Mechanistic studies and biological activity of bioxalomycin alpha 2, a novel antibiotic produced by Streptomyces viridodiastaticus subsp. "litoralis" LL-31F508

Abstract

The bioxalomycins, a novel complex of broad-spectrum antibiotics, were isolated from fermentations of Streptomyces viridodiastaticus subsp. "litoralis" LL-31F508. Bioxalomycin ax2, the major component of this complex, exhibited antibacterial activity. The MICs ranged from s0.002 to 0.008 ,uglml for gram-positive organisms and from 0.50 to 4 ,ug/ml for gram-negative organisms. Bioxalomycin a2 was found to be bactericidal and to inhibit bacterial DNA synthesis preferentially. Bioxalomycin a2 protected mice from a lethal challenge with Staphylococcus aureus Smith. The 50% effective dose of bioxalomycin a2 administered orally was 10 times greater than that when the drug was given subcutaneously or intravenously. These data suggest a stability or bioavailability problem when the compound is administered orally.The evolution and spread of antibiotic-resistant pathogens remain major clinical problems (15). Although the discovery of new antimicrobial agents has become increasingly more difficult, the search for unique metabolites from microorganisms remains an attractive venture (2, 13).

Saccharomicins, Novel Heptadecaglycoside Antibiotics Produced by Saccharothrix espanaensis : Antibacterial and Mechanistic Activities

“…Macromolecular synthesis in E. coli imp and B. subtilis was studied by measuring the incorporation of appropriate radiolabeled precursors into trichloroacetic acid (TCA)-precipitable material (14). Overnight cultures were diluted 1:500 in fresh modified minimal medium (50 ml of medium in a 250-ml Erlenmeyer flask) and incubated at 37°C and 200 rpm to an A 600 of 0.20.…”

“…The in vitro antibacterial activities were determined by agar or microdilution methods as described earlier (9,14). MH II broth or agar was used for nonfastidious aerobic bacteria, and the medium was supplemented with 5% lysed horse blood for Streptococcus spp.…”

Distinguishing On-Target versus Off-Target Activity in Early Antibacterial Drug Discovery Using a Macromolecular Synthesis Assay

“…Although highly valuable in determining the MOA of newly identified natural products or as part of antimicrobial drug discovery efforts, some of the protocols used long incubation times, resulting in the observation of secondary effects that are not due to the initial target-dependent events. 7 This is exemplified by the observation that daptomycin inhibits all four molecular pathways at time points greater than 40 min. 15 The use of cells that are not growing logarithmically or adapted to the test media or the use of a single test concentration at large multiples above the MIC can also result in artifacts.…”

“…3 Incorporation was sometimes measured over long incubation times (1-2 h), where secondary effects of the antimicrobial agent could confound the results. 6,7 Microplate formats were later developed to aid in assay throughput. 7 The E. coli imp (increased membrane permeability) strain, which contains a mutation in an outer membrane protein, has been used in these assays since the strain is more susceptible to a wide range of antimicrobial compounds, enabling assessment of compounds that typically do not permeate Gram-negative bacteria.…”

Identification and Analysis of Bacterial Protein Secretion Inhibitors Utilizing a SecA-LacZ Reporter Fusion System

“…Macromolecular synthesis by E. coli imp was studied by measuring the incorporation of the appropriate radiolabeled precursors into TCA-precipitable material (40). An E. coli strain carrying an imp mutation was grown at 37°C to an OD 600 (10-mm path length) of 0.2 in modified minimal medium.…”