Aminoglycoside antibiotic 66-40G is a minor component produced in the fermentation of Micromonospora inyoensis. Its structure has been established as 3''-de-N-methyl-sisomicin (4) by spectroscopic means and by direct comparison with an authentic sample obtained from photochemical oxidative de-N-methylation of sisomicin (1).
Three new antibiotics, tridecaptins A, B and C, were isolated from culture broths of strains of Bacillus polymyxa AR-110, B-2 and E-23, respectively. All are acyl tridecapeptides differing from each other in the fatty acid components and amino acid residues. They are weakly active against Gram-negative and Gram-positive bacteria in vitro and in vivo.
On examining the structure of the antibiotic tridecaptin A, the constituent amino acids were determined to be: 2, 4-diaminobutyric acid(2D, 1L), Ser(1D, 1L), Glu(1L), Gly(1), Ala(1L), Val(1D, 1L), aIle(1D), Phe(1L) and Trp(1D). The constituent fatty acid was identified as β- hydroxy anteisononanoic acid by gas chromatography and mass spectrometry. Cleavage reaction with N-bromosuccinimide, sequential analysis by EDMAN degradation, partial acid hydrolysis and some additional evidences clarified the structure of tridecaptin A.
Conventional strain and media improvement techniques were of limited success in increasing yields of the antibiotic aurodox (X-5108) above 0.5 g/liter. Higher yields were obtained by reversion of a zero producer followed by the selection of mutants resistant to aurodox. Resistant strains of Streptomyces goldiniensis ATCC 21386 able to grow on 2 g/liter of Aurodox produced greater than 2.5 g/liter of antibiotic. The rate of yield increase leveled off as the strains became resistant to greater than 2 g/liter of aurodox. These strains, in contrast to those sensitive to aurodox, gave a positive response to conventional mutagenic methods for further yield increases.
The antitumor activity of tallysomycins A and B was determined in five experimental tumor systems in mice. Tallysomycins A and B were highly active against B16 melanoma, sarcoma 180 ascites tumor and LEWIS lung carcinoma, and moderately active against P388 leukemia but were without effect on lymphoid leukemia L1210. The antitumor activity of tallysomycin A was 2-3 times that of tallysomycin B and 3-17 times that of bleomycin. Tallysomycin A was about 1.5 and 4 times more toxic for mice than tallysomycin B and bleomycin, respectively, in terms of subacute LD50 values.
Four N-ethyl derivatives of kanamycin A and five N-ethyl derivatives of kanamycin B were synthesized. The antimicrobial activity of N-ethyl kanamycin derivatives was determined against aminoglycoside-sensitive and resistant organisms. The structure-activity relationship of these compounds is discussed with reference to the activity of N-acyl kanamycin derivatives.
The syntheses of 1-N-(S-4-amino-2-hydroxybutyryl)-gentamicin B and 1-N-(S-3-amino-2-hydroxypropionyl)-gentamicin B, designated Sch 20287 and Sch 21420, respectively, by procedures similar to those developed by KAWAGUCHI and co-workers for the transformation of kanamycin A to amikacin are described. The in vitro microbiological properties of Sch 20287 and Sch 21420 are compared with amikacin, gentamicin and tobramycin.
Sch 21420, the 1-N-HAPA derivative of gentamicin B, has been compared to gentamicin, tobramycin and amikacin in a variety of in vitro and in vivo tests. Based on studies with a large number of sensitive and resistant bacteria, it was shown that Sch 21420 has a spectrum and potency essentially the same as that of amikacin. Serum levels in mice, rats, and dogs are similar to those of other aminoglycosides. Sch 21420 was found to be markedly less toxic than amikacin in chronic renal function tests in rats and thus appears to have an advantageously improved therapeutic index compared to amikacin.
The activity against Escherichia coli of a new oral cephalosporin (manufacturer's code: CGP 9000) has been evaluated in vitro. The intrinsic lytic activity of the new compound was greater than that of cephalexin, but less than that of cephalothin. As judged by regrowth studies using ampicillin resistant E. coli strains, the β-lactamase stability of the new cephalosporin was somewhat less than that of cephalexin. When tested in an in vitro model in conditions simulating those of the treatment of bacterial cystitis, cephalosporin CGP 9000 suppressed growth of an ampicillin sensitive E. coli strain for a therapeutically acceptable period of time, but exhibited reduced activity against an ampicillin resistant E. coli strain.
Intramuscularly injected 14C-SCE-963 was absorbed by rats to give a maximum plasma level at 10-15 minutes after dosing and an apparent half-life of 25 minutes. In this species, the plasma half-life after intravenous injection was 27 minutes. Intramuscular injection of the labeled antibiotic to dogs gave a peak plasma level at 30 minutes, followed by decay with a half-life of 53 minutes. In both rats and dogs, the plasma levels of radioactivity were essentially the same as those of the unchanged antibiotic, which was moderately bound to plasma protein. 14C-SCE-963 was hardly taken up by the erythrocytes of these animals. After intramuscular administration of 14C-SCE-963 to rats, the tissue level of radioactivity was maximum at 15 minutes with the highest concentration in the kidney, followed by liver, plasma, intestine and lung, and the lowest in brain. Whole-body autoradiography of pregnant rats showed that 14C-SCE-963 scarcely crossed the placenta. In both rats and dogs, larger amounts of the dosed radioactivity was excreted in urine as the unchanged antibiotic, the remainder appearing in feces via bile. This finding indicated that the metabolism of SCE-963 was only a minor process in the elimination of the antibiotic. 14C-SCE-963 was almost completely eliminated from the body of both animals within 24-48 hours. Radioactivity was detected in the milk of rats given 14C-SCE-963 intramuscularly.
[14C]Bicyclomycin was observed to bind to several inner membrane proteins of E. coli, but not to outer membrane proteins. In SDS polyacrylamide (12.5%) slab gel electrophoresis, 4 major bands and 3 minor bands of binding proteins were demonstrated. Benzylpenicillin showed no competition with bicyclomycin for bicyclomycin-binding proteins (BBPs), and bicyclomycin no competition with penicillin for penicillin-binding proteins (PBPs). The absence of competition and the difference of mobilities of BBPs and PBPs suggested that BBPs differ from PBPs. The molecular weights of BBPs were estimated in comparison with PBPs on slab gel electrophoresis: BBP-1 ca. 93, 000, BBP-2 72, 000, BBP-3 53, 000, BBP-4 46, 000, BBP-5 41, 000, BBP-6 30, 000, and BBP-7 27, 000. The binding to all the proteins seemed to be irreversible in that the antibiotic was not released from the proteins during a 3-hour incubation. From the kinetics of binding it is likely that the binding is a simple bimolecular irreversible reaction. At saturation, 8 pmoles of [14C]bicyclomycin were bound to 1 mg (dry weight) of E. coli, i.e. 2, 400 molecules per cell. An estimate of the number of molecules of each BBP per cell was calculated from measurements of the amount of bicyclomycin bound per cell and the relative proportions of the antibiotic bound to each protein. The results indicated that, besides PBPs, there exist(s) inner membrane protein(s) participating in cell division.
The relationship between the in vitro antibacterial activity of carbenicillin in the presence of leukocytes and the therapeutic efficacy of the antibiotic against experimental infection in animals was investigated. Proteus mirabilis strains 3 and 60 were selected as the test strains. The susceptibility of these strains to carbenicillin was similar in the conventional broth medium, but differed in the presence of rabbit polymorphonuclear leukocytes or defibrinated rabbit blood; the antibiotic-susceptibility of strain 60 increased with blood components, whereas that of strain 3 did not change greatly. Bacterial cells of these strains, which had been treated with carbenicillin at a concentration of 200μg/ml, were injected intraperitoneally in mice and the viable cells which invaded the blood stream were counted at regular intervals. The results showed that the invasiveness of strain 60 from the peritoneal cavity into the blood stream was more strongly inhibited by carbenicillin-pretreatment than that of strain 3. When rabbits were given a single intramuscular dose of 20 mg carbenicillin/kg body weight immediately after intravenous challenge with strains 3 and 60, strain 60 disappeared from the blood stream more rapidly than strain 3. These results suggest that the in vitro antimicrobial activity of antibiotics should be evaluated not only in conventional medium but in the presence of body fluids such as serum, blood andleukocytes.