacteria and Mycobacterium. R4H was converted to racemomycin-A and racemomycinic-A acid by mild hydrolysis.