Abstract
Background: Medicinal plants have now attracted more attention due to their antibacterial activity and also increasing antibiotic resistance among bacteria. Native plants of each region are potential resources for this purpose. Objectives: The aim of the present study was to detect the antibacterial effect of Eucalyptus microtheca (Myrtaceae family) which is currently used as an antibacterial fumigation medicine. Materials and Methods: Using standard disk diffusion method, the antibacterial activity, MIC, and MBC indexes of alcoholic extracts from this plant were tested on some pathogenic bacteria. The structural changes following the exposure to these extracts were also investigated in test bacteria. Results: Significant antibacterial activity was found against gram-positive and gram-negative bacteria, which among them, Escherichia. coli and Pseudomonas. aeruginosa showed the most sensitivity and Staphylococcus. aureus the least. The value of MIC and MBC for both extracts was 8 mg/mL for E. coli, while they were 8 mg/mL and 16 mg/mL for Bacillus cereus, respectively. Both MIC and MBC values of methanolic and ethanolic extracts against P. aeruginosa were 8 and 16 mg/mL respectively. SEM revealed structural changes in the affected bacteria that suggest the cell wall was the main target site of active constituents. Conclusions: It can be concluded that this plant has potential application in infection control, especially against E. coli and P. aeruginosa and regarding their recent reported epidemic, this plant can be a good choice for antibiotic discovery.
Highlights
Medicinal plants have attracted more attention due to their antibacterial activity and increasing antibiotic resistance among bacteria
The maximum effect was observed against E. coli for both ethanolic and methanolic extracts and P. aeruginosa for methanolic extract while the least effect was seen against S. aureus in the case of ethanolic extract even at 24 mg effective dose
There was no significant difference between antibacterial activities of ethanolic and methanolic on tested microorganisms except in the case of P. aeruginosa that methanolic extract was more effective than the ethanolic extract
Summary
Medicinal plants have attracted more attention due to their antibacterial activity and increasing antibiotic resistance among bacteria. Materials and Methods: Using standard disk diffusion method, the antibacterial activity, MIC, and MBC indexes of alcoholic extracts from this plant were tested on some pathogenic bacteria. One of the suitable choices for this purpose is medicinal aromatic plants like Eucalyptus, which is an important source of chemical substances with potential therapeutic effects [1]. Eucalyptus species is famous for its rapid growth; some members of this species attain gigantic sizes and are among the tallest trees in the world with 20 to m high [7] It is indigenous in Australia, Tasmania, New Guinea and its neighboring islands [7]. The members of this species are cultivated, in sub-tropical and warm temperate climates [1, 7]
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