In vitro antibacterial activity of panduratin A and its derivatives against vancomycin-resistant Entercoccus faecium clinical isolates

Abstract

Discovery and development of antibiotics against vancomycin-resistant E. faecium (VREfm) is of high priority. The aim of this study was to investigate the therapeutic potential of panduratin A, a bioactive compound isolated from Boesenbergia rotunda, due to its antibacterial activity against Thai clinical isolates of VREfm. Susceptibility testing of panduratin A using a microbroth dilution method revealed a minimum inhibitory concentration (MIC) of 2 μg/ml against all 39 VREfm isolates tested. The antibacterial effect of panduratin A was bacteriostatic in most isolates. The time-kill data revealed that panduratin A at 1×MIC inhibited bacterial growth for at least 24 h. The inhibitory effect was more pronounced compared with 1×MIC linezolid, a standard antibiotic for VREfm treatment. All VREfm isolates from this study exhibited vanA-type resistance supporting a crucial role of this type of vancomycin resistance in Thailand. Additionally, the antibacterial activity of the modified chemical structure of panduratin A reveals that a modification of the hydroxyl group(s) of panduratin A structure by either mono- or bis-alkylation abolished the antibacterial activity against VREfm. The present study reveals a potential use for panduratin A in the treatment of, at the least, vanA positive VREfm infection.