Periódicos Brasileiros em Medicina Veterinária e Zootecnia

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In vitro evaluation of antimicrobial activities of Eugenia caryophyllata and Origanum vulgare against avian Escherichia coli isolates

Sesterhenn, RenataCosta, Eduardo FreitasBergmann, Guiomar PedroAvancini, César Augusto MarchionattiSainz, Roberto DanielVieira, Sergio LuizKindlein, Liris

Background: The use of conventional antibiotics to prevent this infection is a usual in the poultry industry, specially to reduce the mortality associated with colibacillosis. Essential oils have demonstrated broad spectrums in terms of antimicrobial activities against various pathogens, Escherichia coli among them. The aim of this study was to evaluate the in vitro susceptibility of avian E. coli strains to Eugenia caryophyllata (clove) and Origanum vulgare (oregano) essential oils, at three different concentrations (2, 5, and 8%), and to the conventional antimicrobials, gentamicin and nalidixic acid.Materials, Methods & Results: Seventeen strains of Escherichia coli isolated from broiler bedding were tested and a standard E. coli strain (ATCC 25922) was used as a susceptibility test control. The antimicrobial activity of plant extracts from Eugenia caryophyllata and Origanum vulgare, obtained commercially from Laszlo Aromatologia Ltda., was tested in three concentrations (2, 5 and 8%) using the method of disk diffusion on agar according to the M2 - A8 protocol (CLSI, 2003) adapted to plant extracts and to the conventional antimicrobials gentamicin (10 µg) and nalidixic acid (30 µg), commercially obtained from Oxoid. The results showed that the extract from Origanum vulgare had an inhibitory activity on E. coli regardless of its concentration whereas the extract from Eugenia caryophyllata showed antimicrobial activity in 29.4% (5/17) of the isolated strains only at the concentration of 8%. All avian isolates were sensitive to gentamicin (100% of the strains tested); however, only 23.5% (4/17) of the samples were sensitive to nalidixic acid. Discussion: The impressive antimicrobial activity of the Origanum vulgare against E. coli avian origin was confirmed in previous studies against both Gram-positive and Gram-negative bacteria. The essential oil of Origanum vulgare was more antimicrobial activity that Eugenia caryophyllata.[...](AU)

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