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In vitro antibacterial activity of the manuka essential oil from Leptospermum scoparium combined with Tris‐EDTA against Gram‐negative bacterial isolates from dogs with otitis externa
Author(s) -
Song SoonYoung,
Hyun JaeEun,
Kang Jung-Hun,
Hwang CheolYong
Publication year - 2020
Publication title -
veterinary dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.744
H-Index - 60
eISSN - 1365-3164
pISSN - 0959-4493
DOI - 10.1111/vde.12807
Subject(s) - manuka honey , antimicrobial , microbiology and biotechnology , proteus mirabilis , pseudomonas aeruginosa , tris , otitis , minimum inhibitory concentration , staphylococcus aureus , essential oil , biology , bacteria , medicine , food science , biochemistry , surgery , genetics
Background The increasing prevalence of antimicrobial resistance among bacteria in dogs with otitis externa has led to a need for novel therapeutic agents. Hypothesis/Objective To examine the antibacterial effects of manuka oil combined with ethylenediaminetetraacetic acid–tromethamine (Tris‐EDTA) against Gram‐negative bacteria isolates from dogs with otitis externa. Methods and materials A total of 53 clinical isolates including Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae ssp . pneumoniae and Proteus mirabilis . Antimicrobial susceptibility was determined using disk diffusion; the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of manuka essential oil, with or without Tris‐EDTA, were investigated. Results A total of 44 isolates were resistant to at least one antibiotic and 19 strains were multidrug‐resistant, with resistance to at least one agent in three or more antimicrobial classes. The MICs and MBCs of manuka oil alone were ≥1% (v/v) and ≥2% (v/v), respectively. There was no antimicrobial effect of Tris‐EDTA (1.125:0.3 mg/mL) without manuka oil. However, the combination of manuka oil with Tris‐EDTA significantly decreased the MICs (ranging from 0.06% to 0.5%, v/v; P < 0.001) and MBCs (ranging from 0.06% to 1%, v/v; P < 0.001). There also was no significant difference between multidrug‐resistant and nonresistant bacterial isolates in terms of the antimicrobial activity of manuka oil with Tris‐EDTA. Conclusions and clinical importance The study findings suggest that manuka oil, especially when combined with Tris‐EDTA, may be a promising alternative therapeutic option for Gram‐negative otic pathogens. Clinical studies are needed to assess potential for in vivo ototoxic effects and efficacy.