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Introduction: Pseudomonas aeruginosa, a gram-negative pathogen, is among the most persistent nosocomial pathogen. Pseudomonas aeruginosa over the years has become antibiotic resistant and difficult to treat. There is an imminent need to discover new and alternate agents that can effectively inhibit P. aeruginosa growth under physiological conditions. In this regard, natural sources offer a wide variety of antimicrobial agents that can be exploited for this purpose. In this study, we evaluated the anti-microbial and anti-biofilm activity of three natural compounds (Camellia sinensis, Hippophae rhamnoides, and Juglans regia) under in vitro and in vivo (burn mouse model) conditions.
Materials and methods: We screened Pseudomonas aeruginosa 60 clinical isolates for susceptibility/resistance to eight commonly used antibiotics (Cephalexin, Chloramphenicol, Gentamicin, Vancomycin, Erythromycin, Tetracycline, Ampicillin, and Ofloxacin). Subsequently, the biofilm formation ability of Pseudomonas aeruginosa clinical isolates was tested using microtiter plate assay. The in vitro antimicrobial activity of Camellia sinensis, Hippophae rhamnoides, and Juglans regia was tested using the agar well plate method, while in vivo activity was determined using the burn mouse model.
Results: The Pseudomonas aeruginosa clinical isolates (n=60) were found to be dominant biofilm formers and were resistant particularly against Ampicillin and Erythromycin, while susceptible to Gentamicin and Ofloxacin. The minimum-inhibitory concentration (MIC) of three natural compounds ranged from 0.5-1 mg/ml. Under in vivo conditions, Juglans regia, and Hippophae rhamnoides extracts were found effective in controlling the infection, with 0-4 CFU/ml from the organ homogenate obtained from the infected mice. These compounds also showed appreciable properties of healing burn wounds in mice.
Conclusions: The natural plant extracts used in the study revealed anti-microbial and anti-biofilm activity against Pseudomonas aeruginosa under in vitro and in vivo conditions, suggesting plants to be an excellent source for providing new and effective antimicrobial agents.