In vitro activity of essential oil mixture against Staphylococcus aureus isolated from cats with pyoderma

Staphylococcus (S.) aureus is isolated in cats suffering from pyoderma. A shampoo containing 5 % rosemary (Rosmarinus officinalis), 5 % oregano (Origanum vulgare), and 2 % Turkish thyme (Thymus serpyllum) essential oil (EO) was shown to have in vivo antifungal activity in cats with microsporiasis [1]. The treatment was well tolerated, without any adverse effects. Aim of this study was to investigate the in vitro efficacy of this EO treatment in feline S. aureus-associated pyoderma by testing the EO mixture as well as single components against S. aureus isolated from skin of pyodermic cats. A microdilution test using different EO concentrations (rosemary, oregano: 0.625 %, 1.25 %; 2.5 %, Turkish thyme: 0.25 %,0.5 %,1 %, mixture: 0.75 %, 1.5 %, 3 %, 6 %) and three different incubation times (1, 2, 5 min) was performed, colony forming units (CFU) were determined. Oregano, Turkish thyme oil, and the mixture of EOs exhibited an in vitro antibacterial activity, while rosemary oil did not inhibit bacterial growth [Tab. 1]. Higher concentration of EOs as well as longer incubation time led to reduction of CFU, even a total growth inhibition could be achieved. Overall, the EO mixture showed better antibacterial efficacy than single EOs. EO concentration has stronger impact than incubation time. Interestingly, comparison of single bacterial isolates reveals a heterogenous dose dependent reduction of CFU and different susceptibility patterns of S. aureus isolates have to be discussed. To conclude, the EO mixture is a promising candidate for treatment of S. aureus-associated pyoderma in cats. The antibacterial effect most likely originates from oregano and Turkish thyme oil.

▶Tab. 1

• References

• 1 Nardoni S, Costanzo AG, Mugnaini L, Pisseri F, Rocchigiani G, Papini R, Mancianti F. Open-field study comparing an essential oil-based shampoo with miconazole/chlorhexidine for haircoat disinfection in cats with spontaneous microsporiasis. J Feline Med Surg 2017; 19: 697-701.