Antimicrobial activity of nine extracts of Sechium edule (Jacq.) Swartz

Abstract

The antimicrobial properties of Sechium edule (Jacq) Swartz alcoholic extracts obtained according to the Farmacopea Argentina (6th edn) were tested against bacteria of clinical relevance as nosocomial pathogens. To evaluate antibacterial activity, the disc diffusion assay was carried out with several gram-positive bacteria (Enterococcus faecalis, Staphylococcus aureus, coagulase-negative staphylococci, Streptococcus pyogenes, Streptococcus agalactiae, Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212). This assay was suitable for the screening of a large number of extracts at one time. All ethanolic extracts showed activity against gram-positive bacteria. Minimal inhibitory concentration (MIC) values were determined with a microdilution assay. The highest activity was obtained with the 80% aqueous-ethanolic leaf extract (MIC values of 4.16-8.32 μg/ml against staphylococci and enterococci) and with the 96% ethanolic seed extract (MIC values of 8.32-16.64 μg/ml and > 8.32 μg/ml against staphylococci and enterococci, respectively). The results indicate that both fluid extract and tincture have very good antimicrobial efficacy against all strains of multiresistant staphylococci and enterococci. In this study the minimal bactericidal concentration (MBC) values were identical to the MIC values or twofold higher than the corresponding MIC. This may indicate a bactericidal effect. Stored extracts have similar anti-staphylococcal and anti-enterococcal activity to recently obtained extracts. The results obtained might be considered sufficient to warrant further studies aimed at isolation and identification of the active principle.