Screening of herbal extracts against multi-drug resistant Acinetobacter baumannii.
Antibiotic resistance is increasing resulting in a decreasing number of fully active antimicrobial agents available to treat infections with multi-drug resistant (MDR) bacteria. Herbal medicines may offer alternative treatment options. A direct inoculation method simulating the standard disc diffusion assay was developed to determine in vitro antimicrobial activity of sixty herbal extracts against MDR-Acinetobacter baumannii (A. baumannii). Eighteen herbal extracts inhibited MDR-A. baumannii on agar plates, although the magnitude and quality of bacterial inhibition differed considerably among the antibacterial herbal extracts. Next, minimal inhibitory concentration (MIC) of these antibacterial herbal extracts was calculated using a broth microdilution assay. For most herbal extracts, the larger the zone of inhibition on agar plates, the lower the MIC. In general, hetero-resistance on agar plates correlated with higher MIC. The skip well phenomenon was seen with two herbal extracts. In conclusion, 30% of the screened herbal extracts demonstrated in vitro antibacterial activity against MDR-A. baumannii using similar rigorous testing methods as those commonly employed for assessing antimicrobial activity of synthetic antibacterial agents. Characterization of a specific compound conferring this antibacterial activity of the herbal extracts may help to identify novel antimicrobial agents active against highly resistant bacteria.
Miyasaki
Yoko
Y
Cedars-Sinai Medical Center, Los Angeles, California, USA. yoko.miyasaki@cshs.org
Nichols
W Stephen
WS
Morgan
Margie A
MA
Kwan
Jamie A
JA
Van Benschoten
M M
MM
Kittell
Patricia Emmett
PE
Hardy
W David
WD
D040981:Acinetobacter baumannii / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D010936:Plant Extracts