International Journal of Applied Microbiology and Biotechnology Research
ISSN: 2053-1818
Vol. 8(6), pp. 73-80, November, 2020
doi.org/10.33500/ijambr.2020.08.008

Antibacterial and antibiofilm activity of Alpinia malaccensis and Terminalia catappa extract combinations on Staphylococcus aureus and Listeria monocytogene strains

T. Somarathna^1,5, W. M. A. D. B. Fernando^2,3, K. K. D. S. Ranaweera¹, G. A. S. Premakumara⁴ and N. S. Weerakkody ⁵*

¹Department of Food Science and Technology, Faculty of Graduate Studies, University of Sri Jayewardenepura, Nugegoda, Sri Lanka.
²Centre of Excellence for Alzheimer's Disease Research and Care, School of Medical and health Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, Western Australia 6027.
³Australian Alzheimer's Research Foundation, 8 Verdun St., Nedlands WA 6009.
⁴Industrial Technology Institutes, 393, Bauddhaloka Mw, Colombo, Sri Lanka.
⁵Department of Agricultural and Plantation Engineering, Faculty of Engineering Technology, The Open University of Sri Lanka, Nawala, Sri Lanka.

*To whom correspondence should be addressed. E-mail: thikshanis@yahoo.com.

Received 06 September, 2020; Received in revised form 02 October, 2020; Accepted 07 October, 2020.

Keywords:
Antimicrobial activity, Scanning electron microscopy, Minimum inhibition concentration.

A significant antibacterial effect of Alpinia malaccensis (Ran-kiriya) against foodborne bacteria Staphylococcus aureus and Listeria monocytogenes was reported. However, the effect on biofilm formation and impact of the combination of A. malaccensis with other plant extracts on foodborne bacteria is unknown. In-vitro antibacterial and antibiofilm activity of both plant extracts were determined using micro broth dilution method and 96 well plate respectively. Antibiofilm activity was further confirmed by scanning electron microscopy (SEM). The highest antibacterial activity and biofilm inhibition effect of A. malaccensis against S. aureus and L. monocytogenes were observed at 20 mg ml^-1 when used alone. The combined plant extract of A. malaccensis (2.5 mg ml^-1) and Terminalia catappa (20 mg ml^-1) showed significant (P<0.05) synergistic antibacterial activity against S. aureus and L. monocytogenes whilst 5 mg ml^-1 of A. malaccensis with 20 mg ml^-1 of T. catappa showed the highest antibiofilm activity. The strong antibiofilm activity of A. malaccensis was further confirmed by morphological deformities of cells, release of cytoplasmic constituents and lower number of attached bacteria cells obtained in SEM analysis. The results suggest that combination of these plant extracts may provide a novel approach for the control of biofilms produced by foodborne S. aureus and L. monocytogenes. The synergistic effect of crude extracts on microbial growth and biofilm formation could be potentially developed as a natural food preservative or natural sanitizer.

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