Isolation of Actinomycetes and determination of their antibacterial activity against Eberthella Typhosa and Staphylococcus Aureus

Abstract

In the survey on the distribution of antibiotic properties among actinomycetes twenty-three strains were isolated from different sources in Lebanon, and one was received from abroad. All these were tested for antibacterial activity against Staphylococcus aureus and Eberthella typhosa. These strains varied greatly in their antibacterial activity. Nineteen were found to be bacteriostatic or bacteriolytic in varying degree to staph . aureus, but only three proved definitely bacteriostatic to E. typhosa, ff which two were also partially bacteriolytic. The micro-organisms were not fastidious but grew fairly well on all the media prepared for the production of antibiotics. The influence of the composition of the medium upon the production of the active agents by actinomycetes seems to be of major importance. The original soybean meal medium proved to be the best throughout the experiments. Noticeable improvement was obtained with this medium by buffering it. The different cultures of actinomycetes differed in their capacity to produce an antibiotic substance. The bacteriolytic and bacteriostatic activity of five to seven-day old actinomycetins were studied by the liquid medium as well as the agar media methods, using in every case 24hrs fresh suspension of E. typhosa and Staph. auratus. Of the strains tested, some proved completely inactive, others gave fairly good results and one proved particularly active. The bacteriolytic actinomycetes were found to be more numerous among the bacteriostatically active groups. The independence of bacteriolytic ability seems to be somehow improbable in most cases. Evidence is presented that antibacterial activities observed are not due to depletion of nutrients, prolonged incubation periods, nor to changes in pH. Most active substances were soluble in water and diffusable through agar. It is also believed that failure of some potentially active actinomycete cultures to respond positively to the plate tests is due to the ~w degree of their diffusibility. Finally, the conclusion given states the fact, that, although bacteriostatic and bacteriolytic properties are widespread among the actinomycetes, the production of soluble active principles in sufficient quantity appears to be less widely distributed.