In Vitro Antibacterial Activity of Panduratin A against Enterococci Clinical Isolates

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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 0× MIC to 4× 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 μg/ml. Panduratin A was able to kill all clinical enterococci isolates with a MBC of 8 μg/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 4× MIC. The growth of biofilm-producing enterococcal strains can be inhibited and eradicated by panduratin A at concentrations of ≤4 μg/ml and ≤16 μg/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.