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Antibacterial activity of essential oils for combating colistin-resistant bacteria
Abdullah M Foda1, Mohamed H Kalaba1, Gamal M El-Sherbiny1
1Botany and Microbiology Department, Faculty of Science, Al-Azhar University, Cairo, Egypt.
Objectives:
Colistin (polymyxin E) is a bactericidal antibiotic used to treat severe infections caused by multidrug-resistant Gram-negative bacteria. The product of the mcr1 gene generates transferable plasmid-mediated colistin resistance, which has arisen as a worldwide health-care problem. This study aimed to isolate and identify colistin-resistant bacteria, and evaluate the ability of essential oils in its fights.
Methods:
Twenty-seven bacterial isolates were collected from patients who were admitted to the National Cancer Institute, Cairo, Egypt, and processed using standard microbiological methods. Essential oils were purchased from AB Chem Company, Egypt, screened for antibacterial, cytotoxic activity, and (GC-MS) analysis.
Results:
A total of 5 bacterial isolates were resistant to colistin with minimum inhibitory concentration (MIC) ranging from 6.25->200 µg/ml. Cinnamon oil exhibited the highest activity against colistin-resistant strains followed by thyme and eucalyptus oil. The (MIC) of cinnamon oils against resistant strains ranged from 4.88 to 312.5 µg/ml. Moreover, mcr-1 gene expression was extremely down-regulated after the treatment of bacterial strains with cinnamon oil and decreased to 20-35-fold. Examination of treated bacterial cells with sub-inhibitory concentrations under transmission electron microscopy showed various abnormalities occurred in most of these cells.
Conclusions:
Cinnamon oil exhibits antibacterial activity against colistin-resistant strains, showing it as a promising natural alternative in clinical therapy.
Insights
Cinnamon oil effectively combats colistin-resistant bacteria, including those with the mcr-1 gene. This natural remedy shows promise as an alternative treatment for multidrug-resistant Gram-negative infections.
Area of Science:
- Microbiology
- Pharmacology
- Natural Products Chemistry
Background:
- Colistin (polymyxin E) is crucial for treating infections from multidrug-resistant Gram-negative bacteria.
- The emergence of transferable plasmid-mediated colistin resistance due to the mcr-1 gene poses a significant global health threat.
- Investigating alternative agents against colistin resistance is essential for public health.
Purpose of the Study:
- To isolate and identify colistin-resistant bacteria from clinical samples.
- To evaluate the efficacy of various essential oils against these resistant strains.
- To explore the potential of natural compounds as alternatives in combating antibiotic resistance.
Main Methods:
- Bacterial isolates were obtained from patients at the National Cancer Institute, Cairo, Egypt.
- Standard microbiological techniques were employed for isolation and identification.
- Essential oils were screened for antibacterial activity, and their chemical composition was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS).
Main Results:
- Five colistin-resistant bacterial isolates were identified with Minimum Inhibitory Concentrations (MICs) ranging from 6.25 to >200 µg/ml.
- Cinnamon oil demonstrated the highest antibacterial activity, followed by thyme and eucalyptus oils, with MICs for cinnamon oil against resistant strains between 4.88 and 312.5 µg/ml.
- Cinnamon oil significantly down-regulated mcr-1 gene expression (20-35 fold) and caused cellular abnormalities in treated bacteria.
Conclusions:
- Cinnamon oil exhibits significant antibacterial activity against colistin-resistant bacterial strains.
- The findings suggest cinnamon oil is a promising natural alternative for clinical therapy against multidrug-resistant infections.
- Further research into essential oils could lead to novel strategies for overcoming antibiotic resistance.
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