Synergistic Antibacterial Effects of Geranium Essential Oil against Skin Pathogenic Antibiotic Resistant Acne Related Bacteria

Abstract

Acne is a chronic and sometimes severe skin disorder affecting an estimated 85% of adolescents and 50% of adults older than age 20 years. Bacterial pathogens are associated with acne and hence antibiotic therapy some time lead to development of antibiotic resistant bacteria. Four factors including Androgen-mediated stimulation of sebaceous gland activity, follicular hyper keratinization, colonization of the bacterium P. acnes, and inflammation, play important roles in the pathogenesis of acne. In addition to P. acnes, as the main causative bacteria, S. epidermidis is also present in acne lesions. Therefore, alternative acne control therapies with minimal side effects are in demand. Given the trend of increased multidrug resistance, there is an urgent need to discover and development of promising new antimicrobials. In the present study, the antimicrobial activity of six essential oils (EO) namely, lavender, eucalyptus, lemon, rosemary, tea tree, and geranium oils were investigated against Propionibacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis by broth micro dilution method and synergistic effects in combination with antibiotics and tropical forms of Vitamin-A. From the results of preliminary investigation, among the six essential oils tested, geranium oil was found to be better antimicrobial in terms of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against skin pathogens tested in the present study. The results of the present study confirmed that geranium oil exhibited significant MIC/MBC values ranging from, 128-512 µg/mL, 512-2,048 µg/mL against P. acnes reference and clinical isolate strains tested several other Gram-positive skin pathogens such as S. aureus and S. epidermidis were found to be susceptible for geranium oil treatment MIC in range of 512-2,048 µg/mL. Also the MIC of both retinol and all trans-retinol were ranging from 64-1,024 µg/mL. The analysis of fractional inhibitory concentration (FIC) indices clearly showed a synergistic antibacterial effect between geranium EO and commercial antibiotics, also between tropical forms of Vitamin-A and geranium EO. Thus, the median of ∑FIC values against P. acnes were ranged from 0.09-0.565 and 0.26-0.56 in combination with commercial antibiotics and Vitamin-A. The results of the present study suggested that geranium oil can be a possible natural antimicrobial candidate to control skin related pathogens.