antibiotic k 4

Antibiotic K 4 is an inhibitor of angiotensin I converting enzyme produced by Actinomadura spiculosospora.

IKD-8344 is a macrocyclic dilactone originally isolated from an actinomycete species with diverse biological activities, including anticancer, antimicrobial, and anthelmintic properties [1,2,3]. It is cytotoxic to L5178Y murine leukemia cells (IC50 = 0.54 ng ml) [1], inhibits growth of the mycelial form of C. albicans (MIC = 6.25 μg ml), and potentiates the activity of polymyxin B against the multidrug-resistant pathogenic bacterium B. cenocepacia [2,3]. Additionally, it is active against T. spiralis in vitro and in vivo [1].

Boromycin is a boron-containing macrolide antibiotic that has been found in Streptomyces. Boromycin inhibits growth of B. subtilis (MIC = 0.05 μg/ml) and induces efflux of potassium ions from B. subtilis without affecting Na+/K+-ATPase activity. It decreases the synthesis of protein, RNA, and DNA in B. subtilis when used at a concentration of 0.05 μg/ml. It inhibits the growth of B. halodurans (MIC = 10 ng/ml) and inhibits the futalosine pathway of menaquinone synthesis in B. halodurans. Boromycin (3.4 nM) reverses bleomycin-induced cell cycle arrest at the G2 phase in Jurkat cells. It inhibits replication of the HIV-1 strains LAV-1 and RF and the HIV-2 strain LAV-2 in MT-4 cells (IC50s = 0.008, 0.11, and 0.007 μM, respectively). It also inhibits replication of a clinical isolate of HIV-1, strain KK-1, in MT-4 cells and peripheral blood mononuclear cells (PBMCs; IC50s = 0.14 and <0.1 μM, respectively).

Polymyxin B2, a significant component of polymyxin B, is an antibiotic cationic lipopeptide initially derived from B. polymyxa. This compound effectively inhibits P. aeruginosa, A. baumannii, K. pneumoniae, and E. cloacae strains, exhibiting minimum inhibitory concentrations (MICs) of 1-2, 0.5-1, 0.25-0.5, and 0.25-1 µg/ml, respectively. Notably, in a mouse model of P. aeruginosa bloodstream infection, administration of polymyxin B2 at a dosage of 4 mg/kg has been shown to decrease the number of colony-forming units (CFUs) in the blood.

4-Trehalosamine, a microbial metabolite identified in Streptomyces, exhibits antibiotic properties. Demonstrating efficacy in cup assays, it is active against E. coli, K. pneumoniae, and B. subtilis at concentrations of 0.5, 1, and 2 mg/ml.

MBL-IN-3 (compound 72922413), a potent inhibitor of New Delhi metallo-β-lactamase-1 (NDM-1) with an IC50 value of 54±4 μM, effectively reduces the minimum inhibitory concentrations (MICs) of Meropenem against clinical isolates of E. coli and K. pneumoniae that express NDM-1. This compound is utilized in studies focused on antibiotic sensitizer research [1].