الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The upsurge of antibiotic resistance and lack of novel antibiotics had led to the development of alternative strategies to cope with drug-resistant bacteria. These strategies rely on use of combination of existing antibiotics with natural compounds to enhance the efficacy of antibiotics. Eucalyptus essential oil (EEO) is an extracted organic compounds from the leaves of Eucalyptus globulus evergreen plant native to Australia and Tasmania. It protects the plants from bacterial, fungal and viral pathogens. It had been known to possess wound healing and antimicrobial properties, where it had been used in ancient times as medicinal food and for wound dressing. The major components of EEO are 1,8 -cineole, α-pinene and p-cymene. Antibacterial effects of EEO are related to its major components, mainly the cineole, or from synergistic interaction between all the constituents. It is a very promising antimicrobial agent that may act synergistically with the antibiotics on multiple targets in the bacterial cell to overcome the antibiotic resistance mechanisms.
The aim of this study was to evaluate the efficacy of EEO on different bacterial isolates from infected wounds and burns, and to determine the antimicrobial effect of combinations of EEO with ineffective antibiotics.
The present study was conducted during the period from November 2020 to May 2021 on 90 wound swabs obtained from outpatients and inpatients with infected wounds and burns who attended or were admitted to General Surgery or Burn Departments at Alexandria Main University Hospital (AMUH). The swabs were subjected to standard microbiological procedures for isolation and identification. Eighty two bacterial isolates had been recovered and tested for their antimicrobial susceptibility using Kirby Bauer disk diffusion method.
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Gram negative isolates that were resistant to ceftazidime and gram positive isolates that were resistant to cefoxitin were further tested with EEO for antibacterial activity by minimum inhibitory concentration (MIC) assay. Combination effect of EEO and antibiotics was determined by checkerboard method.
The results of this study showed that:
1. Most of the patients with wound infections were males, 50 out of 90 (55.56 %), and the majority of them (40.00%) were in the age group of 40 to less than 60 years old.
2. Most of skin infections were from outpatients 49 out of 90 (54.44%).
3. Most of skin infections, 81 out of 90 (90.00 %) were wound infections, while 9 (10.00%) were burn infections.
4. The major type of wound infections was diabetic foot, 44 out of 81 (54.32 %), followed by surgical site (24.69%).
5. Eighty two (91.11%) of skin infection swabs yielded bacterial growth, while no growth was recovered from the remaining eight.
6. K. pneumoniae was the most prevalent pathogen of skin infections (42.69 %), followed by P. aeruginosa 13 (15.85%).
7. All nine burn infections were caused by P. aeruginosa.
8. K. pneumoniae, P. aeruginosa and E. coli isolates showed high resistance percentages to ceftazidime (85.71 %, 77.27 % and 77.78, respectively).
9. Most S. aureus isolates (66.67 %) were resistant to cefoxitin; accordingly they were considered as MRSA.
10. Out of 82 bacterial isolates, 68 (82.93%), were MDR.
11. Percentages of MDR isolates from wound and burn were 84.93 % and 66.67%, respectively.
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12. The highest MDR percentages were found among K. pneumoniae and E. coli (97.14% and 88.88%, respectively).
13. Most S. aureus isolates were MDR (66.67%).
14. All K. pneumoniae, E. coli, P. aeruginosa and P. mirabilis isolates showed resistant MIC breakpoints to ceftazidime.
15. All six S. aureus isolates showed resistant MIC breakpoints to cefoxitin.
16. EEO-ceftazidime combination enhanced the activity of ceftazidime against K..pneumoniae using 3.125 and 6.25 μg/ml, and the inhibitory effect had increased using higher concentration of EEO (12.50 and 25 μg/ml).
17. All P. aeruginosa, E. coli and P. mirabilis isolates showed sensitive ceftazidime breakpoints using EEO concentration of 25 μg/ml.
18. Most S. aureus isolates showed cefoxitin MIC values below the breakpoints when combined with EEO concentrations of 12.50 and 25 μg/ml.
19. EEO-Ceftazidime combination showed synergistic effect in only 20.00%, 17.65% and 28.57% of K. pneumoniae, P. aeruginosa and E. coli isolates, respectively, while it had an additive activity in 40.00%, 58.82% and 42.86% of them, respectively.
20. The EEO-cefoxitin combination was additive in 5 out of 6 (83.33%) S. aureus isolates, while it showed synergistic effect in only one isolate.
21. There was a statistically significant difference between the effect of EEO on gram-positive and negative bacteria.
22. The difference between the additive effect of EEO-AB combinations on gram positive and gram-negative bacteria was statistically significant.
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from this study, it can be concluded that:
1. High frequency of MDR bacteria were isolated from skin infections.
2. Diabetic foot infections were the commonest wound infections, followed by surgical site infections.
3. High percentages of MDR bacteria were detected in outpatients and inpatients.
4. Antibacterial activity of EEO was concentration dependent.
5. EEO- antibiotics combinations had additive effects on gram positive and negative isolates.
from the results of the present study, the following recommendations are suggested:
1. Careful selection and use of antibiotics should be adopted in all health care settings to combat high rates of MDR bacteria.
2. Further studies should be conducted to assess the in-vivo antibacterial effect of EEO.
3. Commercial EOs could be potential candidate as natural antimicrobial agents.
4. Pharmaceutical industry should incorporates bioactive compounds such as EOs in the modern pro-healing wound dressing.