Jowenna Xiao Feng Sim1, Manouchehr Khazandi1,2, Wei Yee Chan2, Darren J Trott2, Permal Deo1. 1. School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, 5000, Australia. 2. Australian Centre for Antimicrobial Resistance Ecology, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy Campus, South Australia, 5371, Australia.
Abstract
BACKGROUND: Multidrug-resistant pathogens present a major global challenge in antimicrobial therapy and frequently complicate otitis externa in dogs. HYPOTHESIS/ OBJECTIVES: In vitro efficacy of oregano oil, thyme oil and their main phenolic constituents against bacterial and fungal isolates associated with canine otitis externa were investigated. It was hypothesized that the main phenolic components would have greater antimicrobial activity compared to the relative essential oil. METHODS AND MATERIALS: Antimicrobial susceptibility testing was performed using broth microdilution with spot-plating technique to determine minimum inhibitory and bactericidal/fungicidal concentrations (MICs, MBCs and MFCs). A time-kill kinetics assay was performed to confirm the bactericidal and fungicidal activity of the oils and their phenolic constituents. One hundred bacterial and fungal isolates, including meticillin-susceptible Staphylococcus pseudintermedius (n = 10), meticillin-resistant S. pseudintermedius (n = 10), β-haemolytic Streptococcus spp. (n = 20), Pseudomonas aeruginosa (n = 20; including 10 isolates resistant to one or two antimicrobials), Proteus mirabilis (n = 20) and Malassezia pachydermatis (n = 20) from dogs with otitis externa were used. RESULTS: Oregano oil, thyme oil, carvacrol and thymol exhibited antibacterial activity against all bacterial and fungal isolates tested. MIC90 values ranged from 0.015 to 0.03% (146-292 μg/mL) for the Gram-positive bacteria and P. mirabilis. For P. aeruginosa and M. pachydermatis, MIC90 values ranged from 0.09 to 0.25% (800-2,292 μg/mL). CONCLUSIONS AND CLINICAL SIGNIFICANCE: Oregano oil, thyme oil, carvacrol and thymol showed good in vitro bactericidal and fungicidal activity against 100 isolates from dogs with otitis externa, including some highly drug-resistant isolates. These essential oils and their main phenolic constituents have the potential to be further investigated in vivo for the treatment of canine otitis externa.
BACKGROUND: Multidrug-resistant pathogens present a major global challenge in antimicrobial therapy and frequently complicate otitis externa in dogs. HYPOTHESIS/ OBJECTIVES: In vitro efficacy of oregano oil, thyme oil and their main phenolic constituents against bacterial and fungal isolates associated with canine otitis externa were investigated. It was hypothesized that the main phenolic components would have greater antimicrobial activity compared to the relative essential oil. METHODS AND MATERIALS: Antimicrobial susceptibility testing was performed using broth microdilution with spot-plating technique to determine minimum inhibitory and bactericidal/fungicidal concentrations (MICs, MBCs and MFCs). A time-kill kinetics assay was performed to confirm the bactericidal and fungicidal activity of the oils and their phenolic constituents. One hundred bacterial and fungal isolates, including meticillin-susceptible Staphylococcus pseudintermedius (n = 10), meticillin-resistant S. pseudintermedius (n = 10), β-haemolytic Streptococcus spp. (n = 20), Pseudomonas aeruginosa (n = 20; including 10 isolates resistant to one or two antimicrobials), Proteus mirabilis (n = 20) and Malassezia pachydermatis (n = 20) from dogs with otitis externa were used. RESULTS: Oregano oil, thyme oil, carvacrol and thymol exhibited antibacterial activity against all bacterial and fungal isolates tested. MIC90 values ranged from 0.015 to 0.03% (146-292 μg/mL) for the Gram-positive bacteria and P. mirabilis. For P. aeruginosa and M. pachydermatis, MIC90 values ranged from 0.09 to 0.25% (800-2,292 μg/mL). CONCLUSIONS AND CLINICAL SIGNIFICANCE: Oregano oil, thyme oil, carvacrol and thymol showed good in vitro bactericidal and fungicidal activity against 100 isolates from dogs with otitis externa, including some highly drug-resistant isolates. These essential oils and their main phenolic constituents have the potential to be further investigated in vivo for the treatment of canine otitis externa.
Authors: Sara Scandorieiro; Bianca C D Rodrigues; Erick K Nishio; Luciano A Panagio; Admilton G de Oliveira; Nelson Durán; Gerson Nakazato; Renata K T Kobayashi Journal: Front Microbiol Date: 2022-05-06 Impact factor: 6.064
Authors: Aleksandra Steglińska; Anastasiia Bekhter; Paweł Wawrzyniak; Alina Kunicka-Styczyńska; Konrad Jastrząbek; Michał Fidler; Krzysztof Śmigielski; Beata Gutarowska Journal: Molecules Date: 2022-02-27 Impact factor: 4.411
Authors: Cristina Vercelli; Mario Pasquetti; Giovanni Giovannetti; Sara Visioni; Giovanni Re; Mario Giorgi; Graziana Gambino; Andrea Peano Journal: J Vet Pharmacol Ther Date: 2021-07-13 Impact factor: 1.567