Seven novel antibiotic substances can be produced by cultivation of a microbial strain which has been isolated from a soil sample and which is designated as Microbispora sp. A 34030 (deposited under an access number FERM BP-10505 in terms of Budapest Treaty). These seven antibiotic substances are named as bispolide A1, bispolide A2, bispolide A3, bispolide B1, bispolide B2a, bispolide B2b and bispolide B3, respectively. These bispolides are each novel compounds which have a chemical structure as collectively represented by the general formula (III) shown below:These bispolides have each a high antibacterial activity against a variety of bacteria, particularly Gram-positive bacteria and their antibiotic-resistant strains, and hence these bispolides each are effective and useful for therapeutically treating bacterial infections of Gram-positive bacteria in humans and animals.
