Time kill assay and bactericidal mechanism of action of ethanolic flowers extract of Sphaeranthus indicus

Abstract

The purpose of the study was to identify the bactericidal mechanism of action and time kill assay of a medicinal plant Sphaeranthus indicus Linn against some highly resistant Gram positive and Gram negative clinical pathogens. Antimicrobial action of this plant was compared with four different antibiotics using disk diffusion method. The MIC and MBC of extract was measured by broth dilution method. The bacterial killing mechanism of extract was examined using SEM technique. It was observed that the zones of inhibition produced by the plant extract were higher than that of some well-reputed antibiotics. The values of MIC and MBC indicated that the extract had strong inhibitory and bactericidal activity against tested isolates. The plant extract achieved a more drop in growth profile of S. pneumonia, S. typhi, E. coli, and P. aeruginosa within 20 mins. After 12 h exposure with extract, the SEM images of S. pneumonia showed destruction of cell membrane and cells were completely lysed. It is concluded that ethanolic flowers extract of S. indicus have promising bactericidal potential at very low concentration. Its time killing was extremely faster especially against S. pneumonia. Its flowers extract produced bactericidal action through a cell membrane disruption of bacteria.