Elsevier

Burns

Volume 40, Issue 5, August 2014, Pages 1046-1051
Burns

The antibacterial activity of geranium oil against Gram-negative bacteria isolated from difficult-to-heal wounds

https://doi.org/10.1016/j.burns.2013.11.002Get rights and content

Abstract

Hard-to-heal wounds represent a significant problem to patients, health care professionals, and health care system. They can be formed as a result of mechanical injuries and burns, and any co-existing chronic disease increases the risk of their emergence. Diabetics are at a greater risk of developing chronic wounds because of poor circulation, slow healing times, vascular disease and neuropathy.

The aim of this study was to determine the antimicrobial activity of geranium oil against Gram-negative bacterial clinical strains. Clinical strains were isolated from patients with difficult-to-treat wounds and a comprehensive evaluation of their sensitivity to antibiotics was carried out. The constituents of geranium oil were specified by GC–FID–MS analysis. The micro-dilution broth method was used to check the inhibition of microbial growth at various concentrations of geranium oil. The tested geranium oil was efficacious against Gram-negative pathogens responsible for problems with wound treatment. The results suggest that geranium oil may be considered an effective component of therapy in the case of frequent recurrences of infections caused by resistant pathogens.

Introduction

Hard-to-heal wounds and ulcers present serious health complications and are significant factors in the cost of hospital treatment. This problem is caused by the spread of resistance to antibiotics commonly used in clinical practice. Both Gram-positive bacteria such as Staphylococcus aureus, coagulase-negative staphylococci, beta-hemolytic Streptococcus (S. pyogenes, S. agalactiae), and Gram-negative bacteria such as Escherichia coli, Enterobacter species, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Acinetobacter baumanii are pathogens of great importance in wound infections. Aerobic gram-negative rods also infect wounds late in the course of chronic wound degeneration. Pseudomonas, Acinetobacter, Stenotrophomonas are usually acquired from exogenous sources such as bathwater [1]. From the clinical point of view, significant resistant strains of staphylococci include Methicillin-Resistant S. aureus – MRSA, S. epidermidis – MRSE and S. aureus strains with reduced susceptibility to vancomycin and strains of S. aureus resistant to vancomycin [2]. The presence of constitutive and inductive Macrolide–Lincosamide–Streptogramin B – MLSB resistance mechanisms in streptococci limits the therapeutic possibilities. M-phenotype related to mef(A) gene conditioning resistance to erythromycin and other macrolides [3]. Extended-Spectrum Beta-Lactamases (ESBLs) – enzymes produced by Gram-negative pathogens as Escherichia, Enterobacter, Klebsiella hydrolyse all penicillin-based antibiotics, monobactams and cephalosporins, even those with a wide range of activity. Multiresistant P. aeruginosa and Acinetobacter are resistant to fluoroquinolones, extended-spectrum cephalosporins, carbapenems and aminoglycosides. Clinical strains of Pseudomonas and Proteus produce metallo-beta-lactamase enzymes (Znβ-lactamase) responsible for resistance to carbapenems [4], [5], [6].

Many kinds of dressings are used in wound treatment: absorbent, nonadherent, occlusive and semiocclusive, hydrophilic and hydrophobic, hydrocolloid and hydrogel, as well as alginates and absorbable materials, many of which could be a carrier for the testing of new, more effective antimicrobial drugs. The increasing presence of antibiotic-resistant pathogens strains has aroused interest in topical antimicrobial agents. Wound dressings containing silver have broad spectrum antimicrobial activity that encompasses many multidrug resistant wound pathogens. Jones et al. report that dressings with silver have great antibacterial effectiveness against methicillin-resistant S. aureus (MRSA) and P. aeruginosa [7], [8]. Edwards-Jones et al. demonstrate that geranium essential oil vapors have strong antibacterial effects when used alone, against methicillin-resistant S. aureus when used in combination with grapefruit seed extract, and against methicillin-sensitive S. aureus when used with tea tree oil [9]. Essential oils can also be of huge relevance in Dermatology, especially in the healing of wounds and burns thanks to their antibacterial, antiviral and antifungal activities. In addition, most have anti-inflammatory, antioxidant and anti-tumor properties [10], [11], [12], [13]. For example, according to Maruyama et al. the cutaneous application of several essential oils, especially geranium oil, may suppress the inflammatory symptoms related to neutrophil accumulation and edema [14].

The aim of our study was to determine the antibacterial activity of geranium oil against five genera of Gram-negative clinical isolates from patients with difficult-to-treat wound infections.

Section snippets

Bacterial strains and their identification

The samples of Gram-negative clinical strains were isolated from the swabs of patients in the Clinic of Dermatology, Pediatric Dermatology and Oncology, Medical University of Lodz, Poland in 2012. The study included 63 patients, 38 males and 25 females, with a mean age of 46–58 years, All had wounds arising during the course of diabetes or non-healing wounds after burns. Gram-negative clinical strains isolated from wounds were cultured according to standard microbiological methods with use of

Susceptibility testing

The tested strains were cultivated on Columbia Agar medium and incubated at 37 °C for 24 h. Bacterial suspensions with an optical density of 0.5MF were prepared with the bioMerieux densitometer, spread on Mueller-Hinton II Agar and incubated at 37 °C for 18 h. Susceptibility testing was carried out with the use of the disk-diffusion method, the following antibiotics (Becton Dickinson) being used against all tested E. coli, Citrobacter freundii, Enterobacter sakazakii, Enterobacter cloacae, P.

Tested Gram-negative bacterial strains

Sixty-three samples of wound swabs from patients were examined in the present study. Seventy five clinical strains of bacteria were isolated from swabs, among them were E. coli (n = 14, 18.6%), C. freundii (n = 6, 8.0%), E. sakazakii (n = 8, 10.6%), E. cloacae (n = 19, 25.3%), P. mirabilis (n = 11, 14.6%) and P. aeruginosa (n = 17, 22.6%).

Constituents of the tested geranium oil

The results of the tested geranium oil analysis revealed that the main components were citronellol (26.7%) and geraniol (13.4%). Among sixty-one constituents identified

Discussion

In this study, it was shown that geranium oil exhibits strong antibacterial activity against Gram-negative pathogens responsible for difficult-to-treat wound infections. Geranium oil containing mainly citronellol (26.7%) and geraniol (13.4%) inhibited the growth of all Gram-negative clinical strains of E. coli, C. freundii, E. sakazakii, E. cloacae, P. mirabilis and P. aeruginosa at concentrations from 3.0 μl/ml to 10.5 μl/ml. Susceptibility testing showed that the Gram-negative pathogens

Conflict of interest

The authors declare that there are no conflicts of interest.

Acknowledgements

The research reported in this manuscript was supported by Grant no 503/5015-02/503-01. The authors wish to thank Prof. Danuta Kalemba from Institute of General Food Chemistry, Lodz University of Technology, Poland for geranium oil analysis.

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