Mannopeptimycin δ rapidly inhibited N-acetylglucosamine incorporation into peptidoglycan in Bacillus subtilis and had no effect on DNA, RNA, or protein biosynthesis. aureus and caused spheroplasting of Escherichia coli imp similar to that observed with penicillin G in an osmotically protective medium. The mannopeptimycins were inactive against cell wall-deficient S. The median effective doses of mannopeptimycins γ, δ, and ɛ were 3.8, 2.6, and 0.59 mg/kg of body weight, respectively. The in vivo efficacies of the mannopeptimycins in Staphylococcus aureus mouse protection studies paralleled their in vitro activities. Mannopeptimycins α and β, which lack the isovaleryl substitution and the disaccharide moiety, respectively, had poor antibacterial activities. Mannopeptimycin ɛ was the most active component against methicillin-resistant staphylococci and vancomycin-resistant enterococci (MICs, 2 to 4 μg/ml for staphylococci and streptococci and 4 to 32 μg/ml for enterococci), while mannopeptimycins γ and δ were two- to fourfold less active. Mannopeptimycins γ, δ, and ɛ, which have an isovaleryl substitution at various positions on the terminal mannose of the disaccharide moiety, demonstrated moderate to good antibacterial activities. Mannopeptimycins α, β, γ, δ, and ɛ are new cyclic glycopeptide antibiotics produced by Streptomyces hygroscopicus LL-AC98.
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