The extracts of Eucalyptus camaldulensis Dehnh. and Eucalyptus torelliana F. Muell. (Myrtaceae) were screened against four non-tuberculous mycobacteria species:Mycobacterium fortuitum ATCC 684, Mycobacterium smegmatis ATCC 19420,Mycobacterium phlei ATCC 19240 and Mycobacterium abscessus. The agar diffusion method was used to investigate the activity of these plants at 1 and 2 mg/ml concentration. The methanol extracts exhibited the highest activity against the test organisms, the most susceptible being M. fortuitum ATCC 684. The minimum inhibitory concentration (MIC) value for the bioactive extracts ranged between 1 to 2 mg/ml while minimum bactericidal concentration (MBC) value was 2 to 4 mg/ml. Bactericidal activity of the methanol extracts of E. camaldulensis on M. fortuitum ATCC 684 was investigated using the viable counting technique. The leaf extracts at 4 mg/ml (4 × MIC) and 8 mg/ml (8 × MIC) gave 80.49 and 100% kill of the organism respectively at 24 h exposure time while the stem bark extracts at the same concentrations afforded 67.35 and 100% kill respectively after 24 h of exposure. The activities demonstrated by these plants support their use in the treatment of cough associated with most pulmonary diseases; and suggest that these plants may be of therapeutic importance for the treatment of infections caused by the non-tuberculous mycobacteria (NTM).
Key words: Eucalyptus camaldulensis Dehnh., Eucalyptus torelliana F. Muell., non- tuberculous mycobacteria, antimycobacterial activity, in vitro.
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