Interaction of Folk Medicinal Plants with Levofloxacin against Escherichia Coli

A phytotherapeutic approach to hinder the resistance against clindamycin by MRSA: in vitro and in silico studies

AIMS

This study investigates the potential effects of essential oils (EOs) in enhancing the efficacy of clindamycin against Methicillin-resistant Staphylococcus aureus (MRSA) using in vitro and computer simulations. The research seeks to identify essential oils that exhibit synergistic activity with clindamycin and determine their potential key active components.

MATERIALS AND METHODS

Essential oils commonly used in traditional medicine were tested for their antimicrobial activity against MRSA. The minimum inhibitory concentration (MIC) was determined using in vitro microdilution assays. A synergistic test with clindamycin was performed, and molecular docking studies evaluated the interaction between a key compound (trans-cinnamaldehyde) and MRSA protein.

RESULTS

EOs from Cinnamomum verum, Rosmarinus officinalis, Salvia officinalis, and Thymus vulgaris demonstrated significant inhibitory and synergistic activities against MRSA, standard strain, and human clinical isolates. Gas Chromatography/Mass Spectroscopy identified trans-cinnamaldehyde, eucalyptol, and thymol as prominent antibacterial compounds. Molecular docking studies confirmed trans-cinnamaldehyde's strong binding to MRSA's AgrA protein, elucidating its enhanced efficacy.

CONCLUSION

The study underscores the potential of plant-based therapies to augment the effectiveness of conventional antibiotics like clindamycin in combating MRSA and addressing antibiotic resistance by integrating traditional plant remedies with modern medical approaches.

Modulation of the bacterial virulence and resistance by well-known European medicinal herbs

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia officinalis L., Sambucus nigra L., Matricaria chamomilla L., Agrimonia eupatoria L., Fragaria vesca L. and Malva sylvestris L. are plants that have a long tradition in European folk medicine. To this day, they are part of medicinal teas or creams that help with the healing of skin wounds and the treatment of respiratory or intestinal infections. However, so far these plants have not been investigated more deeply than in their direct antibacterial effect.

AIM OF THE STUDY

Our research is focused on adjuvants that inhibit the mechanism of antibiotic resistance or modulate bacterial virulence. Based on a preliminary screening of 52 European herbs, which commonly appear as part of tea blends or poultice. Six of them were selected for their ability to revert the resistant phenotype of nosocomial bacterial strains.

METHODS

Herbs selected for this study were obtained from commercially available sources. For the extraction of active compounds ethanol was used. Modulation of virulence was observed as an ability to inhibit bacterial cell-to-cell communication using two mutant sensor strains of Vibrio campbellii. Biofilm formation, and planktonic cell adhesion was measured using a static antibiofilm test. Ethidium bromide assay was used to checked the potential of inhibition bacterial efflux pumps. The antibacterial activities of the herbs were evaluated against resistant bacterial strains using macro dilution methods.

RESULTS

Alcohol extracts had antibacterial properties mainly against Gram-positive bacteria. Of all of them, the highest antimicrobial activity demonstrated Malva sylvestris, killing both antibiotic resistant bacteria; Staphylococcus aureus with MIC of 0.8 g/L and Pseudomonas aeruginosa 0.7 g/L, respectively. Fragaria vesca extract (0.08 g/L) demonstrated strong synergism with colistin (4 mg/L) in modulating the resistant phenotype to colistin of Pseudomonas aeruginosa. Similarly, the extract of S. officinalis (0.21 g/L) reverted resistance to gentamicin (1 mg/L) in S. aureus. However, Sambucus nigra and Matricaria chamomilla seem to be a very promising source of bacterial efflux pump inhibitors.

CONCLUSION

The extract of F. vesca was the most active. It was able to reduce biofilm formation probably due to the ability to decrease bacterial quorum sensing. On the other hand, the activity of S. nigra or M. chamomilla in reducing bacterial virulence may be explained by the ability to inhibit bacterial efflux systems. All these plants have potential as an adjuvant for the antibiotic treatment.

Evaluation of the synergistic antimicrobial effect of folk medicinal plants with clindamycin against methicillin-resistant Staphylococcus aureus strains

Antibiotic resistance has become a major worldwide priority, and identifying natural antimicrobial compounds may help overcome this problem. In this study, ethanolic extracts of 12 plants commonly used in traditional medicine were tested against two strains of methicillin-resistant Staphylococcus aureus (ATCC 33591 and ATCC 43300) in terms of minimum inhibitory concentrations (MICs). Furthermore, the effect of combining plant extracts with clindamycin antibiotic was also investigated using the checkerboard method. Among the tested plants, Camellia sinensis, Thymus vulgaris, Rosmarinus officinalis and Salvia officinalis exhibited potent inhibitory activity against both strains with MICs ranges (125-500 µg ml^-1 ). Synergistic activity was confirmed for the four plants combined with clindamycin with fractional inhibitory concentration index <0·5. However, no antagonistic activity was found for these combinations. Our findings suggest that using an antibiotics-plants combination might be a successful technique to reduce antibiotic consumption, which would overcome the antibiotics resistance or delay its onset.