Monika Łysakowska

The Potential of Use Basil and Rosemary Essential Oils as Effective Antibacterial Agents

The considerable therapeutical problems of persistent infections caused by multidrug-resistant bacterial strains constitute a continuing need to find effective antimicrobial agents. The aim of this study was to demonstrate the activities of basil (Ocimum basilicum L.) and rosemary (Rosmarinus officinalis L.) essential oils against multidrug- resistant clinical strains of Escherichia coli. A detailed analysis was performed of the resistance of the drug to the strains and their sensitivity to the tested oils. The antibacterial activity of the oils was tested against standard strain Escherichia coli ATCC 25922 as well as 60 other clinical strains of Escherichia coli. The clinical strains were obtained from patients with infections of the respiratory tract, abdominal cavity, urinary tract, skin and from hospital equipment. The inhibition of microbial growth by both essential oils, presented as MIC values, were determined by agar dilution. Susceptibility testing to antibiotics was carried out using disc diffusion. The results showed that both tested essential oils are active against all of the clinical strains from Escherichia coli including extended-spectrum β-lactamase positive bacteria, but basil oil possesses a higher ability to inhibit growth. These studies may hasten the application of essential oils in the treatment and prevention of emergent resistant strains in nosocomial infections.

The Antimicrobial Activity of Thyme Essential Oil Against Multidrug Resistant Clinical Bacterial Strains

AIM The aim of this work was to investigate the antimicrobial activity of thyme essential oil against clinical multidrug resistant strains of Staphylococcus, Enterococcus, Escherichia, and Pseudomonas genus. MATERIALS The antibacterial activity of oil was tested against standard strains of bacteria and 120 clinical strains isolated from patients with infections of the oral cavity, abdominal cavity, respiratory and genitourinary tracts, skin, and from the hospital environment. METHODS Agar diffusion was used to determine the microbial growth inhibition of bacterial growth at various concentrations of oil from Thymus vulgaris. Susceptibility testing to antibiotics was carried out using disk diffusion. RESULTS Thyme essential oil strongly inhibited the growth of the clinical strains of bacteria tested. CONCLUSIONS The use of phytopharmaceuticals based on an investigated essential oil from thyme in the prevention and treatment of various human infections may be reasonable.

The Biological Activities of Cinnamon, Geranium and Lavender Essential Oils

Acinetobacter sp. represent an important cause of nosocomial infections. Their resistance to some antibiotics, their ability to survive on inanimate surfaces in the hospital environment and their ability to produce biofilms contributes to their virulence. The aim of the study was to determine the antibacterial properties of cinnamon, lavender and geranium essential oils against bacteria of the genus Acinetobacter isolated from several clinical materials and from the hospital environment. A comprehensive evaluation of the susceptibility of Acinetobacter sp. clinical strains to recommended antibiotics was performed. The constituents of cinnamon, lavender and geranium essential oils were identified by GC-FID-MS analysis, and their Minimal Inhibitory Concentrations (MICs) against tested clinical strains were determined by the micro-dilution broth method. In addition, the effects of essential oils on the viability of human microvascular endothelial cells (HMEC-1) and glioblastoma cell line (T98G) were evaluated. Cinnamon bark oil was the most active against clinical and environmental strains of Acinetobacter baumannii with MIC values ranging from 0.5 to 2.5 µL/mL. The MIC values for geranium oil were between 7.5 and 9.5 µL/mL, and between 10.5 and 13.0 µL/mL for lavender oil. These essential oils can be best employed in the fight against infections caused by bacteria from Acinetobacter genus as components of formulations for hygiene and disinfection of hospital environment.

The activity of silver nanoparticles (Axonnite) on clinical and environmental strains of Acinetobacter spp.

Acinetobacter baumannii isolates are responsible for a high number of wound infections. The reason of this study was to evaluate the activity of silver nanoparticles obtained by microexplosion against wide range of Acinetobacter spp. Susceptibility to silver nanoparticles was tested by microdilution method, susceptibility to antibiotics was evaluated by the disc-diffusion method. All strains of Acinetobacter spp. were sensitive to AgNPs at low concentrations. The values of the MIC for strains of Acinetobacter spp. were 0.39 and 0.78μg/mL. In general, strains inhibited by 0.78μg/mL of AgNPs were more resistant to antibiotics than Acinetobacter strains for which MIC=0.39μg/mL (p=0.023). The AgNPs in Axonnite seems to be a good alternative for other antimicrobials to treat wound infections caused by multidrug resistant Acinetobacter spp. strains because of its high activity.

The activity of thyme essential oil against Acinetobacter spp.

AbstractThe aim of this work was to investigate the antimicrobial properties of thyme essential oil against clinical multiresistant strains of Acinetobacter spp. The antibacterial activity of oil was tested against standard and clinical bacterial strains of Acinetobacter genus. The agar diffusion method was used to check the inhibition of microbial growth at various concentrations of the oil from Thymus vulgaris. Susceptibility testing to antibiotics and chemotherapeutics was prepared using the disc-diffusion method. Identification of bacterial strains was carried out with the Vitek system and confirmed by PCR for Acinetobacter baumanii gyrB gene. The results of experiments showed that the oil from T. vulgaris exhibited an extremely strong activity against all of the clinical strains of Acinetobacter. Thyme oil demonstrated a very good efficacy against multiresistant strains of tested bacteria. Essential oils seems to be an excellent alternative for synthetic preparations and that is reason for an extensive assessment of their antimicrobial activity.

The ability of selected plant essential oils to enhance the action of recommended antibiotics against pathogenic wound bacteria

The aim of this work was to characterize the ability of essential oils to support antibiotics against pathogenic bacteria in wounds. Gram-positive and Gram-negative bacteria obtained from wound infections were identified according to standard microbiological methods. Essential oils were analysed by GC-FID-MS. The susceptibility of bacteria to antibiotics, essential oils and their combination was assessed using the disc-diffusion method. The Minimal Inhibitory Concentration and Minimum Bactericidal Concentration of the essential oils were established by the micro-dilution broth method. Although cinnamon, clove, thyme and lavender essential oils were found to have the greatest antibacterial activity when used alone, the greatest additive and synergistic effects against pathogenic wound bacteria in combination with recommended antibiotics were demonstrated by basil, clary sage and rosemary oils.

The activity of silver nanoparticles (axonnite) on clinical and environmental strains of Enterococcus spp.

AIMS The spread of bacterial antibiotic resistance among clinical strains is a growing problem nowadays. Resistance in Enterococcus spp. strains has merited special concern of late, as they have become significant nosocomial pathogens. Hence, the use of compounds such as silver nanoparticles (AgNPs), displaying various mechanisms of action, is a growing new approach against virulent, drug-resistant infections. Therefore, the activity of AgNPs obtained by a physical method (microexplosion method) was tested against 30 clinical and environmental Enterococcus spp. strains presenting diverse virulence and resistance patterns. RESULTS The minimal inhibitory concentration for all the species ranged from 0.39 to 3.125 μg/ml. No statistical differences (p=0.26) were found between resistance to AgNPs and resistance to antibiotics, suggesting high activity of AgNPs even against multidrug-resistant strains. CONCLUSIONS AgNPs obtained by this method seem to be a promising alternative to chemotherapeutics in the treatment or prevention of enterococcal infections.

The Sensitivity of Endodontic Enterococcus spp. Strains to Geranium Essential Oil

Enterococci are able to survive endodontic procedures and contribute to the failure of endodontic therapy. Thus, it is essential to identify novel ways of eradicating them from infected root canals. One such approach may be the use of antimicrobials such as plant essential oils. Enterococcal strains were isolated from endodontically treated teeth by standard microbiological methods. Susceptibility to antibiotics was evaluated by the disc-diffusion method. The minimal inhibitory concentration (MIC) of geranium essential oil was investigated by microdilution in 96-well microplates in Mueller Hinton Broth II. Biofilm eradication concentrations were checked in dentin tests. Geranium essential oil inhibited enterococcal strains at concentrations ranging from 1.8–4.5 mg/mL. No correlation was shown between resistance to antibiotics and the MICs of the test antimicrobials. The MICs of the test oil were lower than those found to show cytotoxic effects on the HMEC-1 cell line. Geranium essential oil eradicated enterococcal biofilm at concentrations of 150 mg/mL. Geranium essential oil inhibits the growth of endodontic enterococcal species at lower concentrations than those required to reach IC50 against the HMEC-1 cell line, and is effective against bacteria protected in biofilm at higher concentrations. In addition, bacteria do not develop resistance to essential oils. Hence, geranium essential oil represents a possible alternative to other antimicrobials during endodontic procedures.