Antibiotic A-16316-C, a new water-soluble basic antibiotic

A new water-soluble basic antibiotic named antibiotic A-16316-C was isolated together with antibiotic A-396-I and hygromycin B from a streptomyces strain identified as Streptoverticullium eurocidicus. The properties of the antibiotic A-16316-C were similar to those of destomycin B. But it was found that the antibiotic A-16316-C was not identical with destomycin B on the basis of NMR analysis. On acidic degradation antibiotic A-16136-C gave N, N'-dimethyl-2-deoxystreptamine, destomic acid and D-mannose. The gross structure for antibiotic A-16136-C was deduced from chemical reactions and spectral data.

Simple assay for clindamycin in the presence of aminoglycosides

The presence of aminoglycoside antibiotics interferes with the determination of clindamycin levels by standard microbiological assay. A new bioassay method of quantitation of clindamycin in the presence of aminoglycosides is presented. This technique is based on the fact that incorporation of calcium chloride into assay agar blocks the antimicrobial activity of aminoglycosides against Sarcina lutea but allows the assay of as little as 0.31 mug of clindamycin per ml. The error of the system is less than 10%. This method is simple and adaptable to existing assay systems for clindamycin.

Requirements for the urease assay of aminoglycoside antibiotics

The hydrolysis of urea by Proteus mirabilis N.C.I.B. 10823 has been investigated and found to be independent of bacterial growth up to 90 minutes incubation and to require only a source of readily available amino acids. Evidence is presented which indicates that the urease of Proteus mirabilis N.C.I.B. 10823 is an inducible enzyme. The induction time of the urease in stationary phase organisms is 20-30 minutes and only those antibiotics which can inhibit protein synthesis within this time (aminoglycosides, tetracycline, chloramphenicol and spectinomycin) have an inhibitory effect on the hydrolysis of urea. Proteus mirabilis N.C.I.B. 10823 is found to be 8-10 times more sensitive to gentamicin at low NaCl concentrations.

The significance of these findings in relation to the urease assay for aminoglycoside antibiotics is discussed.

Tobramycin in bronchial secretions

The penetration of tobramycin sulfate (nebramycin factor 6) into normal lower respiratory tract secretions was studied in a dog model. After a 1.7 mg/kg intravenous dose of tobramycin, the antibiotic was detected promptly in bronchial secretions, but the peak bronchial secretion concentration was not usually reached until 2 h after injection (mean level 1.15 mug/ml). The maximum tobramycin concentration in bronchial fluids was equal to the mean inhibitory concentrations that have been reported for about 80% of Pseudomonas isolates.

Analytical method for streptothricin-type antibiotics: structure of antibiotic LL-BL136

An analytical procedure was devised which can distinguish members of the streptothricin family of antibiotics. It is based upon an analysis of the hydrolysis products of the antibiotics using a Technicon amino acid autoanalyzer under special conditions. The various fragments including the different streptolidine-amino sugar compounds were well resolved. A basic water-soluble antibiotic discovered in our laboratories and named LL-BL136 was compared to other members of this group by this technique. It was not differentiated from the antibiotic SF-701 reported by Tsuruoka. The autoanalyzer results along with other physicochemical data permitted a structure proposal for this antibiotic, which is the N-methyl-desformimino derivative of antibiotic LL-AC541.

Factors influencing the microbiological assay of tobramycin

Tobramycin belongs to the aminoglycoside class of antibiotics. Assay procedures were investigated to determine the most suitable methods for the assay of tobramycin in blood, urine, and pharmaceutical preparations. The agar-plate assay was the method of choice for determinations in urine and serum. The turbidimetric assay was selected for the assay of pharmaceutical preparations. An extraction technique is described that minimizes problems encountered in the estimation of tobramycin in urine. Sample diluents, pH, and molarity were important and were variable depending on assay methods. Evidence is presented to show binding of tobramycin to alpha-cellulose susceptibility discs. Iron and sodium ions demonstrated potential inhibition of tobramycin in all assay methods tested.