Antibacterial Potentials of Three Common Spices against Selected Pathogens

Abstract

Humans are generally most interested in the species of pathogenic bacteria which can cause disease in humans. The antibacterial activities of n-hexane, dichloromethane and methanol extracts of Curcuma longa Linn. (Turmeric) rhizome, Myristica fragrans Houtt. (nutmeg) and Zingiber officinale Rosc. (Ginger) rhizome were evaluated against Staphylococcus aureus ATCC 26923, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25522, Enterococcus faecalis ATCC 29212, S. aureus ATCC 25923, Methicillin-Resistance-Staphylococcus aureus, Klebsiella pneumoniae ATCC 35657 and Serratia marcescens. Inhibition test was carried out using the agar dilution techniques while the minimum inhibitory concentration (MIC) was determined by the agar well diffusion method. Susceptibility testing at 20 mg/mL and 100mg/mL revealed the highest inhibitory activity by methanol extracts of Curcuma longa and Myristica fragrans with diameter of zone of inhibition between 16±0.0 mm and 27±0.0 mm, the most active been Myristica fragrans on E. faecalis ATCC 29212. The MIC and MBC were lowest (12.5 mg/mL) in the methanol extract of Myristica fragrans. Methanol extract of Myristica fragrans had better bactericidal activity on Staphylococcus aureus ATCC 26923 affording  88 %, 95 % and 97 % reduction in population at concentrations equivalent to MIC, 2 x MIC and 4 x MIC respectively at 4 hours exposure time followed by a total (100 %) kill of the population after 8 hours of exposure. The results of the study emphasize these spices as having antibacterial activity on some pathogenic bacteria isolated from human samples and their usefulness in the treatment of infections associated with the test pathogens.

Keywords: Curcuma longa (Linn.), Myristica fragrans (Houtt.), Zingiber officinale (Rosc), pathogenic bacteria, phytochemical screening, antibacterial activities, in-vitro study