TY - JOUR
T1 - In Vitro Evaluation of Rosemary Essential Oil
T2 - GC-MS Profiling, Antibacterial Synergy, and Biofilm Inhibition
AU - Kabotso, Daniel E.K.
AU - Neglo, David
AU - Gaba, Sarah E.
AU - Danyo, Emmanuel K.
AU - Dayie, Alberta D.
AU - Asantewaa, Anastasia A.
AU - Kotey, Fleischer C.N.
AU - Dayie, Nicholas T.K.D.
N1 - Publisher Copyright:
© 2024 by the authors.
PY - 2024/12
Y1 - 2024/12
N2 - Background: Antimicrobial resistance (AMR) has become precarious, warranting investments in antimicrobial discovery. Aim: To investigate the antibacterial activity of rosemary essential oil (REO), alone and in combination with selected conventional antibiotics. Methods: REO was subjected to antimicrobial susceptibility testing (including minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) determination) and investigation of anti-pre-biofilm and antibiofilm activities. Results: The phytochemical composition of the REO was eucalyptol (42.68%), bornanone (33.20%), endo-borneol (9.37%), α-terpeneol (7.95%), linalool (2.10%), bornyl acetate (1.81%), caryophyllene (1.09%), 4-terpeneol (0.94%), and anethole (0.87%). The antibacterial inhibition zones generally increased with increasing REO concentration (i.e., 10, 20, 50, 100, and 200 mg/mL). The MIC and MBC ranges of REO for all bacteria were 3.13–6.25 mg/mL and 3.12–12.5 mg/mL, respectively. The MICs (in µg/mL) of ciprofloxacin, chloramphenicol, streptomycin, tetracycline, and ampicillin, respectively, were Escherichia coli (0.98, 3.92, 1.96, 7.81, and 250), Klebsiella pneumoniae (1.25, 7.81, 125, 7.81, and 1000), MRSA (62.5, 7.81, 3.91, 7.81, and 250), Streptococcus mutans and Bacillus subtilis (125, 15.68, 250, 31.25, and 1000), Pseudomonas aeruginosa (125, 31.25, 500, 31.25, and 1000), and Salmonella Typhi (0.98, 15.68, 125, 1.96, and 1000). The MBC-MIC ratios of REO against all bacteria were in the range 1–2, indicating bactericidal effects. Mainly synergy (FICI = 0.16–0.37) was observed between REO and the conventional antibiotics. The IC50 values (in µg/mL) of REO against the bacteria, pre-biofilm vs. biofilm formation, were E. coli (1342.00 vs. 4.00), K. pneumoniae (106.00 vs. 3.00), MRSA (134.00 vs. 6.00), S. mutans (7259.00 vs. 7.00), B. subtilis (120.00 vs. 7.00), P. aeruginosa (4989.00 vs. 7.00), and S. Typhi (10.00 vs. 2.00). Conclusions: Rosemary essential oil had significant bactericidal effects on the bacteria tested, and its MIC and MBC values were low. Overall, it was synergistic with known conventional antibiotics and, thus, has encouraging prospects in combination therapy involving conventional antibiotics, even in the treatment of infections with multidrug-resistant bacteria, including biofilm-forming ones.
AB - Background: Antimicrobial resistance (AMR) has become precarious, warranting investments in antimicrobial discovery. Aim: To investigate the antibacterial activity of rosemary essential oil (REO), alone and in combination with selected conventional antibiotics. Methods: REO was subjected to antimicrobial susceptibility testing (including minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) determination) and investigation of anti-pre-biofilm and antibiofilm activities. Results: The phytochemical composition of the REO was eucalyptol (42.68%), bornanone (33.20%), endo-borneol (9.37%), α-terpeneol (7.95%), linalool (2.10%), bornyl acetate (1.81%), caryophyllene (1.09%), 4-terpeneol (0.94%), and anethole (0.87%). The antibacterial inhibition zones generally increased with increasing REO concentration (i.e., 10, 20, 50, 100, and 200 mg/mL). The MIC and MBC ranges of REO for all bacteria were 3.13–6.25 mg/mL and 3.12–12.5 mg/mL, respectively. The MICs (in µg/mL) of ciprofloxacin, chloramphenicol, streptomycin, tetracycline, and ampicillin, respectively, were Escherichia coli (0.98, 3.92, 1.96, 7.81, and 250), Klebsiella pneumoniae (1.25, 7.81, 125, 7.81, and 1000), MRSA (62.5, 7.81, 3.91, 7.81, and 250), Streptococcus mutans and Bacillus subtilis (125, 15.68, 250, 31.25, and 1000), Pseudomonas aeruginosa (125, 31.25, 500, 31.25, and 1000), and Salmonella Typhi (0.98, 15.68, 125, 1.96, and 1000). The MBC-MIC ratios of REO against all bacteria were in the range 1–2, indicating bactericidal effects. Mainly synergy (FICI = 0.16–0.37) was observed between REO and the conventional antibiotics. The IC50 values (in µg/mL) of REO against the bacteria, pre-biofilm vs. biofilm formation, were E. coli (1342.00 vs. 4.00), K. pneumoniae (106.00 vs. 3.00), MRSA (134.00 vs. 6.00), S. mutans (7259.00 vs. 7.00), B. subtilis (120.00 vs. 7.00), P. aeruginosa (4989.00 vs. 7.00), and S. Typhi (10.00 vs. 2.00). Conclusions: Rosemary essential oil had significant bactericidal effects on the bacteria tested, and its MIC and MBC values were low. Overall, it was synergistic with known conventional antibiotics and, thus, has encouraging prospects in combination therapy involving conventional antibiotics, even in the treatment of infections with multidrug-resistant bacteria, including biofilm-forming ones.
KW - Bacillus subtilis
KW - Escherichia coli
KW - Klebsiella pneumoniae
KW - MRSA
KW - Pseudomonas aeruginosa
KW - Rosmarinus officinalis
KW - Salmonella Typhi
KW - Streptococcus mutans
KW - antibacterial activity
KW - essential oil
UR - http://www.scopus.com/inward/record.url?scp=85213244034&partnerID=8YFLogxK
U2 - 10.3390/ph17121653
DO - 10.3390/ph17121653
M3 - Article
AN - SCOPUS:85213244034
SN - 1424-8247
VL - 17
JO - Pharmaceuticals
JF - Pharmaceuticals
IS - 12
M1 - 1653
ER -