In vitro antibacterial activity of panduratin A against enterococci clinical isolates.

Panduratin A, a natural chalcone compound isolated from the rhizome of fingerroot (Boesenbergia rotunda (L.) MANSF. A). The antibacterial activity of panduratin A against clinical enterococci isolates was compared in terms of minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) to those of commonly used antimicrobials, according to the CLSI guidelines. Time-kill curves were constructed to assess the concentration between MIC and bactericidal activity of panduratin A at concentrations ranging from 0x MIC to 4x MIC. The activity of panduratin A against biofilm-producing enterococcal strains was also evaluated. The growth of all clinical enterococci isolates (n=23) were inhibited by panduratin A at a concentration of 2 microg/ml. Panduratin A was able to kill all clinical enterococci isolates with a MBC of 8 microg/ml. The time-kill curves demonstrated that the bactericidal endpoint for clinical enterococci was reached after 30 min of incubation at a panduratin A concentration of 4x MIC. The growth of biofilm-producing enterococcal strains can be inhibited and eradicated by panduratin A at concentrations of <or=4 microg/ml and <or=16 microg/ml, respectively. The antibacterial activity of panduratin A against all clinical enterococci isolates was generally more potent than commonly used antimicrobials. Panduratin A has stronger activity against biofilm-producing enterococcal strains than daptomycin and linezolid. Panduratin A is an antimicrobial agent with high in vitro activity against clinical enterococci, including organisms resistant to other antimicrobials.