title: Evaluation of antimicrobial activity of the endophytic actinomycete R18(6) against multiresistant Gram-negative bacteria.
abstract: Endophytic actinomycetes are promising sources of antimicrobial substances. This study evaluates the activity of metabolites produced by the endophytic actinomycete R18(6) against Gram-negative bacteria multiresistant to antimicrobials. R18(6) isolate was grown in submerged cultures under different conditions: carbon source, temperature, pH and incubation time to optimize antimicrobials production. The actinomycete grown in base medium supplemented with 1% glucose, pH 6.5 and incubation at 30 ºC for 96 h with shaking at 100 rpm, exhibited the highest activity against the used Gram-negative bacteria. Minimum inhibitory concentration (MIC) of the crude extract produced by the microorganism varied between 1/32 and 1/256. It had bactericide or bacteriostatic activity, depending on the Gram-negative organism. The active extract was stable at high temperatures, and unstable in medium containing proteolytic enzymes. Micromorphology of R18(6) was investigated by optical and scan microscopy, revealing that it was morphologically similar to the genusStreptomyces.
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Tiele
authors.initials: T
authors.lastname: Carvalho
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
authors.forename: Sueli
authors.initials: S
authors.lastname: Van Der Sand
mesh_terms: D039903:Actinobacteria / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D006090:Gram-Negative Bacteria / Q000145:classification / Q000187:drug effects*; D008826:Microbial Sensitivity Tests
chemical_list: D000900:Anti-Bacterial Agents