Chemical and biological investigation of Eucalyptus cloeziana, E. citriodora, E. saligna, E. grandis and E. microcorys essential oils were evaluated. The essential oils analysis were performed by GC/MS and the antibacterial activity was assayed in vitro by using the agar diffusion method against Escherichia coli O:158, E. coli ATCC 8739, Staphylococcus aureus ATCC 6538 and Salmonella choleraeseus ATCC 10708. The essential oils of E. citriodora and E. grandis showed a major inhibitory activity against Gran negative bacteria.Keywords: Eucalyptus species; essential oils; antibacterial activity. INTRODUÇÃOEm diversas partes do mundo, várias espécies de Eucalyptus vêm sendo cultivados e explorados em grande escala há muitos anos. No Brasil, ele é encontrado em todas as regiões, sendo conhecidas cerca de 400 espécies, das quais são utilizadas desde o caule, de onde se extrai a celulose para a indústria do papel, até as folhas, de onde são retirados os óleos essenciais de diferentes composições químicas.Revista Brasileira de Farmacognosia, V. 11, n. 2, p. 95-100, 2001.

Escherichia coli is a Gram-negative bacterium present in gastrointestinal disorders and is responsible for causing several symptoms, being diarrhea or more common, due to the production of enterotoxins. Note that E. coli strains are becoming resistant due to the use of antimicrobials. Through the search for therapies, medicinal plants have been a source of new research and studies, enabling technical methods in practice. Thus, the objective was to evaluate the antimicrobial and modulatory effect of the ethanol extract of the medicinal plant Achyrocline satureioides against E. coli serotypes. The inflorescences of A. satureioides were collected in March 2019 and, after obtaining the extract, the Minimum Inhibitory Concentration (MIC) assay was performed, and its antibiotic and synergistic activity was evaluated by microdilution. After analyzing the data, it was found that the extract in its form obtained a result of CMI ≥1024μg / mL. A synergistic effect of the extracts was observed when combined with amikacin in the EPEC and ETEC serotypes, as well as with gentamicin in the ETEC serotype. In the other analyzes there was no synergistic or antagonistic effect. The ethanol extract of A. satureioides inflorescences in association with aminoglycosides showed a synergistic effect as tested lines, proving a tendency to the antimicrobial effect, therefore, it is shown that an association of the tested antibiotics increased the antimicrobial potential. Further research will be important for further certification that this is an alternative method in the treatment of gastrointestinal diseases.