Abstract
The development of multiple antibiotic–resistant bacteria has vastly depleted our
repertoire of effective antibiotic chemotherapies. The development of multi-β-lactam-resistant strains are particularly concerning due to our previous reliance
on this class of antibiotics because of their initial efficacy and broad-spectrum
activity. With increases in extended-spectrum β-lactam-resistance and an expanded resistance to other classes of antibiotics, there
is an urgent need for the development of effective new antibiotic therapies. Terminalia ferdinandiana is an endemic Australian plant known for its high antioxidant and tannin contents.
T. ferdinandiana fruit and leaf extracts have strong antibacterial activity against a wide variety
of bacterial pathogens. However, T. ferdinandiana extracts have not been tested against ESBL and MRSA antibiotic-resistant pathogens.
An objective of this study was to screen T. ferdinandiana fruit and leaf extracts for bacterial growth inhibitory activity by disc diffusion
assay against β-lactam-sensitive and -resistant E. coli strains and against methicillin-sensitive and -resistant S. aureus. The minimum inhibitory concentration (MIC) was quantified by liquid dilution techniques.
The fruit methanolic extract, as well as the methanolic, aqueous, and ethyl acetate
leaf extracts strongly inhibited the growth of the MRSA, with MICs as low as 223 µg/mL.
In contrast, the extracts were ineffective inhibitors of ESBL growth. Metabolomic
fingerprint analysis identified a diversity and relative abundance of tannins, flavonoids,
and terpenoids, several of which have been reported to inhibit MRSA growth in isolation.
All extracts were nontoxic in the Artemia nauplii and HDF toxicity assays, further indicating their potential for medicinal
use.
Key words
Terminalia ferdinandiana
- Combretaceae, Kakadu plum - MRSA -
β-lactamase - ESBL
