| abstract |
A compound having the general formula <IMAGE> in which Dab is diaminobutyric acid; A is either leucine, threonine, isoleucine or phenylalanine; B is either leucine or threonine; D is either D-leucine or D-phenylalanine; and C is a substituent selected from the group comprising -Dab-Thr, -Dab-Thr-Dab, -Dab, -Dab-Thr-Acyl and H, in which Thr is threonine, Acyl is a lower acyl group of 1 to 5 carbon atoms and Dab is as defined above. These compounds are useful in sensitizing Gram-negative bacteria to antibacterial agents and to the host defence mechanism complement when subjecting said Gram-negative bacteria to the action of said compounds. The invention also provides a pharmaceutical composition for use in sensitizing Gram-negative bacteria to antibacterial agents, complement or both, comprising a therapeutically effective amount of said compound in admixture with a pharmaceutically acceptable carrier. Polymyxin B nonapeptide having the formula: <IMAGE> is produced by treating polymyxin B with ficin, papain or bromelin. |