Toxigenic studies with the antibiotic pigments from Serratia marcescens

Prodigiosin, obtained from the bacterium, Serratia marcescens, was extracted in five organic solvents, petroleum ether, chloroform, acetone, ethanol, and methanol, and the fractions were labeled PE-1, C-2, A-3, E-4, and M-5 respectively. The effects of prodigiosin and its fractions on embryogenesis showed the whole pigment and C-2 fraction to be highly toxigenic while other fractions demonstrated toxicities approaching LD50 values of 26-30 mug/egg when dissolved in 100% dimethyl sulfoxide. The E-4 fraction in DMSO was least toxic. Ninety-five percent ethanol proved to be highly toxic at a dose level of 0.1 ml/egg indicating that it was an unsuitable solvent for studies of this nature. Disc-agar diffusion sensitivity studies were performed against E. coli, E. aerogenes, S. aureus, B. subtilis, and P. aeruginosa with prodigiosin and fractions dissolved in 100% DMSO. The solvent was found to have no diffusible bacteriostatic activity in vitro. However, prodigiosin and the ethanol (E-4) and methanol (M-5) fractions produced inhibition zones with every organism tested. Data presented below indicate that prodigiosin extracts have toxigenic effects on chick embryos and inhibit the growth of several species of bacteria.