Antibacterial Activities and Synergistic Interaction of Citrus Essential Oils and Limonene with Gentamicin against Clinically Isolated Methicillin-Resistant Staphylococcus aureus.

Apichai Sreepian,Supaluk Popruk,Preeyaporn M Sreepian,Chayanit Phutthanu,Daranee Nutalai,Wongi Min

doi:10.1155/2022/8418287

Abstract

Citrus reticulata Blanco and Citrus aurantifolia are the edible plants which contain several biological properties including antibacterial activity. The aims of the present study were to determine the chemical compositions and evaluate antibacterial activities of citrus essential oils extracted from the fruit peels of C. reticulata (CREO) and C. aurantifolia (CAEO), alone and in combination with gentamicin, against a panel of clinically isolated methicillin-resistant S. aureus (MRSA) (n = 40) and methicillin-susceptible S. aureus (MSSA) (n = 45). Gas chromatography-mass spectrometry analysis revealed that 12 and 25 compounds were identified in CREO and CAEO with the most predominant compound of limonene (62.9–72.5%). The antibacterial activities were determined by agar disk diffusion and resazurin-based microdilution methods. The results found that almost all MRSA isolates were resistant to ciprofloxacin, erythromycin, and clindamycin, and some isolates were resistant to gentamicin. CREO and CAEO exhibited inhibitory effects toward clinical isolates (MIC: 1.0–32.0 and 8.0–32.0 mg/mL, respectively), with a similar trend to limonene (MIC: 1.0–32.0 mg/mL). However, the higher antibacterial effects were found in CREO and limonene when compared to CAEO (p < 0.01). In combination effect, the results showed the synergistic interaction of gentamicin with CREO and limonene on the MRSA and MSSA isolates (FIC indexes: 0.012–0.258 and 0.012–0.375), but that interaction of gentamicin with CAEO was observed only on MRSA (FIC index: 0.012–0.016). These findings demonstrated the potential of these citrus essential oils as natural antibacterial agents that may contribute to reduce the emerging of antimicrobial-resistant bacteria.

Highlights

Staphylococcus aureus, a Gram-positive commensal bacterium, is mainly colonized in the nasal carriage as well as in the skin, axillae, perineum, and pharynx [1]
Methicillinresistant S. aureus (MRSA), caused by the acquisition of staphylococcal cassette chromosome mec (SCCmec) which carries the mecA gene that is responsible for the production of an altered penicillin-binding protein 2a (PBP2a), associated with decreased affinity for all β-lactam antibiotics
The results found that MRSA American Type Culture Collection (ATCC) 43300 and methicillinsusceptible S. aureus (MSSA) ATCC 25923 were inhibited by C. reticulata essential oil (CREO) with minimum inhibitory concentrations (MICs) equal to 4.0 ± 0.0 mg/mL

Summary

Introduction

Staphylococcus aureus, a Gram-positive commensal bacterium, is mainly colonized in the nasal carriage as well as in the skin, axillae, perineum, and pharynx [1]. It can cause a wide variety of infectious diseases, ranging from mild skin and soft tissue infections to life-threatening such as endocarditis, osteomyelitis, pneumonia, and bacteremia. Nephrotoxicity, e Scientific World Journal hypotension, and hypersensitivity reactions are commonly presented; drug monitoring is required [4] In this context, the searching for a new candidate of alternative anti-MRSA agent with a lesser toxicity is required, and one of the possible ways to support this goal is the use of plantderived agents

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