In vitro antimicrobial examination and efficacy of Eryngium foetidum L. extract for skin ointment in animal infectious dermatitis treatment

The development of new antimicrobial formulations for the treatment of animal infectious dermatitis is important as current antimicrobial treatments can have undesirable effects. The purpose of this study was to examine the in vitro antimicrobial activity of an Eryngium foetidum L. ethanolic extract against a bacterium, Staphylococcus pseudintermedius; a yeast, Malassezia pachydermatis; and three dermatophytes, Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes; all of which are the most common animal skin pathogens causing dermatitis. A viscous semi-solid crude extract was obtained at a yield of 30.6% dry weight. Quantitative analysis of the chemical constituents of the extract by spectrophotometry revealed 3.62 mg GAE/g extract of total phenolic, 1.77 mg CE/g extract of total flavonoid, and 10.11 mg/g extract of total carotenoid contents. HPLC-DAD analysis of the carotenoid content showed that beta-carotene and lutein were present at 5.17 and 4.43 mg/g extract, respectively. Antimicrobial activity by broth microdilution test found that the E. foetidum extract had MIC, MBC and MFC values in the range of 6.25 to 25.0 mg/ml; and the time-kill test indicated that this effect was both dose and time dependent. Ointment formulations containing the extract at concentrations of 5, 7.5 and 10% w/w had high microbicidal activity against the tested pathogens and retained their activity and physical properties after repeated freeze-thaw cycles. The results of this study show the potential of E. foetidum extract to be developed as a novel antimicrobial formulation for treatment of infectious dermatitis in pets.