Efficacy of Melaleuca alternifolia and Pelargonium graveolens against Staphylococcus aureus and Staphylococcus epidermidis associated with knee implants

Abstract

Knee replacement surgery is experiencing a surge in demand worldwide; however, knee infections represent a substantial public health threat, particularly for underserved communities. While knee implantology was innovated to restore functionality to damaged knees, the risk of infections due to bacterial colonisation around the implant remains a serious concern. The overuse of antibiotics not only jeopardises patient health but also escalates healthcare costs. Although prophylactic antibiotic regimens are employed to mitigate infection risks, the emergence of antibiotic resistance due to excessive utilisation has complicated this approach. In this context, essential oils emerge as a promising solution to combat these challenges. Essential oils, known for their natural origins, serve as potent antibacterial agents due to their mechanisms of action, which include disrupting cell walls, damaging cytoplasmic membranes, and causing cytoplasmic coagulation. This study specifically investigates the Essential oils' effectiveness in combatting bacteria associated with knee implants. The research examines the bactericidal properties of Melaleuca alternifolia (tea tree essential oil) and Pelargonium graveolens (geranium essential oil) essential oils against the antibiotic-resistant strains Staphylococcus epidermidis and Staphylococcus aureus. The findings suggest that both Melaleuca alternifolia and Pelargonium graveolens essential oils effectively inhibit bacterial growth linked to knee implants, thereby potentially reducing the necessity for knee implant revisions. The essential oils' chemical constituents were examined utilising gas chromatography- mass spectrometry (GC-MS).Terpinen-4-ol was discovered to be a key component of Melaleuca alternifolia essential oil, including α-pinene, γ-terpinene, limonene, and cymene, which are associated with antibacterial and anti-inflammatory properties. Pelargonium graveolens essential oil consists of citronellol and geraniol as major components that contribute to cell wall disruption, loss of cellular contents, and overall bacterial deformation. The research employed bioassay methods to evaluate the antibacterial effects of Melaleuca alternifolia and Pelargonium graveolens essential oils against S. aureus (ATCC 25923) and S. epidermidis (ATCC 12228). Both Melaleuca alternifolia and Pelargonium graveolens essential oils demonstrated significant inhibitory effects on the growth of S. aureus and S.epidermidis. To ascertain the concentration at which these essential oils can inhibit microbial growth, the minimum inhibitory concentration (MIC) method was utilised. Additionally, the study sought to examine the structural transformations induced by essential oils in microorganisms, employing scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The SEM results revealed observable morphological changes, including slight roughness (R) of the cell surfaces, loss cellular content (LCC), and damage to the cell walls (DCW). The TEM results revealed drastic alterations in the cellular structure of S. aureus and S. epidermidis following exposure to Melaleuca alternifolia and Pelargonium graveolens essential oils. Notable changes included damaged cell walls, the formation of holes, and the depletion of cellular contents, ultimately resulting in cell death. This research holds significant implications for the use of natural products like essential oils as potential alternative bacteriostatic agents. During microbial assessments, it was observed that Melaleuca alternifolia and Pelargonium graveolens essential oils compromised the cell membranes of S. aureus and S. epidermidis, leading to cell death. Consequently, this indicates that both essential oils can effectively target multiple bacterial sites, particularly the plasma membrane and cytoplasm. Moreover, the study highlights some advantages of using natural products such as Melaleuca alternifolia and Pelargonium graveolens essential oils, including the need for the healthcare sector to reduce reliance on antibiotics and consider essential oils as viable alternatives in the fight against microorganisms responsible for knee infections, ultimately decreasing the need for revision surgeries. However, despite the promising nature of essential oils as alternatives to antibiotics, further research is imperative. The impact of essential oils on health and integrity of knee implants, the optimal concentrations that ensure bacterial eradication without harming human cells, and the duration of essential oil adherence to implants remain areas requiring additional exploration, as well as investigating the biofilm formation of bacterial strains on the experimental knee implant.