apidaecin-ib and 5-bromo-4-chloro-3-indolyl-beta-galactoside

A solid agar plate assay was devised to discriminate bacteriolytic from bacteriostatic activity for a given antibacterial agent. The assay uses a bacterial culture harboring beta-galactosidase enzyme as reporter of cellular lysis. When a drop of bacteriolytic compound is placed on the agar, beta-galactosidase is released from the bacteria to the external solid medium where it hydrolyzes X-Gal substrate analogue, developing a blue halo at the edge of the inhibition growth zone. The assay was successfully evaluated against several antibiotics with well-known mechanism of action. It was found that bacteriostatic compounds consistently did not display blue halo at the inhibition zone.

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Bacteriolysis; beta-Galactosidase; Chromogenic Compounds; Enterobacteriaceae; Erythromycin; Galactosides; Hydrolysis; Indoles; Isopropyl Thiogalactoside; Microbial Sensitivity Tests; Penicillins; Peptides; Reproducibility of Results; Tetracycline