Efecto antibiótico de cepas silvestres de Streptomyces aisladas de suelos chilenos / Antimicrobial effect of wild Streptomyces strains isolated from chilean soils

RESUMO

Background: the solts of the southern part of Chile, that are isolated, cold, humid, poorly axygenated and with a low acitity, could contain new strains of antimicrobial producing Streptomyces strains with antimicrobial activity towards pathogenic bacteria and fungi. Material and methods: two hundred fifty eight soil and sediment samples were collected from 148 paces in Souther regions of Chile. They were cultured in Kuster-Williams growth media and the presence of Streptomyces was confirmed by microscopic examination and biochemical characterization. The antimicrobial activity against reference microorganisms. Results: Seventy seven percent of soils were positive and 542 wild strains of Streptomyces were isolates; of these, 266 had antimicrobial activity. Fifty three percent of isolates had activity against S aureus 43 percent against B subtilis and 0.7 percent against E coli. Most Streptomyces were active against more than one organism. When there was activity against single organisms, these were mostly eucariotic, such as C albicans and T mentagrophytes. Among clinical microorganisms, 29 percent of S aureus strains were inhibited, while P aeruginosa, Alternaria sp, P vulgaris and Y enterocolitica strains were not inhibited. The most frequent Streptomyces morphotypes were those showing pigmented colonies with flexuous and spiral shaped chains of arthopores. Conclusions: soils of the southern region Chile allow the grouth of abundant native strains of Streptomyces with a promising anticrobial activity