Antimicrobial Activity of Sempervivum tectorum L. Extract on Pathogenic Bacteria Isolated from Otitis Externa of Dogs

Simple Summary Two distinct but strongly related aims directed our work. First, we aimed to evaluate the phytotherapeutic potential of Sempervivum tectorum L., a traditionally well-known but chemically less characterized medicinal plant, through quantitative analysis of its biologically active substances. Modern methods of phytoanalytics (microwave extraction, lyophilization, and UV spectrophotometry) were applied to investigate the polyphenol and proanthocyanidin contents of Sempervivum tectorum L., which have significant biological and pharmacological activities, including antimicrobial activity. Our second aim was to determine the antimicrobial activity of Sempervivum tectorum L. extract against pathogenic bacteria isolated from ear swabs taken from dogs with with chronic and recurrent otitis externa and standard ATCC strains (respectively, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853). Sempervivum tectorum L. represents a particular model plant selected to represent the wide structural and therapeutical variety of phenolics, from simple phenolic acids to macrocyclic polyphenols. The present study investigated the antimicrobial activity, total phenolic content, and proanthocyanidin concentration of ethanolic extracts from fresh leaves of Sempervivum tectorum L. The extracts were phytochemically analyzed and evaluated for antimicrobial activity. The broth microdilution method was used to assess antimicrobial activity against pathogenic bacteria isolated from ear swabs taken from dogs with otitis externa. Many compounds were present in the ethanolic aqueous extracts, which exhibited a broad spectrum of antimicrobial activity. They showed strong antibacterial activity against standard clinical Gram-positive strains such as S. aureus and Gram-negative strains such as P. aeruginosa. In our study, the obtained quantity of total phenolic compounds in the ethanol:water extract of leaves was 126.17 mg GAE/g. The proanthocyanidin concentration in the tested Sempervivum tectorum L. extracts was 15.39 mg PAC/g material. The high contents of total phenolics and proanthocyanidin indicated that these compounds contribute to antimicrobial activity. The antimicrobial activity of the tested S. tectorum L. extracts ranged from 1.47 to 63.75 mu g/mL, starting with 1.47 mu g/mL and 1.75 mu g/mL against S. aureus ATCC 25923 and P. aeruginosa ATCC 27853 strains, respectively. Likewise, S. tectorum L. ethanol extract demonstrated a bacteriostatic effect against S. aureus clinical isolate with a median MIC of 23.25 mu g/mL and MBC of 37.23 mu g/mL; and bactericidal against S. aureus ATCC 25923 with the median MIC of 20.33 mu g/mL and MBC of 37.29 mu g/mL. In the Gram-negative P. aeruginosa clinical and standard strains, the expressed MIC and MBC values were 24.234 and 20.53 mu g/mL for MIC, and 37.30 and 37.02 mu g/mL for MBC, respectively.

Automated summary

The study aimed to evaluate the phytotherapeutic potential of Sempervivum tectorum L. by quantitatively analyzing its biologically active substances. The polyphenol and proanthocyanidin contents of Sempervivum tectorum L. were investigated using modern methods of phytoanalytics, and its antimicrobial activity was tested against pathogenic bacteria. The results showed that the plant extracts exhibited strong antibacterial activity and contained high levels of total phenolics and proanthocyanidin, indicating their contribution to the antimicrobial activity.