Antibacterial potential of crude leaf extracts of Eucalyptus camaldulensis against some pathogenic bacteria

Abstract

The antibacterial activity of the crude leaf extracts of Eucalyptus camaldulensis were determined using the agar well
diffusion method against clinical isolates of Escherichia coli, Staphylococcus aureus, Salmonella typhi, Proteus
mirabilis and Klebsiella pneumoniae. At an extract concentration of 50 mg/ml, the growths of all the pathogenic
bacteria were arrested, though to varying degrees. The least activity in terms of zones of growth inhibition was
shown by aqueous extract against E. coli (7 mm), K. pneumoniae (9 mm), P. mirabilis (13 mm), S. typhi (12 mm) and
S.aureus (12 mm) while the highest was demonstrated by the acetone extract, with a recorded zone diameter for E.
coli (12 mm), K. pneumoniae (13 mm), S typhyi (14 mm), P. mirabilis (15 mm) and S. aureus (14 mm). The effects of
pH and temperature on the efficacy of the crude drug extracts were also determined. The effectiveness of the
extracts were more pronounced under alkaline conditions and lower temperatures. Minimum inhibitory
concentration (MIC) values ranged from 6.25 - 50 mg/ml and minimum bactericidal concentration (MBC) values
ranged from 6.25 - 100 mg/ml. The ability of the crude extracts to inhibit the growth of the bacteria used in this st udy
is an indication that the leaves of E. camaldulensis can be used as a source for the development and formulation of
antibacterial drugs, thus justifying the use of the leaves in herbal medicines to treat a variety of infectious
conditions.