Inhibition of exoprotease production in Aeromonas hydrophila by rhizome extract of temu lawak (Curcuma xanthorrhiza (Roxb.)

Abstract

Abstract. Conventional treatment of infectious diseases is based on compounds that kill or inhibit the growth of bacteria. A major concern with this approach is the systematic development of resistance to antimicrobial compounds. The discovery of communication (quorum sensing system) regulating bacterial virulence opens up ways to control specific bacterial infectious without interfering with the growth. The fish pathogen Aeromonas hydrophila produces a quorum-sensing signal, N-Butanoyl-L-Homoserine Lactone (C4-HSL). C4-HSL regulates exoprotease synthesis, a virulence factor of A. hydrophila. Expression of exoprotease can be blocked by using a quorum sensing inhibitor. The purpose of this study was to investigate the inhibiting effect of Curcuma xanthorrhiza (Roxb.) extract on exoprotease production of A. hydrophila. Extraction was conducted by using n-hexane, ethyl acetate, and ethanol. The qualitative exoprotease assay result showed that n-hexane extract of C. xanthorrhiza did not affect the growth and exoprotease production of A. hydrophila.
Meanwhile, 4% of ethyl acetate and ethanol extract of C. xanthorrhiza could inhibit exoprotease production without affecting A. hydrophilla growth. The quantitative exoprotease assay result showed that 4% of ethyl acetate and ethanol extract could inhibit the exoprotease production by 93,9% and 95,6%. The growth of A. hydrophila was not affected by this extract.